Pinion Size

[J-Lo]

Hi

I have an Schumacher Mi1 with a 13.5t brushless setup with the stock 86t spur fitted. I am intending to race it around an indoor tight track (carpet) and have no ides which pinion(s) would be best suited. I would be grateful for any advice.

I have noticed that there are different 'DP's what does this mean??

Thanks.

J-lo

[sosidge]

*rant mode on* Gearing a brushless motor has become insanely complicated due to the over-complicated timing adjustments on the ESC and motors. Blinky software and fixed motor timing is the only way that on-road will get out of the hole it is digging for itself *rant mode off*

Tell us what motor and esc you are using (as well as the software and motor timing settings) and we might, possibly be able to give you a gear ratio.

DP is the pitch of the gear (size of the teeth), naturally only gears of the same pitch will mesh together, so if you have a 48dp spur (likely, judging by the size), you need 48dp pinions to mesh with it.

[J-Lo]

Hi, Thanks for the reply.
It will most probably be the Fusion Exceed 13.5 combo. I am not going to be getting into motor timings etc (seems too complicated).I also have a Hobbyking 60a sensored/sensorless ESC and a Hobbyking X-Car 13.5t sensored motor.
I am not sure which one to install.

Thanks.

J-Lo

[sosidge]

The equipment you mention is not common racing gear and I can't offer very firm advice. Perhaps someone else has more experience with them.

What I can say is that racing-spec 13.5 system with "blinky" zero timing software and a zero-timed motor should be safe to gear at 5:1 overall on a big track and 6:1 overall on a small track. Adjust from there.

[J-Lo]

Thanks for the advice. I have something to go on with now...
It's a small tight track, so will start with the 6:1 ratio.
Thanks again

[Mad-Wolfie]

personally for tight tracks i would opt for a ratio of around 7-or-low 8's (smaller pinion) rather than 6;1 to give you better acceleration. 6 would suit outdoor tracks better & if you run a bigger pinion you are gearing for top speed more than acceleration so the motor will be working harder & get very hot (which causes damage to the motor & can affect performance) or even themal out your ESC. A lot of people are actually making gearing changes based on motor temperature, hence why this is one of the reasons you often see people using temp sensors straight after a run & pointing them at the motor.

The golden rule is you want to try to reach top speed before the end of the straight just before you need to back off or hit the brakes & the motor should not be so hot that when you touch it you end up burning your fingers & you can actually hold your hand on it.

[J-Lo]

Thanks for the advice. I am going to try a 22T pinion which should bring the ratio to 7.04.
Will keep an eye on the motor temp too.
Cheers.

[Sumilidon]

I'm trying to find out the same thing, cannot get my head around the gearing calculations and how certain gearing ratios relate to actual performance.

[J-Lo]

It is really confusing! I think the main issue is making sure you get the right set up for the type of track and ensuring that the motor doesn't get too hot.

[qatmix]

Gearing is quite simple.

The higher the ratio = faster acceleration
The lower the ratio = Higher top end, slower acceleration.

Your car will have something called an internal ratio.

this is the diff pulley divided by the centre pulley (the centre pulley is the one that is on the same shaft as your spur gear, and rotates when you rotate your spur gear.

To find your ratio, you just divide your Spur gear by your pinion and then times it by your I.R.

(DR)*(IR)=FDR

So for example, on a tight indoor circuit with my non timed 13.5t TRF417 this is how I would calculate it

TRF417 details -
Spur =111t
Pinion 38t
Diff pulley = 37t
Centre Pulley 19t

So I do the sum
(111/38) * (37/19) to get my FDR which is 5.687

the working would be

DR = (111/38) = 2.921
IR = (37/19) = 1.947

2.921*1.947 = 5.687

So if you ask about at your local club you will find a general ratio people use so you can range your pinion or spur to get in the same sort of ball park. As has already been mentioned, you want to get to top speed 3/4 the way down the longest straight or if its a small tight track you want that to be more like 1/2 - 3/4 down the straight as these tracks are more about the infield.

[J-Lo]

Although it looks complicated, I now have a grasp on how to calculate it (I think!) I will try it out tonight and see where I get.
Thank you for your help.

[Mad-Wolfie]

so long as you know the internal ratio of the car, then the easiest thing to do would be to go to gearchart.com & print off a chart to use as a crib sheet. the MI1 should be already listed on the site as a Schumacher mission which should be the exact same ratio.

Although (not sure if this would be relevant) i do remember from my Mi2 days the car had 2 gearing configurations due to an option of using a 20 & a 17 layshaft pulley which does affect the internal ratio.. as the Mi2, was a newer / improved version of the Mi1 / Mission, i'm not sure if it uses the same layshaft arrangement as i've never owned an Mi1 or studied the manual enough to know how it works. The general feeling with the Mi2 was on 48dp run (the standard gearing) go with the 20t pulley, but if switching to 64dp spurs/ pinions, then fit the 17 to give you more fine choice of ratio's.

[J-Lo]

Thanks for the advice. Tried a 22T pinion and it worked well. Enough speed for a novice like me to get enough experience around the track without slamming into the track sides!