# Next Generation T-Jet - simple changes



## Dslot

When I'm trying to fit sports car or racing style bodies low enough to look good, I find the corners of the Tjet brick get in the way. After dremeling out the body, I seem to have to dehorn the chassis to get a good fit.

It occurs to me that most of these chassis mods could have been designed right into the chassis in production, and probably should have.

Assuming we're committed to the same layout, motor, geartrain, wheels, ground-clearance and all mechanical functions - here are some chassis changes that I think would make the T-jet much more versatile.

Dan (*Lenny* on the board) has been working on the *T-jet Evo*, incorporating electrical and mechanical improvements for Dash's next generation of Tjet. If he, or anyone else finds one or more of my ideas useful, they are welcome to them.

Clearly, any reduction in the height of the brick itself would be very welcome. But that would require major re-engineering. My ideas are for simple changes to the current chassis shape. 

In the drawings, the blue outline shows the clearance saved versus a normal chassis.










Starting with the top view. 

Let's chamfer the gearplate's guardrails for their whole length, making them a triangular section instead of square, as shown in the front view. 

And let's also chamfer the motor housing top, getting rid of that outer square edge that tends to snag tight, rounded bodies and keep them high up off the wheels. 

If we can narrow the motor housing by shaving a millimeter off each side, that would make the chassis 10% narrower. It would also open up the motor chamber, which would allow in dust, but also cooling air. Opening up the sides for ventilation used to be a fairly common mod, and Aurora designed open sides into its Slimline chassis, so I'm guessing it couldn't be too bad. (The side view shows too much space opened up. In order to keep the com tips within the body envelope, the opening would be less than half as narrow as shown.)

Starting just ahead of the pinion gear, I'd like to see the guardrails and the gearplate itself start to taper down toward the front. A dished relief lowers the gearplate top in the center but keeps thickness on the sides leading to the dogs which lock it into the housing. Since racing bodies sometimes had a low hood between higher fenders, it might be occasionally useful, but whether it's worth the tooling effort is debatable.

Let's taper the rear end platform and motor housing and gearplate to take boat-tailed and thinner bodies. The taper would remove the guardrail from the last half of the driven gear, so we'd need to bend the rails around the gear to keep it protected from body interference.

Moving down to the front view, you can see the profile of the chamfered rails and housing. The clamp would be modified to fit the new profile. If the complex shape on the left is problematic, the simpler shape on the right would probably do just fine. 

There is plenty of plastic where the clamp sits, so why not engineer a relief channel in the motor housing for the sides of the clamp to nestle into instead of sitting outside the profile as they do now.

In the very front, we probably should keep the front corner of the upright brace in the same place so the body is unlikely to foul the existing shoes when they travel upward. But from there, let's taper the upright braces backward at a flatter angle for more clearance.

The changes don't look like much, but I've found that one or more of them can make the difference between a body riding high off the wheels, and nestling down to look right. 

I think the simplest changes - the chamfering of the rails and motor housing will be the most useful; the rest just extend the versatility of those mods.

What do you think? 
What simple changes would you like to see to the Tjet chassis to make it a Next Generation pancake and take it to its hundredth birthday in 2063? :wave:

-- D


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## vickers83

Very nice presentation D! Makes a lot of sense, Since most of us have to do quite a few mods to make things fit correctly into altered/custom bodies. Hope someone picks up on these ideas! :thumbsup::thumbsup:


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## old blue

The only other suggestion is to consider making more room for the rear wheels where they meet the angle of the chassis holding the magnet. (Next to where the clip holds the top plate) I find I have to grind them out to get the tubbed look of bigger rear tires that don't stick out past the body. I am sure I did not describe it well but you may get the idea.


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## 60chevyjim

I would love to see the whole chassis sitting as low as possible to the track.
your picture shows that there is way too much ground clearance for the custom low riding custom cars that I like to build.
I cut the gear plate back to the front magnet on some of my customs to get them low enough . it works good on wagons and sedan deliverys .
but that don't help to get the back low enough on cars with a trunk lid for me.
yea what blue said too.


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## HO2GO

Very nicely presented and well thought out. My suggestion is very simple indeed. NO MORE SKINNY TIRES EVER ! UTTER GARBAGE ! And how about some wheels that actually resemble the wheels on a car, NOT a skateboard, NOT a kid's wagon, and NOT a scooter for the disabled. Is it really asking too much for slot car wheels to look like their real life counterpart ?  Tetsuo.


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## Paul R

Not sure if it would be possible, but a way to quickly change the rear axles would be great. The challenge is doing in a way that does leave the back end loose and sloppy.


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## Rich Dumas

One of the limitations of the pancake design is the way that the drive pinion has to mesh with the crown gear. There are lots of things that you can do to lower the chassis but the drive pinion still has to be in the same place.
If you don't like the look of T-Jet wheels you should check out Vincent wheels.


