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Old 11-24-2006, 08:39 PM   #601
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joe, RPM make 2 stage dampening shock pistons for associated shocks... and several companies including xray make externally adjusted dampening shocks.. but not sure what more you may be looking for in shocks

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Old 11-24-2006, 09:07 PM   #602
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Well here is what I have been working on after testing my Pantoura.

Well First let me say this car is fast and fun to run!

I am running a Mamba Max 5700 with it set on low and a soft Throttle setup till it gets to 55% Throttle. and I am only running 3300mah batteries.

So this is a picture of the shocks I will start with 2 front suspension setups.

1 A fixed upper control arm with a moving lower and the shock mounted on the fixed upper arm locking pin and the lower part of the shock mounted on the lower arm.

2 Next It will be a dual moving upper and lower arms and the upper part of the shock will be mounted to the upper arm pin mount in the center of your piviot pin and to the lower arm.

I will be looking into the springs once this is done.
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Old 11-24-2006, 09:31 PM   #603
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Marty-Thanks for the report and the schematics.
Well I will vote for the second schematic with dual moving arms. One problem with the current suspension which has a fixed arm is that changes to camber affect the roll center. Increasing negative camber lowers the roll center by tilting the strut pin (kingpin). Our recent roll center discussions have confirmed this for me. It would be nice to have these two adjustments independent of each other like you would have with the twin active arms. You would also get a much more friction free movement of the suspension with the dual active arms that should increase grip on asphalt.
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Old 11-25-2006, 01:43 AM   #604
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John, you described you have no droop in the front suspension on the last page. That's not good! That would mean you're using too much preload on the springs.
The rule of thumb is that you use shimms to fill up the king pin, but not put any preload on teh sping. The suspension will droop when the car is put on the ground. You can remove some shimms to increase droop and improve the car over bumps.

As a second, you commented to marty that you want a suspension with less friction. There should be no fritcion created by your front suspension. Use IRS front pivot balls and use toothpaste to wear them in so that they move freely without play. Remove some material on the upper eyelet to make sure it doesn't bind. The same on the upper arm.

When I build a front suspension I usually tinker around for evenings before I have it right. I tinker with it until I have free movement through its entire range of motion. With the springs and wheels removed, the suspension should drop under its own weight.

Marty, glad you like running pancar! There's nothing quite like it! I hope this gets you fired up to work on that new fornt supseniosn! Your sketches look good! Please keep us posted!
I'm also leaning towards a double A-arm suspension.
Do you still require me to do some CAD work for you as we discussed?
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Old 11-25-2006, 10:49 AM   #605
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Pro-ten Holland- I have no preload on the springs. My car is a little on the light side. Probably like a 4 cell car. The front springs required for good oversteer/understeer balance are still fairly stiff so they don't compress much when I set the car down. I could create some droop by leaving some slack in the pin. I found previously that this did not help performance any. I am making some progress on this by adding front shocks. I found I can use a weaker spring giving me some droop. Possibly two sizes weaker. I am trying 35 weight oil on these Mini T shocks in my next test. The piston does have holes in it so I can adjust the bump and rebound to my liking after a test on the bumps.

Even a well polished dynamic strut front suspension will have stiction. When the car hits a bump the force on the wheel is backwards and upwards. The pin has to slide through the bushings with considerable force back. This creates more stiction than a double A-arm car whose joints only need to rotate. This front end has more suspension friction than any other car that I have owned which is a considerable number even though it drops free from gravity alone and has a well polished pin. I do thank you again for these good tips. I might get those Aluminum coated pivot balls in the future. Hopefully I'll have something better to test before I do.
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Old 11-25-2006, 12:18 PM   #606
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Default I didn't get a change to read all of this thread...so...

I'm in the dark, but looking at the pics, I have an idea. I have always wanted a HPI micro RS4 in 1/12 scale.
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Old 11-25-2006, 12:28 PM   #607
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John, what does your car weigh?
Mine is at around 1200 gramms ready to run.
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Old 11-25-2006, 02:05 PM   #608
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on my 10l3t i have about 1.5-2mm of droop with purple progressive springs and no slop when unloaded..

wouldn't a fixed upper arm and moving lower arm creat very odd camber action when cornering? i just wish someone would make longer springs for the front end even just 2-2.5mm longer would help..
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Old 11-25-2006, 04:41 PM   #609
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Pro-ten-Holland- My car is at 39 or 41 oz depending which body I run. The Peugeot is lighter. Yours is at 42.2. Mine is about 3.5 ounces heavier in back than in front. I need to run the heaviest silver progressive springs (without shocks) for good oversteer understeer balance. (Note there are several heavier than the silver non progressive springs available from MurdockRC) When I say no droop I mean microscopic droop. It is less than 1 mm. I have green springs on it now (two sizes weaker) but with shocks. There is maybe 1 mm or two of droop now. I'll test it tomorrow.

Tally RC-A longer spring would not help my situation. As the car is set up the bottom of the kingpin just clears the wheel. A longer spring and kingpin would contact the rim in the turns. I am using the thin blue spring buckets which give you a tiny bit more clearance. You may or may not have these. You need some clearance between the wheel and the pin as the wheel flexes in the turns. I get a full 6.5 -7 mm of suspension travel. I can bottom the front of the chassis with my finger now. At 7mm there are no contact marks made on the bad bumps. To me this means a longer spring is not neccesary. I still get blowovers on the bad bump, so something else like shocks is needed for me. Even one of the 1/8 scales had a blowover at the Nationals so there are some bumps to contend with. I think that his car bottomed the front out on the bump from my inspection of it. I would like my car to just drive through the bumps just like my well tuned touring car would at the same speed without having to change my line or adjust my throttle lower.

