Project TLR 22
 

I have been messing around with my 22 for a little while now never really happy with the way it handled as a rear motor car. It felt rear heavy and front heavy at the same time. The only way I could make the car work was if I hucked it into corners, but my driving style is VERY smooth, I like to carve corners not drift them. After working on some of my other projects:

http://www.rctech.net/forum/electric...t-xx-24-a.html

http://www.rctech.net/forum/nitro-of...ory-build.html

and after all of the research that I have done to design my own car from scratch I began to realize that my problem with the 22 is its High Polar Moment of Inertia. See picture:

http://i1131.photobucket.com/albums/...lar_moment.jpg

So I began to research ideas on RcTech and ran across this thread.

http://www.rctech.net/forum/electric...2t-thread.html

I liked the idea but didn't like the idea of the brass weight hanging off the back (kind of defeats the purpose of going to mid motor) and flipping the rear arms which shortens the wheelbase, not good for rough tracks. I also didn't like the new drive shaft angle this created.

In preparation I ordered some parts for the long weekend to see if I could get the job done without the compromises listed above.

I researched other cars and realized that every other 2wd buggy, including older Losi biggies, has bell crank steering. I realized that this is to get the proper weight bias. So it became my goal to get the weight bias I want using a sideways battery and bell crank steering. After a quick mock-up on the scale I realized this might be possible. The bell crank I used was a Custom Works CSWC3647. So I started drilling, and this is what I got done today:

Sorry for the crappy pictures the lighting was bad.
http://i1131.photobucket.com/albums/...125-005131.jpg

http://i1131.photobucket.com/albums/...125-005171.jpg

http://i1131.photobucket.com/albums/...125-005141.jpg

http://i1131.photobucket.com/albums/...125-005231.jpg

http://i1131.photobucket.com/albums/...125-005211.jpg

http://i1131.photobucket.com/albums/...125-005251.jpg

http://i1131.photobucket.com/albums/...125-005181.jpg

http://i1131.photobucket.com/albums/...125-005191.jpg

Look; NO BRASS!
http://i1131.photobucket.com/albums/...125-005261.jpg

Notice the new body mount above the motor. I had to use a different body with higher side pods to clear the battery that's sitting sideways.
http://i1131.photobucket.com/albums/...125-005281.jpg

This is the new body. Its a Proline bulldog for a Centro C4.1 PN 3382-00. It took a bit of screwing around to get it to fit around the gear cover but it fits well. Hope to throw a quick white paint job on it this week and I'll post some new pics.
http://i1131.photobucket.com/albums/...125-005301.jpg

http://i1131.photobucket.com/albums/...125-005331.jpg

http://i1131.photobucket.com/albums/...125-005341.jpg

So I haven't had it on the track yet because it isn't done yet, I just ran it in front of my house and it feels good. I hope to get it on the track next weekend; if life doesn't get in the way again!

While the weight redistribution is commendable, you may want to put the steering rack back in. That bell crank will wreak havoc on your steering geometry. Perhaps you can drive the rack with a bell crank to re-locate the servo? To me, you've achieved what you were after simply by turning the battery.

Interesting. Agree steering Ackermann should be considered for the linkage.

Actually he needs the servo to be back farther to achieve the low polar moment of inertia. If the servo in the stock position, the problem still exists.

I definitely put thought into the ackerman and bump steer for this project. This is the first rendition of this modification. I already have plans for modifying the bellcrank with fabricated parts to correct the slight bump steer I have.

As for the acherman, it is almost the same as the factory setup! I moved the ball studs toward the front of the car so that at lock, when the ball crank is at an angle where the linkage is very near the stock angles. Between center and lock the ackerman angles might be slightly different but at lock the tire angle are almost identical to stock. I did alter the bell crank position to change the angle of the outside tire to steer a little more, reducing the ackerman to suit my driving style. I like to carve corners not slide.

Keep in mind that EVERY other 2wd car (as far as I can tell) uses bell cranks. And putting a bellcrank setup on this car will not screw up handling, it just might take some sweaking to get it to work perfectly.

I have done a TON of research on suspension geometry to build my other projects and this is just one other to test of some of my ideas. This might turn out to not work but only time will tell. The limited testing I have done so far, just on asphalt, have been very positive. I like the more positive steering response the car now has.

As far as the weight distribution, it is almost identical to rear motor, in fact it's a little lighter on the front now.

I have one note on your design. You could not attend an event that strictly follows ROAR rules. I couldn't care less about that, but some folks do.

A few things I did to get a stock layout mid motor 22 to work.

1. Flip the rear arms around, and space the hubs forward. It gets more weight on the rear tires.

2. No anti-squat, pro-squat helps quite a bit too.

3. Get rid of some kick up, shimming/ dremel work is required

Why? What rules is this breaking?

I considered all of these but I really didn't want shorten the wheel base.

1/10 2wd must accommodate a full length 2s lipo

A stock 22 in mid motor will not accomidate a full length lipo unless you run a shorty servo and put the ESC and Rx on top of the battery and that requires custom parts. You can barely fit a full length lipo in rear motor.

I was looking at the bellcrank system you have, It looks like you could have still ran the stock slider if you put a link in where the steering ball cups attach. But it looks cool. I tried to get my mid motor to work, but I could never get eneough foward bite out of it. I really like the way it jumped over the rear motor. Still trying to get used to it. Hope the car works for you.

The mid motor car is only legal if it runs saddle packs. ROAR made the stupid rule that cars have to fit the full length batteries and the only means to use short batteries is with foam blocks. Look at the "Electric Chassis Rule Amendment"

http://www.roarracing.com/?cat=26

I have final weight bias numbers for you. These numbers are ready to run with the body (no paint yet). Total weight is 1541g, Front 564g, Rear 977. That's a bias of 36.6% front to 63.4% rear. That's a heavier rear bias than I had with my rear motor setup! On asphalt I can't keep the front end on the ground so that should (with any luck) translate to forward traction on dirt.

Oh yah! That's without a brass weight hanging off the back.

Now I just have to get to the track.

+1