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Old 11-27-2008, 02:43 PM   #391
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Hey John, how well do you think that CRC Pro Strut front end would work on an oval car, say an Associated 10L4.
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Old 11-27-2008, 06:10 PM   #392
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t4mania-I was able to win with it on Ricks Battle axe which he graciously loaned me. I did not have it long enough to do a lot of experiments with it. One thing some of the CRC team drivers of various cars are doing is going with a long ball front end which extends the length of the upper arm a bit.

The graphite part is CRC 33277.

Additionally you need Long Pivot Balls


I would certainly try that after I ran it stock (short)for a while. It would look very much like this first pic with the graphite plate but with prostrut steering arms and axles.

Pic 1: shows the optional graphite plate needed for a long arm front suspension. This is the ruggedized CRC front suspension I will try next. The red parts are optional dressup parts but are also more rigid than the plastic caster blocks.

Pic 2: shows a standard CRC front suspension. Note the spring is upside down and no spring bucket is used at top. The large thin blue spring bucket is used at the bottom.

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Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-battle-axe-finished.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-crc-battle-axe-front-suspension-002-resized.jpg  

Last edited by John Stranahan; 11-27-2008 at 11:34 PM.
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Old 11-28-2008, 07:21 AM   #393
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Thanks much John!
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Old 11-29-2008, 01:14 AM   #394
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You are welcome.


3-link Wide Pan, Road Car, Panhard bar
Rear Roll Center

The rear suspension on this wide pan car is very similar to that on a late model mustang and also Transam race cars which use a solid axle and long beefy links. Both of these full size cars have a Panhard Bar (mustang) or Watts link (trans am car) to control side to side motion of the rear axle. Originally one goal of having a Panhard bar on my wide pan was to have a handle on the rear roll center. On a full size car the roll center of the rear of the car is at the center of the Panhard bar. Over two years I have done many experiments with Panhard bar position. This car used to have a frame extension and a rear mounted Panhard bar (behind the motor). I tried low, med and high positions of the Panhard bar. Thruthfully there is not much change in handling. The oversteer/ understeer balance changed not one Iota as I move the bar up.

On my 200 mm 3-link car, which I raced on the oval recently, I placed the Panhard bar in the front of the motor. This much simplified the Panhard bar installation. There were 3 less complicated pieces that had to be custom made. It worked fine there. Again I tried changing the height. No change in handling.

On a center pivot link car I tried a low roll center kit on the pivot balls. It had lower balls to maybe lower the roll center. Again I noticed no change in handling. As much as we would like to think that the rear roll center is at that center pivot, the car refuses to behave like it is. More likely the rear roll center is at the center of the rear axle and is not affected by this pivot that was added to pan cars. This can be more clearly visualized if we put rear body posts on the pod to mount the rear of the body. The rear of the body and pod would tend to roll about the center of the axle in this case. The rear of the body would be little influenced with what the chassis before the pivot is doing. (Note we don't mount the body this way any more, but some cars still have this capability.)

On T-plate cars some drivers have noticed a change in handling if the chassis is milled and the T-plate lowered. There are a boat load of changes made to the car to do this mod. The changes may not be due to a change in roll center.

Anyway the pan car in my long experience is relatively insensitive to Panhard bar height and center pivot height. Because of this I moved the Panhard bar forward of the battery and just high enough to clear the motor and Battery. This gives me a more compact and simpler rear suspension. I expect the car will handle the same. It will be lighter.

pic 1 After the change. The right side of the Panhard bar (which is perpendicular to the car just in front of the motor) is mounted to a post which attaches to a tab on the front right of the pod bottom plate. A new bottom plate was built. Pic 2 before the change.

john
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-wide-pan-panhard-bar-front-004.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-wide-pan-rubber-caps-resized-001.jpg  

Last edited by John Stranahan; 11-29-2008 at 01:28 AM.
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Old 11-29-2008, 06:17 PM   #395
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Default pan car

that car looks nice john the one in the second pic it looks fast just sitting there......
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Old 11-29-2008, 08:00 PM   #396
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Thanks-The wide pan car has been clocked at 63 mph in a parking lot that was not particuarly smooth. Same gears I run on the big track. Blowovers on bumps limited the car. I think with the new full width diffuser on the front it would do even better. Lap times are considerably better than a narrow pan car on the big track.

