Academy SB How to make it work!

[jerrywasaracecardriver]

First off, I have now built, or rebuilt 4 x sb 4wd buggies. The initial car was my own from new, and now I have rebuilt 3 used buggies. I know this design inside and out. Its a good design, but with a couple fatal flaws. The suspention is superb, as is the overall chassis layout. Where this buggy fails is in the motor mount, and the spur gear situation. How to fix the motor mount? Get a Pro machined unit from Academy, or an Acratech motor mount wich is a proper screw slot type mount. Now, the spur gear situation. This design was initially a touring car, with appropriate gearing. When transformed into a buggy, it carried its touring car gearing. Bad Idea Academy! Off road buggies need different gearing than touring cars. The only way to change this is to fit a larger spur gear, and then this allows you to use a smaller pinion. From stock, the 70 tooth factory gear will only work with a 20 tooth pinion for the smallest, and this renders an overall drive ratio of 8.05/1. This is barely suitable for a wimpy stock motor. A mod motor isnt even feasible. It will overheat. Strange how none of the tests of this car address this issue. Heck, one online magazine even tested the car with a mod motor and never mentioned this. I bought this perticular car off ebay, and when it arrived, it was the biggest mess of all the used SB I had bought! The reviewer couldnt have possibly done an accurate test due to the diffs being nearly dry, the diffs being shimmed soo tight that it would not roll freely. Anyway, back to the spur. Heres how to make it useable for offroad. Go out and buy a duratrax 78 tooth 48 pitch spur, a pack of traxxas slipper pegs, and 2 x losi slipper pads for xx4 buggie. Now, use an exacto blade to carefully ream out the hole in the duratrax spur so it will just fit over the sb slipper plates with no play. Now, use 4 traxxas slipper pegs positioned across from each other in the holes in the spur. These serve to key the losi slipper pads in place so they dont wander off center. Now, place a losi slipper pads on either side of the spur, keyed by the traxxas slipper pegs, and assemble the academy slipper plates as per the instructions using the academy gear shaft, screw and spring. Oh, did I mention, you need an academy slipper clutch set to start. I will get pics of this tomorrow. Iff done correctly, you should have a 78 tooth slipper clutch set up, with full adjustability, and a direct fit to the sb. Just use a dremmel to bevel the opening in the chassis to clear the larger gear.

As for people looking to buy a used sb, beware! Its probably been assembled all tight, and the diffs will need attention. Its best to buy some 5x8 ball bearings(4) and rebuild the diffs using these and with plenty of grease, especially in the thrust ball set up. Now, when you go to assemble the gearboxes, dont just throw 3 spacers on one side of the diff like in academys drawing! Your supposed to shim the diffs for minimum play and best mesh with the bevel gears. This will probably require 1 spacer on one side, and one or 2 spacers on the other side. 2 of the Sb I just recently rebuilt were assembled with 3 spacers on one side making the gear mesh soo tight in both gearboxes that Im surprized nothing melted. One built by an rccar tester, and the other claimed to be built by a factory driver. I recon most people selling used sb will have shimmed them wrong, so please do take time and check things over before putting power through them. If shimmed properly, the sb will roll as freely as any top end touring car. I will be running an sb this year in 4wd stock, and intend to do well with it. Im saving my lazer for mod class!

[RichieRich]

Yeah, I would like to see pictures.  I too have had gearing problems and am not pleased with the adjustability of the ratios.  Have you tried the KOSE motor mount?  Seems like you'd be able to work the ratios better with that type of motor mount.  I wish I could get one for my SB.  Do you have part numbers for the parts you mentioned?

[jerrywasaracecardriver]

I can see about digging up parts numbers, but for now, the parts I mentioned are pretty simple to locate, even if ordering. I just redid my other sb slipper clutch, this time using a 72 tooth kimbro spur, 4 traxxas slipper pegs, and the stock sb slipper pads. I had to notch the ID of the slipper pads so they would key into the traxxas slipper pegs. The OD of the sb slipper pads fit very well within the confines of the 72 T spur. I have been able to get a 16 T pinion on that one for an overall drive ratio of 10.35/1 wich is good for even mild mod motors, as well as any roar stock motor. This is what I will use for stock class I think. So far, I have not used a different motor mount. Im using the Pro machined mount from Academy. Its proven to be good so far in testing. Racing might prove differently. I do know for sure that the cast mount from the sb sport is JUNK. Some other things I have noticed while testing. Stock full time 4wd sb needs more steering. Using a one way up front helps. The front end really also needs more suspention travel, so some droop can be tuned into it for better rough track handling. Once again, this design shows its touring car roots. Im looking into longer front shocks. Also the rear suspention can use more travel. I will post the pics of the slipper ASAp. I have them but they need edited.

[jerrywasaracecardriver]

Pics posted in my showroom, at the very end of the list under extra info.

[RichieRich]

Ok, this looks like a fantastic mod.  What is the purpose of making the

grooves deeper in the slipperplate?  Do you favor any brand of spur gear more than the other?

[jerrywasaracecardriver]

The slipper plates need to be able to squeese slightly closer together. The duratrax and kimbro gears are thinner than the academy gear. When designing this mod, I just used parts I had from other projects. The losi slipper pads I did have to go buy. However, the stock academy slipper pads will work. The kimbro gear seems to be noticeably more concentric. The duratrax gear has a slight wobble and is slightly less concentric. Both work perfectly well though. Also, a Traxxas 48 pitch gear will work, as well as some older losi 48 pitch gears.