B-MAX4iii 'thermaling' indoors; advice please

[andrewc]

Hi all

Not a newbie to the sport, but I am to the BMAX4iii, so thought I'd put this in here and hope for more specific advice/experience than in electrics/1/10th off road.

Bought a used BMAX4iii before xmas, great chassis with everything on it, PSM upgrades, lightweight chassis, YZ rear end etc, all the gear. Rebuilt it completely, renewed all bearings etc, chassis rolls a treat, no bind anywhere.

Running indoors, sports hall (20c probably?) on a large 28x17 carpet track with jumps etc, 1066 Racing on FB if you want track pics for an example.

G-Force 160 ESC and 5.5 motor; I'm aware that's running a quick motor but struggled with thermal cut out ON MOTOR all day. Got thermal cut off set at 105c, can up it to 125c but that seems crazy hot??

MOTOR temps/set up from day, (ESC ran at under 60c all day) in brackets my thoughts...EVERY RUN ZERO BOOST ZERO TURBO ON ESC

Practice: geared 18/87, 10% drag brake, 0 timing on motor, thermal 109c at about 3.5 mins. (Figure this was under geared? Also G-force supplied motor at 20 degrees, and I've learned since they possibly don't like running low timing? It wasn't negative timing, I checked electronically, actually read 7 degrees at zero)

H1: geared 19/87, 5% drag brake, 20 timing on motor, ran the 5 minutes came in hot, 98c BUT no warm up/wind down lap. (better gearing? Timing? Drag brake?)

H2: geared 19/87, 0% drag brake, 20 timing on motor, 1 warm up lap, thermaled on 'wind down' lap after 5 mins, 108c (extra laps the problem?)

H3: geared 20/87, 0% drag brake, 20 timing on motor, 1 warm up lap, thermaled about 4 mins 40, 109c. (over geared?)

H4: geared 19/87, 0% drag brake, 10 timing on motor, 1 warm up lap, steering screw dropped out at 4 mins approx... was at 96c at that point. (obviously inconclusive but less timing might have helped?)

Apologies for so much info, just keen to get some answers...had a 6.5 in a B44.2 previously and never had heat issues on longer runs than this.

Could it be a duff motor? (brand new)
Temps are normal and I should suck it in/up the thermal cut off?!
Put a fan on motor? How much temp difference could this make? (I've noticed this on some EOS pics but not all...why would some need it and not others? G-Force known to run hot?)

I did have a very tight to chassis trim on shell but have opened rear up a little for airflow. Not keen on holes in shell...looks crap and want to be able to run on wet astro.

Ideally need to be able to run a couple of warm up laps and not be running the temp gauntlet. Any thoughts/experiences appreciated, Thank you.

[ayske1]

I suspect it's your esc. I'm currently running the 160a toro and I believe the g force may be similar. I have an ORCA fan on it and the esc stayed within 40 degrees. The indoor track I was at was maybe 23 degrees.

Running g2 v10 6.5t motor, 20/87 gearing. My suspicion is that even if you had a fan the esc would still be very hot, maybe 20 degrees cooler... So I think there's something wrong with your esc. I would return it asap if you run out of ideas and under warranty. I am with mine with my toro...

I'm also running blinky on my esc, stock timing on can. Good to see ppl running the bmax 4 iii on carpet :)

[K-Brewer]

Pretty sure (someone will correct me if I'm wrong) but I'm sure u can go to about 160F. I pull mine off the track at 135 an don't have any issues

[K-Brewer]

Just seen your talking about C, yeah that's bloody hot. I know u don't like holes but if ur running indoors with a 5.5 on carpet indoor ur gonna need to. Cut a couple round holes in the front using a reamer to let the air flow through

[neallewis]

What are your cells? how old are they? could they be high resistance and you are hitting the low voltage cut out on the speedo, not the thermal cut out?

I had this myself with the BMAX4iii and a 5.5 with some cells that were not up to the job. Thought it was thermal cutout, but it was low voltage cut out. Disable it and try it again, or try a new battery pack.

Honestly though a 5.5 is a bit mad for indoors. You will go quicker with a tamer motor. I use a 7.0 in my yz4, and did in the bmax4iii during the summer outdoors.


Edit - I just re-read.
Also put motor timing to 0deg. Gearing, you'd want to be about 18-19/87. Under or over gearing isn't that critical between 1-2 teeth in a healthy system.
This issue reminds me of mine with the low voltage cut out. You can run a motor fan, (the orca or MR33 fan mount works great), but it won't fix this.

[neallewis]

OK a bit more. I really must learn to read properly first time...

The thermal cut out temp isn't read from the outside of the speedo (heatsink) its from inside via a component on the circuit board, but also sometimes inside the FET substrate. This is why it might seem hot.

oh, you mention that the speedo is warm, not hot, but the motor is hot. how are you reading the motor temp at point of cut out?

Where are you reading the cut-out temp from, plugging the progbox in after its shutdown?

by the way, what's the motor?

[andrewc]

Hi all

Thanks for the replies so far, much appreciated.

