Well... Its been a while and with snow coming down and time off around Christmas I took some time to take some pics and update the cars development.





Yuck!!

Carpet season is in full swing and they had the track open over Christmas. So I took the 22 there no knowing what to expect with over a 68% rear weight bias and really soft off-road suspension. But I was really surprised at how well it worked.












I installed the Spektrum 7050 and wired the positive lead straight to the battery. It worked at home then fried upon arrival at the track. Ordered a new one and phoned Horizon Hobbies to clarify the wiring of the servo straight to 7.4v. They said both positive and negative have to be wired to straight to the battery. I did that and it did the same thing, it fried! So I threw my good old 6070 in and finally that worked (not to 7.4v).

Once everything was running I broke the front wing off in a crash and kept driving but I didn't notice a difference. Confused I made a bigger wing (from 90mm to about 120mm) tried different angles and still couldn't feel a significant difference. There is some kind of aero voodoo happening........ I think I need a wind tunnel now!











It was interesting running this car on carpet. I learned a lot! I was pleasantly surprised at how well it did handle. The centralised mass DEFINITELY works and makes the car very responsive and easy to drive.

The four gear tranny does not work on carpet but I think it will work not to bad once some of the other handling gremlins are worked out.

I learned a ton about ackerman and the affects of bell cranks, drag links and what a forward facing and rear facing bell crank does.

Once I got comfortable with the car I started giving the car more steering and started to notice some design flaws. My current design gives the car a little more total ackerman than the factory system due to the nature of the movement of the single bell crank. The way this linkage setup works the ackerman increases exponentially as you steer (unlike the original 22 slider, which would give linear ackerman gain). So, as a result, when I dialed in more front traction the car became very twitchy around center and then had less steering at full lock.

I was very dissapointed at the time until I put all of this together. After some sketching and working things out in my head my current theory goes as follows. A forward facing bell crank (like in my car) will be sensative around center and less so at lock. Adding a second bell crank and a drag link will lessen this affect. Then something like a slider will give neutral steering progression.

Switching to a rear facing bell crank will have the opposite affect to what I have now. In theory this will create steering that is docile around center and progressively more aggressive toward lock. And once again the dual bell crank with drag link offering a middle ground.

So with that "spectacular realisation" I began working on new front end geometry on the second 2wd buggy I referred to in an earlier post. Not knowing if I could make the design work and not currently having a working CAD program (working on getting Solidworks educators edition) I started mocking things up last night in cardboard. I need to make some aluminium posts for the new bell crank setup to complete this prototyping stage. So, instead of stopping I started playing with some of my ideas to further lower the cg and centralise the mass further. The blocks on the back of the upper bulkhead are the new shock towers that place the would be shock towers inside the cab instead of out front disturbing air flow. This is just an idea I am throwing around and checking the ideas feasibility, its looking good so far but the idea will require further prototyping and mock up. One point about this I do want to clarify that I am NOT changing any geometry with this experiment just relocating the shocks. My only concern is additional binding this may cause.





The final sketchs that lead to prototyping. The new bell crank design should put the pivots VERY close to factory 3.0 pivots.



I think that's all for now. I'll try to post more frequently as my theories develop.