Wheel Building - Tongxin in Brompton wheel

[Northern Irelander]

Ahhh I see you went with the old NI method (M10) in stage 3 afterall,

IIRC you had some diffs using the Sheldon Brown (RIP) method (length of timber) in the link above.

You can never have enough thread bar

 

[daniel.weck]

where are you people getting those digital calipers from? Saw a set on Screwfix but they don't look as good..

Mine is a cheap one from China (eBay purchase), it's fine but the hard plastic box is rubbish (oh, and the battery died, I should really replace it ).

 

[daniel.weck]

Oh no what is that!

Well folks its called a bushing for a roller brake.

Well, actually the grooves could hold in place a brake disc, like a Shimano SM-RT77:

 

[jerrysimon]

After spreading the fork arms, I then straightened the lugs / dropouts so they were parallel again (I imagine you did the same).

But the forks essentially remain too straight, they need to bend outwards a bit more, to open-up just like the famous cowboy stance

I haven't yet straighten out the lugs as they seemed square only having to open the forks up 10mm or so.

I need to take another look.

Well, actually the grooves could hold in place a brake disc, like a Shimano SM-RT77:

Thats cool, I may have found a solution for people who want to fit a disk brake with a Tongxin then

Regards

Jerry

 

[jerrysimon]

Ok just spent another 2hrs+ in the workshop

Torque washers now sit flat with nipples fully engaged. Took about another 1mm or so off into the fork cut outs. I really like the setup with the Brompton forks as the washer both stops rotation AND holds the motor up into the forks if the nuts get slightly lose. I may use the steel spacer that fits against the roller brake bush side, and get one of the engineers from work to mill it down to fit, rather than use three washers to get the clearance. For now, this will work though.

Intially I took a little bit off the roller brake bushing, but then realised that like the other side I could just use a spacing washer on this side too. The motor now sits well clear of the fork on this side as well.

Overall I am very pleased. The whole setup is a little wider, about 90mm in the forks rather than a regular 80mm wide Tongxin but its all good considering that when I first got the motor I thought it had all gone horribly wrong.

All that is left now is to build the motor into the wheel. Hopefully my A123 batteries will arrive soon and I can get to work building them to.

Regards

Jerry

 

[1967geezer]

A very interesting thread, thanks.

I'm in the process if kitting up a bike, I've been researching all different kinds of motors. I quite fancied the tongxin for size and noise levels, but had come to the conclusion that it was not compatible with disc (or any other kind of hub-mounted) brakes ...

The pictures you have posted would seem to suggest otherwise...

Do you have links to where you sourced your parts from?

Thanks, Chris.

 

[jerrysimon]

I have tried folding the Brompton and again it all seems fine although the longer shaft will mean that it folds more like a Brompton with a 100mm motor in it. I will try this first even though I could probably take off about 10-15mm of the shaft to close it tighter, but my feeling is the risk of damaging the wire and having a sharp end which may rub the wire as well makes it probably not worth it.

The catch

I will need to use a spacer and have also purchased the extension block mentioned on here by shemozzle999 here

This ensures the catch clears the end of the shaft nut/rubber cover so it can clip on the frame snuggly.

Regards

Jerry

 

[flecc]

Oh no what is that!

Well folks its called a bushing for a roller brake.

As Dan says, it's for a disc brake, roller brakes are never fitted on hub motors. The other type of brake that
appears on these is the band brake, often mis-identified as a roller brake, and that hub motor fitment consists
of a plain drum, here coated with a rust preventing coating since it's not in use on the bike it's fitted to:

 

[jerrysimon]

Flexc I am sure you are right though even Tongxin label it as a motor for a roller brake. Probably a Chinese translation error.

At least I may have found a solution for people who want to use a Tongxin with a disk brake fitted

Regards

Jerry

 

[RobinC]

The splines look to be too big for a centrelock disc mount, so I think it is intended for a roller brake. The larger slots in the pictures of the Shimano disc above are on the lock ring which holds the disc onto the hub. It uses the same tool as used for cassette lockrings.
Shimano XT disc hub
Nexus hub with roller brake mount

Robin

 

[jerrysimon]

Robbin your right the second image does look more like the spline on the Tongxin.

It also has a simlar spacer as shown here

Regards

Jerry

 

[RobinC]

Not easy to find but there is a roller brake to disc brake adapter available:
Cesur disc adapter
Installing adapter

I don't know if it has been tried on the Tongxin hub.

