Tightening Torque MXUS 3k v3

What amount of tightening torque would you recommend for the axle nuts on an MXUS 3k v3?

Get some norlock washer and get out the 4in grinder and cut out a clamping torque arm . weld on two nuts and drill one out for a clamping torque arm. Yes one for each side. You can use two hose clamps on each.

Torque Arms.

At the moment I am using these torque arms on both sides:



I have tightened the nuts with 100Nm of torque and will retighten them after every ride in the first days. Do you think I can tighten with more than 100Nm or will it probably cause damage to the axle thread?

Really impossible to keep the front wheel down at 350 phase amps

I went down to 70Nm now because I don't want to risk to strip the thread. Even though it is a 16mm axle I am not sure if 100Nm will be okay.

Like most hubmotors these axles are not made of very good metal, though they're not as bad as some I've had. So you can strip the threads of the axle itself, but it's more likely you'll take out the nut first.

I don't know what torque is recommended for them, but I can crank the foot-long 1" box wrench down pretty seriously with the old Ezee v1 hubmotor's nuts I'm using on my MXUS v2 and v3 (one motor didn't come with any nuts, and the other had such soft ones they stripped out). I have a torque wrench and I should use that to check what torque they are actually at...but I haven't used it on these yet.

Regarding the torque at the wheel itself (not the nuts, but generated torque by the motor), try not to suddenly change directions on it (electric braking hard at high speed), as it is very hard on the axles and they may shear off at the shoulders. Possible to fix on the non-wire side...not so easy on the wire side. :/

BTW, depending on what wind you have, there is some data on the MXUS threads indicating 250A phase currents might be saturating the motor (meaning lots of excess heat is being made for not significant extra torque).


I don't see any images; if you attach them directly to the post in the attachments tab, then anyone that sees the post can see the images.

It is the fastest winding (3T) in a 17'' MC wheel.

Resistance measured from one motor phase to another is only 67mOhm (including the phase wires).

So I think 350 phase amps should be okay and motor did not get hot at all on my tests so far.
Not sure if 450 amps would be okay, but it is already impossible to keep the front wheel down at 350 amps

I melred a muxus 3,000 with 7,000 watss a 5t. Now have a 4t. Are you running regen ? You Need norlock washers ! The torque arms can be thicker for more support and with a clamping on the axle torque arm you don't need a nut. If not you my spin the axle cutting the wires. Get strong.
What controller and battery are you using.

I plan to run regen braking later (after 5 times charging the lipos). I am using a second throttle for E-brake and have set it to 20A at the moment which has not much effect of course.

Battery is 22S 16000mAh 20/40C. Max charge is 5C (80A), which I plan to set the E-brake to later.

Controller is a Sabvoton SVMC72150 with max current of 200/450 amps

hias9 said:

Resistance measured from one motor phase to another is only 67mOhm (including the phase wires).

So I think 350 phase amps should be okay and motor did not get hot at all on my tests so far.
Not sure if 450 amps would be okay, but it is already impossible to keep the front wheel down at 350 amps

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The current "limit" of the motor is not determined by it's resistance, it's determined by it's magnetic design (coils, stator laminations, etc). At some point (saturation), current thru the coils makes much more heat than it does torque. That point is different for different windings of different motors.

What I've found on ES so far is that around 250A phase should be that point for a "4503", which is a common name for the motor you have (same one I had on the right side of the trike until I broke the axle; it'll go back on once I weld new ends on the axle that won't fail this way).

I haven't tested out higher currents than that on it yet, but will once I get that axle fixed. My trike is heavy enough that those kinds of phase currents won't lift it, just get it moving quickly.

Do you have a display on the bike that shows you your phase currents at any moment, realtime? Or logging in the controller you can read out later to see what it is?

I ask because if you're not actually running at the high phase amps all the time, the motor won't get hot because it isn't past saturation long enough, etc.

And I'm curious to know what hte limits of the motor are.

I would really be suprised if a 3T winding would already saturate at 250 amps. I remeber I read something around 450 amps for saturation here on ES, but don't remeber in which topic.
The difference when going from 225 to 350 phase amps was clearly noticable in torque. But of course I am not using the full 350 amps from a standstill.
I am using the Sabvoton bluetooth app as display, but unfortunately it does not display the current.

By the way, would you choose normal steel nordlock washers or stainless steel nordlock washers?

It'll be nice if it can handle the higher current. The SFOC5 I'm testing ATM can do a lot more than 250A phase, but I already broke the axle with that during a glitch. 150A I had it at after that was relatively wimpy (but better than the Grinfineon).

I used what I think were regular nordlocks on CrazyBike2's front hubmotor; no problems there. That was a pretty low power / low torque motor, just a 9C 2806 or 7, in 26" wheel, with a 40A Grinfineon.

I don't use them on SB Cruiser; it has clamping dropouts on the inboard side of each motor, and a >1/4" thick plate for a dropout on the outboard side.

The whole idea of a properly fit TA is so that you don't need to torque the heck out of the nuts...

That TA isn't really doing much the way it's mounted. There is little to resist motion. It would make sense if it was a one-piece arm but it's articulated in the middle. It can presently rotate quite a few degrees before it runs into significant resistance from the hose clamp part and then the force is essentially parallel to the chain stay so the hose clamp will just slide down the stay (after the extra space in the clamp slot is used up allowing free rearward motion).

