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

I like it! I did a similar thing recently though i'm running a rear motor 22 with the side shorty and the speedo behind the battery.

So far, i prefer it over my b4 w/bb and the stock losi 22. has all the positives of the 22 (forgiving handling and parts quality), and the stability and rear traction of the b4.

nice work.

Had the car at the track a few days ago and had some issues putting the power down. The slightest bit of steering input while applying the throttle and the car came around. I tried a ton of things including making the wheelbase shorter and adding weight to the rear end and nothing worked, I felt no difference.

I think it was the gear diff I had in the car with 4000 wt oil. I stood on the track and watched it and noticed the car diffing out a bit the around it went! Even when it did hook up and weight transferred to the rear the car wandered badly down the straight. Unfortunately I didn't have time to throw the ball diff in it and test it. That will have to wait for another day.

I am looking forward to seeing the difference and trying to figure out the problem. If the ball diff cures the problem then I want to try the gear diff with something like 20,000 wt oil to see what that does.

Planning to go to the track this weekend and do some more testing. Ill try to get some pics and possibly some video.

Try taking away some anti-squat, and maybe adding some pro-squat. I know I've said it before, but if you still can't get the stability or on-power traction this will help tons. I also notice your running calibers, so traction is probably quite low....... good luck to you.

I have taken the car to the track 3 times now and I finally have the car handling well. My biggest problem was tires. Once I changed to clay compound the car really started to work. I had the fastest 2wd car in practice, and just had a few minor handling issues that might have simply been driver issues. The car seemed to hook fairly bad when turning into the face of a jump or a bump in the track. Gonna try some geometry changes and maybe thicker shock oil next time. But at least it pulled a few of wheelies, one slap wheelie and a few when hitting bumps. Finally getting that forward traction.

Ill post some pictures and front / rear weight bias numbers after all the mods I've done since the pics. Prolly include the setup as well.

By the way I picked up a B-Fast diff rebuild kit. KICK ASS! That builds a nice diff.

Any updates on this mod? Thanks

i tried the shorty pack sideways a year and a half ago. it works fairly well. other than the servo relocation i started flipping the arms and turning the pack sideways. haha.

Matt

I just don't see how 63% of the weight on the rear is more rear bias than the car was in rear motor. Every 22 I've ever seen have 67-68% rear bias in rear motor. My CR2 (mid motor XXX) had 63% stock and after I made a new chassis and went crossways with it I ended up with 68% rear with no added weights. The X6 is over 65%.

There are 2 types of rear traction that people get mixed up. The first is forward traction. With the 4 gear setup you shift tons of weight rearward so wheelies on a mid car can actually be easier than a rear motor car. I fought this like crazy on my CR2 and came to the conclusion that a 3 gear mid setup would be better since the second form of rear traction is more important.

That is sideways traction. If there isn't enough weight on the rear wheels they slide out going into a corner and it slides around when you get on the power mid corner. A 4 gear setup may shift weight onto the rear wheels but it will do it at the expense of front traction which reduces steering.

My opinion is that an MM3 setup with 78%-79% rear bias and little to no anti squat is the way to go. I liked it much better.

Sorry for not posting any updates lately, I have been crazy busy and haven't been to the track in a long time. The good news is that there is only one week of teaching left and two weeks of cleanup after that then I am off for the summer! I plan to do a lot of racing, practicing and fabricating.

I haven't posted pics of the car since I got it running. Although I have plans to develop the idea further and do a body with a nice paint job there shouldn't be any massive changes.

Since my last post I have changed my shock package and went to some thicker oil. I also added two pieces of lead to the rear bumper. The weight bias is now 65.3% rear and 34.7% front with a total weight of 1505 grams. I do want to try and remove a little more front weight so I can get rid of the lead on the rear bumper.

After making the changes to the car it became very easy to drive. It no longer rotated in the corners but carved them. If I did get the back end to break loose in a corner it was very predictable and easy to recover. It didn't have that heavy pendulum feel of a rear motor car. The car is also very easy to control in the air with the centered mass.

