cmross13

iTrader: (17)

im looking for some reliable all-in-one info on the aforementioned topic. i am admittedly a newb, and i'm trying to learn as much as i can about this stuff. since setup is required to get the info im looking for, here's mine:

xxx-sct, 2.43:1 trans ratio
88t spur, 23t pinion, 3.83 "final drive"
orion vortex pro stock 13.5 & hobbywing SCT pro, 2s lipo
can timing is zero, esc timing is maxed out at 26.25°
TLR motor plate if it matters, otherwise no fan/heatsink on motor, no air holes in body, etc
track has a 400ish ft centerline, with a 90-100ft straight. im running 25s fast laps and averaging 28s(again, im a newb lol)

with that out of the way, here is where i am at: after about 15-20 solid minutes of running, i am thermaling out. i use this truck exclusively for racing, no speed runs, no parking lot bashing, no grass, etc. so after 15-20 minutes of practice, my motor is burning hot(waiting for FedEx to bring my temp gun), but the esc & packs are ambient temperature. my ESC shuts it down, i let it sit for 20 minutes.

I've been reading online and have found most people agree that hot motor + cool esc = over geared. someone said the reason the motor is hot is because the motor is running at its max rpm for too long, which causes the motor to heat up but since its not drawing much current the esc is staying cool.

I've been told i should go down a tooth or two on the pinion to keep the motor temps down.

here are my questions:

am i just bring overly cautious? 15-20 minutes of racing would heat up anything, right?

if going down 1-2 teeth on the pinion would raise my final drive, wouldn't that bring my max RPM up quicker and keep them there longer? how would that cool down the motor? the full scale racer in me tells me i need to go up a tooth or two, broadening my powerband and hitting max RPM at the end of the straight

perhaps the 26° of timing is the culprit? open up a little timing on the can and turn down the timing on the esc? dump the 13.5 altogether and install a 9.5 and just learn how to harness the power?

comments?

i'm a mess lol

Hotbodiesd4

Hey mate, most of our trucks are geared to run a 6min race so we don't run for that long. you should gear for corner speed but you want it so its still competitive down the straight. Run your truck for your race time (normal 6min) then check the temp. If its running cold (under 75 degrees Celsius) and your happy with your top end speed and corner then bingo you have you ideal gearing =)

RC_nooberton

iTrader: (4)

Hey bro I'm a noob too but I quickly found out that adding a lot of timing will raise your temps a lot. I melted plastic spur gears a couple of times after just a short practice runs because my timing was set too high I was shocked at how hot the motor got in just a short amount of time when I cranked up my ESC timing.

justpoet

iTrader: (16)

Dangit, I had a nice thing written up and then rctech ate it. Here goes again.

There are 4 main things that will cause you heat:
1) binding in the driveline (including gear mesh and bearings)
2) too small a pinion
3) too large a pinion
4) too much timing

If you have a lot of timing on the motor can, cut it in half and then proceed. If you have a lot of timing on the esc, cut it in half and only have it kick in at high RPM, rather than a broad range, so you only get it at top speed.

Once you do the above...
If you find yourself on full throttle most of the time, and more than 1/4 of the straight has you at full speed, you probably need a larger pinion.
If you find yourself never at full throttle except the straight, and you don't get up to full speed until near the end, you probably need a smaller pinion.

Most normal can style motors like yours will run well around 160° F. I tend to gear and set up my cars so that I run around 150°, which allows me to just go pack after pack and not go above 160, but there can be a slight performance tradeoff in a race to do that. I'd rather be able to run forever though and not worry about it.

Generally the ESC heats up more when the motor is under heavy load (high amp draw due to hard acceleration and braking) and partial throttle with speed changes, while the motor will heat up more from being at high rpm or having more timing. That's not a rule though, and your temp gun will help you a lot in figuring out what to do.

cmross13

iTrader: (17)

I don't exactly know when I'm at full speed on the straight, but I'm willing to guess its before the halfway point. I was thinking of going up a tooth or two on the pinion to get a higher top speed but I don't know if my wimpy 13.5 can afford the loss in acceleration. I am currently winning my heats in my class with the truck exactly as is, so maybe I just need to limit my runs to 12 minutes.

Then again, perhaps I could go up one on the pinion or drop two on the spur, slightly crank up the timing on the can to make up for the loss in acceleration, and just keep my run times limited to 10-12 minutes. Maybe that would allow me to bump up to the "A" class with the same motor. Those guys are running 10.5t or better, but my current average laps are in the middle of their range.

