View Full Version : RJR's new S16D arm

Dan Tyler
02-26-2003, 08:25 PM
Hows it going? I am a first time user.
Heres what I've got. We are running the Champ turbo flex chassis with late model bodies. We run S16D American arms any manufacture. No quads, no berings. I am running the Parma can with EXP magnets with the new RJR .560 di. arm. I am trying to figure out what gear to run. We run on a 150' paper clip. Lots of straight away and three big bowls. I have tried several different gears from 9-27 to 10-31. but the car still seems very slugish. Can you help? Thanks :cool:

02-27-2003, 12:00 AM
Try 10-28

02-27-2003, 03:29 AM
Are you using the 500 series can or the rotor can? With the 500 can, the EXP magnets may be too strong. These arms produce gobs of torque because of the reduced airgap. I've found that the large diameter arms work better in the rotor can with Champion light (red) springs. This allows these arms to rev a little more and still make plenty of torque. Try somewhere between 10/26 and 10/28 gearing.
I'm running rotor setups in Turboflex chassis with 2.64 to 2.84 ratios (64 pitch) which would be like running 10/27 or 10/28, which is about the same as Circuitguy70 suggested. You'll have to experiment with gearing to see what works best for your drving style and doesn't cook the motor.
Try one of the Fast Ones "Big Bruiser" arms next time you build a new motor. We've had excellent results with these at the local track. Also, Ron at Fast Ones does really nice reconditioning on arms. All the ones I've sent him have come back balanced much better than they were when new.


If these 16D armatures get any faster,,,,,,,,,,,
we'll be looking for a "Cobalt 16D Class" next.

02-27-2003, 08:15 AM
Come on guys. Let Chicky® answer first or he is gonna get pissed off and quit doing this board.

02-27-2003, 03:21 PM

02-28-2003, 09:33 AM
If I sounded sarastic I apologize. Its just that we have been through this before and Paul gets pissed when people dump it in before he gets a chance to. Im just stating what his rules are.

:rolleyes: :rolleyes: To you too.....;)

02-28-2003, 01:17 PM
Didn't mean to step on any toes. I had been scanning "new posts" and should have double checked the header before putting my two cents in.

Sorry if this offended. I'm sure everyone would like to hear your advice on gearing these arms.

stone ......

Paul Ciccarello
03-03-2003, 05:47 PM
Sorry Dan but, luckly for Stone I have never used these new arms so I really have no idea how to gear them. Sorry. If anyone else want to chip in go for it.


03-03-2003, 06:33 PM
I spoke with Scott at PCH a couple of months ago and ordered a Fastone's setup and a big RJR arm. He told me they were gearing them with 11-12 tooth pinions (48 pitch). I tried it, and didn't have a lot of luck. I evenutally got away from the RJR and went with a 45 degree Proslot and advanced the endbell about 5 degrees....using 8 tooth pinions (48) pitch.... Still, I haven't attained the results I've been looking for, but I haven't given up. As Monty suggested, I'm looking for the weakest "matched" magnets I can find.....sorry Mr. Gilbert..... I'll see what happens then.


03-03-2003, 06:47 PM
I Tested 2 of them and I also went with 1 or 2 more teeth on the pinion like Mr. Root suggested. I then started going smaller on the pinion and the lap times decreased. I ran one at Raceworld yesterday at the USSCA nats and I was geared at 8-29 on the oval and 8-30 on the scorpion. The magnets I used were the weakest that I could find sticking to the refrigerator door. Each one measured about 290 on my Trik Trax meter and they were a good match. I had plenty of straight line speed and I was able to pass on the outside on the oval with no problem. I was talking with Nick Cina at the track and he was using a larger than normal pinion. Maybe it was just the arms themselves.

03-03-2003, 06:54 PM
A few of us ran the fat RJR arms in the Southern USRA series this year.

The trick to these arms is to use huge pinions. Robert Root emailed me to start with 2 teeth more than we normally run with .513 arms and my testing indicated that wasn't enough. I ran 14-15 tooth pinions (64 pitch gearing); I know of one of the pro class racers who was using a 17 tooth pinion! These arms have gobs of torque and will pull tall gear ratios without getting hot, while retaining very good brakes.

I mostly ran the fat arms in the new Kelly 16D setups. The pro racer referred to above was running his in Rotor setups with Parma EPX magnets. We both were running short tires, .765-.750 diameter.

