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Old 06-30-2010, 08:42 PM   #31
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Thank you sir!

I figured as much. I've used the shock holes when i thought i needed just a touch more adjustment.
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Old 07-02-2010, 07:47 AM   #32
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I've been messing around with a TC4 the last wee while to help find a good easy to drive setup for my mate's car. The biggest problem I've found the car is the wedge you are talking about John.

I have the left to right balance perfect on the car with 40g of lead on the battery side and the car is 1420g fully loaded The front to rear bias is close to 50/50 but still has a bit of extra weight in its ass and I have already spaced the motor forward 6mm, the car just as too much weight in its ass especially on the motor side.

So the right rear and left front are always heavily loaded and the other two wheels are much lighter even after setting ride height all the way round the car not just front and back. I don't have two sets of identical scales to check but I have used a digital luggage scale to lift each wheel off the ground one at a time and there is about 100g a difference between the light loaded wheels and the heavy loaded wheels.
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Old 07-02-2010, 10:00 AM   #33
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Front to rear weight bias
The tires are most efficient in a corner when they carry equal light loads. Unfortunately we have weight transfer to deal with. No special tricks can save us from side to side weight transfer on the road course except making it even front and back. (On the oval we can bias weight left as there are only left turns.)

There is also some back to front weight transfer as we are slowing for the apex. What we really need is even tire loading front and back for the dynamic condition of hard cornering while the car is slowing. For this reason 50-50 is not the optimum weight balance front and back. We should bias the weight to the back a litttle. Because the car has a long wheel base this back to front weight transfer is low compared to side to side weight transfer. A couple of ounces extra in the back is sufficient. (On the oval we can put as much as 12 ounces extra on the left side.)

Conrad- So if you do this preloading on the rear your TC4 may have good corner weights. Mine has 1.7 extra ounces back. It drives OK and can be adjusted to suit my oversteer understeer preference.
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Old 07-02-2010, 03:39 PM   #34
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If your adding your extra preload at the shock, how even is the ride height after? Just looking at my car I can see the difference in collar heights for each side L/R of the car. Granted it is better with the motor forward than when it was mounted all the way to the back. I might pick up a couple of scales and try it your way mate.
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Old 07-02-2010, 04:19 PM   #35
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Conrad
"The front to rear bias is close to 50/50 but still has a bit of extra weight in its ass and I have already spaced the motor forward 6mm, the car just as too much weight in its ass especially on the motor side."

You cannot fix this with shock collars. You have to move physical weight in the car. What I suspect is that in your efforts to have a 50-50 front to back weight split you have created this excess weight at the right rear. Instead slide the battery back and be happy with a 2 ounce excess in the rear. The car will drive better this way. Then you will have a car with corner weights in good shape as well as you will move weight back on the left side to match the existing right side.

This photo shows my car with perfect side to side, good front to back preload of 1.7 ounce rear, and even corner weights left and right. The motor is not spaced forward.

Later on to restore even left and right tire loading we will just adjust tweak on the tweak station. This involves only moving shock collars. This is most effective when we have set good corner weights by moving weight previously.
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Old 07-03-2010, 01:05 AM   #36
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John, glad to see you back at it with some 'vintage' composite! Im really enjoying the newer electronic tech in the ol' tub car!

Quote:
Originally Posted by SVODude View Post
I have been working on Carbon Fiber Driveshaft design and finally made a prototype. I have managed to cut the weight in half and so far have had no reliability issues. I have not had a chance to race the car with this new drive shaft (next race on July 11th), but so far I seem to be off to a good start.
I have issue with shaft flex at high RPM, and it does it with the driveline loaded or unloaded (i have video if you guys are interested).

Im currently using one of the original carbon shafts from AE (i have several). It is the best out of the shafts i have (AE Tc3/4 aluminum/carbon, and Niftech titanium), and i think its primarily because of its lack of weight. While you can clearly see its lack of balance and precision at low RPM, it doesnt flex as much at higher RPM as the Niftech shaft that looks to be a better piece.

I also took both drive cups (from the Tc3/4) and turned them on a lathe and reamed the interior to remove excess material in hopes of better balance. It helped somewhat (as did using a cut center foam from an AE VCS foam shock insert, in each drive cup to reduce the 'float' effect), but a better shaft would increase my confidence of the cars performance in modified. My current tubbie does quite well for its age in 17.5.
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Old 07-03-2010, 01:32 AM   #37
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Quote:
Originally Posted by Conrad View Post
I have the left to right balance perfect on the car with 40g of lead on the battery side and the car is 1420g fully loaded The front to rear bias is close to 50/50 but still has a bit of extra weight in its ass and I have already spaced the motor forward 6mm, the car just as too much weight in its ass especially on the motor side.
Be sure to run the smallest spur gear possible for your gear needs. This moves the motor closer to the center, and will help alleviate some of your added lead for crossweight.