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## sethndaddy

the only thing i would like to see would be an extra set of front axle holes to make a longer wheel base.


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## tasman

The sad thing is that in another thread on this site if given the choice most people at HT would rather have Dash produce a slimline chassis and bodies. No one but me seemed to be interested in the EVO.

I can't fault people for what they want but if all we want is remakes of 50 year old desgins without any improvements and bodies from the 30's - 70's how is the hobby going to attract anyone who isn't a baby boomer?

The EVO has the potential to be 3 chassis in 1 - pankcake platform using a traction magnet, weight or nothing.


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## Dslot

HO2GO sez:


> NO MORE SKINNY TIRES ... wheels that actually resemble the wheels on a car, NOT a skateboard,


Great point. I'd like to see a double-width (or thicker) skinny as the standard tire, but with a slightly larger diameter for the tire and an even larger increase in diameter for the wheel. Standard Tjet skinny tires look better if you use a paint pen around the hole to enlarge the apparent wheel diameter (assuming you can keep it regular enough). Chrome paint or body-color paint can work on rubber skinnies.

Now _there's_ a product - a very thin washer of colored plastic with an i.d. the size of the standard Tjet wheel. Glue them to the tires to increase the apparent diameter of the wheel.











Old Blue sez:


> ... more room for the rear wheels where they meet the angle of the chassis


Not a problem I've had yet, but I see exactly what you mean. For the Jaguars and other '60s racing bodies, 

http://i.imgur.com/zg65pMd.jpgI'd like to have a thin, close-set wheel/tire big enough to go up into the fenders, and that would mean taking a bit of plastic out of the chassis at that point. (Hmm ... the centers of those Jaguar wheels look a fair amount like standard T-jet wheels - now if I just had a washer with holes (or black dots) ...)

-- D


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## tasman

Paul R said:


> Not sure if it would be possible, but a way to quickly change the rear axles would be great. The challenge is doing in a way that does leave the back end loose and sloppy.


I remember a post from Dash when he first described the EVO saying he was planning on a pop-out rear axle.


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## Dslot

60chevyjim said:


> I cut the gear plate back to the front magnet on some of my customs to get them low enough . it works good on wagons and sedan deliverys .
> but that don't help to get the back low enough on cars with a trunk lid for me.


If we could cut the gearplate back in the front, that would leave extra room, more even than tapering it down. But suddenly interchangeability with the normal T-jet parts goes out the window if the locking dogs are moved backward. Now the new gearplate won't fit a standard chassis, an the new chassis won't take a standard gearplate (unless it has recesses for the dogs in both positions). In a way, it's no longer a T-jet. My original suggestions created parts that were entirely interchangeable with standard T-jet parts. Does that matter?



> I would love to see the whole chassis sitting as low as possible to the track ... there is way too much ground clearance for the custom low riding custom cars that I like to build.


I'm a bit ambivalent about lowering the body on the wheels. It sure would help fit bodies lower, but I like the bridges and humps of the original T-jet era lock and joiner track and the bump of the Aurora Daredevil Obstacle set that can be added to Tomy track. But the lowered-body magnet cars high-center on those; low-clearance cars require a flat course with very gradual rises and falls. If we want the Tjets to be able to take humps and bumps like the originals did, then we need the extra ground clearance, or at least some of it. Is that important to anyone but me?

The ideal solution would be two sets of axle holes front and back, one for high and one for low clearance. Whether that's workable on the rear axle and still maintain crown-gear/pinion engagement, I'm not sure. It might be as easy as making a thicker pinion (or putting two on the shaft?) and eliminating the bearing spacer on the gearplate. Or maybe a smaller diameter crown for the axle in the high hole? Would that inevitably change the gear ratio for the worse? Could you fiddle pinion teeth to compensate?

While we're at it, let's add SethnDaddy's extra front hole for longer wheelbases.

And Paul R's snap-in rear axle (though Dan has already announced that for the Evo - hopefully he can do it for the Slimline, when and if) Can we put a snap-in slot going up to a second axle hole from the first? How about the front axles?

So now we're *here*, eh?









:thumbsup: Keep it up.

-- D


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## 60chevyjim

I like the chassis idea with the 2 sets of axel holes + A extra front axel hole.. 
with being able to lower the chassis there is no more need for me to cut the front off the gear plate . I don't see A need a snap in rear axle myself .. 

bill hall made a lowered tjet chassis and it needs a clearance hole in the gearplate 
for the rear axel gear. it was lowered to the same height of A AFX chassis .
I know he lowered the rear of it but I don't remember if he lowered the front of it too ?


