# Bouncing Thunderjet - What could cause this?



## Scafremon (Dec 11, 2006)

I bought my first slot car that wasn't a Super G+ that came in a box set of track. It is the AW Thunderjet GTO. I hooked up a small track to compare this to the G+ cars, but this new car doesn't run so well.

As soon as you give it power, the rear end slides to the side about an 1/8th to 1/4 inch, and then the car kind of bounces as it goes crooked down the straight. I really have no idea where to start troubleshooting this, but wondering if possibly one rear tire is a different diameter then the other, and if this would cause the problem.

Suggesstions on how to troubleshoot this would be appreciated.

Also, I've seen people touch upon 'breaking' in a new car. Are there some general guidelines on what should (and shouldn't) be done, possibly by type of car?


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## Crimnick (May 28, 2006)

Sounds like the spring tension on the pick ups is a bit high...and tire swap both front and rear is probably best as well judging from the AW TJ's I picked up...

They both run real strong...but one of them does the front hop as well...I just havent taken the time to tweak them as the home track is stored and I started running super mag racing (wizzard,BSRT, slottech) with a local group...

I'm sure one of the TJ guys will give you some tips...like how to limit shoe travel, etc...

I love slip sliders...but I'm going in another direction at the moment..  

BTW...thanks for the track update...I will be using some of your ideas for sure....be patient...you'll get the track you need at the prices you want eventually.... :thumbsup:


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## Bill Hall (Jan 6, 2007)

Crimnicks right, 1: After market tires. Go for it! There's a lot of unround, flatspotted, lumpy tires out there. 2: Check your front and rear wheels for true and the axles for bent or binding. 3: If that's all good, the pick up springs are to firm. Squishem' a bit. If that doesnt work remove 1 coil of the spring by slipping an exacto blade into it and fold a single loop up. Then cut it of with a sharp scissor. No more than two coils. If you go too far the spring can be stretched a skoshe. Keep in mind that there are more than one kind of spring available. Get some extras. Check "HO World" archives for all the How To's on break-in and other great tips. Oh yeah, check your guide pin for bent or dragging. Good Luck


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## noddaz (Aug 6, 1999)

Like Bill & Crimnick said, start with the wheels & tires..
You can buy tires from JAG http://www.jaghobbies.com/ or from JW http://users.cescowildblue.com/jwsteed/JW.HTM or from Super Tires http://www.supertires.com/ or even from Weird Jack... http://altair-four.com/rsl/
New tire make a big difference with these cars...
Enjoy.


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## Hornet (Dec 1, 2005)

Crimmick,if you're still looking for Storm R/O tricks try here,look through the poly mod section

http://ho-tips.org/


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## roadrner (Jul 21, 1999)

Don't give up on them. Once you get them dialed in, you'll have some real fun. :thumbsup: rr


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## mking (Apr 25, 2000)

*AW Tjet tuning*

ok...other people will disagree but here is what i consider the 3 most important changes you can make.

1. change the rear tires. i prefer the silicone tires BudsHO sells, there are about $10 a dozen. A close second are Weird Jacks tires. Weird Jack often sells bulk tires at a discount, he calls them rejects b/c they have some bubbles in the silicone but they work fine. 

2. change the rear axle. i hate the AW/JL rear axles so much i replaced almost all of mine with smooth axles. its not so much the axles themselves, its the axle bores/holes are too large, and you get alot of rear axle slop. hold the rear tires and wiggle the axle back and forth and you will see what i mean. i use 1/16 drill rod or 1/16 piano wire (hobby shops carry this). slightly larger and takes care of the slop. you can reuse the stock hubs, but you need a wheel press to get them on straight. 

3. restrict the pick up shoes. you can fold them, but i prefer to use heat shrink tubing. place the tubing over the part of the shoe that attaches to the front of the chassis. you want to limit the up and down travel of the shoe. at a rest position, you want the bottom of the shoe to stick down just below the tires as you look from the side. i think i have been using 1/16 and 3/32 tubing from a hobby shop.

if you send me your address, i will send you samples of the tires, tubing, and axles. i have tuned about 50 of the cars this way, and quite enjoy them now. 

an additional improvment is to add a wider weighted front end. 


here is a link to a heat shrink tubing thread
http://www.hobbytalk.com/bbs1/showthread.php?t=169451


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## micyou03 (Apr 8, 2003)

mking said:


> 3. restrict the pick up shoes. you can fold them, but i prefer to use heat shrink tubing. place the tubing over the part of the shoe that attaches to the front of the chassis. you want to limit the up and down travel of the shoe. at a rest position, you want the bottom of the shoe to stick down just below the tires as you look from the side. i think i have been using 1/16 and 3/32 tubing from a hobby shop.


I tried this on one of my AW cars. Now when I acceelerate down the straights and it tries to pull a wheelie the car sputters down the track.

After that I removed the restricters from the shoes and cut a turn and a half off the pick-up spring the car goes down the straights pretty good.

When using the restrictor method is there something I need to know but don't?


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## noddaz (Aug 6, 1999)

*shoe adjustment*



micyou03 said:


> I tried this on one of my AW cars. Now when I acceelerate down the straights and it tries to pull a wheelie the car sputters down the track.
> After that I removed the restricters from the shoes and cut a turn and a half off the pick-up spring the car goes down the straights pretty good.
> When using the restrictor method is there something I need to know but don't?


When doing the restrictor trick you must leave the pick up shoes so they hang just below the edge of the front tire... It is also importanbt for the flat of the pick up to be flat against the rails for best power transfer...
Scott


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## mking (Apr 25, 2000)

*you can restrict the shoe travel tooo much*

...and cause electrical contact problems that will slow you down. the neat thing about the heat shrink tubing is that its not permanent, you can fiddle with it until you get it right. 

i understand cutting the springs can work, but i never got the hang of it, and i lost way too many springs trying......


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## Bill Hall (Jan 6, 2007)

*Find middle ground*

Hi Scaf, What Scott said about power transfer is very important. Either way, undersprung and restricted pick up cars will run weak and slow if they cant transfer current. There's a lot off gobblydygook about pickups and mods out there. What they dont tell, but is implied, is that cars in stock trim IE: front wheels and tires, generally only require minor shoe and spring adjustment. Keep in mind that t-jets and their like have virtually no suspension to speak of, and what little they do have can be compromised quickly. Like a 1:1 car that has been backyard lowered by torching out some coils. Stiff and boingy! On super smooth routed "skating rinks" pick up restriction is great and the norm. On standard track (county roads, like mine LOL) with joints, lumps and bumps; a little give in the pickups is helpful. I have yet to meet the stock trim car that couldnt be dialed in with careful attention to the basics. The aforementioned, concentricity of tires wheels and axles, the shoe contact patch, hangar window matching, spring adjustments, and ensuring that the shoe meets the chassis at the rear shoe step when fully compressed. Again keep in mind that that slot cars have seven contact points with the track, two of which (the pick ups) should be flexible enough to adapt to variations in the rail surface. Crimnicks original comment regarding tires/wheels usually solves most of the rodeo and bouncing problems. Good Luck!


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## mking (Apr 25, 2000)

Bill Hall said:


> . Crimnicks original comment regarding tires/wheels usually solves most of the rodeo and bouncing problems. Good Luck!


for JLTO and AWTO, i have to disagree. the axle bore issue is real, and significantly contributes to wheel hop. i have replaced many, many axles using wider stock to reduce the size difference between the bore and the axle, and in doing so i ran into very, very few hubs that were out of round. i never really checked the tires, as i generally replace the stock tires anyway.


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## dlw (Aug 17, 1999)

Another thing to consider is the ohmage af controller you're using. JLTO/AWTO cars require at least 75 ohm resistors to have decent control of them. Low ohm controllers are like on/off switches and will cause somer of the hopping problem.


Usually, checking for and replacing bad axles and rims fixes the hop problems. Also check the tires for little tree nubs, and un trueness. You can grind them down (but not too much) to get them smooth and true.

As far as the springs go, its better to just crush them between your fingers abit to compress them (in case you get an abnormally strong pair).

As said before, these cars have big fun potential, and can help your 'driving' skill by forcing you to slow down at the bends.

Another thing to check is the wear pattern of the pickup shoes. New cars have the shoes pointed too far at the rails. To check this, just press the shoes slightly past the edge of the tires. If they're are slanted upwards towards the front like (but not as dramatic as) this - \ - , you need to tweak them.