Dave H

I don’t have the answer, but some thoughts occur while reading your post that may (or may not ) help, as you mentioned you want to learn as much as possible.

Going by your quotes, perhaps you already realize this, but when folks mention Final Drive Ratio / FDR, it’s the entire drive reduction ratio, 2.48 x 3.83, or around 9.3 FDR.

Can timing at zero, do you mean you haven’t adjusted it, or you moved it to a zero marking? This can be confusing, as brands differ, and I’m not familiar with how that brand is set up. But 13.5 generally likes some timing, say 20~30 degrees or so (Possibly some less timing for lower winds). If by chance you reduced it, suggest going back to the factory setting unless you’ve done some testing to support.

I have the similar Speed Passion ESCs, I most always run the 26° timing with 13.5-17.5, never seemed to be a heat problem even with 10.5 (at least with lighter stadium trucks and buggies).

A note of caution, getting the motor hot will reduce the rotor magnetism, which will both reduce power and make the motor run even hotter. If not overdone it can be fixed with a new rotor. Don’t think you’re there yet based on your later post, just be aware.

I’ve never seen much ESC heat with a 13.5, especially unboosted. Don't think 13.5 uses enough amps to generate much current heat, and doesn’t spin fast enough to generate a lot of switching heat.

Could be. If geared to be competitive for typical race heats really long runs can be a problem. Especially with the heavier weight of a short course. Gets worse with lower wind motors, at least some of the big mod guys time limit their practice heats.

Can work both ways with brushless. From what little I know about short course I think you are in the ballpark gearing wise. Need to get that temp gun, some pinions, and test away.

I wouldn’t add can timing unless you turned it down . At least not without the gun and testing (and you are willing to limit practice run time for a little more performance).

If you’re driving well a 9.5 might make you faster, but sure won’t solve your temp and run time concerns! Kudos on thinking 9.5 or maybe 10.5, jumping any farther at once is a mistake for most folks.

Lol, don’t expect that to change much. I’ve seen the best and most experienced fret over motor setup. Just enjoy the journey… Good luck and hope this helps more than adds to the confusion.

cmross13

iTrader: (17)

i wasn't sure what to call it, but in full scale vehicles your final drive is your ring & pinion gear, which i figured here the closest thing to a R&P was spur/pinion ratio. thanks for that tho


when i got the motor(lightly used by a carpet racer) the can timing was one notch off from the larger center mark. i thought maybe that was causing my temps so i put it on center. at the same time, assuming a loss in power from moving timing, i cranked up the esc timing all the way


never had a heat problem in the motor or in the ESC? again, my ESC is staying around ambeint temp, no heat at all

hopefully my ESC thermal protection has been keeping it in check. temp gun should be here this week


could you explain "unboosted"? i thought "boost" referred to timing, of which im running the level 8 26.25°


this is exceptionally confusing to me lol. i asked the local track guru if going up a tooth or two on the pinion would have a drastic loss in torque, he said something similar with "you might pick up some torque". while theoretically impossible, i could see it seemingly increasing torque because the motor uses the available torque a little longer

if its going to keep me on the podium and get my laps down into the 26-27s range, im willing to limit my practice runs to 10 minutes. during fridays race with a new track surface and slight alteration to its layout(basically new to everybody involved) my lap average was low 29s in the "c" or "beginner" class, while the top 3 in the "a" class(with guys using 10.5 or faster) were averaging 26-28s. my fast laps were about 1s off from the fastest 2wd sc guys there(and around 4s off from the fastest 2wd buggy buggy guys lol). i need to get into the 26-27s range but i'm not sure a hotter motor is the ticket for me right now. admittedly, i don't think i could handle all the extra power.


thanks a lot for the reply

Dave H

Makes sense… but wait that’s backwards in order… oh drat me head hurts again.
Would be better if we called it Overall or something, is rather silly eh?

Not much to either in my experience with higher winds like a 13.5, but mostly the motor, maybe a tooth worth or so. Mostly seems to shift the powerband some, I haven’t even changed it in ages, even with 8.5/10.5.

As far as I know the standard timing you have is a static timing, always the same.

