Burnt up my TFL/HK Bolt's 2040, what new motor?

[Dashunde]

Just got back from running my little Bolt, and I'm perplexed..

Using 3s 2200 and a Octura x430 I managed to smoke the stock 2040.
It ran fine the first few minutes, not silly-fast or anything else odd, then it slowed down a bit so I pulled it out and checked it over, drive-line and water flow seemed fine.
I raised the strut as far as possible (torquing to the right pretty hard) and ran it again... no dice, barely got it back to shore, I took the hatch off and it threw one last insult my way in the form of a stunk up truck.

The Turnigy 30a esc didnt break a sweat.

The cable drive has a bit too much drag for a boat this size (.098"), but aside from that.. where did I go wrong?
Is the x430 too much prop for a 2040 2600kv on 3s? I wouldn't think so, its basically the metal identical to the 30mm plastic that came with it.

I'd kinda like to move it up to a 28x35 ~3000kv... but not sure which one to buy, and the stock brass and motor mount dont leave much room for larger couplers.
(My Tenshock Mini Eco has a nice ~2830'ish (Tenshock Viper VZ1515) that would be perfect for this Bolt, but I cant find a 16 turn/3500kv for sale anywhere)

Your thoughts?

[NativePaul]

These minis take such little power to push that a sticky drive shaft is a really big deal, an x430 on 2600KV should only be about 15A, and you could be pulling that much again just to spin a sticky shaft at 26krpm.

I have used a few in the past (1 x hacker, 2x Tenshock), but I am not a fan of 20mm motors as they run very hot compared to 28mm. I run Mega motors in my minis, the 16/15/3 is 28x36.5 3000KV, I normally use it to race in the Naviga Mini Hydro class, spinning a detongued X432 I get 5 minutes run from 3s 1700mAh with throttle control, but I have used it for sprinting too and it will take a P735 on the same battery for 6 laps flat out at much higher speed.

HET's 28mm motors are ripoffs of Megas, the EDF 3W is the 16/15/3 clone if you want to avoid paying for R&D.

Or the HK Rotorstar 2839 2700kv outrunner is good, maybe not quite the step up in KV you wanted, but it has proved to be more efficient than the Tenshock Viper 1515 for 5-6 minute runs and is a lot cheaper, although probably less capable of propping up if you done need that much run time or use bigger batteries.

[Fluid]

Low quality Chinese parts are a more likely cause of the burn down. Motors (not just Chinese) can wear out or short out and burn. The OP may have been a victim of 1 - low quality or 2 - motor finally wore out by operating over the true design parameters..


.

[ray schrauwen]

Just got back from running my little Bolt, and I'm perplexed..

Using 3s 2200 and a Octura x430 I managed to smoke the stock 2040.
It ran fine the first few minutes, not silly-fast or anything else odd, then it slowed down a bit so I pulled it out and checked it over, drive-line and water flow seemed fine.
I raised the strut as far as possible (torquing to the right pretty hard) and ran it again... no dice, barely got it back to shore, I took the hatch off and it threw one last insult my way in the form of a stunk up truck.

The Turnigy 30a esc didnt break a sweat.

The cable drive has a bit too much drag for a boat this size (.098"), but aside from that.. where did I go wrong?
Is the x430 too much prop for a 2040 2600kv on 3s? I wouldn't think so, its basically the metal identical to the 30mm plastic that came with it.

I'd kinda like to move it up to a 28x35 ~3000kv... but not sure which one to buy, and the stock brass and motor mount dont leave much room for larger couplers.
(My Tenshock Mini Eco has a nice ~2830'ish (Tenshock Viper VZ1515) that would be perfect for this Bolt, but I cant find a 16 turn/3500kv for sale anywhere)

Your thoughts?

I'm slow getting up but, I have a very nice 28mm x 35mm 6 pole motor and jacket. I have a Leo water jacket that fits it and the shaft is I think the same size as your motor. If interested, I'll post up a pick when I find it.

It's a Mega clone basically.

[ray schrauwen]

Pick and specs. Made in Taiwan. 16 and 19mm mounting.

These sold for $50+ or so new, as mine is new, just bench tested.


https://www.amazon.com/Brushless-Pol.../dp/B0015H1DUI

[Dashunde]

Ray, thats just what I'm looking for, except I need a 2.3mm or larger shaft.

[Dashunde]

Well... in the meantime I have a couple of new Venom 2040 3500 KV Motors I can toss in it, what diameter do you think I should cut the plastic prop down to?

