Gearing question

[jimny82]

Hi, in my Schumacher Cougar SV2 I'm currently running 8.5T motor with gearing set to 83/23 or 24 pinion (can't remember which). If I switched to a 76/28 or 30 set up, I understand that I will loose a bit of acceleration and gain a bit of top speed, but does anyone know if this will be quite drastic or just a slight change?
Thanks

[chrispattinson]

Moving from 83 / 23 to 76 / 28 is a drastic change.
You effectively have a delta of 7 pinion teeth. If keeping the same motor, I have never had a delta of more than 3 pinion teeth.

[mattr]

It'll be a massive change, and you may cook your electronics.

Though i can't understand why you'd want to, an 8.5 in a car like that shouldn't run out of speed anywhere reasonable. Or are you trying to blunt the acceleration for some more control?

[jimny82]

Hi Chris. Ok thanks. If I'm looking for bit more top end speed and not so crazy acceleration (as it is at the moment), is there a gearing ratio you would recommend me trying?
Thanks
James

[jimny82]

Hi Matt, yes ideally blunten the acceleration a bit, as it seem quite 'skitty' having such punchy acceleration at the moment, as can be hard to control. But maybe its just my driving needs improving :)

[mattr]

Thought that might be the case ;)

Few suggestions:-
Turn all the toys off, no boost, no timing, no nothing. Just run the motor as is. Even remove the physical timing on the endbell.

You may even have some limitations available in your ESC to restrict power on start up (current limit IIRC)

Play with transmitter settings. You can either cut off the top 20/30/40% of the throttle (EPA) or change the response, think it's called curve on mine (may be exponential). Means that 50% trigger is only equivalent to 30% throttle, sort of. Blunts the initial kick off the line. You'll still get full speed with exponential/curve, but lose a tiny bit with EPA.

Slower motor (maybe 10.5) then as you get better turn the timing and boost up, you should be able to get almost back to 8.5 performance eventually, then pop your original motor back in and start turning the wick again.
You can probably find second hand or cheap motors for 30 quid. Hobbyking/club/eBay would be good places to start.

If motor temps are ok now, i'd not be doing much on the ratio front, maybe a tooth up/down on the pinion, or 3 each way on the spur. At most.

[chrispattinson]

I've been looking through my setup sheets, and with a Thunder Power 8.5, I would run a 25/76 when used, so thats quite a move away from where you are at.

Your gearing needs may vary considering track, and motor specifics.

You can see gear charts on page 42 of your manual. If you dont have a manual, you can see a pdf of it here:

http://www.racing-cars.com/images/Technical_Info/Schumacher/Current%20Cars/Cougar%20SV2/Instruction%20Manual/Cougar_sv2_manual.pdf

[jimny82]

The crazy thing is that since unboxing the (Speed Passion V3) motor and ESC I haven't even touched the tuning gizmo that comes with it, so I think I'm running it as standard already lol. Excuse my ignorance but I don't know what the physical timing on the endbell is. I've just come back into the hobby/sport from a ten year gap where I was used to brushed motors and NiCad batteries :lol:, so the power delivery of these new set-ups is quite an eye opener :woot:.
To be fair I have been running on quite a lose surface, so I think I need to get down to my local astro track where I should get a lot more grip, and I may find I can control the acceleration better.
Does the 83/23 or 24 gearing sound about right for average driving style/capability?
Thanks for your help and knowledge Matt! :thumbsup:

[jimny82]

Thanks. So if my motors running a little hotter than I think it should be (not much I don't think), and if I stick with the standard 83 kit spur, should I be putting a bigger or smaller pinion on to allow a little cooling? I think the max this spur can fit is 25t.

[mattr]

IIRC the standard/factory settings on that ESC add timing and boost in (DRRS or DDRS i think it's called.) Think mine defaults to setting 5.
But it possibly depends what firmware you have on the ESC.

Also, the endbell of the motor has a slot at the bottom. If you loosen the 3 screws on the front (slightly) you can adjust physical timing to 0 in the slot. (then retighten the screws)
Think stock might be 5 degrees.

http://rchobbymart.com/image/cache/data/frontBell/201043013618SP1EB02-800x500.jpg

[mattr]

And don't worry, i can back to RC after a 25+ year break!

BTW, only really reliable to measure motor and ESC temp is with an IR gun. Using your thumb isn't much use, as anything over about 60 degrees is pretty much too hot to distinguish. And most ESCs/motors will be usable (but not too happy) up to 80/90 degrees. Some (not the speed passion stuff you have) will hit 100+ without damage.

(One of my ESCs is rated to 120 or 130 degrees on the cooling plate! Certainly don't want to test that with your thumb......)

[jimny82]

Haha, yes my thumb is probably not the best thermometer ;)
Yes I do seem to remember twisting the cap slightly on my old brushed motors now I think about it.
Will reducing the timing essentially soften the motor output a bit?
I really appreciate you help Matt & Chris, thanks very much.:thumbsup:
Regards
James

[mattr]

Yes, reducing timing will soften everything down a bit.