Neal;

Brand new g-force motor

Temps read after the run via programme box on ESC (immediately after, but found later it stores the last peak temp when plugged in, so I'm sure they're correct

All lipos are brand new Team Orion 4500 Shorties, the latest ultra ones with 5mm connectors...

[andrewc]

Neal

Tried the timing on 0 in practice and was far worse temp wise...but could have been gearing too low for that one run? All data as above.

Ayske1

The temps I've quoted are motor not ESC; the ESC temp (around 60c at end of run) seems ok to me?) Running speedo with fan.

[xtreme-rc]

andy,
it was hot on sunday, alot of people were having trouble with thermoling, a couple of things that have helped us,
a fan, with the b-max , there is space behind the motor so get a fan in there
gearing, 18-19 87 with a 5.5
the motor, best results we had was 30 degrees motor timing
les

[neallewis]

Neal

Tried the timing on 0 in practice and was far worse temp wise...but could have been gearing too low for that one run? All data as above.

Ayske1

The temps I've quoted are motor not ESC; the ESC temp (around 60c at end of run) seems ok to me?) Running speedo with fan.

Sure. stick with the standard (as shipped) motor timing then. by he sounds of it its doesn't like that. the Gforce (and Toro) progbox can run a test to check the exact set motor timing.

Sounds like your cells are ok then if new, they should be.

Ok, like the Toro that I use the progbox will read the motor temp from the sensor board. Remember its not the motor can surface temp. Use a infrared temp gun to test that. I'd set the cut out to 125degC or disable it. It looks like you are just hitting the cut out temp, a fan should help reduce it.

The gearing (with 18-19 pinion) is right, try a fan and also use one of these mounts:
http://www.rccarshop.co.uk/electrics/fans/mr33-mh--mr33-motor-fan-mount-p

http://www.rccarshop.co.uk/electrics/fans/ofm022ba-orca-adjustable-fan-mount-black-p

I used to use one with a 30mm fan on my bmax4iii when it was hot. fits fine in shorty or saddle mode.

Good luck sorting it out.

[mes]

It is your motor for sure. The other day, I was running on a tight indoor track (Racing Arena Limburg) with a buddy, both with 6.5 motors in our YZ-4s, a Muchmore Fleta in mine and a G-Force in my buddy's car. I could stay longer on the track and my motor remained pretty cool while his G-Force would temp out. Another friend of mine experienced similar things when he tested the G-Force 13.5 as a possible spec motor for our SC Stock class (which has meanwhile become a modified class).
Many fellow racers around me have switched to the Muchmore motors meanwhile, coming from various other brands. I've been very happy with them since I first got one about a year ago and have accumulated several windings for my cars and truck. Other great motors are Reds Racing (got one, like it) and probably Yokomo and Reedy, which at least share the design and sensor board with the Muchmore Fletas. I also liked my Team Orion VST2 Pro, which is totally different in design and quite pricey.
I am not sure about motor prices in your area, but in Germany, Muchmore are around 80 euros and thus cheaper than their Reedy and Reds brothers and of course the Team Orion stuff.

[skyaflake]

With the SkyRC/G-Force stuff it's a bit of a hit and miss. Some are good, some are bad. With other stuff (Muchmore, SP, Orion, etc) most are good and some may be bad. I personally run Muchmore and Trinity (the best imho) motors and they never get hot. I guess you have a bad motor.

[andrewc]

Many thanks again to you all, appreciate your time.

Les; thanks also for all the advice on Sunday. I ran out of heats to try upping the timing further still, will do next time and monitor difference. See you soon I hope, great turnout Sunday : ) Will try a fan next.

Neal; thanks again for all the replies. Will try a fan for sure. With regard to upping cut off temp, am I not risking damaging the motor at those temps?

Les/Neal...Fan blow ONTO motor or sucks air AWAY from motor? Better on chassis or a mount?

Mes/Skyaflake thanks also; I run Orion in my 2WD. Will see how this plays out...!

[ayske1]

I also misread as well like Neal lol

Yeah I think most are correct stating the motor. I used to do outdoors on a medium large track with 30 second lap times on mild days 22-23 degrees and after a full pack the motor would be about at low 60 degrees. I use a yeah racing fan behind the motor, standing, in shorty setup. Much like the few examples on petitrc. The only times my motor exceeded that was when the air temp was 24+ degrees after a full pack/or when the fan had gone bust.

[andrewc]

Hi all, thought I'd update and say thanks...Added a 30mm fan to rear/diagonal of motor (shorty chassis) and problem solved with no other changes.

Temps dropped by 30 degrees C! Was surprised it was that much but have checked several times.

Can do warm up laps and play after the tone!! Very pleased, thanks to all for the advice.

[The Doctor]

5.5 is probably a bit too much indoors on that track. 6.5 should be plenty. Gearing sounds fine, assuming it wasn't a mega-tight track layout. Also I assume your drivetrain is nice and free..?

[andrewc]

As my previous post earlier today, fan solved problem...thanks though!

5.5 is more than necessary for sure, but great fun. My 2WD remains the sensible weapon! (7.5!)