Robin

 

[flecc]

The splines look to be too big for a centrelock disc mount, so I think it is intended for a roller brake. The larger slots in the pictures of the Shimano disc above are on the lock ring which holds the disc onto the hub. It uses the same tool as used for cassette lockrings.
Shimano XT disc hub
Nexus hub with roller brake mount

Robin

Thanks Robin, interesting. That's a first for Tongxin, using a roller brake on a hub motor, the other hub motor
companies all using the band brake or disc brake on these. I don't like the idea though, given how weak roller
brakes generally are.
.

 

[1967geezer]

Jerry, any chance of a link to where you bought the motor & controller from? The tongxin site doesn't appear to handle internet sales.

http://www.tongxin.net.cn/en/product.htm

Chris.

 

[RobinC]

Thanks Robin, interesting. That's a first for Tongxin, using a roller brake on a hub motor, the other hub motor
companies all using the band brake or disc brake on these. I don't like the idea though, given how weak roller
brakes generally are.
.

The smaller roller brakes were very under-whelming, the IM70 is OK-ish and the new IM80 might be a decent brake.
Look at IM80 vs IM70 halfway down page

Robin

 

[z0mb13e]

where are you people getting those digital calipers from? Saw a set on Screwfix but they don't look as good..

Maplin do them for £20, but keep an eye out as they are often on special for a tenner.

100mm Digital Vernier Calliper : Enviroment Testers : Maplin

 

[jerrysimon]

Maplin do them for £20, but keep an eye out as they are often on special for a tenner

Those are only 100mm/4" ones. I think 6" or 8" ones are far better for general purpose use.

PS I have been PMing people details of the supplier/contact I have.

Regards

Jerry

 

[jerrysimon]

Ok had a little time after the Boxing day walks to intially lace up my wheel.

I am pretty sure its NOT quite right. The pattern is right but my inside spokes are leading not trailing when the wheel it rotated in the correct direction for the bike to move forward. I need some of you expert wheel builders to comment

This picture was taken near the end of the process where I found it necessary to place the wheel on my lap and push down on the hub to get the last few spokes in.

Ok here is a picture of the wheel from the side. In this picture the wheel will roll clockwise towards the right for forward movement. Note how the trailing spokes are then on the outside of the flange rather than the inside for this movement. I think technically this is wrong. Interestingly my Cytronex wheel appears to be the same though on that, the spokes go over one spoke and under a second spoke before entering the rim. On this smaller wheel the spokes on the outside of the hub just go over those on the inside of the hub as there is not enough flex/room for them to go under.

So in summary if you turned the wheel anti clockwise i.e the bike was moving backwards, the spokes would be correct i.e. inner hub spokes would be trailing and outer hub spokes would lead. Ok final picture looking down.

Its all loose at the moment so easily taken apart again. The spokes on the outside of the hub do bend out a little and are not touching the spokes on the inner side of the hub where they cross. I assume as I tense up the wheel they will touch/rub ?

I have each set of spokes going into the correct offset rim holes left and right. Interestingly at this stage all the spokes on the inside of the hub are rattley loose whereas the spokes on the outside of the hub have some tension in them as they had to be bent over slightly to get them into the rim holes. Is this correct ?

Regards

Jerry

spokes are

 

[jerrysimon]

Here is the Cyrtonex wheel which is identical to my build above except as I said the spokes are laced over under on each side of the hub flange.

Regards

Jerry

 

[JamesC]

Jerry

I don't qualify as an "expert" wheel builder, but have enjoyed building 700C large diameter wheels for the Bafang motor on the Torq, and more recently for the hub geared wheels on the back of the Kalkhoffs. I am a big fan of Roger Musson's techniques, and the wheels have given no trouble !

Correctly, you have used a "1 cross" lacing pattern because of the large diameter hub and the small diameter rim (mine have all been large diameter rims like your Cytronex, using a "2 cross" pattern).

With the wide spacing of the hub flanges, personally, I would prefer that the "trailing" (or "pulling") spokes arrive at the inside face of the flanges, giving a straighter pull.

This is not a hard and fast rule, and you will find wheel builders are divided on the subject.

As you begin to even up the tension on the spokes, it is most important to work on the stress relieving of the spokes. Wear leather gloves and "squeeze" pairs of spokes together, such that the 90deg elbows are moving towards 95deg for those on the outside of the flange, and 85deg for those on the inside of the flange.

This aims to make a straight spoke from flange to rim, rather than an arced spoke which is flexing continuously at the elbow.

As you apply more tension to the spokes, you might interrupt the work 4 or 5 times to stress relieve the spokes. Some consider this the most important step.

James