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## dtomol

*Next Generation T-Jet- simple changes*

I always though thought that a their should be a hole for the third wheelbase under the truck/ hot rod wheel base for car with shorter wheel base so their would be short medium& a long wheel base options. On ho world their was a chassis mod to lower the top gear plate i believe Gary Cullen was the one that wrote the article. It shows a drastically lower T-jet. i AM AT WORK I CAN ATTACH THE FILE LATER THIS PM.


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## dtomol

*nEXT gENERATION t-JET -SIMPLE CHANGES*

Any one hear any more information on the dash evo chassis? I really hope he makes this item!


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## mrtjet

vickers83 said:


> Very nice presentation D! Makes a lot of sense, Since most of us have to do quite a few mods to make things fit correctly into altered/custom bodies. Hope someone picks up on these ideas! :thumbsup::thumbsup:


It seems that a lot of these issues have been addressed. Connect Rad! Scale motorsports.


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## Dslot

mrtjet said:


> It seems that a lot of these issues have been addressed. Connect Rad! Scale motorsports.


Could you be a bit more specific about _where_ on the Rad! site they've been addressed. I looked in the most likely spots - nada. 

A URL would be great. 

Thanks.

-- D


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## mrtjet

Try, Rad Scale Motorsports.


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## Dslot

mrtjet said:


> Try, Rad Scale Motorsports.


I googled *Rad! Scale Motorsports*, and it sent me to their site. I looked in Hints & Tips, Store, Blog, plus the five most likely topical subforums. But I could not find info on Tjet improvements on the site.

Do you have a specific URL for the page with this topic or topics?

-- D


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## dtomol

*next Generation T-Jet - Simple changes*

Please find attached articles on T-Jet chassis mods.


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## dtomol

*next Generation T-Jet - Simple changes*

I have modified a Tjet Chassis it now has a snap in rear axel, as well as I sanded down the top of the chassis to get the top plate to site lower. My next Modification is going to be to make the magnet pockets where the magnet site to be deeper. This will allow me to further lower the top of the chassis. I have also installed brush tubes in the same chassis. I got the original idea from the post below.

(This post came from HO world.net) 
Thunderjet Chassis Mod - Cook Up a Low-Profile Pancake
–––––––––––––––––––––––––––––––––––––––––––––––––– ––––––––
By Mark Owyang


This article was originally published in the Fall '99 (v.13, no.2) issue of HO-USA. 
When I returned to slot racing a few years ago, I didn't expect to be working much on t-jets. I had fond memories of running and modifying t-jets as a kid, but remembered giving them up when Aurora introduced the AFX. The AFX was the latest, so I figured it had to be the greatest, right? Like the t-jet, the AFX was an ideal platform for modification and improvement, so I was soon drilling holes, cutting brass, and trying out ideas to make it run faster and handle better. Not that I ever had much success! My parts box was always littered with the hacked up carcasses of pancake chassis experiments gone awry. But for me, this process of experimentation was perhaps the most enjoyable part of the hobby.
I missed out on the Magna-Traction chassis somehow. With high school in full swing, I was devoting less time to the hobby. But I sure do remember seeing the first G-Plus cars. Though slot cars had slipped down on my priority list, that beautiful Aurora Ferrari 312 body drew me back in. And man, were they fast. It was clear to me then that the pancake motor era was over, once and for all. Or so I thought.
Fast forward through college, marriage, and the birth of two kids. Slot cars were just a fond memory. Then in 1995, I discovered through the Internet that slot cars were still very much alive. I was drawn back in again. My first new cars were the Super G+'s included in the race set I bought in 1996. Snapping off the body and studying the chassis for the first time, it was obvious the design had evolved from the original Aurora G+. While learning to tune the cars, I found that the hobby was still fun.
Yet the cars were so fast, any major modifications seemed unnecessary. I found myself missing one aspect of the hobby I'd really enjoyed from my youth: innovation and experimentation in chassis development.
The Fray in Ferndale got me back to running and enjoying t-jets. It was just a matter of time before I wanted to build a modified car again. Remembering the rewound arm, drilled gears and wide brass pan on racing pioneer Carl Dreher's creation from Auto World's 1970 HO Racing Speed Secrets, I thought I'd try to recreate a vintage "pro" car. However, as is often the case, I got sidetracked with another project, and my first modified t-jet ended up being a quite different car altogether.
One of the most common goals when modifying a t-jet is to lower its center of gravity. Brass pans, drilled gears, and vacuformed bodies all contribute towards this goal. On a hard bodied car, trimming the body posts and thinning the plastic allow the body to be mounted as low as possible. But the stock t-jet chassis puts strict limits on how low you can go. Staring at the venerable t-jet chassis one night I had a brainstorm: what about lowering the gear plate into the chassis to create more clearance for the body? A low-profile pancake. A flatter flapjack!
I made the low profile t-jet by sanding the gear plate and the inside floor of the chassis to about half their stock thickness. The magnets sit lower in the chassis, allowing the gear plate to drop down as well. Though the chassis is lighter than stock, the center of gravity is now lower. The chassis is nearly 1/16" lower than an unmodified chassis. The body, of course, can now be lowered that much more. The car handles better, and it looks a lot better too. Check out the effect on Aurora's Porsche 904 (bottom). Now that's closer to the stance that a Porsche should have! Bodies with a flat rear deck or trunk lid benefit the most from this modification.
It's a lot of work, but I think these changes lead to a mighty cool t-jet. The car is great fun to drive, retaining but improving upon the characteristics of a stock t-jet. Of course, now I want to build one with a rewound arm, stronger magnets, and a brass pan!
.