I was also very particular about my LiPo purchase, primarily for weight reasons. I was more concerned about car balance than 'C' rating, and felt those results would "outweigh" any advantage the overhyped 'C' rating would provide.

As John mention previously, you need to remove the ribs in the battery bay of the Tc4 tub to clear your typical HC LiPo. Once this is done, you have some room for side to side battery movement. I used a thin strip of self adhesive foam to push the LiPo away from the center chassis rib to help Tc4 tub balance.

For my Tc3/4 hybrid, i need the battery closer to the center rib to balance it properly. With my current setup its 1426g RTR with NO added weight, and balanced perfect on a balance beam with shock preload set for 5.5mm of ride height measured at all four corners. I DO however have to retweak the car before every run, to compensate for motor heat induced chassis tweak. A 40mm fan helped this dramatically, but thats somewhat off topic.
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Old 07-03-2010, 09:40 AM   #38
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Quote:
Originally Posted by John Stranahan View Post
You cannot fix this with shock collars. You have to move physical weight in the car. What I suspect is that in your efforts to have a 50-50 front to back weight split you have created this excess weight at the right rear. Instead slide the battery back and be happy with a 2 ounce excess in the rear. The car will drive better this way. Then you will have a car with corner weights in good shape as well as you will move weight back on the left side to match the existing right side.
Tried that already mate and the car was horrible to drive, far too much weight transfer to the front on corner entry. Only after taking alot of droop of the rear did it calm down the weight transfer to the front. The car was still better and easier to drive with the lipo forward and the front/rear weight bias closer to the 50/50. I'm running rubber tires on carpet with a diff, I don't like spools the shaft drive more than makes up for the extra punch out of the corner you get from running a spool in a belt car.

Yup like you guys my battery ribs have been removed to move the lipo closer to the edge of the chassis, the chassis has also been slotted for tape instead of a brace, the motor recess has been lengthened to allow for spacing the motor forward and the cross brace cutout at the servo has been enlarged for when I had a low profile servo in it.
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Old 07-03-2010, 11:54 AM   #39
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DaveW-welcome to the thread. Thanks for the posts.

Pitch Roll and weight transfer
Weight transfer is the result of g force acting on the center of gravity of the car. There are only two factors really. How high the center of gravity is and how strong the g force. Pitch and roll do not affect weight transfer to any degree. When a car pitches forward the front end goes down and the rear end goes up. Changes to the center of gravity are minimal. When a car rolls we have the same situation as the left side goes up the right side goes down in a left hand turn. There is little change to the center of gravity. Pitch and roll do slow down the weight transfer and make the car more forgiving. Reduced pitch and roll (like from stiffer springs) makes the car very responsive but may make it suddenly break traction.

When we reduce droop in the rear what is happening is that as the car rolls in a corner, it comes up against the outboard droop screw quicker. There is an increase in roll stiffness. That end will slide better.

When I was racing on indoor asphalt with rubber tires at Performance in Houston the guys would go race at the carpet track at K&M. There were no changes needed to the setup.

If there are difficulties in handling with a couple of ounces of extra weight in the back, these can be tuned out with changes to the roll stiffness front and back (springs, shock position, sway bars). A very good handling car can result. Enumerate the problems and solutions will come from the very good team that is assembling here. If corner weights are off, the car will have trouble cornering in one direction.
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Last edited by John Stranahan; 07-03-2010 at 12:10 PM.
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Old 07-03-2010, 12:07 PM   #40
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Current Setup
Battery back and on the outside rail, Motor in with a 66 spur, 1.7 ounce excess weight in back with body off.

Front end
4 degrees caster
0 toe in
Green Springs all the way out on top
chrome .050 inch sway bar
35 weight oil
Wheelbase slightly forward
no kickup
Low roll center, Inner A-arm fully down
camber link inside with two washers under ballstud, no washers outboard
Camber 1 degree to wear tires more flat
Front slipper spool with Losi JRXS slipper pads cut from the slipper spool diff pulley, lightened steel outdrives, Aluminum drive axle bone.
Ackerman outer hole on arms, no washers behind inner steering link ballstuds

Rear end
2,5 degrees toe in
Rear camber link on inner hole with two washers under ball stud, outer end is on a Losi JRXS .5 degree hub on the wrong side with a short ball stud.
Wheel base middle
Ball diff with plastic outdrives and plastic drive axles.
Green Springs All the way in on top. outer hole on A-arm
Chrome Sway bar
low roll center with inner A-arm pivots all the way down. No antisquat.

Motor 13.5 66/34 x 2.5 = 4.85

I will make changes to this posted setup as I experiment with settings.