John

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Old 11-29-2008, 08:00 PM   #397
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Hi John,

Good to see someone trying different things with pan car suspension. I'm wondering what you are gaining with a 3 link vs a pivot ball style? The reason I'm asking is that a 3 link appears to put the motor in a fully unsprung state, vs a pivot ball, which gives a partially sprung condition ( I'm assuming that the 3 links are all the same length and a full width bump). Do you think the better isolation of single tire suspension movements outweighs the additional unsprung mass?
As a side note I figure that the pivot style also gives some interesting traits that are arguably beneficial. I think that the pinion trying to 'climb' the spur under acceleration giving a bit of anti-squat, and an opposing effect happens under braking. This would apply to the single pivot style only. I've also wondered what would happen if the pivot style was modified to have the pivot point theoretically inline with the motor shaft. In theory the motor would be fully suspended, although the geometry would be (severly?)comprimised. Any thoughts on this?

Scott
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Old 11-29-2008, 08:20 PM   #398
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Antisquat is a suspension setting that causes the rear of the car to lift on acceleration. This loads the tires and on a solid axle rear drive car, you get better forward bite. (on a touring car you just make the car loose.)


Do you think the better isolation of single tire suspension movements outweighs the additional unsprung mass?

Scott- Yes. I think this is the key to the advantage of the 3-link. Each tire is forced down from a bump much more effectively with that shock right near the wheel. This is especially true on an uneven bump (not full width).

The 3 link has better antisquat properties than the center pivot and it is fully adjustable. What you do to calculate it according to Carrol Smith is first find the virtual center of the 3 links much like you do with dual A-arm front suspensions. (see the diagram below). You then connect a line from the tire bottom to the virtual center. The higher this line the more antisquat. He gives antisquat a percentage number. The lines height at the center of mass divided by the height of the center of mass times 100. My car is set up with near 100% antisquat. Going higher does not seem to help and hurts cornering a little.
I had a 3 link antisquat video. I'll see if I can find some Web space to post it in a week or so.

Antisquat of three pan car types compared

The center pivot car has antisquat properties like you mentioned. I have driven three types now and can rate the antisquat. You can also calculate antisquat as the ratio of center pivot height to distance from axle to center pivot. What is different on these three types of cars is the distance from the axle to the pivot.

The Woods Racing T-plate car is actually a center pivot car as the rear of the T-plate does not flex up and down. There are three pivot balls on the leading edge of the pod to help the pod just pivot on the T-plate. It has the best antisquat and the best corner exit bite (even without the inerter) of all the stock pans that I tested. The reason is the pivot is as far back as possible. It is on the front edge of the pod.

Next the center pivot side link. Here the pivot is positioned at the back of the frame on a tab that leads the bottom front edge of the pod. Antisquat is still good.

Last is the standard T-plate car. Here it is said the pivot point is just forward of the back pivot ball on the frame. I think it is at the back pivot ball, but there is indeed flex in the T-plate in front of this ball. This car has the least antisquat.

Making a car with the pivot just under the motor shaft would give the car mad antisquat. On a wide pan car there is room to the side to do this. The pod would not rotate up so freely though from a bump as the distance from axle to pivot is now small. The suspension would act more solid I think. It is like having a front suspension with very short arms. It just does not work as well.

pic: left side schematic of a 3 link car. The green lines are the upper and lower links. This car has 70% antisquat dialed in.

Thanks for the posts guys.

I can send the short 3-link antisquat video by e-mail. Send a request to [email protected] 757 kb
John


Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-pitch-instant-center-antisquat012-resized.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-3-link-narrow-chassis-c-resized.jpg  

Last edited by John Stranahan; 12-02-2008 at 07:44 AM.
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Old 11-30-2008, 09:55 PM   #399
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Woods Racing Test Mule Road Car, Inerter Test

I made some changes to this car "to bring in" several difficult parts of the track. It is a 1/8 scale track and is not as smooth or compact as most 1/10 scale tracks. I narrowed the oval chassis to bring in the high speed sweeper at the end of the big straight. I had the extended battery tray dragging previously. With heavier rear and front springs the car was too loose. After the chassis trim, I went back to blue Wind Tunnel Side Springs. I would have used the softest orange but one dissapeared in a blowover early on.