There is a chance your springs have sagged. I don't see any problem in stretching them back out until you get the your desired suspension travel.

That fixed upper arm has the same camber action as the old Nissan 240 Z, the Fox body Fords that include the Mustang, and many other full size cars. it is not as good as twin A-arms but it is OK. It is called a Macpherson strut on the full size cars. The upper fixed arm would need to be a little shorter than the lower movable arm for the proper camber curve and camber. This may not show up on these early sketches.

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Old 11-25-2006, 07:04 PM   #610
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John, have you considered adapting a buggy front suspension to work on the car???
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Old 11-25-2006, 07:32 PM   #611
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Marty is engineering and building a bolt on front suspension for these cars as well as a car to go with it. The goal here is to be able to use a low GTP body, so the suspension has to be low. There are several tall suspensions already pictured in the thread. I think that mine is about the best that you can make a dynamic strut. It is also nice and low. I have long springs, good travel and the shocks are showing some promise.

Marty- where did you get those tiny shocks in your last photo. Are these custom made. I did notice that Associated offers a .56 inch shock body for the RC10L2. This is shorter than my Mini-T shocks, but are not offered with threads that I know of for an adjustable spring seat. Also you have considerable bump toe in with your current Pantoura setup. See if you can get a smaller servo saver (Kimbrough #201) and shim the outer links up at least a little for a fair test of the car.
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Old 11-26-2006, 04:55 AM   #612
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Marty, I agree with John go with the diagram on the right. The strut (on the left) will induce positive camber in bump and, on the out side wheel, in roll as well.

John. Have you considered this.
softening your front spring (so you can run some droop), adding a larger sway bar or increasing your front roll centre ( or a little of both).
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Old 11-26-2006, 09:27 AM   #613
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Josh-I have run a sway bar. It needed to be custom made for the wide pan car. The size that I made allowed the use of one size smaller spring. The front of the car would then bottom the chassis on the bump and lift the nose into the air. The suspension was still too springy.

Then I added new shocks, which are also a custom install. They have allowed me to run a softer spring without bottoming the chassis on the bumps. I am still tuning the shock and spring combination. It is showing some promise. I have some droop now. I plan to try the lower front roll center today. I can shim that upper outer pivot back up to get a higher roll center if that does not work. With the stock roll center and low body the car feels like you are driving a board with wheels attached rigidly. I think the low roll center is going to be the ticket.
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Old 11-26-2006, 09:52 AM   #614
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Lowering your inner upper arm will raise the roll centre. I feel that if the car is bottoming out that you may just have to yield and raise the ride hieght a little.

On another note I should be able to post up some CAD drawings of my chassis and if I get time I will post up a schematic of the shocks that I intend to build. For the most part they will probably use and existing body, but with some mods.
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Old 11-26-2006, 04:20 PM   #615
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Wide Pan Car Setup with Front Associated Mini Truck Shocks

Well I have achieved Pan Car Nirvana. I can use every part of the straight. The front chassis does not bottom. I made three passes on the inside lane, a lane which previously I just avoided. This was achieved by adding front Mini-T shocks. Grip on the sweeper is extremely good. I was making up about 10-15 feet on a couple of the Nitro cars on the sweeper. The car is now supple with the flat Peugeot 505 B body. Wickedly fast acceleration on the short straight leading up to the first hairpin near the drivers stand. This is due to the lower body weight and steeper rake that I put on it which gave the car more rear wing. I can use full brakes and even steer some at the end of the braking without a spin. This improvment is from having a more supple car with front shocks. The suppleness was achieved by lowering the front roll center and using 2 sizes softer front springs. The front shocks allowed this without creating too much grip on corner entry. Mid corner is just super now with the green springs. Somebody else should try this to see if I am just blowing smoke. The car looked really fast today. Race next weekend.

.030 cut off the top of the steering blocks to lower the outer upper A-arm pivot. This lowered the roll center.
Green Progressive MurdockRC springs with a long kingpin. No slack but no preload either. This is two sizes weaker than I can run without shocks.
Front Associated Mini truck shocks with 35 weight oil or blue ones
3.6 lb rear side springs with 20 weight oil, Associated TC3team shocks.
.049 inch 4 coil rear Losi JRXS center spring. 35 weight oil.
GRP pink Rears, GRP purple fronts, Corally Jack the Gripper for 20 minutes.
6.5 mm front and rear ride height.
4 degree caster, 5 degree reactive caster block.
2 mm of rear pod droop when held in the air.
2.5 degree negative camber (outside sweeper tire) left
1.5 degree negative camber right.
1 LiPo battery, Novak 4.5 R motor, LRP Comp brushless speed control mounted on top of the battery strap.

2 inch spoiler chord, rear of body set high,4 7/8 inch to top of spoiler.
body front at chassis height plus 3 mm soft dam below this.


I like these minit truck shocks better than the Aluminum VCS micro shocks because they are more ruggedly built and have 2 holes in the piston for easy tuning. I have not beveled the piston holes yet for easier bump yet, but plan to. I'll put up a picture of the front again as it worked out so well. The only problem with the car is that it is some trouble and expense to improve the front suspension. It would be better for most customers to have the car work well from the get go on a variety of tracks. Note that this is a wide pan car now.

You velodrome guys should try these shocks. Only 10 bucks a pair. You just have to figure out how to attach the bottom pivot without having to buy a KSG sway bar. Maybe left hander RC can be persuaded to have KSG make up a custom lower shock mount that does not cost $50.
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-front-shock-mini-t-installed-b-resized.jpg  

Last edited by John Stranahan; 12-01-2006 at 08:36 PM.
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