Sunday, December 4, 2016

Rear End

Before the 'junk in the trunk' jokes enter your mind, consider this. There IS alot of stuff in the back of these.

  1. Rear Axle and Bearings
  2. Brake disc and caliper(s)
  3. Drive Sprocket
  4. Chain
  5. Gas tank and gas lines 
  6. Throttle mech
  7. Engine & Flyweel
  8. Exhaust & Intake Manifolds
  9. Starter mechanism (pull start or starter nut...or for the crazies an electric start)
  10. HEAT
Sharp, hot, spinning objects in the space of a milk crate. Not an easy packaging layout to manage especially the heat issue. the Predator 212 likes to get hot, so air cooling becomes an issue with these rear/mid engine layouts. Air needs to enter and exit in a clean way, and extract heat whenever possible.

Here's what the Type-69 Rear End looks like in a 3D model:

I chose a 1.25" aluminum axle for lighter weight and flexibility. I chose a 70-tooth split sprocket which is also aluminum. The brake here is an 8.25" steel disc with an MCP caliper. Two 1.25" axle bearings are attached on the sides of the wood chassis. The engine and Torque Converter are positioned so the engine intake manifold and mounting bolts are on centerline. This puts the chain on the left about 6 inches off center. The gas tank is removed and there is an ARC throttle plate in its place. The Gas tank is remotely located in the front portion of the body under my legs. The exhaust manifold is a high output tube without a silencer. It's necessary to remove the pull start assembly, and advisable to replace it with a billet aluminum ARC flywheel. 

I probably forgot to mention this before but my chassis is all wood.

There are however a few areas that make sense to reinforce with steel plates. I did some research and found that from the era there were dozens of plans that called for wood frames, with steel joints. I even found a small book titled 'BUILD YOUR OWN CYCLE CAR' where the instructions call for plates to be cut and welded from mild steel. The Jappic from 1925 used this technique, a favorite of mine. I will delve into the Jappic later but for now accept the fact that it is possible (and preferable in most cases) to use wood for a chassis.

This may surprise some of the die-hard Stevenson formula apostles, or at the very least get them to chuckle a bit. Suffice to say that wood is light, flexible, easy to work, fix, and shape, is VERY affordable, and can be assembled with little know-how or expertise.

Welding on the other hand is a developed fabrication skill that takes years to perfect. I like that also, and will do that eventually in this Blog, and in my shop. I plan on building an all aluminum design soon. And eventually an all carbon design.

 But for now lets keep it basic. Wood frame, steel bits to help it 'not break' where needed, and lightweight go kart parts.


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