A couple of pics of the quickly painted body. I plan on doing a nicer paint job when I have time.

http://i1131.photobucket.com/albums/...ps06874863.jpg

http://i1131.photobucket.com/albums/...ps71f1b4d9.jpg

http://i1131.photobucket.com/albums/...psf579a85e.jpg

The new body fits the chassis fairly well, when I switch to outdoor racing I will see how well it keeps the dust out.

http://i1131.photobucket.com/albums/...ps55f76f40.jpg

The lead I added to the rear bumper.

http://i1131.photobucket.com/albums/...ps9a31e2bf.jpg

http://i1131.photobucket.com/albums/...pse54a58d6.jpg

Pics of the bell crank as it is right now.

http://i1131.photobucket.com/albums/...ps95d280e5.jpg

http://i1131.photobucket.com/albums/...psfed737b2.jpg

http://i1131.photobucket.com/albums/...ps6760aaea.jpg

Flipping the ball studs upside down allowed me to get the steering as close to the chassis as possible, eliminating the slight bump steer I had before. There is NO BUMP STEER any more. The standoffs allow easy adjustment of this.

http://i1131.photobucket.com/albums/...pscc75c7b5.jpg

http://i1131.photobucket.com/albums/...psc423d9d8.jpg

This battery hold down was going to be temporary but I like it now. The standoffs are something I found in my junk box, I think that they are OLD Ofna shock standoffs with big washers on top. I do plan to turn my own custom standoffs at some point just so its prettier.

http://i1131.photobucket.com/albums/...psb9cacef2.jpg

http://i1131.photobucket.com/albums/...ps1c981517.jpg

Pics of the ackerman with this setup.
http://i1131.photobucket.com/albums/...ps44be5cc4.jpg

http://i1131.photobucket.com/albums/...psc2972299.jpg

Now I have to make it work as well or better for outdoor racing this summer!

Here are some update pics on some of my other projects.

http://i1131.photobucket.com/albums/...ps9d544985.jpg

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

I am learning to use Solidworks and designing a new 1/8th buggy. Next week I should be picking up my own CNC machine! It needs some work but when its working it should be awesome.

http://i1131.photobucket.com/albums/...ps7ef99141.png

This car is now stupid fast! I think that this is the first car that makes my butt pucker every time I squeeze the trigger. It is far faster than my driving abilities will allow. It is also very well balanced and rips through the corners without over rotating, it just carves.

http://i1131.photobucket.com/albums/...827-004441.jpg

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

Here are a few pics of my latest changes.

http://i1131.photobucket.com/albums/...psd3b5e353.jpg

I wanted to experiment more with my idea and try to centralize the mass more and make the weight bias adjustable so the car would work on loose and medium to high grip tracks, and feel the difference of changing weight bias.

http://i1131.photobucket.com/albums/...ps9a798446.jpg

You can see how far back the servo is now. Its just shy of an inch further back.

http://i1131.photobucket.com/albums/...ps01d26332.jpg

http://i1131.photobucket.com/albums/...ps55eee700.jpg

I removed the motor cover piece and trimmed the motor plate and gear cover to move the battery back. This allowed me to move the servo way back. I moved the esc on top of the battery to get even more weight back. I installed a Tekin esc when my Novak final died after I think close to 8 years of use. I am switching back to a Novak because the are far smoother and linear IMO.

http://i1131.photobucket.com/albums/...psfdd55ff0.jpg

http://i1131.photobucket.com/albums/...ps7d65537f.jpg

Without the brass weight system the car is at 67% rear weight bias.

Ran it a few weeks ago and it started to get pretty quick toward the end of the night, despite having the wrong front tires and not having raced in almost 3 years. Came in 3rd overall behind 2 fast guys. And this was on a fairly loose surface. I was in the lead until I made a mistake.


Might take it to an indoor clay track this weekend and play with the brass weight system I just got to see the affect. With the weights in place the car now has 68.5% rear weight bias. I want to try combinations of longer wheel base and different weights to see the affect.

Ill try to get some better pics soon.

Had it at the track a few days ago for some practice. I left the brass on and liked it as it was. I definitely have more forward traction. It was spooling the diff so that needs to be adjusted, I'd like to try the gear diff again to see what that does.I think that with the diff tightened i can tighten the slipper a bit and get better acceleration out of corners. I think I have everything where I want it I just have to switch the esc out for the Novak and mess with the geometry and shock package to make it perfect. Hopefully the next time I'm at the track I will be feeling better and drive better to see what its really doing.

I'm always interested in experimentation but I can't help understanding what was the point about weight distribution.

