Motor Plate Design...

In the beginning Motor Plates were used simply as a way to mount the motor and related parts to a chassis. This worked well for years until the tires got better and we started making more HP. At the time we were using 6061 T-6 Aluminum which isn't really that strong (It is the strongest alloy that is weldable) but it was adequate.

Pretty soon we started to notice that as the bikes were going faster the plates started to bend so we went thicker aluminum and this worked for a little while then we noticed that this to was starting to bend Sooooo... We changed to a stronger alloy which is 2024-T356, This is almost twice as strong as 6061-T6. This alloy seems to be holding up pretty good so far.

As the HP increased we noticed funny things starting to happen with the chassis. Through testing we discovered that the pull on the chain between the sprockets was trying to bend the chassis in half. It was actually lifting the rear wheel up on the sprocket side and because the rear sprocket is so far offset from the chassis center ( with the 14 inch tire ) it was trying to pull the rear of the bike out to the side. We made a fixture to simulate the pull on the chain and found that the force was actually trying to push the seat forward along with the backbone and of course the steering head. Now that we knew the problem we had to figure how to fix it...I added a few tubes to the inside on the chain side to help stop the rear from pulling out and went to larger diameter tubes in the rear section to help stop the rear from lifting up. I also started using side bars that went around the engine and tied the seat area to the front down tubes near the area where the motor plates attached. Recently I have raised the mounting point of the rear of the motor plate in an effort to stiffen up the seat area. I couldn't go all the way to the seat because we have to get exhaust pipes out of there.

This is where we stand at the moment but as the HP increases and the times get quicker, I'm sure that new problems will pop up and we, as chassis builders, will have to figure new ways to fix them. If I could just get these guys to stop making more HP all the time life would be a lot easier. I don't see that happening though....

I have included a few pictures of McClures new bike to show what I'm talking about...

Pup...