(this came from Nitro Slots board)
If anyone is interested in doing this, I found it pretty easy to do. Front tabs are cut off of top plate, and plate just rests on additional front magnet. Between plate clip and screw I've had no problems with plate moving. Though Ron (bondoman2k) has told me of someone that has a clip that fits plate over front magnet. Magnet pockets are cut down to chassis floor in line with inside of side pocket walls. This will leave a small projection that keeps additional magnets from shifting. 
sides of chassis are cut to floor just behind top point of plate tab pocket. Everything between the cuts cleaned out to floor. T-jet sized magnets fit between chassis floor and plate (like they were made for it). In rear magnet pockets are cut the same way. Then second cut was done by putting original magnet with additional magnet attached in top of magnet pocket to get point where to make cut in chassis. Did this on an AW chassis and magnet fits between traction magnet housings and top plate (again t-jet sized magnet). Inside of chassis (between sides) where hole for plate screw is needs to be arched for clearance. This can be done without interfering with hole for plate screw. Do this a little at a time, and trial fit magnets till right. Put back together with additional magnets and your done. If anyone going to try this and has any questions, just a


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## mrtjet

Hmmm....just want to throw this in the mix. Why not just run an AFX or a magnatraction car and do any handling improvements on them? I'm just saying. I wonder how a comparably set up AFX car would be against a Fray tjet. As they are now the gearing would make the AFX faster but that could be addressed (Hear that DASH!) That is assuming the fray cars use stock tjet ratios. I wonder how the Handling compares. Or am I :beatdeadhorse:?


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## Rich Dumas

Fray cars have to use the stock T-Jet 9 tooth drive pinion or an aftermarket equivalent. Most clubs that run T-Jet SS cars allow 12 or 14 tooth drive pinions.


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## mrtjet

So if the gearing was the same, to me it seems the AFX has an advantage being lower to begin with.


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## slotking

> Why not just run an AFX


we had a AFX non mag class, brass pans were allowed
silicone covered sponge tire and any arm. We had a rull that a slower car could also run.

people started to use FRAY cars and started winning with them.
the key was the turns!


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## noddaz

*Lowered chassis?*

For a "brand new" modified chassis the only parts it could really share would be the gears, arm and magnets. Everything else would be tweaked like in the Mark Owyang mods. I have always wanted to build one of those. Looks like fun to do. Just never have.
Of course these days with rapid prototyping (and extra money to spend) someone might be willing to break convention and do this. I can see it. Just can't make it happen.

Scott


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## foxkilo

One thing I don't understand why don't you get away with the holding clamp at all?
Faller did it with their F1 chassis which was nothing else than a modyfied t-jet. Just look at this tread that Marty started a few years back. It could give a few hints for mods on an improved tj.

Mario


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## Dslot

Why not do away with the holding clamp altogether? It's an excellent question, Mario.

Here's *Marty's thread* on the Faller F1.

And here's the relevant picture:










My point in starting this thread was coming up with simple changes to make to a next generation chassis, that would be improvements, but still be essentially a T-jet, and would interchange most parts with a conventional T-jet. This one, like some of the others, is a bit borderline.

If we could ditch the clamp, it might be worth trading away some interchangeability. But I'm not sure Faller has the right solution. I think I'd rather be able to pick off a clamp with my fingernails than have to get a screwdriver and remove and replace two screws every time I wanted to fiddle with the commutator or the brushes or rear pinion.

It's a judgment call, though. Ditching the clamp _would_ make body-fitting easier. And by giving the new pieces _both_ screw-holes _and_ clamp-pockets, you could probably retain the interchangeability with the old parts, and let the customer use the system he prefers.

Definitely worth thinking about.

-- D


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## foxkilo

Hi D,

it wasn't ment to degrade your suggestion, which many of us already do to varying degrees to fit chassis to bodies. Your idea put it further by combining all areas on the chassis where material could be shed to loose width and height is 
IMHO already a step to the slimline. And therefore why not go step further as all parts except chassis itself remain interchangeable. Okay may be longer shoes for a longer wheelbase.
Your suggestion of bending the clamp might work only in part as the vector of force should be straight and not bent. Anyway this might be only of acadamical nature. 