I had no blowovers today even with strong headwinds. The full width front diffuser worked extremely well. I ran about 10 minutes of good track time. The wind gusted to about 35 mph. This always brings dust with it. In spite of this I had outstanding forward traction on the straight. The car jumped to top sped in about 1/3 of the straight. The inerter is now adjusted to a useful value. The picture shows the lever length I used. Inside, I fused the two very clean center gears to their common shaft with superglue. I removed the upper gear over the motor. I removed brushes and magnets. I oiled rather than greased the gears. I believe a center shock pan car with this device would have an edge on a road course with powerful motors. There is an unanticipated advantage on smooth short straights. The antisquat in the car is much more effective. Without the device there is only an oil resistance in the shock as the front of the pod lifts. With the device there is a strong inertial resistance that plants the rear. Does it make the car 10 % better, no. Maybe 1-2 percent. The acceleration early on the straight is the best I have seen. I'll get some more speed data with it later as I test the durability. It was faster today than the last test by eye. It is a fun car to drive.

The inerter fits well. It adds needed ballast for good side to side weight and decent car weight with LiPo.

Wind Tunnel Purple front springs, 15 lb center spring, 35 weight shock oil all around. Blue Wind Tunnel side springs (light). GRP Purple fronts, CRC World GT spec rears.

Custom Works Aggressor retune on the OVAL

As I stated above the wind created some dust issues which always hurts traction on the pan car. You could see definite tracks where the cars tires passed. We did something different this time. We swapped cars for a bit. Jimmy called mine planted. He noted he could give it a lot more throttle in the corners and on corner exit. I felt his custom Works Aggressor had a little more acceleration on the straights but it was much harder to drive error free. I felt it was darting around on the bumps which caused some mistakes.

We had red fronts installed. I felt that was about right, but I wanted to make the car more supple. The problem on dissasembly was a large amount of preload on the red springs. .080" worth. This was making them act a least a size stiffer. We took the preload out and put on white front progressive springs. We now had a couple of mm of droop. You can see the droop as space that appears under the steering arm when you set the car down. There was no droop previously. We removed the upper spring bucket and mounted progressive springs pointy side up (Ala GenX10 or Battle Axe) to gain kingpin rotating clearance on the rim.

We changed the left rear spring from a 12 lb gold associated to a 11# Green Wind Tunnel. We reoiled the side shocks with 35 weight oil. The car was supple now like I like it on this track. Jimmy drove quite a few laps without mistakes. The car looked good under difficult conditions. We may go back to red fronts when the dust is not bad and traction is higher.

Jimmy was running pink rears. Pink left front purple right front. I had loaned him a set of XXPINK/purple rears. I convinced him to try them. The car drove very well. Corner speed picked up from less scrub. Acceleration was still good.

All my road experience with a 3.5 tells me those rears are too hard, but then we are not running a 3.5, only a 13.5. What we need here is less scrub.

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-inerter-003.jpg  

Last edited by John Stranahan; 12-07-2008 at 09:36 PM.
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Old 11-30-2008, 10:59 PM   #400
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Questions?? help !

hello john, i hope u can help me on which car to buy??? i am starting in to 1/10 pan class. the track i will be running at likes the gen x 10 car. world gt class and 1/12 is all we run there. i have been looking at the crc car and the rc10r5, which is a better made car? how strong are to parts of each car??
which one would u have to race on road with?
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Old 11-30-2008, 11:51 PM   #401
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Default RC10L3T for World GT?

I have tried to search for an answer to this and I appologize if I missed it or if I'm in the wrong place but here it is:

I just got an RC10L3T (the 190mm one) and I was wondering if there is a way to convert it to 200mm to run in the World GT class. Would it work to simply shim it wider or would I need a new rear axle and some way to move the front suspension out 5mm per side? Any other issues I might need to be aware of?

I'd really appreciate any feedback on this...even if it's just to direct me to a place/thread where I might find the answer

Cheers,
Mike
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Old 12-01-2008, 07:21 AM   #402
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Mike-You should be able to add about a 5 mm shim to both sides of the rear axle. You can use two of these per side.

Associated8321Aluminum Axle spacers 1/8 inch, blue, (2)$2.99 8

To tell if the axle is long enough you would have to space it out and then check if the left side hub has good support. The axle should go near the end of the surface that touches the axle inside the hub.

