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Author Topic: Uj joints for brushless motors  (Read 3506 times)

Klunk

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Uj joints for brushless motors
« on: August 13, 2023, 06:31:44 am »

As above.
I've tried the crown version from CMB.
RUBBER joint version, and huco ones. All have problems with crap alignment or smashing to pieces, huco and crown.  I was getting some from Germany as they were solid couplings, and very good, but pricey at £30 a throw.
Any ideas where to get some uk ?
Otherwise I might have to buy a lathe!
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Andyn

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Re: Uj joints for brushless motors
« Reply #1 on: August 13, 2023, 10:50:07 am »

Another lesson this morning in why huco couplings are garbage…



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Subculture

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Re: Uj joints for brushless motors
« Reply #2 on: August 13, 2023, 11:16:54 am »

Plastic cardan couplings work fine provided they're used within their limits. Not suited to high speed fast scale or fast electric craft

Have you tried a constant velocity dogbone type e.g. https://raboeschmodels.com/product/coupling-101-01/#
Also-
https://www.cornwallmodelboats.co.uk/acatalog/Amati-Coupling-Assembly-A6561_04.html#SID=740
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nemesis

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Re: Uj joints for brushless motors
« Reply #3 on: August 13, 2023, 03:51:43 pm »

I have just got some of those red couplings, there is nothing on them to show they are HUCO as huco have they name on the side. So these must be the usual rip offs. I had to use a vise to get the ends home in the housing. If I was using one in a brushless set-up I would have put shrink wrap over the centre. The last time I used brushless, I was give some stiff  tubing, hydraulic oil pipe? and the brass ends were forced into it and it all worked fine, looked neat as well. nemesis
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Tug Fanatic

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Re: Uj joints for brushless motors
« Reply #4 on: August 13, 2023, 04:07:14 pm »

Those are some impressive (old?) capacitors that you have there.  :o

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tonyH

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Re: Uj joints for brushless motors
« Reply #5 on: August 13, 2023, 06:34:02 pm »

All have problems with crap alignment or smashing to pieces, huco and crown.  I was getting some from Germany as they were solid couplings, and very good, but pricey at £30 a throw.
Probably a very stupid question but what is the difference between solid couplings and alignment thingys at £9.60? {:-{
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Andyn

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Re: Uj joints for brushless motors
« Reply #6 on: August 13, 2023, 08:06:57 pm »

Those are some impressive (old?) capacitors that you have there.  :o


They’re absolutely not mine. I’d not be dim witted enough to use a huco coupling and the motors are missing pistons %)
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Subculture

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Re: Uj joints for brushless motors
« Reply #7 on: August 13, 2023, 08:56:28 pm »

Any idea what these 'crown' couplings are. New to me.
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Tug Fanatic

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Re: Uj joints for brushless motors
« Reply #8 on: August 13, 2023, 09:38:06 pm »

Any idea what these 'crown' couplings are. New to me.
That is a Private Group. Unless you are a member of the group you cannot see anything.
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Subculture

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Re: Uj joints for brushless motors
« Reply #9 on: August 13, 2023, 09:58:42 pm »

No skin off my nose, sunbeam.
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Sonar

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Re: Uj joints for brushless motors
« Reply #10 on: August 14, 2023, 07:32:55 am »

There are metal  ones. But I don’t know if they make assorted sizes


https://www.amazon.co.uk/6x4mm-Universal-Coupling-Coupler-Connector/dp/B01GPTUVRG



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SailorGreg

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Re: Uj joints for brushless motors
« Reply #12 on: August 14, 2023, 11:17:42 am »

I have recently bought an all-metal UJ from Prop Shop but I haven't used it yet - boat not finished!  But if it's up to normal Prop Shop standards, it should be fine.  The website does say it's not for fast electrics, but a speedy scale model (MTB, Riva, etc.) should be fine unless you go way, way overboard on your motor and prop.




Greg

roycv

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Re: Uj joints for brushless motors
« Reply #13 on: August 14, 2023, 08:16:17 pm »

'scuse me but a dog bone coupling is a free floating centre dog bone just held within 2 sockets.  I have some old plastic ones from SHG, not suitable for the thrashing I can see in above piccys.
Pete you have cracked and near melted that red U/J plastic coupling!  Plastic won't do much for you there.  I have the ball, with a bar, and socket metal couplings but they always seemed to cause electrical problems.
Anyway these days I can't run fast enough for anything over 30 watts!
Regards
Roy 
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Martin (Admin)

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Re: Uj joints for brushless motors
« Reply #14 on: August 14, 2023, 10:43:09 pm »


Are these any good?
Are they robust enough?


eBay item number:283138679258
eBay item number:283783204646
eBay item number:284997911742


       
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ChrisF

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Re: Uj joints for brushless motors
« Reply #15 on: August 15, 2023, 09:52:46 am »

Klunk - what boat and motor do you have which is eating couplings!

I've got some of the better quality Huco type for use in low powered/slow models and wouldn't touch those red plastic ones with the proverbial.

I've pretty much standardised on the alloy/rubber/alloy sandwich ones, which are supposed to be heavy duty so I hope I dont have any problems.

Chris



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Backerther

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Re: Uj joints for brushless motors
« Reply #16 on: August 15, 2023, 10:35:21 am »

I have been using all metal disc couplings of industrial use for my 1m (40 inch) class cabin cruisers
with no problems regarding the strength. Bench test of the coupling in my Najade showed 24100RPM for 10 seconds.

Another reason is its calmness when rotating at higher speed. :-))


1; A disc coupling installed in my Najade.  Screw shaft is 4mm dia. The brushless motor is 1800W 2050KV.
2; 24100RPM with 3S lipo in Najade
3; Another pic of dic coupling in my Jupiter F-99. Screw shaft is 4.5mm dia. The motor is 1200w 2200KV.
4; The Jupiter in the rough water sailing with 3S lipo.


 I ordered the couplings from Misumi (a Japanese company ). They carry  wide range of couplings for industrial use.


See ;  MISUMI – Configurable mechanical components – buy online (misumi-ec.com)


Enter "coupling"  "disc coupling" or whatever you like for your needs. !! :-))
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Circlip

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Re: Uj joints for brushless motors
« Reply #17 on: August 15, 2023, 10:58:49 am »

Nothing adequately compensates for miss alignment. It generates noise power loss. Never had a problem after correct alignment and use of the 'Rip Max' U/J which was steel and could be classed as a half Dog Bone, ONLY type to isolate end thrust between drive/driven shafts unless we play with the disc and pin drives.


  Regards  Ian
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chas

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Re: Uj joints for brushless motors
« Reply #18 on: August 15, 2023, 11:36:55 am »

Tony H's question is a good one for many of us. Just what is the difference between an alignment coupling and a solid coupling?





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mrzippy

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Re: Uj joints for brushless motors
« Reply #19 on: August 15, 2023, 01:27:17 pm »

Hi BB - which type are you using please?  there are many different types on Misumi's website.
thank you Paul.
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roycv

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Re: Uj joints for brushless motors
« Reply #20 on: August 15, 2023, 01:44:52 pm »

Hi the Huco couplings are not constant velocity joints, which may be part of the trouble.  I am using for no more than 40 watts thick wall plastic or neoprene tubing fitted over the Huco brass parts.  Normal alignment is dead straight (the only time the Huco C.V U/J's are CV).

Have been interested in the posts of different options.
Roy
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John W E

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Re: Uj joints for brushless motors
« Reply #21 on: August 15, 2023, 03:29:12 pm »

Ian, disc and pin - I bet there are a few people who have to look it up in Vic Smeed's Boat Modelling book - unless of course you are as old as us  :-)


On page 74, fig 161 in Vic Smeed's Boat Modelling revised edition for those who want to know  %%


John
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Geoff

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Re: Uj joints for brushless motors
« Reply #22 on: August 15, 2023, 03:53:20 pm »

I've always used the Huco couplings but typically two of them on each shaft which effectively makes them constant velocity joints and takes care of any slight linear misalignment but to be fair they are not designed for very high speeds and power which is where the problem lies. With brushless motors the speed is very much higher and they are just not strong enough at those speeds.


Also the actual clearances to get them on to the shaft takes effect at very high RPM along with the imbalance of the grub screws which causes vibration and can destroy the couplings. Also some modellers tend to have two speeds, full power and off, which puts a huge strain on couplings. Some people I know are very guilty of this and don't seem to understand its best to work up to maximum speed.


Just my experience here but to be fair I tend to model scale craft so excessive speed is not a problem.


Cheers


Geoff




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Subculture

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Re: Uj joints for brushless motors
« Reply #23 on: August 15, 2023, 06:31:37 pm »

'scuse me but a dog bone coupling is a free floating centre dog bone just held within 2 sockets.

If you follow the link it's actually how they describe the coupling. I suppose if you want to be precise then half a dog bone perhaps,  just trying to give a description folk will understand.

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Subculture

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Re: Uj joints for brushless motors
« Reply #24 on: August 15, 2023, 06:33:15 pm »

A simple technique that works exceedingly well is to solidly couple the motor to the shaft, but have the inner bearing in the stern tube flexibly mounted with a piece of silicone tube.
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