# Four Gear with double rear



## sjracer (May 25, 2008)

Whilr browsing through the different forums I thought I stumbled across a link called " what is your favorite". In the link I saw that Bill Hall had created a Woodie Bus with a double rear. I remember seeing a double rear four gear chasis in Bob Beer's book but never thought of attempting to build one until I saw Bill's. I was wondering if anybody could give me a few tips in attempting to build such a car.


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## Bill Hall (Jan 6, 2007)

Here's the dope SJR. I've done a dually in t-jet, magna traction, and four gear. Bobzilla has both the 4 gear magna Bus and the standard magna Semi-tractor duallies. So I'm working mostly from memory a few scant pix. 

Of the three versions the magna four gear was the easiest to build because of the chassis/gearplate holding screw. It was not in perfect working order when Bob got it so he sent it in one of his infamous care packages.

I broke it all apart into it's components and worked towards squaring things up. As with all others I began with the gear plate. The additional piece of gear plate was originally mounted askew. Another piece was cut and fit from my stock as the originally modified piece would gear bind once the plate was squared. In other words it was short.

The trick is to keep checking your fit and carefully removing material until the two sections fit and the gear mesh is perfect. The two chunks are CA'ed together so you can diddle the gears around during fit and can be snapped apart with a flick of the wrist should adjustment be required. Once youve got the mesh correct the most important part is making sure the modified gearplate is assembled totally flat! I assembled mine on a piece of glass and CA'ed it. Then only the exterior seams were welded together with a fine tipped iron. the interior seams are left clean to prevent any undue gear friction. I personally dont like to use epoxy or goobery adhesives around gearsets nor do I have the time or patience when I'm chassis fabbing. Note: Dont forget that the fifth gear must have a good fit from the git go and be installed for final assembly! It is captive and cannot be removed or inserted later. Trust Mr. Duh here! LOL

You'll note that a side gusset is added to the plate on the AFX versions. While my t-jet version doesnt require the added gusset due to the way the gearplate is dovetailed together. The AFX version has a straight butt joint to mate the two sections so the gussets provide some needed rigidity. I would dove tail the AFX versions as well, but it would require re-rivetting the driven cluster. So we proceed cave man style with giant brackets LOL. Just keep in mind that they will interfere with the huge Ansen rears rims/tires if you dont plan ahead. I dont add the gussets until last on the standard magna traction dually....but thats another story.

At any rate the actual twin screw protion is just the tail of another four gear chassis tub. So with modified gearplate installed the extra chassis bottom is cut a hair long and whittled away until it fits snuggly and can be retained with it's factory mounting screw. The "why" of getting the gearplate as perfectly flat as possible was evident in the original...all four wheels didnt touch. It is your registration point for the height of the second set of drivers.
A careful file fit of the final section is important to keep undue flex/stress from the gear plate joint. It should brace firmly against the front chassis/driver area so that the gearplate doesnt take the full torsional load. 

I lapped the bejeezus out of the plastic gear train with ultrabrite toothpaste to get it is free as possible. Once youre sure you wont have to knock it apart go ahead and add your side gussets. Bob's Bus may also have my standard AFX crown gear modification as well. Never cared for the factory "skeeeeeezer" gear. It's a simple after the fact modification should you encounter gear skip down the road. 

Once ya got it nice and smooth you can begin track tuning. If memory serves I gave it a little stretch in the pick up springs to help current draw. Sorry I dont have more concise step by step build pix, but the cam-dammera slows me down.

Pic 1 shows the rear driver module attached to the modified gearplate

Pix 2&3 are yer over and under views compared to the wider rear spaced t-jet

Pic 4 shows the proximity of the gusset to the rim. Originally the rim was mismounted wide and wobbily. A sizeable chunk was removed so the rims could be pressed in tight factory like.

Pic 5 my favorite was the standard magna dually...a sheer joy to drive! Just ask 'Zilla

On a final note: While the Beers bible picture is tantalizing it does not reflect the fact even in standard magna traction form the dually chassis will not fit the standard semi tractor body. Missed it by that much!:freak: It requires a removal or rework of the mudflap area to fit.

All three versions are a flat hilarious gas to run on the track.


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## bobhch (Apr 22, 2007)

*I am a Lucky Dog!*

Bill,

WOW! Those are Sweeeet!:woohoo:

Bb...Bill is amazing...zilla


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## sjracer (May 25, 2008)

Forgive me for asking but what do you mean by the term CA' ed together?


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## sjracer (May 25, 2008)

I am not familar with all the terms you used, please forgive me. However, I was wondering would it be better to reinforce the sides of the gear plate perhaps a sturdy but thin piece of brass or some other metal? Wouldn't this be an easy fix to the clearance issue for the specialty rims?