Mario

BTW I don't where the link to Marty's tread went, I most certainly inserted it.


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## Dslot

foxkilo said:


> ... combining all areas on the chassis where material could be shed to loose width and height is
> IMHO already a step to the slimline. And therefore why not go step further as all parts except chassis itself remain interchangeable. Okay may be longer shoes for a longer wheelbase.


Mario, that's another good question that's been bouncing around in my head --

If it's possible, through slight re-engineering and modern magnets, to get a Slimline that can equal a T-jet in performance, why even bother with tweaking the wider chassis? Just make the new standard T-jet a slimline-width machine, and work the refinements (tapering the chassis, modifying the rails, adjustable height, etc.) directly on the slim chassis?

I know one problem is with racing organizations possibly not being willing to change the rules to allow the slim chassis. Another is the affection many people have for the standard proportioned T-jet chassis.

Do we need both - a second generation T-jet, _and_ a second generation Slimline?  Let's get some opinions.

-- D


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## foxkilo

To my knowledge the original slim line had a few flaws which are not easily addressed in standard layout. Correct me if i'm wrong cause unfortunatelyI never had a slimline. Although I'm somewhat a Faller afficionado I don't have my pink tainted specs when it comes to their short comings. Faller F1 for example runs really well straight out of the box and would have been really great if it weren't for the abysmal tires and high center of gravity. Although Faller took provisions for it by raising the axle holes. But is still a tjet at heart only with a different approach.
But as far as I understood this discussion, some are asking for more options in wheel base and height position of the axles. Others asking for a snap in axle. I'd say why not have a look over the fence and take the best of both worlds and create a new evo slimline out of it.

It is time for modern chassis that behaves like a Tjet and incorporates the progress in technology and the knowhow we gained while working with the original for over 50 years.


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## dtomol

*T-Jet Slim line Chassis*

Has anyone heard if Dash Motor sports is still planning on making the updated slimline style chassis?


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## Ralphthe3rd

dtomol said:


> Has anyone heard if Dash Motor sports is still planning on making the updated slimline style chassis?


 Dan made a public announcement a month or so ago, that any plans for a SlimLine style chassis have been scrapped, end of story on that front


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## vaBcHRog

foxkilo said:


> To my knowledge the original slim line had a few flaws which are not easily addressed in standard layout. .


Weak magnets sup par motor brushes and a clearance problem on the crown gear were the major flaws. All three should be easily correctible in a new run of chassis.


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## vaBcHRog

Something I was thinking about is why not a remake that has a longer wheel base that would fit most of the 1/64 diecast of today. Something with a wheel set up similar to a slim line but with an extra axel hole on front of the pickups like the TYCO. and a slightly stretched TJET chassis more like a TJET and less like a 4 Gear


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## alpink

Roger, good point.
and the whole reason for the 4-gear concept was to allow the narrower rear that could accomodate wide wheels/tires.
if you aren't familiar, check out Shapeways and find SL1 chassis.
not pancake and not built, but has very adjustable wheel base and narrow chassis


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## Grandcheapskate

Great diagrams once again David.

Here are my added suggestions for a modified T-Jet chassis while maintaining complete interchangeability with an original.

1. Rework the chassis electricals and copy the Magna-Traction design. This eliminates the weakest point of the original T-Jet (and AFX) - the brush springs. The chassis would now use the same comm springs as the MT. Note the T-Jet now uses two pieces of metal to run from the pickup shoe to the brushes, whereas the MT uses only one.

2. Modify the underside of the chassis to expose the motor magnets, like the MT, which allows the use of MT magnets and creates MT-level downforce. Create a filler piece which could be placed in the magnet pocket to close off the exposed area and let you use standard T-Jet magnets and remove the downforce. Two chassis in one.

3. Replace the underside rivets with screws which would allow the electricals to be replaced and or removed and cleaned. This would require a threaded metal sleeve embedded in the chassis floor. 

4. This would be a bit harder...instead of front axle holes, create two slots; one slot running along the line of the lower holes and the other along the upper hole. This would allow you to position the front axle anywhere along the slot. The only catch, and it's a biggie, would be how to lock the axle in place.

Joe


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## Dslot

Grandcheapskate said:


> Here are my added suggestions for a modified T-Jet chassis while maintaining complete interchangeability with an original.
> 
> 1. Rework the chassis electricals and copy the Magna-Traction design. This eliminates the weakest point of the original T-Jet (and AFX) - the brush springs. The chassis would now use the same comm springs as the MT. Note the T-Jet now uses two pieces of metal to run from the pickup shoe to the brushes, whereas the MT uses only one.
> 
> 2. Modify the underside of the chassis to expose the motor magnets, like the MT, which allows the use of MT magnets and creates MT-level downforce. Create a filler piece which could be placed in the magnet pocket to close off the exposed area and let you use standard T-Jet magnets and remove the downforce. Two chassis in one.
> 
> 3. Replace the underside rivets with screws which would allow the electricals to be replaced and or removed and cleaned. This would require a threaded metal sleeve embedded in the chassis floor.