Boosted refers to a software trick, dynamic, or ramping, timing advance. The timing is varied by RPM to optimize power across the RPM band and increase the band even. Low timing at low RPM so it doesn't bog and burn up, then progressively more as it winds up, achieving much higher RPMs. Then terms like turbo or supercharger are used for even more advance after a time at full throttle for the blast down the longer straights. Typically, but not always, involves a downloaded update to the firmware. Makes a “stock” 17.5 motor dramatically faster, in some ways nearly the equal of a modified. Use lower gearing, as the peak motor RPMs go way up.

Has recently been outlawed for most stock class racing, to get stock back to where it should be, slower than modified. It’s also commonly called “blinky”, as ROAR requires the ESC to display a particular light blinking pattern for an approved stock no timing ESC for teching purposes. Not even the static timing we are discussing is allowed. Still allowed to crank the motor endbell though, a topic of some discussion.

For reference the approved list, see the Notes:

ROAR Approved Non-Timing ESC

Yes, very understandable reaction. But it’s not a static mechanics problem. Brushless motors with good lipo batteries are capable of incredible power for short bursts, but need to be loaded up to generate it. Geared medium the car simply accelerates away without generating the big power. Gear them up, and they just keep pulling, well at least until we overdo it and burn them up anyway (or get them hot and fade during the run). Did we mention getting a temp gun yet?

Wise to proceed with some caution, work on those lines and general car setup. (and get a buggy, the nimbleness is cool)

Always glad to help where I can.

cmross13

iTrader: (17)

thanks for the timing and boosted explanation. im pretty sure i've seen a "boosted" firmware somewhere for the 60a and 120a hobbywing V2/2.1 escs, but not for the sct pro that im currently using.

i found the motor manual on horizons website and it says my final gear ratio should be somewhere in the neighborhood of 8.5:1. with the 88/23 and 2.43 trans, i was somewhere in the 9.30:1 range. maybe it wasn't loading the motor enough to get the strongest power out of it? i just so happened to have an 84t spur, so i popped it in for a closer 8.87:1. i also cranked 7.2° of can timing in, and i dropped the esc timing down to 22.50°. we'll see how it does on the track this week and see what my fast/avg laps are and how its doing with heat, go from there with timing and gearing.

as for the 2wd buggys, not for me just yet. i have the coordination and reaction needed for it, i just don't think i can handle the power of the 7.5t motors these guys are running. theres probably only two months left in the season so i'm going to do the best i can with what i have, try to hone my driving skills before i change or upgrade the chassis.

also, i'm looking to run 17.5 1/12 in the winter. there is an indoor track an hour away so if i can master that, it should be a huge advantage next year in off-road, maybe i will hop up to a mod buggy

cmross13

iTrader: (17)

well i went to the track for some more practice, and the 84/23 combo is worse than it was before. its faster, but still has issues. also, the motor is still getting uber hot, the esc and battery staying ambient temps. also, it WAS a little muddy, so i'm sure the heavy tires and added weight weren't helping. i took notes:

84/23, 7.2° on can, 22.5° in ESC starts cogging bad after around 7 minutes. once i get it up to speed, it seems to run fine but with a loss in power. wont start out up hill on its own

84/23, 0.0° on can, 18.75° in esc same results

84/23 0.0° on can, 15.00° in esc same results

was running a little slower before at 88/23 0.0° on can, 26.25° in esc, but lasting at least twice as long before it would start to get quirky. again, Orion says i should be around 8.50:1. with 84/23 im at 8.87. when it was 88/23 i was at 9.30, unless im wrong and my xxx-cr trans ISN'T 2.43:12

i really need some advice here

cmross13

iTrader: (17)

went back to the 88/23 due to lack of options and came in 2nd in the A-Main, averaging <1s behind the lead truck(running a 10.5t IIRC). also had the fastest lap of the day, almost 0.5s faster than the 1st place truck(again, 10.5t i think).

8 or ten minute a-main, no cogging, no heat issues

cmross13

iTrader: (17)

bought a revtech 10.5 on someone on here today, can anybody tell me if the gearing thing is pretty much universal? ie: most 13.5s like around an 8.5:1 final, most 10.5's like 9.5:1, etc? my temp gun & motor should be here Thursday, along with a fresh set of Holeshots & a 6 pack of pinions, but i cant find any gearing support on Trinitys website.

Dave H

Gearing can change slightly brand to brand, partially because of different amounts of built in endbell timing. Sorry I can't comment on that exact pair, no direct experience. But I think your starting thoughts, going up 1 in FDR, as a reasonable start, just check temps as you go.