Just put a small screwdriver under the pickup, but directly in front of the step, and press down on the very tip, where the rectangular hole is up front. That should give you an even wear pattern.


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## Bill Hall (Jan 6, 2007)

mking said:


> for JLTO and AWTO, i have to disagree. the axle bore issue is real, and significantly contributes to wheel hop. i have replaced many, many axles using wider stock to reduce the size difference between the bore and the axle, and in doing so i ran into very, very few hubs that were out of round. i never really checked the tires, as i generally replace the stock tires anyway.


Hi Micheal, No slight to the axle size/and bore issues intended! It is of concern. It's hard to cover all the bases without writing several volumes LOL. It's all important. I was just trying to say check the obvious, before Scaf tears the whole car down. I'm a bone head. It's just my personal checklist of examining the frequent and obvious, before I bypass the forest for a tree. I do check every tire/wheel, new or used regardless. It's a carryover from a long 1:1 career. Hopefully Scaf will keep us posted. Tacoma's not to far from Shelton so whoever hits the Crystal Ball diagnosis can buy lunch! I'd like to get hooked up with Jerry "Win 43" from Pt. Townsend as well. I'd sure like to hit one of the upcoming G-jet events. Are you part of that event, or game for a road trip? BH


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## mking (Apr 25, 2000)

*puget sound racing*

hi bill. 

yes to both. ive tried to email you a couple times but they have all bounced. i am up for road trips to shelton or port townsend, and i am almost part of HOPAC, the g-jet group. i have been to 1 practice, and am going to another tomorrow night in bellevue. i expect to go to the next race, had to miss the first HOPAC race of the year due to family being in town. the HOPAC guys race g-jets and G-3s. we also have a small group of routed track owners who like tjets, 2 in renton, 1 in maple valley (marty who posts here) and 1 in yelm. i also have a routed track (4x8) and its a bit small to race anything but tjets. we hope to get together regularly to race tjets. if you interested in setting anything up (even just a casual afternoon or evening or running cars) email me at [email protected]

mike


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## A/FX Nut (May 28, 2004)

Hello, 
Everyone who replied here has covered just about all the bases. 
You could use the stock tires if you grind them true. Some of us prefer the stock tires, little looser handling. I modified a Dremel bit to hold the tires and insert it into my trusty Dremel, I use a fingernail sanding board or 220 grit sandpaper, work slowly and carefully. I have a tire gauge and check for the diameter I want. I also true the front tires.
This also works for silicone tires. I've found a smaller diameter tires helps with handling and acceleration.
Make sure the axles are not bent and the hubs are not out of round. I've seen this problem in the rear hubs. New Old Stock replacements are availible.
Pick up shoe tension can be and sometimes is a problem. Compressing the springs between your fingers is an easy fix. And bend the shoe so it rides flat on the rail. You can place the car on a piece of track and check for this, it's the best way. Limiting the shoe travel can also help.
When the rear end of the car kicks out as you get on the throttle that would be the armature torque causing that. 
When I get on the brake the rear end kicks out sometimes, I think it might be excessive brush tension.
I repeated most of what was already mentioned but, I hope it helps. These cars are the most fun to drive, these and the A/FX nonmagnatraction.
Randy.


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## Crimnick (May 28, 2006)

Hornet said:


> Crimmick,if you're still looking for Storm R/O tricks try here,look through the poly mod section
> 
> http://ho-tips.org/


Thank you sir!...but we arent running RO's at the moment...

Still running stock....

I love the super mags...and yes...you get used to the speed very quickly...

I just need to learn how to slow down now...hehehe


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## rodstrguy (Feb 14, 2002)

I have found that a lot of the hopping comes from something that is on the p/u shoes themselves. Most of the ones I have that hop stop after either polishing the shoes or just running the heck out of them. The rest comes out to bad tire/rim or too much spring tension...


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## Hornet (Dec 1, 2005)

Well you're on the right track Crimmick,listen to Jeff,he's a pretty good guy,and his racing program has come a long ways in the last few years.


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## Scafremon (Dec 11, 2006)

Thanks all for the great information!

I look forward to trying out all of these valuable tips and ideas. 

It's exciting to know that once I get my track built, the fun is going to continue as I learn more and more about tuning the cars. I'll let you know what fix cures the problem I am having with this particular car, but all of the tips and pointers are excellent, and have given me a broader understanding of what to look for when cars behave eradically.