What you got there is basically what I got putting my lipo in the front... I'm running on carpet most of the time and the car has a lot of traction and enough steering...

I'm not sure of what you are trying to achieve? I mean what negative behaviour are you trying to fight with such disposition?

Mine:
http://t.imgbox.com/adiVCZkw.jpg
Rear 930.3g (61.32%) Front 587g (38.68%)

Double post, sorry!

(Damn quick reply is not quick anymore!)

WHAT? Triple post! Wow, sorry again...

He's trying to combat high moment of inertia by centralizing mass. I used this concept when designing a putter last year (except I wanted high MOI so that the face rotated slower).

The concept of MOI can be understood by looking at a ice skater. Stick your arms straight out (with weight away from your center of rotation), and the skater spins slowly. Bring your arms in towards your body, and the skater spins faster.

So by centralizing mass, the car will rotate quicker in corners (in theory)- it's not just about weight distribution to the tires.

Your design looks similar to the new Serpent mid motor, though the steering servo is in a more traditional position.

I am racing on low traction dirt and I an trying to make my mid motor handle better than all of the rear motor cars at the track. I tried rear motor and hated the feel. I realized that the problem was the high moment of inertia, and started this project.

I have learned that in theory mid motor is superior to rear motor if weight is kept the same, because of moment of inertia and the rotation of the motor planting the rear tires.

My mods have worked and I love the feel. I am now just making minor changes and experimenting with things to see the effect.

Ok I think now I understand better. I was not considering the inertia moment on the right axle... So if we keep the mass centered at maximum (on the axle front-rear but also on the axle right-left), the car will rotate faster in tight corners... Very interesting... I will study the behaviour and the installation of others Losi racers next time...

Thank you for your explanation.

.

Its not just in the corners its everywhere. In the air, rough areas of the track. The big one I am noticing is how much better the mid motor plants the rear tires, this makes sense when you think about the motor rotating the tires into the ground as opposed to lifting the rear tires as does rear motor.

I have been working on some stuff, nothing major yet but I have some ideas on centralizing the mass even more. I am going to try getting the rear shocks in front of the rear drive shafts and a few other ideas I want to test. But, more on this soon.

Everything came screaming to halt on this project. I moved, you know how that goes. Setting up my hobby room soon and getting started on my projects again. And I have a new one, focusing on aero, its a super light 4wd scte. Thread coming soon.

Its been a while..... Life's hard! New job and other projects are keeping me busy. Recently I started screwing around with my 22 again. I spend a lot of time thinking of ways to centralise the mass even more. My goal is to get rid of the rear brass weight and I would like to experiment with a laydown tranny and see if I can get that to work in low traction situations. With that in mind I did this next round of modifications to see how far back I could get the CG in anticipation of a laydown tranny.

First, this is the apex of the development I did on the last round of modifications.

http://i1131.photobucket.com/albums/...pso96pkqjd.jpg

Everything is pretty much the same as before but with a couple of little changes. I got the Novak Impact in the car, much smoother. I also got the shocks on the front of the arms, again to centralise the mass.

http://i1131.photobucket.com/albums/...psfjnr5iz7.jpg

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

I had to move the shock tower forward a little bit to get the shocks close to vertical. You can also see the diffuser that I stared to experiment with. It turns out it was kind of the jumping off point for the next stage of development / testing.

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

After some careful measuring I re-located the camber link to the front of the shock tower because moving the tower forward covered the holes.

http://i1131.photobucket.com/albums/...ps3ipmm2qd.jpg

Its a close fit but it works!

http://i1131.photobucket.com/albums/...ps7uajzvie.jpg

http://i1131.photobucket.com/albums/...psvutffq0j.jpg

For a while I have been looking at the arms on off road cars thinking there was a huge opportunity there for aerodynamic gain. I did some testing with my SCTE and a students HPI Blitz and found huge gains. I am now transferring what I learned over to this project. These are "arm mud guards" and wings. I haven't finished or tested this yet.

http://i1131.photobucket.com/albums/...psno26p7km.jpg

Well this was about the time the car went under the knife to test a number of new ideas!

http://i1131.photobucket.com/albums/...psavcjis8l.jpg

I am going to try a couple of air plane wing servos wired in at 7.4v. Both have around 65-75 oz/in of torque. That should be enough for skinny 2wd buggy tires.

http://i1131.photobucket.com/albums/...psj8d5lahx.jpg

Originally I thought of putting the ESC on the side of a laydown tranny but for this test I thought I would try it on the end of the motor. Shouldn't affect cooling, might cause other problems...... But that's why your test things.

