Guide: fixing deadband of Wuxing hall throttle

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larsb   100 MW

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Guide: fixing deadband of Wuxing hall throttle

Post by larsb » Feb 23 2016 5:18am

Hello, thought i'd give something back to thank all who have helped me by their posts. :D

I use a half twist throttle from Wuxing, they seem to be pretty common since they are cheap but the throttle response on my setup is sluggish to say the least, 20% of the twist of the throttle does nothing.
In hall sensors a voltage difference is created in the sensor when it is exposed to a magnetic field. If this voltage diff is not enough for your controller to start driving the motor then it will behave like mine. The modification i do below places the magnet closer to the hall sensor when throttle is in the resting location.
Please remember that modifications like this are done at your own risk, having a throttle that does not work properly can kill you.

Wuxing hall sensor throttle:
Wuxing half twist throttle
half-twist-throttle-parts-001.jpg (18.65 KiB) Viewed 3332 times
The throttle is held together by plastic snaps that can be seen in this picture.
throttle snaps
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The plastic is flexy so the snaps can be bent without breaking. It is a bit difficult to get the snaps to release fully since they bite on the full perimeter. I used several flat screwdrivers jammed between the inner and outer part to free the snaps. Some damages from disassembly can be seen on the pics but this throttle was disassembled many times in my trials.

Here you can see the throttle partly disassembled. The hall sensor is shown in the red ring on the second picture.
Partly disassembled throttle with magnet
10.jpg (35.72 KiB) Viewed 3332 times
hall sensor location
5.jpg (44.65 KiB) Viewed 3332 times
The magnet is snap mounted into a recess and is symmetrical. The throttle is designed quite cleverly so the left handed and a right handed throttles are basicly the same but the magnet approaches the hall sensor from the opposite direction between LH and RH throttles. This means that the only differences between LH and RH throttle are the rotation of the magnet and the return spring winding direction.
The magnet on the throttles are rotated so that north pole is always facing/approaching the hall sensor when throttle is twisted.
disassembled magnet
7.jpg (45.04 KiB) Viewed 3332 times
measuring magnet polarity
8.jpg (63.07 KiB) Viewed 3332 times
return spring winding direction
9.jpg (26.05 KiB) Viewed 3332 times
Now how to modify the throttle:
Before doing any disassembly you should mark the deadband of your throttle. I turned my bike upside down and turned on the controller. I used tape and a marker to mark the amount of twisting needed before the motor started moving.
marking of deadband width
3.jpg (40.97 KiB) Viewed 3332 times
The tape was cut to this width and then the tape was transferred to the edge that stops the throttle rotation. I have done these modifications on a LH twist throttle so if you want to do the same mods on a RH throttle then the material should be added to the opposite side.
Adding material to offset throttle resting point
4.jpg (16.78 KiB) Viewed 3332 times
I used hot glue to extend the edge that stops the throttle rotation. The parts are covered in grease and it can be risky if the new material comes loose and jams the throttle. Therefore the surfaces needs to be thoroughly cleaned with degreaser. I wiped first and then cleaned the area with rubbing alcohol.
An oversized blob of glue was allowed to cool a little and then i shaped it with wet fingers. Take care not to burn yourself as the hot glue will stick to your fingers if you do not wet them. When the glue has cooled you should give it a tug to verify that it is securely fastened in it's location.
The edges were trimmed to the final shape using a sharp knife. Here care must be taken so that the formed shape is not outside of the original inner and outer surface of the throttle as this will cause the throttle to slide roughly or jam. A touch of the original grease was smeared on the final surface to lower friction.

I assembled the throttle and tried the response but found the first attempt too twitchy, motor started driving as soon as i lay my hand on the throttle. This would be dangerous with a powerful setup so i recommend that some deadband is left on the throttle. I ended up cutting 1 mm/0.04" off the added material to create some deadband, in my setup this works OK but i am running 1kw at the most.

Good luck folks, hope someone finds it useful! :D

ccmdr   100 W

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Re: Guide: fixing deadband of Wuxing hall throttle

Post by ccmdr » Feb 23 2016 6:17am

larsb - Thank you for the disassembly guide with picture's to boot. This'll be handy for eliminating the deadband and general throttle maintenance/waterproofing too :).

This'd be good to see in the Sticky e-bikes Technical thread. I've searched for something like this before and come up dry. Anyone else agree?
Evidence backs up solid ideas, otherwise your thoughts are a figment of your imagination or a lesson learnt :D

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spinningmagnets   100 GW

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Re: Guide: fixing deadband of Wuxing hall throttle

Post by spinningmagnets » Feb 23 2016 6:45am

...This'll be handy for...waterproofing too...

Firedog   10 W

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Re: Guide: fixing deadband of Wuxing hall throttle

Post by Firedog » May 29 2019 2:20pm

It is a bit difficult to get the snaps to release fully since they bite on the full perimeter.
That's "difficult" how about "nearly impossible"!

Get a short length of 3/4' pvc sprinkler pipe. It is the perfect OD and the perfect thickness to release the snap. I suppose a piece of 3/4" schedule 40 would work if you reamed the inside of the end the right amount with a conical reamer.

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