Thanks again!!!


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## Scafremon (Dec 11, 2006)

Now that I have a working track I started trying to tune-up this T-Jet.

I put the heat-shrink tubing at the top of the pick-up shoes to limit the shoe travel. This has solved the problem of the car driving straight through a corner because the guide pin was out of the slot.

I still need to try silicone tires as the stock tires do not seem to grip very well, and the car does burn-outs down the straights. I also want to fix the axle slop, and then work on other tips you all have posted.

The car is a noisy little guy, compared to the SG+ cars I have. If the SG+ cars sound like a sport-bike, then the T-Jet sounds like a Harley. Since I only have one T-Jet, and have never been around another one, my T-Jet could be all messed up and I would none the wiser. It reminds me of the poem by Richard Brautigan called "Walter":

_Every night: just before he falls asleep
Walter coughs. Having never slept 
in a room with another person, he thinks
that everybody coughs just before they fall
asleep. That's his world._


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## mking (Apr 25, 2000)

.....


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## mking (Apr 25, 2000)

*this is for jeff/scafremon*

you can get tools lots of places. i think you will want at least a wheel/gear puller and a wheel press.

slotfather on eBay! sells both (i think these are bsrt products, and you can also order from scaleauto). 

slot father: http://stores.ebay.com/Slotfathers-Slot-Cars-and-Parts_HO-Tools_W0QQcolZ4QQdirZ1QQfsubZ4397764QQftidZ2QQtZkm 

i like this gear/wheel puller better: http://cgi.ebay.com/AURORA-T-JET-AR...1QQcmdZViewItem

i have both the rtho and bsrt gear puller, and i exclusively use rtho's tool. 

i think a really good wheel press is the P04 by JW. http://www.csonline.net/vwalters/ne...listpg.htm#tool

a thing to know about wheel presses. most aftermarket performance hubs are not solid. they have an annular rim with a large opening in the center of the hub. the wheel press has a sleeve or male portion that engages the opening. the better the fit between the sleeve and the opening, the more likely the wheel will press on straight. You can buy extra sleeves for JW's tool for different hub designs (they vary). for pressing on silicone coated sponge tires w/ high performance hubs (with the opening) i use JW's press. for stock JLTO hubs, i use the bsrt press, and i remove the stock flange/sleeve from the wheel press. the jlto hub fits nicely into the opening for the sleeve, letting me press the stock hubs onto new axles very cleanly. if i am using a large size axle (larger than 1/16, say wire size 49-51), i ream the stock JLTO hub first using a larger than stock axle (say a 1/16 axle) to avoid splitting the hubs. most of the time when i replace the JLTO axles, i use a 1/16 axles (0.625). the JLTO hubs can usually take that size axle w/o splitting.


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## mking (Apr 25, 2000)

*hey jeff*

i did get your email, i have some samples to mail you. i dont know if my return emails got thru

[email protected]

mike


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## dlw (Aug 17, 1999)

Just posting to let you know, JW's Speed Parts have a new url:

http://users.cescowildblue.com/jwsteed/JW.HTM

I'd second that about getting JW's presses.....they're very good.


P.S. Forgot to mention another thing that makes tjets hop. The stock tjet (Aurora) rims, and the front rims of any TO car (Aurora, JL, AW) may have flashing on the rear of the rim (the side that faces the chassis), where they are plucked from a parts tree. This nub of flashing will cause hopping. Carefully sand/grind it until smooth and this will help cars run smoother.


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## Rockclimber (May 10, 2021)

Scafremon said:


> I bought my first slot car that wasn't a Super G+ that came in a box set of track. It is the AW Thunderjet GTO. I hooked up a small track to compare this to the G+ cars, but this new car doesn't run so well.
> 
> As soon as you give it power, the rear end slides to the side about an 1/8th to 1/4 inch, and then the car kind of bounces as it goes crooked down the straight. I really have no idea where to start troubleshooting this, but wondering if possibly one rear tire is a different diameter then the other, and if this would cause the problem.
> 
> ...


First check for bent axel , if that's ok then it's out of round tires or wheels . Also dirty tires cause spin and wheel hop . But in most cases it's bent axels or out of round wheels and tires


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