[Dashunde]

I installed the Venom motor (it's actually 3350 KV), at wide open throttle spinning the 30mm prop in the air the cable draws 3.5 amps, and the strut gets pretty hot in 10 seconds or so.
Its all greased up, and of course has a curve to it, but it spins smoothly and feels about like I'd expect.. is a freewheeling 3.5a too high?

I changed the esc timing to 7deg, down from the 15deg setting that maybe helped smoke the stock motor?

I cut the plastic prop down to 28mm and detongued & sharpened it, then dunked it in the utility sink, its drawing around 30 amps static worst-case, after 10 seconds or so of this treatment the motor was cold to the touch immediately and a minute later.

I have some other anomaly that showed up tonight, occasionally the motor will run away as if a ghost is pulling the throttle trigger.. the servo holds dead still, never twitches.
No idea whats causing that yet, but I sure don't like it.

[NativePaul]

A 3300kv 2040 should have an io of around an amp, meaning that the driveline is soaking up 2.5A, that sounds reasonable to me but then again it will be over 10% of your running current.

I have never measured the current consumption of mine as running Wot without water to lubricate the lead Teflon bearings in most struts will cook the Teflon out in short order, but I do have one with ball races in the strut that I would now be interested to measure, it is a wire drive so not apples to apples but it may be an interesting comparison anyway.

You venom being cold after 10 second at 30A surprises me, in my experience 3000ish kv 20mm motors run hotter than I would like at over about 20A and those I have seen at SAWs show little improvement in speed above that current, maybe that is indicative of a relatively efficient motor but an inability to dissipate heat as even for SAWs a trip in both directions and back in is probably about 40 seconds.

I have no idea about your runaway motor problem, normally I would blame the radio but the solid rudder makes it seem unlikely that the signal is dropping out, maybe try swapping the Rx plugs around so the motor is on the rudder channel and visa versa, if the rudder now twitches and the motor remains static then it is a radio issue and if the motor still runs away with the rudder static then it points to an ESC issue.

[Dashunde]

Can I pull out the teflon for less drag? Pos & cons?

[NativePaul]

Well I ran the test with the shaft attached the amp draw was smooth and consistent at 1.1A, but totally unloaded I can see some fluttering variation in the amp draw and power. I repeated the tests several times and that built up a picture of approx .9A unloaded, so around 0.2 of an amp to spin the 1.2mm wire drive with, 1/8" ballraced strut, 2 short unlined brass stuffing tubes, and 1 silicone stuffing tube seal in my mini hydro at 36,600 RPM out of the water, freshly lubed, with no prop attached.



In this graph the first run is with shaft attached and the second was without, the flat parts of each are 1.1A but the dips in the second (shaftless) run make it average of .9A, I did see a slightly smoother one with the flats at .9A and peaks up to 1.1A in a previous test, but I didn't save it as I thought I could get a flat one which I never managed, all the shafteless runs averaged .9A when i took out the high current acceleration phase and the start and low current deceleration phase at the end, and I think I ran 5 pairs of tests so while not 100%, I think the data is fairly sturdy.

That is a debatable issue, many people have gone fast with or without liners. Fluid has done testing and found that linerless had less drag. I suspect that he was using a thicker than ideal Lube for the liner as liners can get away with using a thin oil, and a greased shaft seems very sticky to me, but I have not done any testing, and some say grease heats up and thins out at high speed. Pros are a possible drag reduction, and better water sealing, cons are a possible drag increase and you would need a smaller stuffing tube. I prefer wire drives to either.

[ray schrauwen]

Ray, thats just what I'm looking for, except I need a 2.3mm or larger shaft.

it is 2.3mm shaft

[Dashunde]

it is 2.3mm shaft

Ah.. the link you sent me to says its a (odd) 2.1mm?

If that shaft is confirmed positively 2.3mm its a nearly perfect motor for this little Bolt.. how much do you want for it shipped to 63367?

[ray schrauwen]

I'll confirm Tuesday next week. I just got to my GF place for our version of 4th of July weekend.

Funny it says that. I checked with calipers but I'll double check Tuesday.

If it's too long to wait I'll understand.

Price, not sure. Let me see what shipping is first.

Like my last transaction, I shipped it first before I received payment.

Small stuff I try to do on an honor system. I'm in Canada so shipping will take about 7-10 days like the turn fin I just sold.

[Dashunde]

Ok Ray, sounds good.

So I ran it again today on the new 2040 Venom... now it kinda stinks a bit too :/
I messed around with the driveline some more... the cable/liner is ok, not a whole lot of resistance there, real drag is coming from the strut. I wiped the grease off and replaced it with 90 weight gear oil and that reduced the turning force required by about half, so I did the same to the cable.