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## LDThomas (Nov 30, 1999)

"CA''ed" = SuperGlue


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## sjracer (May 25, 2008)

Bill could you post some pics of the bottom and sides of the three chasisses and gear plates?


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## sethndaddy (Dec 4, 2004)

sjracer said:


> Forgive me for asking but what do you mean by the term CA' ed together?


Speaking of super glues, I have been wanting to ask this for awhile. 
What SuperGlue do you (anyone) find works best? I think the dollar store no name brand is equal to the brand name "super glue".


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## bobhch (Apr 22, 2007)

*This "WAS" Bills favorite to run...just ask him...LOL*

sjracer,

Here is the Bill Hall Magna traction version taken apart. Hope this helps.

Hilltop sent me this crazed zilla guy (it roars & lights up) to help me tear this apart. Thanks man!























































Was giving the 4 gear to Bill to keep for himself but, he sent it back to me because, he saw how badly I messed this thing up. He felt sorry for me as I have almost no God given Mechanical abilities...har

Was zipping this thing around the track before taking these pics today with my bob...zilla trailer & didn't wreck once. Gonna have to push it harder next time I guess. Thanks again Bill you da man...man!:woohoo:

Bob...fun to run...zilla


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## sjracer (May 25, 2008)

Thanks alot Bobhch, 


The added pictures helped give me a little better perspective. I was actually hoping to see the four gear version a little clearer because it appears me that the rear wheels aren't connected (glued, epoxyed or goooped ) to the primary chassis but merely connected by the rear screw, am I correct?


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## bobhch (Apr 22, 2007)

sjracer said:


> Thanks alot Bobhch,
> 
> 
> The added pictures helped give me a little better perspective. I was actually hoping to see the four gear version a little clearer because it appears me that the rear wheels aren't connected (glued, epoxyed or goooped ) to the primary chassis but merely connected by the rear screw, am I correct?


sjracer,

You're very welcome.

Will take some pictures of the 4 gear chassis and post them here later this week. I have no idea untill looking at it myslelf...lol

Bob...Bill did it...zilla


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## Bill Hall (Jan 6, 2007)

sjracer said:


> Thanks alot Bobhch,
> 
> 
> The added pictures helped give me a little better perspective. I was actually hoping to see the four gear version a little clearer because it appears me that the rear wheels aren't connected (glued, epoxyed or goooped ) to the primary chassis but merely connected by the rear screw, am I correct?


Yes you are correct-a-mundo SJR! 

Unlike the standard maggy version the four gear's second chassis section is not bonded to the primary chassis. The rounded tail section of the four gear was resisting any immediate ideas or brainstorms to hook it all together. It worked just fine abutted against the rear of the primary chassis using the factory hold down screw. 

Too touch on your gusset question I'll first mention that proper clearance between the chassis and fatty Ansens is a few thousandths otherwise they can get all wobbly if not properly seated on the axle. I want them hubbed up tight.

[Interim note: As the standard magna traction chassis uses only the motor clamp to retain the gear plate; the added nylatron gussets act as a brace to keep the secondary chassis section from rolling forward and up towards the gearplate. The clamp exerts enough force that a support is required to keep things parallel. In this application the gusset serves two purposes. To re-inforce the gearplate and to provide a stable horizontal support for the secondary chassis to abutt.] 

Secondly you'll note from Bob's pics that I use the spot weld technique for bonding nylatron. For several reasons; one is that I detest epoxy... it slows me down when I'm prototyping an idea. The spot welds are more precise, although they look very Neanderthal...epoxy can run into a gearplate I just spent an hour prepping and ruin it in seconds! Where as the spotweld method takes only seconds to do with little or no risk...badda bing badda boom I'm off to the next step. 

Thirdly, I have a steadfast aversion to bonding "dissimilar" materials with "gooberschlobber", especially when I have a viable and impact tested method to weld nylotron. Admittedly I've use CA's and epoxies my whole life I just prefer a less sloppy more time saving and reliable method. Purely a matter of personal preference! 

Ultimately there is no real right or wrong, just a rough idea of how I got from point A to point B. Could the method be improved?...Lord yes!


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## sjracer (May 25, 2008)

Then could perhaps a piece of track rail be used as a gusset ( it could run from the back of the magnets to the rear end of the chasis on both sides) to re-inforce the gear plate and attach the rear and then perhaps to use some gobberslobber to cover the rail? Now I was wondering if the track rail could be welded to the plastic on the gear plate which is attached to the chasis, adjust the rear/gearing, then weld /attach ? If I attempted to cover with the gooberslobber would that some how chemically undo the previous steps?


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## videojimmy (Jan 12, 2006)

If you used a magna chassis for the back half, you could add a traction magnet there too


darn cool chassis!


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## Bill Hall (Jan 6, 2007)

videojimmy said:


> If you used a magna chassis for the back half, you could add a traction magnet there too
> 
> 
> darn cool chassis!