You can see the receiver on the side of the tranny.

http://i1131.photobucket.com/albums/...psq9f3o8pl.jpg

Decided to use the Spektrum wing servo because of its aluminium case. I also removed the side pods and installed Delrin chassis braces. I designed these to be able to adjust the amount of chassis flex by adding or removing screws.

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

After my parts came in I started to finalise the design. The focus is on centralising the mass and aero. So the chassis is narrowed and I am starting to channel air to key areas. Again this is the first iteration and I am sure it will change drastically before it is all done.

Everything got mocked up in cardboard.

http://i1131.photobucket.com/albums/...psj7wvl3an.jpg

I got my new J concepts body and cut the side pods off for air slow to the rear arms.

http://i1131.photobucket.com/albums/...pskzbyo5op.jpg

I am also going to try out the LRP super shorty to make the chassis narrower for aero.

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

I got a carbon front shock tower and cut the brace joining the two sides together off. I did this to make the front wing more effective. You want to make the airflow under the wing as fast as possible to create lower pressure and more downforce.

http://i1131.photobucket.com/albums/...ps0qxdbb2n.jpg

Now that I had everything mocked up and was sure it would work I got to work narrowing the chassis. But..... My band saw still needs to be restored (I found a cast iron bench top 1960's band saw for almost nothing, it just needs to be restored) so I made a DIY band saw. I took my Jig saw and stuck it in my vice upside down. It actually worked pretty good for being super getto!

http://i1131.photobucket.com/albums/...psv9fre0ps.jpg

http://i1131.photobucket.com/albums/...psvlug7okp.jpg

After a little filing.

http://i1131.photobucket.com/albums/...psv2keqn3z.jpg

http://i1131.photobucket.com/albums/...psrpi30s3m.jpg

I then started transferring the cardboard templates to lexan.

http://i1131.photobucket.com/albums/...psxhtoy1ha.jpg

And started bending it up.

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

http://i1131.photobucket.com/albums/...ps48jj0lci.jpg

Once again I have to say this is all experimental! I think the side pods / floor
are a little to large and will probably be cut down to prevent kiting. The cover attached to the gear cover are the former side pods.

The canards attached to the side of the front window is also something I am going to experiment with. Fortunately these are bolt on, so they are easy to remove.

http://i1131.photobucket.com/albums/...psfi0lh5e4.jpg

Everything pretty much fabricated.

http://i1131.photobucket.com/albums/...psynlmyt2w.jpg

http://i1131.photobucket.com/albums/...psgsb30pof.jpg

http://i1131.photobucket.com/albums/...psimcg2lgf.jpg

Here you can see the battery slot. All the pieces still need to be sanded before paint.

I didn't spend a tone of time on the body because I am not sure how it will work. Once the design is finalised and the aero is fully developed to my satisfaction I will make it pretty. But at this point I have a bunch of stuff I want to try.

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

The body with the side pods removed.

http://i1131.photobucket.com/albums/...psggpehzs7.jpg

A closeup of the window canards. I have made these adjustable!

http://i1131.photobucket.com/albums/...psg4uxwg4b.jpg

Next I got started on the wiring, shortening and laying out all the wires.

http://i1131.photobucket.com/albums/...pss5xmqxvo.jpg

http://i1131.photobucket.com/albums/...psr4cyflxc.jpg

All done and tucked! The positioning of the electronics turned out awesome.

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

I also made a new battery hold down.

The only thing I don't like is the color of the LRP battery!


I've got the steering done, but no pics yet. Might weight until everything is painted. But soon I hope.

I personally love experimenting more than anything else. Don't worry about naysayers or even rules. Test your ideas and find out if they work or not. That's how you learn.

Have you seen hobbyking's super shorty?

http://www.hobbyking.com/hobbyking/s...arehouse_.html

Very much this.

You realize putting the shocks on the front of the tower moves weight off the rear axle, and it looks like every other effort you make is to put weight ON the rear axle.

Where'd you get your engineering degree from?