[Monkeysmate]

Just to reiterate the point made earlier... Out of the box the SP stuff is not set to "zero" as it where. It's set quite punchy as I recall, so you should strip all that off too.
Can't remember which way round it is, but you can leave it with Zero timing, and then boost it after a present time delay on full throttle on them ESC can't you? To make it more manageable on the Infield, but give it some poke on the straight??

[jimny82]

Ah ok I see. No I don't think the motor timing is set to zero out of the box, I think its set mid-way. I haven't actually plugged the tuning gizmo in yet either to see what it's capable of adjusting regarding the ESC (probably afraid I wont understand what I'm doing lol), but it might be worth me giving it a go. It sounds like I've got some experimenting to do on the electronics. :wtf::confused:

[Monkeysmate]

Yeh. You need to get the programme box hooked up. It's dead easy.
Don't get confused between mechanical and electronic timing. Mechanical timing is on the motor bell as described. Electronic timing is an electronic way of producing a similarly effect done within the ESC, and changed using the programme box.
Just hook the box up and set ddrs to 1, and turbo and timing to zero.
Give it a go and see what it's like...

[jimny82]

Ok I will do, thanks!!

[dodgydiy]

before changing anything else, gear it properly. 24 or 25 tooth on a 76 spur, as said earlier works out about the same ratio as i use with a speed passion 8.5 in my 2wd.

gearing up will gain both torque and speed but make it a bit smoother. less timing will add more torque and take away top speed, more timing can take away torque, smoothing acceleration and gain top speed but everything runs hotter and less efficiently

[jimny82]

Can anyone explain why I might cook my electronics changing from a 23/83 to a 25/76 ratio. I don't really understand the 'delta' of toot difference, but just thought the motor & ESC would be able to handle either ratio, and it would just be the power delivery that would be affected?

[MiCk B.]

Can anyone explain why I might cook my electronics changing from a 23/83 to a 25/76 ratio. I don't really understand the 'delta' of toot difference, but just thought the motor & ESC would be able to handle either ratio, and it would just be the power delivery that would be affected?

Hi,

Have a look at a gear ratio chart for the car you are running. There is a serious difference between the two ratios you have above.

Assume internal gearbox ratio is 2.6:1, but check for the car you are running.

23/83 overall is 9.3
25/76 overall is 7.8

The difference between then is far too much, to be usable on the same motor.

(9.3 is gearing for 7.5t motor, 7.8 is gearing for 10.5t motor.)


If your gearing is in the right area, try a pinion up or down and see how the car reacts.
So in the above going to 24/83, which will give more top speed, your overall is now 9.0

MiCk B. :-)

[jimny82]

Hi Mick, Thanks for the info. I'm currently running a standard internal ratio of 2.58.1. I don't think my gearing is in the right area at the moment for my 8.5T motor, as my top speed seem far too low.

When you refer to the ''overall ratio'' to be 9.3 & 7.8, is this what some call the final drive ratio?

So if that overall 9.3 is for a 7.5t & 7.8 is for a 10.5t (im assuming this is approximate and not exact), how can I find out what will be best for a 8.5t motor? Am I judging this purely on how the electronics handle things, i.e don't get too hot? Overall/final drive ratio of 8.5 would be somewhere in the middle of the above, and then I could just play around with a pinion one or two teeth either way to see what works best(?).

Or I may have completely misunderstood this lol

[mattr]

Can anyone explain why I might cook my electronics changing from a 23/83 to a 25/76 ratio. I don't really understand the 'delta' of toot difference, but just thought the motor & ESC would be able to handle either ratio, and it would just be the power delivery that would be affected?There is a sweet spot for ESC and motor related to load and speed. You get too far one way or the other you'll either cook the motor, or the ESC, as you'll be stressing them. (Too fast/low load, too slow/high load)

Most combos will handle some variation. But you're looking as a massive change, the sort of change you'd see going from something like 8.5T to 13.5T motors........

The proper way to change punch and speed is to get the motor/ESC at the right ratio for the car/motor then to play around with things like EPA, punch, current limits. And others. You can probably get a 8.5T motor to behave like a 13.5T, or a 5.5T by playing with settings (with certain limitations of course!)

[jimny82]

I've been looking through my setup sheets, and with a Thunder Power 8.5, I would run a 25/76 when used, so thats quite a move away from where you are at.



So can anyone explain why I couldn't run this gearing ratio (without cooking my electronics) with my speed passion 8.5 if its worked for others?

I don't think the combo's you buy come with recommended ratio limits stated on them.

[mattr]

It's generally the cars that come with the gear charts. And it's not that you can't run them way out of ratio, it's just that most drivers with most motors will find the best trade off between heat, acceleration, top speed, battery life etc with that ratio. A couple of teeth either side on pinion/spur won't hurt, depending on how you drive. But a huge change might.

FWIW i managed on my 2wd for a long time with (almost) stock set up, bang in the middle of the recommended ratio. Gave the car to a mate who is a *far* better driver, he cooked the motor (thermal cut out) as he was able to be "on power" for far more of the track than me. Added about 30 degrees to the hottest i'd ever seen.

[jimny82]

Ah right ok, I see what you mean now Matt. Thanks for your help :thumbsup: