Rear hub motor juddering when spun by hand /pedalled

Ianb84

Pedelecer
May 12, 2018
29
6
39
Edinburgh
Hi guys.
my new hub motor is juddering when I spin by hand , I can then rotate opposite way for a few turns then spin other way and it will be fine for a wee while . I’ve not connected better yet , any ideas?
thanks guys
 

saneagle

Esteemed Pedelecer
Oct 10, 2010
6,148
2,898
Telford
Hi guys.
my new hub motor is juddering when I spin by hand , I can then rotate opposite way for a few turns then spin other way and it will be fine for a wee while . I’ve not connected better yet , any ideas?
thanks guys
It sounds like the clutch is sticking. Is the juddering the same whether you rotate the wheel backwards or forwards when it does it.
 

Ianb84

Pedelecer
May 12, 2018
29
6
39
Edinburgh
Yeah when spun both ways . It’s not a geared hub motor though if that makes a difference. If I spin backwards And forwards a few times it sorts itself for a wee while . Is it likely to do the same when I connect battery?
 

saneagle

Esteemed Pedelecer
Oct 10, 2010
6,148
2,898
Telford
Yeah when spun both ways . It’s not a geared hub motor though if that makes a difference. If I spin backwards And forwards a few times it sorts itself for a wee while . Is it likely to do the same when I connect battery?
What motor is it then?
 

saneagle

Esteemed Pedelecer
Oct 10, 2010
6,148
2,898
Telford
Just a standard hub motor, 1000w , I’m not sure the exact term? I’ll try attach picture ,
That's a normal direct drive motor. They all cog in both directions to a greater or lesser extent. If you get more resistance than the normal cogging and the motor is disconnected, then there is a short on the phase wires somewhere. When the cable isn't connected, it's easy for the bullet connectors to touch each other, which would increase the resistance to turning a lot. If the resistance increases when connected to the controller, it's probably because the regeneration is not switched off.
 

thelarkbox

Esteemed Pedelecer
Aug 23, 2023
1,016
310
oxon
Any wobble in the axle? - bad bearing??..
If ive read correctly these are all pre connecting power tests with just the wheel on its own?

May i ask why that motor/kit @Ianb84 ? while police interest in ebikes outside the regs has been slow to start, it seems that in some areas at least this is changing and the dinner plate motor is a easy to spot from a distance violation if looked for.

Depending on your needs a within regs set up might be available for less long term hassle allowing you to get your money back (distance selling rules) on the dinner plate kit?? after all its only the motor rating thats limited to 250w.. nothing is said about controllers and batteries feeding X000w when needed ;)
 

Ianb84

Pedelecer
May 12, 2018
29
6
39
Edinburgh
That's a normal direct drive motor. They all cog in both directions to a greater or lesser extent. If you get more resistance than the normal cogging and the motor is disconnected, then there is a short on the phase wires somewhere. When the cable isn't connected, it's easy for the bullet connectors to touch each other, which would increase the resistance to turning a lot. If the resistance increases when connected to the controller, it's probably because the regeneration is not switched off.
Ok thanks, I will check with power and see what’s happens
 

Ianb84

Pedelecer
May 12, 2018
29
6
39
Edinburgh
Any wobble in the axle? - bad bearing??..
If ive read correctly these are all pre connecting power tests with just the wheel on its own?

May i ask why that motor/kit @Ianb84 ? while police interest in ebikes outside the regs has been slow to start, it seems that in some areas at least this is changing and the dinner plate motor is a easy to spot from a distance violation if looked for.

Depending on your needs a within regs set up might be available for less long term hassle allowing you to get your money back (distance selling rules) on the dinner plate kit?? after all its only the motor rating thats limited to 250w.. nothing is said about controllers and batteries feeding X000w when needed ;)
I will double check for wobble but sure it felt pretty solid , but I will need to try and wiggle when it is shudder and when it stops . I will check with battery once I have fitted but I’m expecting it be the same
 

Ianb84

Pedelecer
May 12, 2018
29
6
39
Edinburgh
Any wobble in the axle? - bad bearing??..
If ive read correctly these are all pre connecting power tests with just the wheel on its own?

