Dark Impact Gearing Help

[max_crox]

Hi there,

I have a dark impact and Im stuggling to find the correct gearing for it. I'm running a 12 and 13 double with Tamiya 0.5 module pinions and spurs.

Can any one suggest a pinion and Spur combination for me for a tight and twisty track like Kidderminster?

Cheers.
Mark

[max_crox]

Any one?.......

Mark

[jimmy]

I dont suppose you know the internal ratio of this car do you mate?

[max_crox]

Well... using this formula

Overall Drive Train Ratio = (# teeth on spur gear / # teeth on pinion gear) x Tranny Gear Ratio

and using a 78 spur and a 26 pinion the manual says it gives a overall gear ration of 9.17:1

So Ive worked it out that the internal gear box ration is 3.05:1.

Plugging this back into the formula gives a Overall ration of 9.15:1 so I think its right.

and who says you'll never use A-Level maths again (actually I think that was more GCSE level )

Mark

[jimmy]

I didn't see that ratio in the manual, but then I didn't finish building the car yet! haha

I installed the 85t spur when building because the kit gearing is for the kit 540 motor. Even with the larger spur I thought it might be a little over geared so something smaller than the kit pinion might be in order.

I'm not really the best person to advise since I have the gearbox built and thats about it..

[DCM]

I would guess, trying a 24tooth first and working up, the biggest hangup for the car, is heat build up on the motor.

[Elliott Hopkins]

Normally I'd be all over this thread, BUT I don't think I should comment as I'm only bashing with SPEC motors.

I have an Excel gear chart and graph if you are interested.

The kit pinion and larger white kit spur will give you a final drive of 10.00. It will fit with a little extra dremeling.

I think I'm running a kit pinion (26t) and the black slipper spur to give me a ratio of 9.64, but it's not as fun as the 25t pnion, final drive 10.02.

Elliott.

[max_crox]

Cheers Guys,

Jimmy - just underneath where it states what pinion you need (column on the left it states what ratio it give.

I can get it geared right for my 19T (I think I used 25 or 26 with 82T) but I had a 12 double and now a 13 double and it doesn’t seem to be working right.

I took it out on the street a couple of days ago with the 13 Double in it with 23/85 (the lowest kit gearing possible) and it seems that that was a bit over geared as it only lasted about 3 mins before it stated to die (stated to low and I would loose steering when on full power), and that’s on-road, so no way would it be able to last in a race. I don’t think its the batteries as they are new IB4200's the motor was new and run in, the ESC is not new (LRP Quantum
Pro Sport - 7T limit) but should be ok for the job. I checked the gearboxes and they don’t seem to be binding so the only think I can think it is, is the gearing.

I have got the lower tooth pinions (down to 17t i think) in the 0.5 module but I was thinking that this might be too low?

The manual that came with my motor suggested that for off road the gearing should be 10.4:1. I tried this at Kiddy (24/82), the first lap was great but by the 3rd lap it was getting slower and by the 5 I had to stop as I was loosing stearing. Which I think is a sign of too much battery drain. When I did stop there was smoke/steam coming from the motor.

So..... Does the symptoms sound like over gearing or could it be something more sinister and expensive?

Cheers

Mark

[max_crox]

Originally Posted by Elliott Hopkins

Normally I'd be all over this thread, BUT I don't think I should comment as I'm only bashing with SPEC motors.

I have an Excel gear chart and graph if you are interested.

The kit pinion and larger white kit spur will give you a final drive of 10.00. It will fit with a little extra dremeling.

I think I'm running a kit pinion (26t) and the black slipper spur to give me a ratio of 9.64, but it's not as fun as the 25t pnion, final drive 10.02.

Elliott.

Yeah I have already had the dremel out cutting the mounting slots longer so I can use the smaller pinion which I was told you need to do.

I know the car can fly as there was another one at the Kiddy MAM im just kicking myself now for not asking the guy what gearing he was using! Doh!!

I might just try the std silver can with the kit gearing to see what its like...

Mark

[Elliott Hopkins]

We're runnning the same gearing for SPEC motors then.

Did you get the Super Astute pinions?

Elliott.

[max_crox]

Originally Posted by Elliott Hopkins

We're runnning the same gearing for SPEC motors then.

Did you get the Super Astute pinions?

Elliott.

Yeah I got them of ebay but I havent used them yet as I though it might make it too under geared but Im thinking I may be wrong....

Mark

[Elliott Hopkins]

Don't forget the wheels and tyres are bigger than average too and the back ones are heavy (I weighed them to compare).

Probably doesn't make that much difference.

Elliott.

[DCM]

I will confess, when I first bought it and run it, I thought I had checked in an Integy Stock motor in it, but in my hurry, it was an 11x3 and it lasted 5 mins no problems at all, even with the kit tyres on a tight grass track.

[max_crox]

Originally Posted by DCM

I will confess, when I first bought it and run it, I thought I had checked in an Integy Stock motor in it, but in my hurry, it was an 11x3 and it lasted 5 mins no problems at all, even with the kit tyres on a tight grass track.

Hummmm... was that with the stock gearing from the manual as well?

Mark

[DCM]

Yes, hence the thinking I put a stock in there.

What gear are you using, maybe there is an issue somewhere, causing the problem.

[darryl]

using an 11x2 on saturday night with the large spur and a 23 tooth pinionthe fimal ratio was around 11 that iswhat richard isherwood reccomened it was a little under geared so next is a 25 tooth which gives final drive of around 10.39,and the car had no probs with five minutes plus 2 practice laps

[jimmy]

You still running the 48dp pinions with the kit spur darryl?

[max_crox]

Originally Posted by darryl

using an 11x2 on saturday night with the large spur and a 23 tooth pinionthe fimal ratio was around 11 that iswhat richard isherwood reccomened it was a little under geared so next is a 25 tooth which gives final drive of around 10.39,and the car had no probs with five minutes plus 2 practice laps

Umm Thats what I started off with and its was a no go... I'll do a strip down and rebuild and see if I can find any gearbox issues.

Cheers

Mark

[Eotz]

Hi.

In this link from tamiyaclub one guy speack about the Super Astute pinions and show a complete chart about the gearing until the 20T pinion. I think that is easy to calculate the ratio for the 18T and 19T pinions using this chart as reference.

http://www.tamiyaclub.com/showroom_m...53812&id=17039

Anyway I take this pinions until te 18T. I hope this helps.

Bye.

[darryl]

Originally Posted by jimmy

You still running the 48dp pinions with the kit spur darryl?

still tryin to get hold of the tamiya pinions as as you heard its a little on the noisy side using 48dp,but no damage to the spur gear which is quite fortunate