Hey, Joe. The Magnatraction electrics sound like they'd be more reliable and consistent, at the negligible additional cost of two extra brush springs.

The MT magnets in the deepened recesses of course provide MT-level downforce only if the axles were in the high axle-holes and the wheels small, lowering the chassis to something like Magna-Traction ground clearance. But even with the standard chassis-clearance, there would be _some_ additional downforce.

Here's a drawing of the underside as you describe it.












> 4. This would be a bit harder...instead of front axle holes, create two slots; one slot running along the line of the lower holes and the other along the upper hole. This would allow you to position the front axle anywhere along the slot. The only catch, and it's a biggie, would be how to lock the axle in place.


I can't illustrate that one without a specific proposal for locking the axles. There's very little space to do anything with, unless we redesign everything forward of the front magnet. I think we may have passed the edge of the "simple changes" concept with this one. 

How about some comments. Would the MagnaTraction electrical system, tall magnets in deeper wells, and screws replacing the rivets would be a significant improvement?

Any comments on the axle-slots or proposals for simple ways to lock the axles?

-- D


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## Bubba 123

vaBcHRog said:


> Something I was thinking about is why not a remake that has a longer wheel base that would fit most of the 1/64 diecast of today. Something with a wheel set up similar to a slim line but with an extra axel hole on front of the pickups like the TYCO. and a slightly stretched TJET chassis more like a TJET and less like a 4 Gear


Ya's took' Woids right outta' Me mouth :thumbsup::drunk:

Bubba 123 :thumbsup::wave:


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## vaBcHRog

Grandcheapskate said:


> Great diagrams once again David.
> 
> Here are my added suggestions for a modified T-Jet chassis while maintaining complete interchangeability with an original.
> 
> 1. Rework the chassis electricals and copy the Magna-Traction design. This eliminates the weakest point of the original T-Jet (and AFX) - the brush springs. The chassis would now use the same comm springs as the MT. Note the T-Jet now uses two pieces of metal to run from the pickup shoe to the brushes, whereas the MT uses only one.
> 
> 2. Modify the underside of the chassis to expose the motor magnets, like the MT, which allows the use of MT magnets and creates MT-level downforce. Create a filler piece which could be placed in the magnet pocket to close off the exposed area and let you use standard T-Jet magnets and remove the downforce. Two chassis in one.
> 
> 3. Replace the underside rivets with screws which would allow the electricals to be replaced and or removed and cleaned. This would require a threaded metal sleeve embedded in the chassis floor.
> 
> 4. This would be a bit harder...instead of front axle holes, create two slots; one slot running along the line of the lower holes and the other along the upper hole. This would allow you to position the front axle anywhere along the slot. The only catch, and it's a biggie, would be how to lock the axle in place.
> 
> Joe


What if you did make it like a magnatraction but kept the magnets the same size as a TJET but made the chassis shorter so the top would be lowered by the amount the magnets dropped down. This would allow all of the TJET bodies to set lower


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## Grandcheapskate

vaBcHRog said:


> What if you did make it like a magnatraction but kept the magnets the same size as a TJET but made the chassis shorter so the top would be lowered by the amount the magnets dropped down. This would allow all of the TJET bodies to set lower


 Hey David, thanks for the updated diagram of the underside of the chassis. 

Roger,
I think you need the entire existing space between gear plate and chassis bottom for the armature. You can't reduce that space.

Joe


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## vaBcHRog

Someone lowered the magnets in a TJET and thinned the gear plate and the chassis a tad a couple years back and posted here. When I get a chance I'll have to look for the post.

I found it and bumped it to the top. http://www.hobbytalk.com/bbs1/showthread.php?t=272675

But this is the size I would love to see or as close as you could get.


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## Grandcheapskate

That is truly an impressive job of lowering a chassis.

The purpose of this thread was to suggest changes to a T-Jet chassis which would keep complete compatibility with the original T-Jet design. The lowering of the chassis to the degree shown in that thread would require a flatter armature and different size magnets just for starters.

So while it's a great improvement, it does require quite a few modifications. Although a small cutout for the crown gear in the bottom of the gear plate would be something that could be done to a standard gear plate without losing compatibility. And depending on the room available for an unmodified armature, it's possible the gear plate could be slightly thinner.

