View Full Version : Fdr Help???

26-02-2008, 12:50 PM

Could someone please help me sort this little equation - i am being recommended to use a FDR of 5.9 at my track with my current setup. Now my problem is which way would you go about getting to it i.e. if you look at gearchart.com you can use different pinions and spurs to get there? Which is the best way to get to the FDR and why???

Many thanks in advance!

26-02-2008, 01:28 PM
I've assumed its a cyclone.

100spur, 41 pinion would work


5.9 fdr divide by internal ratio (2.4375) = 2.42
spur size - 100 (standard spur) divided by 2.42 from above = 41 pinion.

26-02-2008, 03:28 PM
Ok thanks but why would you go 100/41 when you can get to 5.9 using diff spur and pinion too? such as 102/42 or 97/40 they all come out about 5.9 ??? whats the difference and advantages/disadvantages please?

26-02-2008, 03:38 PM
I went 100/41 as that is the standard spur, so you would already have it.

There are a few advantages to doing it different ways, such as motor position, and apparently a bigger spur will give more efficiency (i think thats right). I suppose a bigger spur is lighter than a bigger pinion too.

Personally, if I needed 5.9, I would use the combo i first mentioned, as I have pinions from 32 to 52 so that pinion is right in the middle and would give me plenty of adjustment either way if needed.