The idea for a conversation came in the third or fourth race of the LRP-HPI-Challenge (Indoor season) in which I am participating. The last races ended very good for me with being on the podium several times in the 17.5t-class. Then a race with a highgrip carpet came. No matter what I did, I just wasn't able to cure the understeer my TC6.1 WC had. It was frustrating! The win in the D-Final was not helping as I got a cup for it which will remind me forever...
I start thinking about how I could prevent myself from these experiences. I couldn't find the right car balance, I needed more steering, but on the quest for it you will often end up with oversteering (a sliding rear in the worst case) and/or a braking effect through too much wheel angle. My thought then was: If these are the problems then will a four wheel steering be able to cure these?
Since I put a TC6 into CAD two years ago it was easy to play around with the solids and check if my idea could work, or what needs to be changed on the existing car to make it work. This were the first results:
In addition to the four wheel steering the car includes two other ideas:
1. the use of Shorty LiPos
2. a special LiPo brace which should allow a unhindered chassisflex while holding the battery.
Conversations are expensive. I tried to reduce the costs by needing only a few prototype parts. I was proud when my first design needed only six special parts. I took the motormount and the spurgearbulkheads and placed them 12mm forward to make space for the rear steering rack. Together with the new wholes for the LiPo brace (I called it LiPo flex base) a new topdeck was needed; two new belts for the changed distance from belt pulley to the differentials also; and finally a 120mm long turnbuckle to connect the servo with the front steering arm after I put it behind the shorty LiPo. A double sided servoarm had also to be found
Thats it with the "special" parts. Of course in comparison to a normal TC another pair of front suspension parts are also needed. But since I have so much spares I could save money.
The next step then was to contact my miller to check my parts geometry and order some cfk. The steering turnbuckle and the doublesided servoarm came from HongKong and took some weeks. The cfk was ordered in a german shop like the belts and came with the milled prototype parts very fast to my home:
Like always I couldn't resist and assembled everything:
I couldn't wait for the small parts arriving from HongKong and annoyed a friend to bring a doublesided servoarm from a Savöx servo (I threw my away just some weeks before
). So I could prepare the car for its maiden drive:
I chose the indoor carpet track of Günzburg for the first outing. The car was equipped with a 10.5t which is too much power for a protoype on its first meters. Whatever I was too lazy to change the motor and began.
The steering setup was completly wrong. The rear had more steering geometry than the front and it looked strange. After getting used to the new behaviour the car was everything else but not slow! It loved switchbacks. Direction changes happened incredibly fast. In fast corners I had an understeer. This is something I think can be solved with a setup tweak. For the first day I just wanted to concentrate on the steering. For the second run I reduced the rear steering angle to have always the same angles front and rear. The understeer stayed, but steering a little earlier reduced it.
Driving a car with four wheel steering is another world. Interestingly I had to steer earlier than with my TC6.1. Driving it after the 4WS it seemed to steer much stronger and angular. The 4WS race line is just a perfect smooth curve (like ice skating). What seems to be a fight between front and rear axle when driving my TC6.1 on the edge is much more relaxed, swinging, just without overstressing the tires. I could go the same speed as my LRP-HPI-Challenge TC6.1 WC with 17.5t motor. Of course the 4WS had the stronger motor, but still I was not unhappy with its maiden drive.