Joe


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## Dslot

When Joe talked about not being able to reduce the height of the chassis itself, I immediately thought of Mark Owyang's low-profile chassis mods. I found a different thread
http://www.hobbytalk.com/bbs1/showthread.php?p=5682914#post5682914
which I have also bumped up to current status with a post about 3-D printing the slammed chassis and gearplate.

Mark published an article on the process on another site, but I haven't been able to find it on the web, so maybe it's gone. Luckily, I did download it, with pictures. If I can find it and figure out a way to post the whole thing, I will, though it may be the same as the one *DTomol *posted in post 21 of _*this *_thread. 

Maybe someone with access to 3-D printing or injection molding could put out a run of them. As long as we're printing/molding, it could include some of the mods from this thread, maybe even Joe's Magna-style electrics.

Then we could get to work on the "slammed Slimline." 

-- D


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## Dslot

The threads that Roger and I bumped up to current status are in the *Slot Car Modeling/Customizing* section of Hobbytalk Slots.

The article I downloaded _*is*_ the same as the one DTomol put in Post 21 of this thread. (Oops. CORRECTION: not the same, but contains some of the same material.) My version has pictures, but I don't have time now to convert them and upload to Photobucket, etc. I'll do it tonight if I can.

Cheers,
D


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## slotcarman12078

I've pondered over this for quite some time. Here's a few "what ifs" that I haven't run across. I may have missed them in this thread or elsewhere as I have skipped a few pages, and haven't been around much. My apologies if I did. Heck, I may have even suggested some of this last year and don't remember! :freak:

What if someone were to take the top plate concept from an AFX with the riveted 2 stage driven gear, and made it set up for T Jet? Raise up the axle holes to somewhere between a T Jet and and AFX. This will allow some ground clearance, and allow T Jet bodies to sit lower at the same time. 

There's quite a bit of wasted space inside the arm cavity that could be trimmed down and allow a lower chassis height. I also wonder is there would be more than a minimal loss of power by trimming the back of the magnets at the ends. This would allow wider back wheels to be installed without them sticking out from under the car body.

I've also pondered over a sliding wheelbase up front. Rather than holes, have slots at the front of the chassis. A metal clip can be locked by the front post to set the wheelbase. For standard T Jet wheelbases, the clip would line up the front axle to the proper wb by the post location. For customs, you would set the required distance by custom mounting the post.

To really slim and possibly slow things down, I've contemplated a worm drive in place of the pinion shaft. Rather than 2 big gears up top, have a small gear behind the arm gear, and then a driven gear behind that. This will allow the worm gear shaft to be behind the magnet, and have a vertical worm gear drive the crown. This idea will allow the bulk of the chassis over and behind the rear axle to be eliminated. Something slope backed like a VW bug will no longer have a gear rubbin' the hood (trunk) what ever. 

I haven't tinkered with any of these ideas. They've just been rolling around in my mostly empty head for the past couple of years... They might work, they might not even be remotely possible... At least I'm trying to think. :tongue:


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## mowyang

Grandcheapskate said:


> 1. Rework the chassis electricals and copy the Magna-Traction design. This eliminates the weakest point of the original T-Jet (and AFX) - the brush springs. The chassis would now use the same comm springs as the MT. Note the T-Jet now uses two pieces of metal to run from the pickup shoe to the brushes, whereas the MT uses only one.
> 
> 3. Replace the underside rivets with screws which would allow the electricals to be replaced and or removed and cleaned. This would require a threaded metal sleeve embedded in the chassis floor.


Though many seem to prefer the Magna-Traction brush spring setup, I've always felt the design to provide poorer electrical conductivity to the commutator brush than the standard tjet design. The tjet's spring arm provides a solid conductor to the commutator brush while the Magna-Traction system depends upon a good connection between the commutator brush, the coil spring, and the spring support plate (newly invented term!). The standard tjet design also provides a way to prevent the brushes from rotating if desired. 

While the standard tjet brush springs are indeed easy to mangle, if idea #3 were to be implemented, then a mangled spring could be easily replaced.


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## vaBcHRog

I remember my first M/T, going from an AFX to M/T I was surprised that they made it so much harder to change motor brushes. I always liked the notched brushes for their ease of use.

What I don't understand why all the rules require flat bottom motor brushes. Is their any advantage over the notched ones? And why did Aurora go to the notched ones when they designed the AFX.


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## alpink

Aurora notched/dome brushes have a high silver content.
they aren't so easy to come by anymore.
there would not be a level playing field in competition if some folks couldn't lay hands on.
Aurora also made silver content flat brushes which are a little more common and occasionally someone will make a new batch.
but they aren't always available.
carbon/copper brushes in different recipes are made by at least(or distributed) three main manufacturers.

not knowing the real reason that notched/dome brushes are not allowed in many classes of pancake racing, I cannot answer this question definitely.
but, you can draw your own conclusions.

anyone else?


