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I have always wanted to build a "Topcat on steroids". So with mid-motor all the rage these days and my local track switching from dirt to carpet the time seems right for a "Topcat mid". I have been thinking about this for a while and collecting parts.

The backbone of the build is a custom 2mm aircraft grade aluminum chassis that I cut, bent and drilled myself. It just came back from powder coating yesterday.

That looks like a great project for this build-off. It's gonna be fun seeing everyone's creativity and what they end up with!

So basically I am going to mock this up. Overcome any obvious problems and then tear it down and rebuild it with a bunch of new and trick parts to complete.

I mounted the transmission and noticed one big problem. The tranny sits on a severe angle. This cuases the rear bulkhead and shock tower to lean into the middle of the car a little too much for my liking.



So, I made a nylon block to sit under the tranny. Now, there is a slight angle still but not enough to notice. This also seals up the bottom of the tranny to prevent dirt from getting in.



I then added a rear bumper/skid plate I made from nylon and bolted it down.





And mounted the front.

The mockup continues! Everything seems to be going together well. No glaring issues. I am starting to collect parts for the most ambitious part of this project which is to modernize the drive train while keeping the belt drive. I plan to use a B4 diff and cvds mated to a pro diff belt pulley.

Stay tuned!

Looking good. I'm looking forward to seeing this build completed.
I have a thing for mid motor conversions. Especially custom jobs.

Looking great so far, I like the rear skidplate.

So I finally had a chance to work on the most ambitious part of this build. The drive train. I wanted to use a B4 diff so I could replace the rings and balls from the LHS and not have to scour the bay for parts. I wanted to keep the belt drive so I set upon making the B4 diff fit in the belt pulley.



Looks like this may actually work!



I drilled out the center to install the B4 center bearing.



And assembled.



The fences would not fit over the B4 slipper plates but since I will be running on carpet dirt is not an issue. So out comes the dremel and CA glue.



And voila! Belt drive B4 diff. YAY!

Really good job on the diff

I like that the rear axles are going to be inline rather than trailing. Are you going to run B4 CVD's as well?

Paul.

I dont know yet. The problem is I dont know what arms and carriers I will be using so its hard to know what length of CVD to get. I am going to mock up some Losi hub carriers and see if I can nail down a length. Most likely it will be B4 CVD's.

So the bearings finally came in from Boca. I had to order special bearings to fit the B4 out drives and the Schumacher eccentrics. There was a little play in the diff from side to side but 2 1mm shims solved that.





I also got the Schumacher Cougar SV saddle pack holders. They are already made, look awesome and I got em cheap. A clear choice over custom made. Now to rig up some posts.

Those SV saddle lipo holders look like they will work perfectly with this.

Is there any fouling issue with the motor plate/spur gear and the bodyshell? It looks like it might be a bit tight in there.

Paul.

Is there any fouling issue with the motor plate/spur gear and the bodyshell? It looks like it might be a bit tight in there.

There will certainly be a clearance issue. The body will fit over everything but the slipper shaft. Not wanting the marshals to lose any fingers I will need to rig up a gear cover of some sort. I think for the MMV build-off I will go sans cover and just trim the body normally.

I wouldn't worry about it too much, 8rad...your build is further along than mine, I don't think Barney has a hope in hell of being complete--body fitted & painted and the whole 9 yards--before the end of November. Your car is coming along nicely, I like the gearbox & diff modding.

So the mock up is done.

Sweet! I wonder...are the rest of you guys participating in this MMV buggy competition probably going to look upon your eventually-completed projects with more pride, more "sense of ownership" than you do with other builds, due to the extra work & frustration & attention-to-detail that you don't really need with other "by-the-manual" builds?

That's what I'm thinking, anyway. Nobody is gonna have cars like these!