You might want to start at something like a 3:1 gear ratio and then keep going higher (lower number). IIRC I ended up well below 2.5:1 and the car was fast.

03-03-2003, 07:24 PM
Didnt work for me. Smaller was better here.

03-03-2003, 07:30 PM
Bob, the difference is likely to be magnets and track power. The Kelly mags I used measured in the high 500s on my Trik Trax matcher and the tracks we run on all have good strong power . . .

03-03-2003, 07:38 PM
That is probably the reason then. I had very weak magnets in since it was a 16D arm. I'll try some stout ones and gear it up and see if its any better.:)

Dave Fugate
03-03-2003, 07:55 PM
Guys why not try raising the bushings in the chassis, and using a bigger diameter tire. that will effectively give you the higher gear ratio you want, without going to the huge pinions.

Just a thought.

03-03-2003, 08:12 PM
I always like to have the chassis as low to the track that is legally possible. If the track minimum clearance is .062... I'm at .063 when I tech in. Also in North Central its not legal to move the bushings up or down in the chassis. Of course you do have to open them up a bit to get the axle lined up correctly. Mike Dennis told me that you were in Ottawa last Saturday? I didnt think you raced scale. Dont let the Swissinator® find out;)

03-03-2003, 08:20 PM
Dave, that's certainly one way to do it.

But we race four classes in the Southern Div II series (4-inch, 4-1/2 inch, GT1, and GTP) and I'd rather not get into running different tire diameters for the 16D classes as compared to the 16C classes. I agree with the advice Monty has given in the past: run the smallest diameter tire you can.

Plus my tire bill is ugly enough as it is!

Dave Fugate
03-05-2003, 01:43 PM
Bob, Just use the JK off set bushings, and a jig with a set of jig wheels.

Cheater, Use the larger tires on the s16d's, and when they get too small, simply true them up and use'm on the other stuff.

03-05-2003, 02:28 PM
Im an old dog set in my ways. I agree with Monty as far as using the smallest tires that will work. You didnt answer my question Dave.... Whats up with you scale racing?:)

03-05-2003, 03:15 PM
Originally posted by Dave Fugate
Guys why not try raising the bushings in the chassis, and using a bigger diameter tire. ...
I don't think that will work.

Several racers have been trying those new RJR arms around here and I've yet to see anyone get them to go with less than a 13t pinion. I had one that went OK using 13/35 and some of the other guys are using like 14/38. There are rumors of some guys going fast with a 15. This is with a tire approximately .750. To get that kind of drive ratio using a 11t pinion, a tire about 1 inch in diameter or more would be required. With a tire that big I doubt the body could be mounted properly. Also, the strength of the upright would be greatly reduced by the large cut to get the bushing in place.

03-05-2003, 04:04 PM
Dave Fugate,
It's a terrible idea.Bigger tires are heavier, but more important it
would place the axle higher, raising your center of gravity. You
can pay me for correcting you if you come to Dixon the 15th.

Bob Boyd,
I don't care if Dave races scale stuff. I don't make fun of you
for swinging from both sides of the plate.

03-05-2003, 08:09 PM
I just didnt realize that Dave was a switch hitter:D

Dave Fugate
03-05-2003, 09:18 PM
For starters, If you raise the axle height, the center of gravity remains the same, by going to bigger tires raises the gear ratio, so you don't have to use those large gears. And as for the minimumal extra tire weight, in a scale car I really don't think that would matter, as you are already adding lead to the car anyway.

Maybe Paul would be able to better explain what I am talking about, as they figure the rollout on carpet cars in RC all the time.

And yes I have been running at a local track down here! Anything more than a stock 16d in major overkill on this track. Besides I think it is helping my driving, and after the last race @ Scoott's, I think it is working.

Got my daughter on the 15th, Sorry Mike.