Funny Jim: I did consider it for a second, but I didnt have any extra crispy mag chassis, nor could I bear to sacrifice a good one. In retrospect it turned out rather well. what downforce it does have is sufficient to keep her in line. The added pendulum/weight out back is just enough to hang the tail out at the ragged edge... so in essence I cheaped my way into a good thing.
Certainly another magnet within the added rear housing could be effective...but in long run I dont feel it would be as predictable handling wise for my driving style.

I've always preferred the tail out slide as opposed to the tail tucked in...a slight twitch and combination cartwheeling barrell-roll launch. 

SJR: No reason one couldnt laminate anything you wanted together. The original four gear was just repaired and tweaked as it was built by whoever 'Zilla got it from. At no point was I ever trying to build a better mouse trap. It just has to kill mice.

Ya see I really have no specific rules or guidelines regarding how anything should be built....I work more from a perspective of what not to do. Through my rats, rods, and dragster builds where I'm forever blending brass tube frames to nylatron pancake chassis it has been shown repeatedly that some sort of mechanical fastener or weld is superior to any attemts at adhesion through "Elmer" technology (Glues).


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## videojimmy (Jan 12, 2006)

man, I want one of those chassis. I wish you guys would put a few up on ebay


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## Bill Hall (Jan 6, 2007)

you have mail


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## sjracer (May 25, 2008)

O.K Bill, I "hacked at it" and now I have a battery tested chasiss ( have tried it on the track yet). When you lap your gears does it matter that you used ultra brite or will any toothpaste do? I was thinking some may be grittier than others.n Also, do you thin out the ultra with some type of lube?


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## tjd241 (Jan 25, 2004)

*No Grit....*

Sorry to barge in, but wanted to stop ya before ya started brushing. You want smooth toothpaste. Colgate, Crest, Ultrabrite, even the store brand, but no grit though!!... I now return you to your regularly scheduled program. nd


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## Bill Hall (Jan 6, 2007)

*Hmmmmm....*

Lemme go taste...

Honestly I never give it much thought...polishes whether they be water base like toothpaste; or oil base like say Mothers magpolish or simichrome matters little in the greater scheme of things. Again it's a matter of personal preference and perhaps more over what is in arms reach.

I prefer tooth paste because it's almost cheaper than dirt and is specifically designed to rinse with WATER! Would I use a rouge made from common kitchen cleanser and light machine oil in a pinch...Heck yeah! The end result is what you are after. I find the huge chunk toothpaste is no different than an initial gear scuff with some 320 paper to knock the burrs off. The chunks are no match for brass t-jet gears and are pulverized quickly into a fine rouge as well.

Plastic gears are another matter! As Nuther specified, go chunkless! The Colgate carp with limestone stalagmite fragments is a NONO! All you want to do is loosen them up and ensure that they are a freewheeling assembly.

So heres what I do. I prelube the gear set, crown gear and axle holes. Then I load a little ultra bright on all the running surfaces with a toothpick and rollit across my hand to distribute it. I spin the chassis on my test tranny at half voltage. You'll hear one of two things happen. Either things will loosen up and you'll hear the RPM increase or it'll start to gum up and bog the RPM down. Obviously if she bogs you have to stop immediatly and add some lubricant so ya dont burn up the arm. Again I use whatever light machine oil is handy and again roll it across my hand to prelube/work it in before adding voltage. As things loosen up I add more current until the chassis will throttle up and down nicely. Basically what yer trying to do is centrifugally sling the grit out of the gear sets and pile it on the edge of the gear plate.

Eventually you'll hear things loosen up and sing properly. I like to run them in both directions a coupla times so that the backlash side of the gear tooth gets a little love too. Last pass in the direction of travel!

You'll have a smeared up yucky mess on yer hands which is easily cleaned with some citrus kitchen cleaner like Orange Fresh or good ole Simple Green with some warm water. Scrub it lightly with Coaches toothbrush and blast it with water. From there it's catch as catch can...I blast mine with the aircompressor and CRC contact cleaner. Then a proper relube before hitting the track.:thumbsup:

Other guys just toss them in the sonic cleaner or scrub them old school like a peasant cleaning lady...what ever works given what you have!


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## tjd241 (Jan 25, 2004)

*That reminds me...*



Bill Hall said:


> Scrub it lightly with Coaches toothbrush


Bill... Before ya send that brush back to Coach's TM for her to swap out his current one and send back to ya, forward it along to me. I have a little chassis work to do too. I'll send it to TX when I'm done. SJR... The point here being don't use yer own toothbrush...lol!!! :lol: 

....Seriously though, what also can help with chassis cleaning are those mini brushes used for cleaning dental braces, dentures, etc. They look like teeny tiny bottle brushes. When you're done with the lapping process they can help to get the toothpaste and any other gunk scrubbed out of all the nooks and crannies on the chassis. nd


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