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Old 12-30-2006, 08:55 PM   #766
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Originally Posted by John Stranahan
Mathijs- I will try short stroke shocks first, but will be able to put some long stroke shocks on if neccesary for a test of huge droop. Who knows exactly what this suspension is going to do on corner entry. The full size car guys like lots of droop with a solid rear axle.

Three Leading Link Rear Suspension with Panhard Bar

I have come up on a problem of scaling which I will describe briefly. When you scale a car up 10 times (1/10 scale to full size) the dimensions and thickness of every part would increase by a factor of ten. The strength of each part increases as the square of a dimension so would go up 100 times for simple shapes. The weight however increases by a factor of 10 x 10 x 10 or 1000. So if you take an RC car and scale it up keeping every shape the same you would have a very wimpy car. The weight increases much more than the strength. The weight has increased by 1000 but the strength by only 100. Conversely if we scale a big car down to RC it becomes very stiff.

When I built a new top plate for my four link this made my four-link setup really stiff in roll. It would not roll at all. For a four link to work there has to be flex somewhere as one top link tries to lengthen and one tries to shorten. This is not a problem of angle as I have parallel links now. On a big car, parts flex to solve the problem. The rear axle tube acts as a big sway bar and probably twists some to compensate for the length change. On my car I have decided that I need a three link. Identical to the mustang suspension whose URL is above.

Man is the rear of the car supple in roll now. Almost done. We are machining lower shock mounts in Aluminum, but I need to locate a 2.5 mm tap.

The speed control and receiver may be mounted high and back now, the speed control close to center, and receiver close to the outboard edge now that I lost my center postion.
you have alot of time on your hands
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Old 12-30-2006, 09:33 PM   #767
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I have as much time as you do. I wish you guys would quit quoting entire post. Go in a delete the parts not relevant to your own post which in this case would be the whole quote.
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Old 12-30-2006, 09:47 PM   #768
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Originally Posted by John Stranahan
I have as much time as you do. I wish you guys would quit quoting entire post. Go in a delete the parts not relevant to your own post which in this case would be the whole quote.
didnt mean it in a bad way ,just to find the time to design and make the parts then test it and make more parts again to improve the design
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Old 12-31-2006, 08:41 AM   #769
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how much of a problem is the contracting of the shape? as the pod rotates, regardless of where your links are, the pod will be drawn forward.. is this causing unforseen binding?
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Old 12-31-2006, 12:41 PM   #770
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No binding at all. Very stiff laterally. Very supple up and down and in rotation side to side. I have enough clearance at the front as I made a custom lower plate that does not have as much material in the front as the stock lower pod plate. Things are looking good. The movement forward over the amount the chassis can roll is small as is the effect of the arc of movement on the long Panhard bar.

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Old 12-31-2006, 07:42 PM   #771
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Happy New Years.

3 link car nears completion
More progress. I put a rectangular tab of graphite under the cross bar to reinforce the front pivot and to add a platform for the Speed Control It also pushes the batteries lightly down so the speed control is as low as possible. The shock towers are installed. It looks like these gold RC18T front springs will support the rear of the car fine. The car is at ride height supported by the springs (less lower shock mount, I still need a 2.5 mm x .45 mm/thread tap) I have two lighter tensions as well as some heavier tension springs available.

When I run dual packs I don't need to remove them from the car for racing. I will be able to charge these MaxAmps packs at a reccomended 4 amps each side for a combined rate of 8 amps. This is sufficiently fast for the racing that I do. They will not have a 100 % fill during qualifiers, but will for the main. The front of the packs are held with tape the rear is supported by side dams built into my frame rails and possibly a rear bulkhead to come. I will remove two of the four nuts to change the packs.

The capacitor from the high temperature kit was less one lead on this speed control (LRP competion). I need to give it one more test with a new cap.
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-3-link-speed-control-002-resized.jpg  

Last edited by John Stranahan; 01-02-2007 at 08:22 AM.
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Old 12-31-2006, 08:00 PM   #772
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what plugs are you using? are those just deans that have been cut in half?
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Old 12-31-2006, 09:26 PM   #773
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Yes. That's the short answer. Here is some more detail. Just Deans Cut in half. The big advantage for me on these cars is the ability to use the large shrink wrap that covers the entire plug. I never like the looks or dinky shrink wrap (which always preshrinks before you get it in place on a short lead)of the original plug. On some cars like offroad truck you use considerably less wire with half plugs. I also have the flexibility to wire my two batteries in several ways (maybe series with the new Tekin) by just changing the harness. After a few months, I replace the shrink and the plug looks brand new. I cut the female plug right along side one of the conductors and discard the short half. This keeps the original spring tension of the plastic. I cut the male plug right in half and get two good pieces. The females are available cheaper in a 5 pack. I stretch out 1/4 inch shrik wrap with needle nose pliers to go over my half plugs.

