Help with gearing 17.5

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Old 05-02-2009, 04:08 PM
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Default Help with gearing 17.5

Hi guys
I've just changed to LI-PO brushless 17.5 on my Bj4 and need some
help with the gearing as im not sure where to start.

Ive heard that you need a large pinion and small spur i already
have a 72 and a 75 spur and the largest pinion i have is 26.

Can some one help me out with the ratio.
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Old 05-02-2009, 11:47 PM
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I am running my B44 with FDR 5.7 for the 17.5. I think it depends on the motor brand you are using as some can be geared as low as 5.0. Temp is your guide, never let is cross 80 degrees C.
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Old 05-03-2009, 12:38 AM
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Yup 72t spur 36t pinion here. Some ppl advance timing on motor/esc and run a taller fdr.
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Old 05-03-2009, 12:53 AM
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Thanks for the replys

At least now i know where start.

So if i keep the motor about as hot as i had my
brushed motor witch i could still hold after a run
would be good start.

Im running the tekin ecs and 17.5 motor.
Cheers Jay
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Old 05-05-2009, 02:08 AM
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check out this topic, there is also input from one of the Tekin guys, great info on gearing for those using the new tekin RS and PRO ESC's with the hotwire unit http://www.rctech.net/forum/electric...s-offroad.html
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Old 05-05-2009, 04:29 PM
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Thanks for that link Muzza ill check it out.
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Old 05-06-2009, 01:50 AM
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I am using rspro too, my settings are sensored with boost timing of 5. Motor is about 70C. ESC software is 194. This setting allowed me to obtain my fastest timing with a 17.5t since I bought my B44 6 months ago.....Just 8s shy from the track record (driver was using a 13.5t).

Last edited by spawn; 05-06-2009 at 03:06 AM.
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Old 05-06-2009, 05:50 AM
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hay,

In my b44 I run 78/35 at 0 degree timing. This is a bit over geared but it does not get too hot and is quite a good setup for me. I am using the Tekin/Fantom by the way so same motor you are using.

I think I worked out the gearing should be about 78/33 also, if this is the case I would probably go 10 degree timing.

Ryan
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Old 05-06-2009, 11:18 PM
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Originally Posted by ryan_c View Post
hay,

In my b44 I run 78/35 at 0 degree timing. This is a bit over geared but it does not get too hot and is quite a good setup for me. I am using the Tekin/Fantom by the way so same motor you are using.

I think I worked out the gearing should be about 78/33 also, if this is the case I would probably go 10 degree timing.

Ryan
I am using Team Orion 17.5t. I have tried 81/36 and its overgeared. I guess different motor requires different gearing.
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Old 05-07-2009, 02:25 AM
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I have not run the car yet.
Hoping to get up to Maitland for Sunday racing
to do testing in a feild going to start with 5.80 72/31
running the tekin 17.5.
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Old 05-07-2009, 02:54 AM
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Are you running the Tekin 17.5 combo, if so do you have the hotwire, if you don't you'll be in dual mode and you'll have to gear it to up to get speed, if you've got the hotwire, run in sensored only mode, maximum of 35 degrees split between you ESC and motor, ESC gives power higher up the rev range, motor timing gives you more bottom end grunt, Start at about 26 t pinion with a 72t spur and see what temps you're achieving, gear up or down accordingly, motor should not go over 80 degrees centigrade,
The problem with the BJ4(and b44) is no circulation around the motor, you'll probably have to get a heatsink and fan combo but be warned there is not much space in the car (as I've found out) best to take you car to the hobbyshop and try out various cooling methods
Hope this helps you
Steve
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Old 05-07-2009, 04:09 AM
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Yes the i got the combo Tekin rs pro with 17.5.

Ive only just put it in the car last week end have not
conected the hotwire yet so the speedy is still set at
factory setting.
Also have sensore conected.
Jay
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Old 05-07-2009, 04:20 AM
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Ye the bJ4 dose not have much room i do have a small
heat sink that i ran on the brushed motor that worked ok.

Where is the timing mark on the end bell got timing on the
can ( for the tekin 17.5)
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Old 05-07-2009, 04:34 AM
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Originally Posted by J-T9959 View Post
Where is the timing mark on the end bell got timing on the
can ( for the tekin 17.5)

There should be a little mark on the edge of the end bell , probably around the 10 to 12 degree mark if you havent already adjusted the motor timing.
You really should get a hotwire and the latest software, its amazing what it can do to a 17.5!
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Old 05-07-2009, 04:36 AM
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Originally Posted by J-T9959 View Post
Ye the bJ4 dose not have much room i do have a small
heat sink that i ran on the brushed motor that worked ok.

Where is the timing mark on the end bell got timing on the
can ( for the tekin 17.5)

Is it the Fantom tekin 17.5 or the Tekin brand itself? It should be on the top of the end bell near where the screws go in. it will say 10 20 then 30.

Cheers

Ryan
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