lee
Hitting the Tyre
Posts: 33
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Post by lee on May 4, 2017 19:47:12 GMT
Hello I was wondering what pinion gear would be best for a BSR BT-4 since yesterday my car was going quite slow compared to the other cars and i have the same ESC and motor as a few others.
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ianlloyd
Lapping the Back Markers
Posts: 932
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Post by ianlloyd on May 4, 2017 19:58:12 GMT
Shaun was running a 71spur and a 37 pinion in his BT4
That is about the maximum with that spur though. You need an FDR of around 3.6.
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Post by kennedylanduk on May 5, 2017 9:44:37 GMT
I've attached a FDR (Final Drive Ratio) chart for the BT-4. All the entries in orange should fit the car. FDR Chart.pdf (203.03 KB) We've found an FDR that works for our motors, so really you'll need to ask someone with a Speed Passion motor (I think Steve used to run one, possibly Darren still does).
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Post by kennedylanduk on May 5, 2017 9:57:14 GMT
PS. We have 75, 77 and 83 tooth spur gears, that's why the lines are highlighted in yellow in the chart.
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Post by kennedylanduk on May 5, 2017 9:59:21 GMT
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 5, 2017 17:11:18 GMT
I have a 79t spur and 26t pinion which would give me 5.8 FDR. So if i am correct i would need 75t spur and 40t pinion to be at a FDR of 3.6 but wouldn't you go slower of you had a much larger pinion gear. Also is higher the rating of FDR mean more torque, acceleration, less heat, etc and the opposite for the lower FDR rating.
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ianlloyd
Lapping the Back Markers
Posts: 932
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Post by ianlloyd on May 5, 2017 18:54:56 GMT
The lower the FDR the higher the top speed and the higher the heat, the higher the FDR the better acceleration but lower top speed. The idea is to find the optimum balance. 3.5 to 3.7 is pretty much the range in my opinion for 17.5 on our track. Go 3.7 to 4.0 if you want to be safe.
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 5, 2017 19:40:34 GMT
Do you think that 75t spur and 40t to 41t pinion be a good combo in your opinion or i should decrease the amount of teeth on both gears and get the same FDR?
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ianlloyd
Lapping the Back Markers
Posts: 932
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Post by ianlloyd on May 5, 2017 19:49:03 GMT
As long as they will actually fit in. You need to check the amount of adjustment on the motor mount.
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Post by kennedylanduk on May 5, 2017 20:29:04 GMT
Do you have a 75t spur?
75 and a 40t pinion might not fit. It should, but you might be better off with a smaller spur.
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 5, 2017 20:38:15 GMT
Sadly not, the only spur gear i have is a 79T
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Post by kennedylanduk on May 5, 2017 21:29:49 GMT
I'll see what pinions I have in the spares box tomorrow when I get home.
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 5, 2017 22:12:58 GMT
Thanks!
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Post by theslacker on May 8, 2017 12:14:23 GMT
Im pretty sure a 75 spur with a 40 pinion wouldn't fit. Shaun was running a 71 spur with a 37 pinion and that was about the limit. Id suggest getting a smaller spur than 75.
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Post by kennedylanduk on May 8, 2017 13:26:35 GMT
The smallest spare spur I have is 77t (and I'm not sure it will fit the BT-4).
I can loan you a pinion on Wednesday night so you can go a little faster. And you can increase the timing on the motor as well to get a bit extra speed.
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 8, 2017 19:19:24 GMT
Thanks, I am going to get 71t spur with 37t pinion
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Post by kennedylanduk on May 8, 2017 19:45:32 GMT
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 8, 2017 20:54:16 GMT
On hobbyking they have Robinson Racing "PRO" Machined Spur Gear 70t and 72t and Robinson Racing Black Anodized Aluminum Pinion Gear 48 Pitch 37T. Would having 1 extra or less Teeth be noticeable in speed?
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Post by kennedylanduk on May 9, 2017 6:57:24 GMT
I doubt one tooth will make much difference.
It might be cheaper to get them from RW racing though, send an email and ask (http://www.rwracing.co.uk/contact.html).
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Post by wessex88 on May 9, 2017 8:58:58 GMT
I believe Terry intended bring spurs and pinions down for sale
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 11, 2017 21:07:09 GMT
Sadly the screws to hold the spur gear onto the plastic belt holder thing isn't long enough, there is less then 1 mm exposed from the other end which isn't enough to grab onto the other side. Is it possible to get longer screws to hold it in place or would that mess up the drive belt since the spur is thicker. What type of spur would be compatible/ work with the car?
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Post by kennedylanduk on May 12, 2017 7:59:39 GMT
I'll dig out the spares later today and see what screws will fit. I've almost certainly got something suitable.
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Post by kennedylanduk on May 12, 2017 10:44:10 GMT
I think I have a solution for you. I've tried some longer screws, but they don't really work as they sit too proud of the spur, so the other gear "thing" does not sit properly. I tried using 6mm M3 grub screws. Screwed a couple of them into place (see the pic below) and then clipped the spur onto that. This should work ok, but you will probably need a small shim to hold it all together when it's on the car. I've got some grub screws you can have, and some of the right sized shims. Sean and I will not be there Wednesday night (the mrs is away), but if there is a race on Sunday, you could pop down and put them on your car. _ Attachments:
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 12, 2017 21:18:56 GMT
Thanks, sadly i cannot go to the race meeting on Sunday. Is it a certain make of company that's too thick or i just choose the wrong spur, also the spur looks different to the rest of them.
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Post by kennedylanduk on May 13, 2017 13:39:10 GMT
Spurs often do look different. But most have a standard set of mounting holes, but as you've found out, sometimes they need a little effort to get them to fit snugly.
I'm hoping to get to the track in the morning to cut the grass, I'll leave the bits needed to get you running with Dave.
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lee
Hitting the Tyre
Posts: 33
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Post by lee on May 13, 2017 17:27:37 GMT
Thanks, I also cannot go on Wednesday due to family coming around.
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