If the pinion won't fully cover the spur after the conversion there are some extended pinions from corraly and recently from Robinson Racing that would help.

You don't have to go a full 200 mm. The rules would be 200 mm maximum, 200 mm bodies. You can run well with a car that is narrower than the body. The front I would just leave alone. The pan cars run well with 185mm front 200 mm rear. The front tires don't look quite as neat in the wheel well but they have plenty of clearance. If you want the front wide you would need to build or buy some graphite plate adaptors and redrill some holes in the chassis. CRC and Darkforce both make the plates to widen a narrow pan, but I don't know if they will sell them separately. Check out the CRC widening kit for a pic of these plates.

John
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Old 12-01-2008, 03:20 PM   #403
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John,

Thanks very much for the quick response! That's pretty much what I was expecting. I'll see if the axle is long enough to space out to 200mm and then figure out if I really want to go to the hassle of widening the front.

I guess that's what I get for trying to do things on the cheap

Cheers,
Mike

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Originally Posted by John Stranahan View Post
Mike-You should be able to add about a 5 mm shim to both sides of the rear axle. You can use two of these per side.

Associated8321Aluminum Axle spacers 1/8 inch, blue, (2)$2.99 8

To tell if the axle is long enough you would have to space it out and then check if the left side hub has good support. The axle should go near the end of the surface that touches the axle inside the hub.

If the pinion won't fully cover the spur after the conversion there are some extended pinions from corraly and recently from Robinson Racing that would help.

You don't have to go a full 200 mm. The rules would be 200 mm maximum, 200 mm bodies. You can run well with a car that is narrower than the body. The front I would just leave alone. The pan cars run well with 185mm front 200 mm rear. The front tires don't look quite as neat in the wheel well but they have plenty of clearance. If you want the front wide you would need to build or buy some graphite plate adaptors and redrill some holes in the chassis. CRC and Darkforce both make the plates to widen a narrow pan, but I don't know if they will sell them separately. Check out the CRC widening kit for a pic of these plates.

John
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Old 12-01-2008, 08:46 PM   #404
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Mike- You are welcome.

Cleveland Indoor Champs World GT results.

Congrats to CRC and the GenX 10 for a convincing win at the Cleveland indoor champs.

A-main results here.

http://www.rc50.com/results/2008cleveland/mains/R5_Race_16_WORLD%20GT%2013.5_A-Main.pdf

"Just a quick note to let all the forum members know that the CRC Gen-X 10 had great success this weekend at the U.S. Indoor Champs in Cleveland. Tom Firsching took his Gen-X 10 to a dominate T.Q. and A-main victory. A number of Gen-X 10’s joined Tom in the A-main."
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Old 12-01-2008, 08:53 PM   #405
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Quote:
Originally Posted by T4-RC8 RACER77 View Post
hello john, i hope u can help me on which car to buy??? i am starting in to 1/10 pan class. the track i will be running at likes the gen x 10 car. world gt class and 1/12 is all we run there. i have been looking at the crc car and the rc10r5, which is a better made car? how strong are to parts of each car??
which one would u have to race on road with?
Sorry I missed this post.
I think you will find the main difference between the associated RC10R5 car and the CRC Gen X 10 is the placement of batteries. The associated with center shock is built for 4 cell packs sideways at the rear. The gen X 10 has batteries down the center; this is certainly not a disadvantage looking at race results and is my preference. You can place electronics to get the weight distribution you like. The Gen X 10 can use 4 cell NiMH in the World Gt class or later 6 cell or LiPo's for play or if the club decides to add a faster class later. The GenX10 and battle axe are certainly exquisitely machined and detailed cars. Plenty of pictures of each earlier in the thread. I pick the Gen X 10 just for the flexibility in batteries that you can use.

Some cool RC10R5 features
You can't help but love the shocks if you understand how they work. No hydraulic lock. No entrapped air needed. No foam thingies. No bladders. No rebound.
"The RC10R5 features new shocks that have a through-shaft design, making for equalized damping throughout the full stroke of the shock in both directions, without any unwanted rebound."
Front axles may be stronger if they are steel. They are trailing, but I could not see a pic of them. The rest of the car is similar in strength to CRC.

John

Last edited by John Stranahan; 12-01-2008 at 09:12 PM.
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