03-06-2003, 08:14 AM
Well Dave,
If you have the chassis jigged to tech at .062 in the rear with large tires and you have to move the axle up to achieve this, your center of gravity will be higher because the AXLE will be higher in the uprights as compared to smaller tires with the axle sitting lower in the uprights with the car teching at .062. I also beg to differ on the weight issue. I try not to use ANY weight in my cars. If I do add weight I want to be able to put it where I want it and not have it in the rear tires. Like I have heard Mr. Swiss say time and time again regarding axles that arent cut off at the hub, (Insert your best Mike Swiss impersonation here), "That is the WORST place to have that weight". I have found with my driving style less sidewall flex makes stock cars drive better. Hence another reason to use smaller tires. Why would you rather change tire size than do a quick gear change anyway? I enjoy your insight though Dave. Its fun to argue with someone of your statue in the racing community.:p What track are you talking about where over a 16D is overkill? The LTD?

Dave Fugate
03-06-2003, 01:54 PM
Mike McCoy put a seventy ft. Hillclimb in his basement. Very short straightaways. Tried a Flexi-4 with a super 16d and an Ultimate Mercedes. WAY TOO MUCH HORSEPOWER. Gt-12 was unreal, boxstock was a laugh and a half.

03-08-2003, 05:52 AM
Originally posted by Dave Fugate
Mike McCoy put a seventy ft. Hillclimb in his basement. Very short straightaways. Tried a Flexi-4 with a super 16d and an Ultimate Mercedes. WAY TOO MUCH HORSEPOWER. Gt-12 was unreal, boxstock was a laugh and a half. :D It was really a laugh when Milwaukee got hit in the back of the head.

Dave Fugate
03-08-2003, 10:03 PM
That was a good shot wasn't it.

Dan Tyler
03-09-2003, 08:47 AM
Well guys we have tried several deferent
thing. Everything from a 14 th pinnon to a 8th pinnon. with every sper in between. So far I have had the best luck
with a 12/36 on .790 tires. I am going to try a little biger tire next week and see what happenes. The info you guys gave me was a huge help, and I want to say thank you to all of you for your info. I hope that at some time our paths will cross so that we can do some racing together and have a good time doing it.


03-25-2003, 07:53 AM
what is a good gear ratio to run them on. they have excellent power but i just can't get a good ratio?

03-25-2003, 07:44 PM

Hey man, hows it goin. i got to race with dan neely the other day at rebel. i barely caught him for 9th(in the second heat i completly lost a pinion) if that wouldnt have happened i would have won. anywho- back to your latemodel. for your track i would get that body as LOW as possible. Also, what TYPE of tyre are you using? i know chris loked those kellys. There is a kew kind called the bulldog. i like them. but they bend pretty easy. i told dan to get some alpha supernaturals and full big hub pirrinas in. i ran those in bush on sunday. i have some more tips for the 4.5 on that track if u e-mail me( i re did my adress book, lost everything)
talk at ya later man

Bent rim
03-28-2003, 08:24 AM
I ran into the same problem, seems RJR did all his testing on a 220ft track. This allowed them to use big pinions, without loosing brakes. Being that most of us do not run on 220ft tracks, getting these arms to work have been a challenge.
First , I tried weaker magnets, that helped, but was not the answer. I then opened the air gap by honing the EPX magnets (not legal) I found it was alot better. I then sent all the arms back to RJR and had them turn them down to 550 dia. This has been the best. Problem still is that the motor only runs good for one or two races, then die's off. On a 155ft King, we had to gear 9/27 in order to keep it cool. I give up! Sticking with the Proslot arms for now. Anybody who wants a deal on some RJR arms, give me a call!!!!!

Tom Marsteller
03-28-2003, 01:23 PM
Try cutting the comm smaller by about 0.10" and using Parma/Chinese brush springs (should get you more RPM's). You guys use the Deathstar setups too don't you? That makes it even trickier if you are trying to get them to "spool up" like a .518" arm does. Did you try going the other way? Lower timing with that famous PJ power? My best luck to date was building torque motors and forgetting about trying to rev these arms up.


Bent rim
03-28-2003, 10:00 PM
I'll try anything once! I can really get these things to rev up, I just figured to go with it! I'll give it a shot and let you know.

03-28-2003, 11:51 PM
Try what Tommy is saying, it works.
Have been building them in Kelly cans for 2months and have great results running RJR-16D 32degrees w/48P - 10- 28-29, track power is 13.40volts.
Have been running super cool too.

Tom Marsteller
04-16-2003, 07:23 AM

Some of the racers at the Nats were having their Big Bruisers re-ground to medium Bruisers (around .540" I think) to get them to rev. Then they were gearing around 10/38.