3660 4200kv 80a Brushless Combo. Asking for Trouble?

[bigbristv]

I'm currently running a 3650 3900kv 60a combo in my Senton 4x4 and was thinking of going with the 3660 size motor and found this combo at a reasonable price but there are no reviews on it.

I know there are better brand options out there but my question is: since it seems a longer can [motor size] should deliver more torque (3650 vs 3660), and the larger kv (3900 vs 4200) should spin faster, and they're selling it with an 80a esc (which looks like the 60a I'm running now without problems) this should theoretically make the truck run faster, right?

I get the slightest bit of cogging with a 23t pinion (48 mod setup) and have reached 48.7mph so far on 3s.

Am I bugging here? (Sorry for teh maffs)

 

[ahr43]

Hey bigbristv. Pretty much the route I'm going with my Senton 4x2. Presently powering it also with a 3650 can x 4000Kv. It's a bit down on torque. Coming on order is a 3660 can x 3700Kv. No problem fitting it physically. May I suggest installing the Boost 3S power module if you don't have one? I'll be upgrading to that along with the 3660/3700. Good luck. Cheers. 'AC'

Boost 3S Power Module

 

[bigbristv]

Hey bigbristv. Pretty much the route I'm going with my Senton 4x2. Presently powering it also with a 3650 can x 4000Kv. It's a bit down on torque. Coming on order is a 3660 can x 3700Kv. No problem fitting it physically. May I suggest installing the Boost 3S power module if you don't have one? I'll be upgrading to that along with the 3660/3700. Good luck. Cheers. 'AC'

Boost 3S Power Module

I decided to skip the power mod because I hear the aluminum can bend and stay bent.

I just took my rig out trying to blow it up and the only thing that happened is the esc got hot enough to loosen the double sided tape and go dangling. Not sure if it was a crash that helped dislodge it but the fan stopped so that may be why it was so hot.

I know going up to the 3660 will immediately provide more torque but I'm wondering if the higher kv would just cancel it out.

I guess there's only 1 way to...

Hey bigbristv. Pretty much the route I'm going with my Senton 4x2. Presently powering it also with a 3650 can x 4000Kv. It's a bit down on torque. Coming on order is a 3660 can x 3700Kv. No problem fitting it physically. May I suggest installing the Boost 3S power module if you don't have one? I'll be upgrading to that along with the 3660/3700. Good luck. Cheers. 'AC'

Boost 3S Power Module

AC, what pinion are you running? Have you speed tested yet?

 

[ahr43]

Regarding the aluminum motor plate bending: Yeah, I've read that. I want the 32P stronger gear over the 48P standard. My plan is to support the outer end of the 3660 can with a neoprene pad to take the bend leverage off the motor plate. My runs are flat and straight - drag racing and speed runs. So there will be no impact loads on the motor plate from jumps and landings as I suspect that is the culprit. Dunno if the plate is 6061 or 7075? Perhaps neither. Safe siding it with the support pad. The 3660 on order comes in at ~8oz//~1/2 pound. Lot of leverage on any motor plate.

Regarding gearing: Ha. Curious you should ask that. Still running out-of-the-box 17/91 for 5.35 gearing. Actually planning a run tomorrow with a 19/91 for 4.78 install. Want to get a baseline in place with the 3650 before change-over to 3660.

By the way, bolt my ESC's down when there is a tab option to do that. I use a spacer nut on the install bolt to allow an air space for heat dissipation under the ESC. My experience is the ESC runs hot on the bottom, even with a topside fan.

Basically, a 2S runner here but want the option to go 3S. 3660 3700Kv gives me that option over a 4000. At least for the motors I considered in my price range. 80A ESC. That may change out to 100A. Dunno.

 

[bigbristv]

Interesting take on 2s & kv. And if you go 3s you will not go back to 2s if you like speed runs.

Also, you don't have to change out the whole motor mount to upgrade to .8 mod spur. Jenny's has one I'm looking at in case I chew up my 48p set.

