[Origineelreclamebord]

Originally Posted by MHeadling

So are you thinking of going into production with this car??

I hope so be great seeing some of these ripping round a track

A production car/conversion kit? I can only hope! I would love to, I think it's up to a few factors: Demand (with the curious faces and the responses so far I think there's a market for a conversion), Performance (That it will be a nice drive I'm pretty sure... whether it's a true RWD-eater or even competitive compared to these days' RWDs I've yet to find out) and what Jonathan's opinion is on making a conversion.

Originally Posted by Rebelrc

Any chance of talking us through your design concept?
And how and why the car ended up looking the way that it does?
Great job
Well done

Eh, I haven't prepared my speech, but here it goes!

I started this project last year in november. I had a TRF201 as a runner, and I wanted an FF buggy next to it. To reduce the amount of spares I'd need, I wanted to use a TRF201 (and some 4WD Tamiya buggy bits) as a donor car/base for the car . I decided that I wanted to use as many existing parts as possible. This is where my initial choice of the double wishbone rear suspension came from, together with my lack of knowledge about setups for cars (so I thought using a suspension system I knew would keep things understandable for me).

To be honest, Initially I barely had knowledge on vehicle dynamics, so I was modeling what I thought would work well and look good based on existing cars. The main challenge was to make everything fit around the front suspension, so I wanted to tackle that first.




This proved very difficult: I managed to make the dampers fit in an upright position, but tolerances were tight and there was no room to place the damper differently (and thus not enough room to change the setup). I was very unhappy with the way the front shocks mounted. I've always been a fan of different stuff, and both technically and aesthetically an inboard suspension system appealed to me. However, I had doubts on my knowledge to solve that puzzle.

However, that didn't hold me back: I was going to model an inboard system on the front end. The first thing I did was mock up how the dampers would need to be positioned to clear everything. It seemed possible (at least as possible as the shock tower system), so I decided to go with that.

I looked at an inboard system on the rear as well, but decided against it: It was going to make the suspension more complicated than it needed to be - even though a slightly forward weight balance and potentially lower CoG could help the car's performance.

By this time I had had my first two or three track events, which really helped a lot to get an understanding about how these vehicles actually 'work' (how different geometry and the properties of the car such as weight balance, rigidity, tires and suspension setup affect handling), even though I was still a novice at it.

When I pretty much had the Double Wishbone car finished Jonathan first replied in the topic I believe... He mentioned he'd really change to using trailing arms - and wide rear wheels to make it BRCA legal. This is where contact with Jonathan started.





From there I had to rest the project a bit because school was busy... a month later I managed to pick it back up. In that time I thought about all the opinions, replies, advice etc... And I decided to ditch the whole rear end of the car and go for trailing arms.

The main reasons for this are several things... The successful FF buggy protos from the late 80s/early 90s had this system, and with the knowledge of those people back then and of many people that posted in the forum stating it needed more weight on the front, I had the feeling I should listen to that. It was going to be easier shifting weight to the back than to the front if it needed to be changed. Also, I shouldn't make a car that's limited to my knowledge in making setups etc - I should hone those skills to learn make good setups for that car instead! And by then it was apparent there was a lot of support on the forums and the 'local' racing community, so in the end I'd get a good setup. Lastly, I had some offers to help me on the production of the parts for the car and I had some success with 3D printed parts for mechanical use, so I was less worried about using many custom components on the car.

Throughout the project I started taking this project way more seriously. The goal was no longer just to create a nice FF buggy (like it was in the beginning), it became my goal to make a serious prototype as a base to test how much potential there is in an FF buggy (thanks to the advice on the forums and the discussions with Jonathan about the car).

I think my change in mentality is visible on the car: On the double wishbone version car I still really felt there wasn't going to be a later version of it - once the car was built I'd drive it and have fun with it, so the finished result had to look the bomb! Also, it had to be adjustable to the max without making changes to the design of the car.

However a month later when switching to a trailing arm rear end I knew this car would be open for development and improvement, opening potential for simplifying the design.

As the car will be updated and improved, it doesn't need adjustability everywhere: the 20mm adjustable wheelbase was ditched, as well as pretty much all other adjustability on the rear end (toe, camber etc) - The rear end is just there to keep the car stable really, the main focus has always been on the front of the car (makes sense as the power and steering is on that end of the car, right)?

As for some other choices on the car that haven't yet been mentioned... The low profile servo was chosen to keep a low CoG and more freedom for the layout on the chassis. It wouldn't make the chassis too wide if it was fitted beside the battery lying flat, standing up it would still be low and at the right height to fit to a steering rack (without turning it upside down), etc.

The choice for Shorty LiPos came with the trailing arms. If I was working on getting the weight balance as far to the front as possible, why not use a shorter battery? They easily have enough capacity.

The choice to remove the battery from the back was purely practical: Removing from the side was difficult without messing with side to side weight balance. Removing from the top or bottom would require extensive redesigning. It did somewhat determine where the rear arms were going to mount, but going by the short test run they don't seem to be in a wrong spot

The wing mount was a headache: I had pretty much the whole design done and I hadn't done that yet! I wanted a strong wing mount as it's so long, in the end I decided to combine the battery plate/retainer with the wing mount, this also removes the bulky frame and wing when you're trying to do work on the car.

The choice for the elaborate rear arms and mounts came from my thoughts about the loads these long arms have to carry. They are about twice as long as the front suspension arms and get a huge sideways load at all times. As machined or printed parts are pretty valuable I wanted carbon plates on the suspension arms as the pivoting points of the arm: It's strong, and if it breaks, it is 'just' a plate. The suspension blocks are reinforced with carbon plates on both sides of it to take the peak loads off the block and/or to spread them over the entire block. I just hope it works as good in practice as it would according to my theory.

I've got plenty of ideas now to try out on this car - looking back on it I probably would've used a different donor car, and I wouldn't have kept the rocker arm geometry for last (no big issues showed up - I was very lucky there), it could have spelled disaster if big mods were needed. All in all though I'm very proud of the result. This project is way more complicated and technically challenging than I've been prepared for in my study. I learned a lot on the front of vehicle dynamics, about how to handle this size of project and I feel the help I got from others was essential to keep the project heading in the right way.

That's all for tonight I guess... Are there questions about what I just wrote or what I didn't write?