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Last edited by John Stranahan; 08-05-2010 at 10:38 PM.
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Old 07-03-2010, 01:49 PM   #41
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Quote:
Originally Posted by John Stranahan View Post
DaveW-welcome to the thread. Thanks for the posts
I dont post much. I do more reading than anything. Ive always enjoyed reading your threads though. Theory and experimentation are what i love most about this hobby.

Have you considered modding the Tc4 tub and trying out the Tc3 rack? I know it has its drawbacks, but for me its linearity and lack of slop rank high over a little excess maintenance. The flanged bearings i use help keep maintenance to a minimum, primarily because there just isnt a lot of surface there to collect tire rubber and debris. A little air between runs and i have yet to have any problems over the years.

Quote:
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I'm running rubber tires on carpet with a diff, I don't like spools the shaft drive more than makes up for the extra punch out of the corner you get from running a spool in a belt car.
Definitely use a front diff for carpet/rubber racing. If you venture outside onto the asphalt, the spool is where its at. I ran a front steel diff on asphalt for a few months, tried a modded steel diff as a slipper spool and havent gone back.

Laptimes are so much better with the front spool. You cant drive it the same as a car thats front diff'd, but the change isnt as drastic as when running a front one way. GAWD i hate one ways in a shaft car. So far from consistent on anything less than glass smooth.

Try to run a plastic rear diff if you can. Rear weight transfer is more consistent and adds a level of 'tossability' to the car (once the rest is sorted out of course). You will notice it most when changing directions last second to make your way through traffic, even having the sure footedness to throttle punch past belt cars in chicanes... and regain your line immediately.

Ahhh the advantages of shaft drive!!

I prefer the battery forward in my car as well, and it makes it easier to balance it out F/R and L/R without adding weight. This does depend on driving style too, and not everyone likes the same thing. For me the car is better balanced, offers consistent tire wear, and helps the car rip through medium to high speed chicanes. My setup is fairly unconventional though... i dont even use droop screws.
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Old 07-03-2010, 04:00 PM   #42
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Hey guys. I run an FT TC4, I used to run the tub car. I got my FT used from a friend at the track. It was already set up when i got it. With some fixing up, it was fine to race. It came with a one way in the front, and I put my old steel diff in the back. I fixed up the shocks and set it up with some help from another guy at the track. I'm using 32.5 wt oil all around and blue springs in the front, silver in the back. I'm running on a medium size outdoor asphalt track with rubber tires. Referring to Dave's last post, should I be using a spool? What exactly is a spool, and how is it different from a one way or diff?
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Old 07-03-2010, 08:03 PM   #43
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Okay I suppose this is somewhat of a newbie question, but when you guys are talking about a steel diff, are you talking about the outdrives rather than the plastic outdrives? It might have been mentioned earlier, I just missed it. Thanks!
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Old 07-03-2010, 08:31 PM   #44
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Originally Posted by flyintrtle View Post
Okay I suppose this is somewhat of a newbie question, but when you guys are talking about a steel diff, are you talking about the outdrives rather than the plastic outdrives? It might have been mentioned earlier, I just missed it. Thanks!
Yep, youre right. Steel or plastic outdrives. There are two sets of steel outdrives though, standard and lightweight. You can use either, unless you want to turn a steel ball diff into a slipper spool.

The lightweight steel outdrives have material removed under the diff ring, and the slipper pads dont seat too well. The standard steel outdrives are full faced under the diff rings and work best in slipper spool format. If you need pix, let me know. The front of my car is currently apart and it wouldnt be a problem.

Quote:
Originally Posted by TC4Racer123 View Post
Referring to Dave's last post, should I be using a spool? What exactly is a spool, and how is it different from a one way or diff?
Thanks
Dan
A spool is basically a straight axle tying both wheels of that end of the car together. A front spool gives you more steering off the corner, and a diff gives you more steering into the corner.

The major downside of a spool is potential driveline damage in a crash, John went fairly indepth about that earlier. This is where the slipper spool comes in, and helps relieve the driveline stress during a crash. And yes, a slipper spool handles differently than a fully tightened ball diff.

Is a spool for you? You will honestly have to try it for yourself. For me it was night and day, and worth several tenths per lap. You have to drive it a little differently than a diff'd setup, but again you wont know till you try it.
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Old 07-03-2010, 08:38 PM   #45
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Yep, youre right. Steel or plastic outdrives. There are two sets of steel outdrives though, standard and lightweight. You can use either, unless you want to turn a steel ball diff into a slipper spool.
Thanks Dave, that's what I thought. I have a FT spool infront of my sons TC4 with the steel outdrives in the rear. Just can't remember if they are lightweight or not.

If it's possible, do you think you could help me make his car easier to drive for him one of these days? It's set up to the one setup sheet from T.A. with CS-27 tires & outdoor.
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