B4 -7.5 Gearing

[Chris Green]

Hello,

I am looking for a starting point for my B4, running on a large-ish indoor track.

GTB with LRP X11 7.5 Motor. Lipo Cells.

Thanks,

Chris.

[V-Rossi]

23/81

[Chequered Flag Racing]

ran a Nosram 7.5 on 26/78 @ Worksop over the weekend on Demon 35c saddle pack LiPo

[Medders]

26/78 with a 7.5 !!! You sure !!!!

Christ, I was going to start my new 8.5 with 23/81.

[RudeTony]

Standard spur gear with a 23 pinion on a X12 LRP 7.5 - Perfect!!

[Southwell]

I was running 24/78 last year.

[Chequered Flag Racing]

Originally Posted by Medders

26/78 with a 7.5 !!! You sure !!!!

might have been 62/87 , if I did a typo but I could take a pic if you really don't believe me

[V-Rossi]

26/78 is quite heavy, but the big pinion makes the car easier to drive, makes it less punchy. Normally I use 24/78, indoors as well as outdoors, as this ratio is the best of both worlds (smooth power delivery, easy driving and a high top end).

The choice of spur gear is personal I think, I like the 78T more, but it's nearly impossible to use small (21-22) pinions with it on the B4 and S2 without modifying the motor plate. But Neil Cragg etc. seem to opt for the 81T ones with a 22 or 23 pinion.

[Medders]

Looks like I might have to buy some bigger pinions for my 8.5.

Still can't get my head around the 26/78 . Could you fry an egg on that motor after the race?

[Chequered Flag Racing]

Originally Posted by Medders

Could you fry an egg on that motor after the race?

No, just nice to touch

[Medders]

Your tempting me to try a 28/81 with my nosram 8.5, but it just doesn't sound right - thats the same gearing as I run a 20T 540 with

[millzy]

im on 25/81 on a tekin 7.5

[V-Rossi]

Originally Posted by Medders

Still can't get my head around the 26/78 . Could you fry an egg on that motor after the race?

Depends on the motor you're using and your driving style, the LRP X12 for example gets very hot, a friend of mine had 95°C with 24/78 after a 6 min. final. My CS 7,5T on 24/78 never gets over 50° C, even after 10 min. of driving.

[Mike Hudson]

24/78 is completely perfect 26/78 sounds abit hot to me thats what i run for a 8.5!

[V-Rossi]

Originally Posted by Mike Hudson

24/78 is completely perfect 26/78 sounds abit hot to me thats what i run for a 8.5!

One of the X-Factory team drivers was using 28/78 on a 5,5T X11 motor at an indoor track during our first national of the year

[Mike Hudson]

which xfac driver was that and where? Didn't know indoor nationals existed!

[V-Rossi]

S. Mesker during the Belgian and Dutch indoor national @ Charleroi. He won every qualifier and final though

[charles08]

Hi,

A bit off topic but i see that some people are using the GTB with other motors such as LRP.
I bought a second hand GTB and tried it with a LRP X11 6,5 and it "stutter" or has some cogging issues .
Do you guys do something special like change the timing on the motor ?
What is your original timing , 2, 3, ?
I've tried it with a speed passion 9,5 and it seems ok ....

HELP !!!!

[jcb]

Ran my orion 7.5 on 26/78, with a orion 3800 race LiPo. That was outside round Stotfold, for indoors on a flat astro track I have been running 24/78 with it only just getting warm after 5 mins of racing.

[Medders]

Right, this thread has really opened my eyes, time to buy some larger pinions

As for cogging, your 6.5 turn will be drawing much more current than your 9.5. Try gearing it down, check all your connection are well soldered and your wires aren't overly long, failing that if could be your cells if they are old/duff.