 

[Chubaka]

Interesting take on 2s & kv. And if you go 3s you will not go back to 2s if you like speed runs.

Also, you don't have to change out the whole motor mount to upgrade to .8 mod spur. Jenny's has one I'm looking at in case I chew up my 48p set.

I had 2s in my traxxas mini. I regretted it. My vxl had 3s after the night kept dieing. I like it just to have the speed on tap, and to help her slide when needed.

Now I'm debating on 4s with my copper head.

 

[ahr43]

Thanks for the JRC link. I keep hearing good things regarding about them. Bookmarked it.

Regarding your topic question, bigbristv, think 4200 is pushing the limit. Probably o.k. depending on what C-rating your battery is. A higher C-rating will help keep battery voltage from sagging. Hi-Kv motors the higher the battery voltage the better. At least that's been my experience. Dunno if the motor you are considering has adjustable timing? May have to dial back the timing? 4WD demands a lot of a battery/ESC/motor package.

Hope this helps. 'AC'

 

[RustyUs]

I decided to skip the power mod because I hear the aluminum can bend and stay bent.

I just took my rig out trying to blow it up and the only thing that happened is the esc got hot enough to loosen the double sided tape and go dangling. Not sure if it was a crash that helped dislodge it but the fan stopped so that may be why it was so hot.

I know going up to the 3660 will immediately provide more torque but I'm wondering if the higher kv would just cancel it out.

I guess there's only 1 way to...


AC, what pinion are you running? Have you speed tested yet?

Yes, aluminum can bend, but in the right places & the right composition/thickness, aluminum is great. I'd much rather have the upgraded motor mount of the 3S BLX Senton than the stock plastic motor mount of the Mega Senton when wanting more "oomph" onboard the chassis. The BLX motor mount is at the right location on the chassis to take a lot of abuse IMO. The whole power module design is not my favorite in the hobby, as it is a bit tough to get in/out until things get broken-in, but for a composite chassis RC, the design makes better sense to me.

 

[bigbristv]

Thanks for the JRC link. I keep hearing good things regarding about them. Bookmarked it.

Regarding your topic question, bigbristv, think 4200 is pushing the limit. Probably o.k. depending on what C-rating your battery is. A higher C-rating will help keep battery voltage from sagging. Hi-Kv motors the higher the battery voltage the better. At least that's been my experience. Dunno if the motor you are considering has adjustable timing? May have to dial back the timing? 4WD demands a lot of a battery/ESC/motor package.

Hope this helps. 'AC'

My packs are 5200mah 80c 3s. The motor is sensorless 4 pole. I ordered the set so we'll see how it goes

Yes, aluminum can bend, but in the right places & the right composition/thickness, aluminum is great. I'd much rather have the upgraded motor mount of the 3S BLX Senton than the stock plastic motor mount of the Mega Senton when wanting more "oomph" onboard the chassis. The BLX motor mount is at the right location on the chassis to take a lot of abuse IMO. The whole power module design is not my favorite in the hobby, as it is a bit tough to get in/out until things get broken-in, but for a composite chassis RC, the design makes better sense to me.

I made the aluminum mistake with one of my drifters. I like customization and set out to get my Senton upgraded all the way up, but seeing how the stock parts, save bumpers, are holding up to insane abuse, I just keep leaving it as is.

I keep looking at mojaves but I'm still just loving the Senton.

 

[ahr43]

Hey bigbris. I may have been too conservative in my comments regarding your purchase of a 3660 x 4200. In retrospect and based on my yesterday's performance it should be O.K.

Pulled 28mph on the Senton 2WD yesterday with the 3650 x 4000 install. It pulled well in both 'speed runs' and 33ft drag test (24mph). So your choice of a longer can higher Kv should be right in the ball park.

Yesterday was WAY undergeared at 20/91 giving a 4.55 ratio. 12.96 O/A when multiplying in the 2.85 rear end ratio. Real low gear O/A for anything on-road. Guess the take-away is, "How big a pinion will fit to overcome the diff ratio for a respectable on-road speed." A good indication of how undergeared at 20/91 was 24mph at 33ft drag test and only a 4mph increase in speed when running out to a full 132ft measured course.