Axle rotation is counter to wheel rotation - look at the picture and imagine the TA turning clockwise and the nut being a loose pivot point. If you twisted the axle part of the TA with breaker bar, do you believe it will be locked in place or that it will rotate?

I believe you find this alternate mounting for the same two parts much more effective. Needs a drill, a hacksaw, and a 5mm or 6mm bolt. If you run out of length because the new hole runs into the unused clamp slot, pick up a piece of 1/8" flat steel bar from Home Depot or the hardware store to use instead.

teklektik said:

The whole idea of a properly fit TA is so that you don't need to torque the heck out of the nuts...

Click to expand...

OTOH, the testing Justin did almost 10 years ago showed that the amount of torque on the nuts was a substantial contributor in resisting spin out. I think he showed that tightening to 60 Nm made a big difference vs. 30 Nm. But my memory is fuzzy on it.

With the amount of power this guy is planning on using and with his intent to use regen, there is no way I'd be comfortable with the two-piece torque arm he's using - even with the better attachment scheme you outlined. And if I did use it, I'd sure torque to at least 60 Nm. I'd much prefer either a single piece torque arm with thicker metal, or something that clamps to the axle flats as previously mentioned by 999zip999 earlier. And I'd probably still tighten the nuts down to 60 Nm if I went single piece.

BTW, I use 1/4" mild steel single piece torque arms (shaped hole, no slot) partly because I don't want to torque the nuts down a lot. I like being able to attach and remove my wheel easily with a 6" adjustable wrench for repairs on the road. But at around a mere 1000 watts, I'm not using anything close to the power he's using.

Thanks a lot for that attachment scheme! I would also prefer single piece TAs, but I did not find anything for a 16mm axle.

An idea would be to install 2 TAs in a way like you outlined instead of the 2 spacers additionally to the 2 TAs which are already mounted.
It would not be 100% symmetrical (what does not matter I think), but the force would be distributed to 4 TAs. Additionally I will get some nordlock washers and still tighten the nuts to 70Nm.

hias9 said:

An idea would be to install 2 TAs in a way like you outlined instead of the 2 spacers additionally to the 2 TAs which are already mounted.

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Since you are restricted in choices for off-the-shelf 16mm TAs, that would be a huge (if not necessary) improvement. No need to double the arm part, but the thickness at the axle is important.

Frankly, at the phase amps you're discussing, I would be making up some hefty 3/8" mild steel slotted torque plates or clamping dropouts. This is a bit of a PITA if you don't have a drill press and angle grinder or band saw, but a small vise, drill, hacksaw, files, and patience can yield very nice results.

Also, you can always take a two piece arm, fit it, then remove it held in alignment by the pivot bolt and take it to a welder or auto body shop and get the pieces tacked together for cheap. Just show them where they can run a bead so it won't interfere with fit/mounting. Pull the bolt while you're there after the tack and have it plug welded. Instant one-piece.

The Torque Arm Picture Thread might inspire you as well...

Did someone say Torque Arms??????????

Brand spanking new, a few hours old 8)
View attachment 1


For some odd strange reason these beaut's below (my previous) fell off somewhere.



I know you all love my handiwork
BTW I am selling these :wink: :lol: 8)
Notice the Grinder skills it takes to accomplish such a forbidable, hard, almost impossible task.
Oh you had a question, my bad, darnit if I know, I just tighten them hose clamps until they are snug, but dont giverrrrr too hard otherwise them hose clamps break on ya, gotta triple up on em.

markz said:

I know you all love my handiwork

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I hope you put one on each side so as to avoid bike lean. :^)

wturber said:

markz said:

I know you all love my handiwork

Click to expand...

I hope you put one on each side so as to avoid bike lean. :^)

Click to expand...

Good point, that might be tomorrows project if I dont get out the door and cast a line. Which reminds me I have to stock up on hose clamps tomorrow. What really got me was a frocker in a drift boat caught one right in front of me today fly fishing and it was a big one. I havent fly fished yet but atleast I know that spot is good. World Famous Fishing in them dirty dirty waters, Bow River. Its great, ebiking up and down the river on a whim, go down river or up river and do 5km in no time. While them drift boats cant do much but go down river or stay put. Big advantage for them though is access to the center of the river.

One word, "pontoons". :^)

wturber said:

One word, "pontoons". :^)

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I'd use a drone if they were legal, have a radio controlled release mechanism. That'd be ultra cool IMO.

So I wonder, getting back on track, do people want a specific ft/lb torque rating or what, because all I do is get my adjustable wrench out and tighten them bolts, and hose clamps just be sure not to break the slot because I've done that plenty of times of useless crap from dollar store or Princess Auto's / Harbour Freights PowerFist junky clamps.

I meant pontoon FOR the ebike. I guess that's the problem with one work responses.

As for the torque amount, I went back and re-read portions of the 2009 torque arm testing thread and it does not provide a definitive answer. My thumb-to-the-wind take is somewhere between 30 Nm and 60 Nm will do fine if you use a thick well anchored torque plate.

https://endless-sphere.com/forums/viewtopic.php?f=2&t=14195

My main takeaway was that when in doubt, use a thick, single piece torque arm that is well anchored - preferably directly through a bolt to a rack eyelet or something similar. Two piece torque arms with hose clamps can certainly work, but for me they just introduce too many extra variables.