Losses are very low with this plug. Better than hardwiring a NiMH, even, because you use two fewer battery bars.

Last edited by John Stranahan; 01-01-2007 at 11:43 AM.
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Old 12-31-2006, 10:48 PM   #774
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Nice job there John...It's given me some ideas but I'm not sure I'll be able to get parts machined to make my idea as it will take different motor pod bulkheads.
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Old 01-02-2007, 01:11 PM   #775
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InspGadgt-Thanks. Good luck with your project.

3 link continued Lower Shock Mount.
Here is a pic of the lower shock mount. It is made of 6061, T6 temper, aluminum. It is installed Losi JRXS style with a threaded pin to the rear and one 4-40 screw to the front. The other side is installed at 180 degrees to this one (with the ball-stud hole in the same position) to suit the space. Thanks to my nephew James for helping to machine this set of parts. I await my 2.5 mm tap to complete the project.
John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-3-link-lower-shock-mount-resized.jpg  

Last edited by John Stranahan; 01-02-2007 at 02:32 PM.
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Old 01-02-2007, 02:24 PM   #776
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Three-Link Wide Car Complete

I have some ball studs in the lower shock mounts. I have reshimmed the shocks on the shock towers. Everything looks good on the bench. Delightfully smooth. I'll give it a try later in the week. Pic of the installed shocks below. I will have to remove the lower shock mount (one screw) to remove the spur. More details on the lower shock mount construction can be found here.

Wide Pantoura
The wide pantoura (Stranahan Edition, Pics, Parts List) has the new MaxAmps 4000 mA-h dual battery pack installed now. The Weight of the car ready to race is 45 ounces with 8000mA-h on board. This is just a couple ounces over the minimum regulation weight. It should be really fast with the Novak 3.5R and a good speed control. Race on January the 7th. Gear is 7.50. I have GRP pink rears in hand now.

John
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-3-link-lower-shock-mount-finished-005-resized.jpg  

Last edited by John Stranahan; 01-02-2007 at 10:11 PM.
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Old 01-03-2007, 07:18 PM   #777
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AmpMax 4000 mA-h 2S1P Lipo

I had an opportunity to test the new AmpMax Batteries. I was pleased with the results. If I had to guess the chemistry from the results, I would guess that they are Lithium Cobalt Dioxide packs due to the good voltage. These packs are as small as the Orion Avionics LiPo. They should make the car sizzle on the track.

AmpMax Pack A 746 seconds at 20 Amps, 4144 mA-h, 7.16 V average
AmpMax Pack B 735 seconds at 20 Amps, 4083 mA-h, 7.19 V average


Orion 3200 mA-h 2S1p Avionics LiPo when new
20A discharge, 574 seconds, 3194 mA-h, 6.87 V average
The guts of this pack are identical to the graphite edition 3200 mA-h pack.

Apogee Magnum 3800 Lithium Manganese LiPo
Pack C 20 Amp discharge, 6.94 V average , 3744 mA-h tested when new. This was my most recently purchased pack.
Pack A and B tested better when new but deteriorated to about this voltage fairly rapidly with only a few months of age and use. The capacity deteriorated to about 3100 mA-h at present after a few months of hard use.

Scorpion Lithium Cobalt Dioxide Pack 3200 mA-h
20 A discharge, 612s, 3400 mA-h, 7.19 V
This pack maintained voltage and capacity extremely well with use and time.

3-link car weight
46 ounces with the two AmpMax Batteries on board. About 39 ounces with only one. This is one ounce heavier than the other wide Pantoura car, but this test mule has aluminum adaptors at the front to make it wide and also a larger receiver. I would say the two rear suspensions weigh about the same.

Last edited by John Stranahan; 01-03-2007 at 07:32 PM.
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Old 01-03-2007, 07:29 PM   #778
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Hello Cristian
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Old 01-03-2007, 08:14 PM   #779
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3-Link with Panhard Bar vs Center Pivot with Side Links and Center Shock

In the red corner consisting of a Narrow Pantoura Chassis with home made 3 link suspension.

In the Blue corner a wide Pantoura consisting of a Powell chassis and rear pod plates.

Cars are within 1 ounce of each other. I can run both the 3.5R and 4.5 R motors in both cars. Both can use standard pinions which allows easy use of 7.50 gears with the 3.5.
Attached Thumbnails
Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-three-link-finished-resized.jpg   Pantoura, 1/10 Pan Car, 2S LiPo, Brushless, Tips and Tricks.-three-link-comparison-link-car-008-resized.jpg  

Last edited by John Stranahan; 01-04-2007 at 05:12 AM.
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Old 01-04-2007, 03:21 AM   #780
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John, could you measure front and rear width of the cars for me?

It looks like either your cars' front ends are narrower or the rear ends are wider than on my car.

This might be an area I could win some steering in.
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