May i ask why that motor/kit @Ianb84 ? while police interest in ebikes outside the regs has been slow to start, it seems that in some areas at least this is changing and the dinner plate motor is a easy to spot from a distance violation if looked for.

Depending on your needs a within regs set up might be available for less long term hassle allowing you to get your money back (distance selling rules) on the dinner plate kit?? after all its only the motor rating thats limited to 250w.. nothing is said about controllers and batteries feeding X000w when needed ;)
Yes I never thought of that , perhaps a smaller 250w motor with a bigger controller and battery
 

thelarkbox

Esteemed Pedelecer
Aug 23, 2023
1,016
310
oxon
IF you detail your expected use and donor bike, include terrain details (hills?) and speed/range expectations and budget.
Im sure the best minds in here could suggest set ups and kit that could provide what you want within the regs.. - Then you will be able to get theft insurance on the bike, and if anything bad happens on the rd you wont automatically be in the wrong..
 

Ianb84

Pedelecer
May 12, 2018
29
6
39
Edinburgh
IF you detail your expected use and donor bike, include terrain details (hills?) and speed/range expectations and budget.
Im sure the best minds in here could suggest set ups and kit that could provide what you want within the regs.. - Then you will be able to get theft insurance on the bike, and if anything bad happens on the rd you wont automatically be in the wrong..
Flat terrain , mix of roads and paths , around 20miles range with most usage between 15-22mph
 

AGS

Esteemed Pedelecer
Feb 12, 2023
605
187
You can easily test the motor for potential shorted windings by connecting two of the phase wires together.

Then when you rotate the wheel in either direction you should feel more cogging on the motor.

Then connect all three phase wires together and the cogging resistance should increase significantly.
 

thelarkbox

Esteemed Pedelecer
Aug 23, 2023
1,016
310
oxon
imho a Nice big 48v battery 17ah matched with a 17a 36v/48v kt sinewave controller and suitable lcd display (there is a selection) which on paper could supply (54.6V x 17A = 928W) to a 250w motor..

Match that with a 36v 250w hub motor of your choice (fwiw i fitted a yose-power kit last summer - very happy with it) . and you should be very happy imho..

Generally A motor rated at 250W 36v will have a max rpm which will provide a max speed above the 15mph limit, circa 19-22 mph if unrestricted.. Supplying with power from a 48v batter/controller will increase this by circa 30% and also provide a similar increase in torque to get there..

KT controllers are more fully configurable than other options And have a number of compatible lcd display options.

Tho im not an expert, just a chap 1 yr into playing with his own ebike conversion and other bikes..

edit Just set the max speed to 15.5 mph for rd use and its totally legal, and you can ebay an en19154 sticker from ebay although kit conversions dont strictly require them.......
 
Last edited:

Ianb84

Pedelecer
May 12, 2018
29
6
39
Edinburgh
You can easily test the motor for potential shorted windings by connecting two of the phase wires together.

Then when you rotate the wheel in either direction you should feel more cogging on the motor.

Then connect all three phase wires together and the cogging resistance should increase significantly.
This is even when there is no power to the motor? I’ve not even connected battery yet
 

AGS

Esteemed Pedelecer
Feb 12, 2023
605
187
This is even when there is no power to the motor? I’ve not even connected battery yet
You don’t want to connect the battery when you do this test.

What you are currently experiencing is probably normal cogging, but it’s worth doing the short circuit test for peace of mind.
 

Ianb84

Pedelecer
May 12, 2018
29
6
39
Edinburgh
Hi guys. Turns out I was being really stupid, the phase wires that I took out the little joining block (to get some washers over and left them loose) were randomly touching causing the juddering, when I moved the bike they must have moved enough not to touch to let it spin freely . Thanks for everyone’s help and especially the guy who mentioned phase wires
 
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