Anyway, good luck with the new install. Post up one of your famous vids on the results, o.k.? Cheers. 'AC'

 

[bigbristv]

Hey bigbris. I may have been too conservative in my comments regarding your purchase of a 3660 x 4200. In retrospect and based on my yesterday's performance it should be O.K.

Pulled 28mph on the Senton 2WD yesterday with the 3650 x 4000 install. It pulled well in both 'speed runs' and 33ft drag test (24mph). So your choice of a longer can higher Kv should be right in the ball park.

Yesterday was WAY undergeared at 20/91 giving a 4.55 ratio. 12.96 O/A when multiplying in the 2.85 rear end ratio. Real low gear O/A for anything on-road. Guess the take-away is, "How big a pinion will fit to overcome the diff ratio for a respectable on-road speed." A good indication of how undergeared at 20/91 was 24mph at 33ft drag test and only a 4mph increase in speed when running out to a full 132ft measured course.

Anyway, good luck with the new install. Post up one of your famous vids on the results, o.k.? Cheers. 'AC'

Was your test on 2s? I was able to get around those numbers on 2s using a 20t pinion. Jumped up 10 or so mph on 3s and with the 23t pinion jumped to near 49mph.

I'll post my speed and findings when the 3660 x 4200 system comes in.

I wasn't planning on doing a vid but depending on what happens I may. Thanks

 

[ahr43]

Yes. 2s x 5000 100C. Good info. Thanks. Thinking if I do another run before the long can install it'll be with a 23T on 2S.

Have a 3s at the ready for try once the 32P gears and 3660 3700Kv go in. 5000MAh x 50C. Thinking will probably eventually upgrade to 100A ESC over the 80A in there now. 100A has more profile features than the 80A. Want a bit more tunability in the ESC once the battery/motor/gearing/handling gets sorted out.

Cheers. 'AC'

 

[bigbristv]

Yes. 2s x 5000 100C. Good info. Thanks. Thinking if I do another run before the long can install it'll be with a 23T on 2S.

Have a 3s at the ready for try once the 32P gears and 3660 3700Kv go in. 5000MAh x 50C. Thinking will probably eventually upgrade to 100A ESC over the 80A in there now. 100A has more profile features than the 80A. Want a bit more tunability in the ESC once the battery/motor/gearing/handling gets sorted out.

Cheers. 'AC'

View attachment 173947

Sounds good

In other the same news, my kit came in today, got installed and speed ran.

I did a few pulls to feel it out and stripped the spur. Oh well, guess I'll have to upgrade

New question: I'm looking at 0.8 mod gears now but since I need a pinion for a 3.175 shaft, my options may be limited. So if I go stock blx gearing (57t x 20t) how is that going to work with the fact that my motor is now 4200kv?

 

[ahr43]

Hey bigbristv. Here is a YT vid that will help answer your questions. I find it both useful and helpful. And, most importantly, for the data I've input gives accurate, reliable results.

I don't know how to build formulas on a spread sheet but am learning that skill. For now working out the math longhand. Hope this helps. Cheers. 'AC'

[ EDIT: Error in the audio at ~16min:40sec. The author states to get axle RPM, multiply Mtr RPM * FDR. Actually, what works is Mtr RPM/FDR = Axle RPM. The formula displayed in the vid is correct; author merely misspoke. No biggie, but I did bang my head against the wall for quite a while until figuring that out by re-watching the vid a number of times. ]

 

[bigbristv]

Thanks bro. I took the seat-of-pants approach and like 10 Arrma SKUs and almost as many hours later I had replaced/rebuilt my rear diff, built the .8 mod slipper gearing, added a 20t pinion, installed and went ripping.

Got up over 46mph but the body catches air and flips over. With the body removed I got 56mph on an almost dead 3s batt. Nice!

Have a new body coming and then I think imma just take it easy. She's done well.

Then why did you order roof rails, bris?

[Shrugs]