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## Grandcheapskate

mowyang said:


> Though many seem to prefer the Magna-Traction brush spring setup, I've always felt the design to provide poorer electrical conductivity to the commutator brush than the standard tjet design. The tjet's spring arm provides a solid conductor to the commutator brush while the Magna-Traction system depends upon a good connection between the commutator brush, the coil spring, and the spring support plate (newly invented term!). The standard tjet design also provides a way to prevent the brushes from rotating if desired.
> 
> While the standard tjet brush springs are indeed easy to mangle, if idea #3 were to be implemented, then a mangled spring could be easily replaced.


 In trying to compare apples to apples, I find almost always the Aurora MTs outperform standard AFX with both in stock form. There are three main diifferences in those two chassis...(1) size/strength of the motor magnets, (2) 6.x ohm armature for the AFX compared to 16.x for the MT and (3) the electrical/brush combination.

As just a general observation on my part, I find MTs seem to have far better electrical conductivity than AFX and are generally faster and smoother. Part of the reason may be the MT also provides an electrical path through the pickup springs so it doesn't depend completely on the hinge for the pickup shoes.

Thanks...Joe


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## foxkilo

Or get even closer Joe compare a Faller chassis to a tjet. Faller is a tjet clone already equipped with a spring brush combo. Size of both is similar t's have slightly larger wheelbase. Faller lower resitance in the armature. But in general Faller is closer to the Tjet than AFX or magna. Some of you had already the chance to compare the two. What's your opinon on it.


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## vaBcHRog

The JL and AW have notched brushes, what do the Dash have in them?


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## alpink

the JL and AW notched/dome brushes are carbon copper.
the DASH chassis also have notched/dome brushes, I don't know what the composition is.
based on the fact that he got his armatures from the same source as JL/AW I would say they are most likely carbon copper


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## vaBcHRog

But why did Aurora go to notched brushes what was the advantage. Does anyone anyone recall anything in the old Car Model Magazines on this?

The positives is they don't spin but you have less contact surface on the commutator, I don't know if that was a good or bad thing.


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## alpink

it would seem that since they changed to flat brushes supported by coil springs upon introduction of the MagnaTraction chassis that they were convinced that the domed/notched brushes were inadequate.

perhaps the reason they went to the domed/notched brushes when the AFX was debutted was because so many people were notching the flat brushes in T-Jets to prevent spinning.
of course, I was a child at the time and was not privy to such behind the door discussions and I could be quite wrong.
I was wrong ....
.
.
.
.
.
once!!!!!
.
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.
.
.


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## vaBcHRog

Al, I found it Car Model magazine. Ed Bianci did a test and a great write up in the Jan 72 issue.

To quote him "The armature brushes are slotted on the underside to keep them from rotating. They are beveled on the top to keep them from wanting to rotate. This apparently helps provide more uniform electrical contact."


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## warnergt

I don't believe spinning brushes hurts anything. IMO, the benefit of the notched brushes was that they created a larger electrical contact area with the brush springs.
MagnaTractions eliminated the brush notch because they also eliminated the 'V'-shaped brush spring. MagnaTractions made no effort to prevent brush spinning because it was a non-problem.


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## slotking

> I don't believe spinning brushes hurts anything



I disagree agree and I have spent time making cars faster by stopping the spinning!

Here a video I did.

http://www.ho-tips.net/showthread.php?tid=1961


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## vaBcHRog

Nice Video it speaks for itself. Are you just lightly holding the rear of the Chassis so it does not bounce up and down? I broke down and bought his Dyno. I notice some cars bounce a bunch and some don't. I attribute most of the bouncing to the rear tires/wheels. Does balancing the motor make a difference in the bounce?


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## slotking

yes
to reduce bounce

I also use it to check axle/tire sets to make sure they are true.


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## vaBcHRog

What is average Dyno Reading for a TJET vice a really good one?

Do you use a test chassis to test all your armature and gear plates or do you just test the chassis you are building.


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## slotking

from my experience, I only use the dyno to compare 1 car to itself after I make a change to it.

Yes I have had cars that look great on the dyno and ran great
But I have had them look great on the dyno but sucked on the track
I had ok dyno readings that flew on the track.

a car with weaker magnets may have higher dyno readings
there is torque VS top end. handling, the driver or what ever.

So if I start to work on a car, I dyno it 1st to get a baseline
then I start to tweak, but I try to make 1 tweak at time to determine the affects of that tweak.

If I want to find a motor, I test it in the car it goes in. I start with a tach and get the rpms for that motor in that chassis/gear plate,

This lets me get 3 or 4 arms I will test with, If the 1st arm looks good, I with put the gear on the motor and test.

I look for how fast it spins up to top output on the dyno.

if it sucks, I go to the next arm! ie.. my RTHO tools come in real handy.

hope that helps


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