Brad,
You didn't characterize how swoopy the track is, or how much power it has, but here's my favorite combo for spray glue: Body, O/S Viper, cut approx. 5 7/8" long and 1 1/8" high. .005 spoiler, with three or four folds resulting in a forward curve. Alpha supernatural tires, possibly even the hard version, or as an alternative, SRT wonder rubber at about 22 to 24 durometer.
Other bodies that I would expect to work well would include the O/S Infiniti, O/S Avenger, D&D D2, Parma Phantom (if you're loose), Koford Porsche, or if loose, Peugeot.
The track sounds too long for a high downforce body like a D3, O/S Vette, Camen Mirage or Hanson. On the other hand, if its fairly swoopy, a really low drag body like the D1 or O/S Tiga might work.
My usual advice still holds: Go do some homework!
Good luck, and good racing. Techman

We recently started experimenting with the new Mura 16D armatures. They are pristine in appearance with well laid windings and big coms, however we can't get them to run fast. Myself and one of our other top racers have tried various gear ratios and hav e not been successful in getting any of them (we have tired 4-5 arms) to run nearly as fast as our Parma arms. We are setting these 25 degree arms up in the Trinity AT setups exactly like we are building our other motors with blueprinted cans and endbell s, precisely matched magnets, bigfoot brushes and medium trinity springs. I have not tired light springs yet. I have noticed that the Mura arms have a lot less wire on them. How does that affect performance and how do we adjust for it? They sound grea t on the power source, but just don't have any get up and go on the track. Generally speaking they are running 2 to 3 10ths slower than our other motors. We have tried to run them on both battery powered tracks and conventia! l power sourced tracks. Any suggestions would be appreciated. Thanks for you consideration and keep up the great work!

Joe,
That big comm is probably the culprit, along with assuming the setup should be otherwise be the same!
The effect of a large comm is that the brush contacts a smaller section of the diameter, reducing the total time that the segment is powered, but also reducing the time that the setup is effectively shorted. This generally results in less heat, but a lower equilibrium speed. Rotational speed in a permanent magnet DC motor is governed by how much voltage the unused pole (and, at any given moment, there should be one) generates counter to the voltage driving the motor. When they are equal, terminal RPM has been acheived. The terminal RPM will vary with the torque load and applied voltage, and very little else - except, in the 16d, balance.
The effect of timing is to make the motor less efficient as a counter EMF generator, thus increasing the rotational speed. You don't really vary the torque load - thats a function of gearing and car weight and drag. So, the higher timed motor draws more current to reach the same equilibrium point.
All your previous 16d experience has trained you not to drive the current draw up very high, or POOF! But, the american 16d arms, with welded comms, better epoxy, and more efficient blanks, don't poof so easily. What you need to do is challenge them. Try much higher timing, and somewhat lower gearing. And yes, at least try the lighter springs, although you may have to go back if you get TOO hot.
Also remember that there is also a ProSlot made 16d arm marketed by FastOnes: The combination of american quality and a comm that is midsized between the Chinese and Mura comms, may be just what you need.
That last factor, balance, becomes more critical as timing (therefore RPM) increases. Despite the neat windings, balance still varies considerably on any long, large diameter, armature.This is yet another reason to force them to put out more torque through the gearing.
Good luck, and get back to us with your findings. My experience is limited mostly to Super 16s and the ProSlot stock 16s, and I would like to know for sure that the Mura arms react the same way.

Also, horsepower is not the problem right now for us. We're having trouble spinning the tires down the straights, which over the course of a race pretty much destroys them. We're running as high a downforce body as we can use and have to meet the 1.625 US RA rear height rule. My thoughts are that I might want to go for more air gap and RPM and gear the car not to shock the tires quite so badly. We're running 10/37 gears. Any thoughts?

Have enjoyed your posts on the boards. Too many slot folks don't try to apply intellect to the problems, as you obviously try to do.

G . . .

Greg,
You left out the critical part of the info to me, namely, the type of track and power you're racing on. Also important would be the brand of motor setup and armature.
In my area, airgaps are generally a bit closer than .530, but then C can races here are all for X-12 arms. I don't think you could be far off the ideal at that dimension. As for .001 making a difference, sure it could - but not in a predictable way. Anotherwords, the .001 may change one motor a lot, and another much less so even if they are quite similar otherwise. As always, the amount of different setups you are willing to try, and take notes on (i.e., doing your homework) will determine how close to ideal you can get.
As for tires, well, its a pretty rare race that I finish and can still use the tires in another race! I do feel that wheelspin in the turns is far more abrasive to the rubber than wheelspin on the straight. There is one major exception: High banks! They eat tires big time, and there is very little you can do about it.
The changes you mention may indeed help reduce the tire wear, but softening up the bottom end of a car tends to overheat motors, give up lap speeds, and can even hurt handeling. I've long been an advocate of gearing for punch specifically so you CAN spin the tires on demand. A car set up that way is normally much easier to drive. Since brakes are also improved, lap times should improve too, and you gain a few more places on the track where you can pass easily. Your gearing actually sounds pretty tall for me, as I might well be using a 9 tooth pinion in the same situation. Lately, I've been running 8's on the X-12 motors, with great success. My correspondants elsewhere in the country typically report gear ratios of over 4:1 for the super wasp motors.
My final comment concerns your brief mention of body height. My best GTP setups seem to be with the body at about 1.56", which with a JK Ultimate Peugeot puts the body right down on top of a C can. I realize that you may not be able to use 'ultimate' bodies, but back before ultimates, it still seemed to be true for me: Lower was faster! When you bring the back of a body up (as opposed to just running a taller spoiler), you increase drag. You also move the center of pressure forward, which can REDUCE traction. As a matter of principle, give it a try - and let the clock be your judge.
God luck, and good racing. Techman

We run on a resurfaced American Orange (with the wiggle on top made much gentler) using a power supply. I am using Mura, Koford, Pro-Slot, and one RJR setups. Have the best luck right now with the Kofords, although the Muras aren't far behind and the Pro-Slots are getting real close. Use the RJR Hornet arm almost exclusively, although I have a couple of Super Wasps. Can you suggest another arm to try, perhaps the Pro-Slot?

We're running a big local race this weekend and I'll let you know how things go. Based on your comments, I may try a few motors with slightly smaller air gaps.

Thanks again.

G . . .

Greg,
On a track as short as an orange, I would definitely be running 9/38 or therabouts. I would bet that your tire wear problems are mostly from the bank. If you have time, rotate the tires in the middle of the race.
Good luck! Techman

Frank,
Unfortunately, you are exactly correct. You need individual connections between each band on the contact block (except the brake) and places along the external resistor. Connect the top lug of the resistor to the white wire, then divide its length by the # of contact bands to get the spacing more or less equal along the length. The connection from the band closest to full power goes to the resistor tap point closest to the top lug, and sequentially down the resistor.
Chances are, if the local track had the parts, they also have an assembled controller you can look at to get an idea of how to route the wires.
For what its worth, the only real improvement you will see from this modification is cooler operation, since all the heat will be generated outside the handle. If heat wasn't a problem, you probably shouldn't bother. Also, the 2 ohms will make your car a bit more 'touchy' to drive than it was with 2.5 ohms. Of course, if it felt sluggish before, then thats what you would want.
If you make it through this operation - and you can by working carefully - you will come to appreciate why the assembled Parma version is so expensive!
Techman