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Old 10-27-2008, 11:43 AM   #1
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I have a FT RC10B4. I had a 13x1 Orion motor. I ran a 81 spur with 19 pinion.
I wanted to go up on spur. I ran a 87 spur with 21 pinion. With slipper turned all most all the way in.
Won't my buggy go faster?

I was slower then a stock buggy at the racetrack. How come I can't get the 87 to work?
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Old 10-27-2008, 11:47 AM   #2
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the fdr's were different.
if you know how to find fdr's id suggest you see which one was lower because that is most likely your problem with speeds.
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Old 10-27-2008, 11:52 AM   #3
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the fdr's were different.
if you know how to find fdr's id suggest you see which one was lower because that is most likely your problem with speeds.
OK, this is stupid question but, whats fdr?
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Old 10-27-2008, 12:03 PM   #4
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FDR = Final Drive ratio

It's the number of turns your motor makes, to the number of turns your drive shaft makes.

Everything else aside, the lower the FDR, the more torque you need to turn the drive shaft.

So, if you have a higher turn motor, you have more torque, you can have a lower FDR.

THis is of course simplified, as motors are not all createde equal, and things like hand-wound vs machine wound armetures, motor timing, number of winds etc all play a big part.

If you get a calculator and do:

Spur size / pinion size x IR = FDR

IR is internal ratio, which is a B4 is 2.6
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Old 10-27-2008, 12:05 PM   #5
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Also, with your slipper cranked up your acceleration will be poop on a 13 turn motor. The slipper helps the motor get up to revs and it creates less resistance, and gets the motor into it's "power band"
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Old 10-27-2008, 12:06 PM   #6
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OK, Thanks you
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Old 10-27-2008, 12:09 PM   #7
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So losen up my slipper? ok.
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Old 10-27-2008, 12:23 PM   #8
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Yeah, you need to adjust it to your track conditions, it should slip for about 2 to 3 feet before hooking up.

Your acceleration will improve massively.
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Old 10-27-2008, 12:46 PM   #9
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Also remember that with a 13x1 you are going to need to maintain the motor more often than a stock. Expect to cut it at least every 6 runs and look at the brushes often.

I've seen a lot of guys out at our tracks that get all upset at why their mod cars are slower than our fast stocks... I tell them to take the motor out and let me look at it... the come is "black".. brushes are chipped up and less than half the original size.. and there is dirt everywhere inside..

I like brush motors.. still have many.. but anybody starting out especially with mod... go brushless and save yourself a lot of grief!


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Old 10-27-2008, 04:11 PM   #10
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Yup, single winds love rpms, so you'll need to gear lower to get them into their preferred power range, I'd suggest maybe a 15-16T pinion as a starting point as that 19T gives a n FDR that is looking for torque at the low end that your 13S just can't produce. Last year I ran a 12S in a xxxt with a 14T and it worked great. Smooth low end, insane mid and top end.
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Old 10-27-2008, 10:26 PM   #11
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i'm running a 10.5 brushless on my lazer zx-5 sp. using the stock 78t spur gear. any advice on what size pinion for best race performance? my local track is medium size indoor w/med traction.
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Old 10-27-2008, 10:54 PM   #12
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Quote:
Originally Posted by JeromeK99 View Post
Also remember that with a 13x1 you are going to need to maintain the motor more often than a stock. Expect to cut it at least every 6 runs and look at the brushes often.

I've seen a lot of guys out at our tracks that get all upset at why their mod cars are slower than our fast stocks... I tell them to take the motor out and let me look at it... the come is "black".. brushes are chipped up and less than half the original size.. and there is dirt everywhere inside..

I like brush motors.. still have many.. but anybody starting out especially with mod... go brushless and save yourself a lot of grief!


Jerome
Yea, I know there is more to maintain on these mod motors. I like brushed motors myself. I have a bunch of old school mod motor from the mid 80's and early 90's that I had when I had an old RC10 gold tube. I bought a stealth tranny and put a 90 tooth spur on that car. That was a fast RC buggy. This where I had the idea to put a 87 spur on the B4. Bring it to life just like 10 years ago.
I will have to go to the brushless setup sometime. I hate coming in last in the C-main.

Quote:
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Yup, single winds love rpms, so you'll need to gear lower to get them into their preferred power range, I'd suggest maybe a 15-16T pinion as a starting point as that 19T gives a n FDR that is looking for torque at the low end that your 13S just can't produce. Last year I ran a 12S in a xxxt with a 14T and it worked great. Smooth low end, insane mid and top end.
I will try 16t for a starting point.

Thank you everyone who wrote in for your help. I really appreciate this.
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Old 10-28-2008, 09:02 AM   #13
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Ok, you are SERIOUSLY undergeared. The Orion's are more torque oriented compared to say a checkpoint and 87/21 is the gear I used to run on my T4 with a 12 turn checkpoint. You need to go back to the 81 tooth spur and keep the 21 tooth pinion and just watch temps.
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Old 10-28-2008, 09:44 AM   #14
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Going with a 16 pinion is the wrong way. A single wind motor is all torque and needs a taller gear. The 87 is never necessary for the B4, 84 at most. Start with the 81 and a 21 pinion. You should be able to go clear up to a 23 and be just fine in racing conditions.
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Old 10-28-2008, 11:30 AM   #15
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Quote:
Originally Posted by Krio View Post
Ok, you are SERIOUSLY undergeared. The Orion's are more torque oriented compared to say a checkpoint and 87/21 is the gear I used to run on my T4 with a 12 turn checkpoint. You need to go back to the 81 tooth spur and keep the 21 tooth pinion and just watch temps.
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Going with a 16 pinion is the wrong way. A single wind motor is all torque and needs a taller gear. The 87 is never necessary for the B4, 84 at most. Start with the 81 and a 21 pinion. You should be able to go clear up to a 23 and be just fine in racing conditions.
So stay with the 81 and go up on the pinion. If anything go to the 84 if I want alittle more speed out of B4.
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