Wheel Building - Tongxin in Brompton wheel

[jerrysimon]

This post is part of a set of posts following my project to "E" my Brompton :

A. Wheel Building - Tongxin in Brompton wheel

B. Building a small A123 Battery Pack

C. E-Brompton First Ride/Tweaks

D. Taking a Tongxin motor apart

You may also like to check out daniel.weck's post here which covers the simlar use of Tongxin & Bafang motors and inpired me to give this a go.

A couple of related links as I was building

Throttle Controls

Connectors

Now a few bits are arriving for my E-Brompton project I am going to start a couple of threads. The first is this to follow progress building the Tongxin motor into a Bromtpon front wheel.

A couple of points to make clear from the begining.

1. I have never built a wheel from scratch before

2. I am using a Tongxin 80mm wide 36v, 260RPM front wheel motor. (Also known as a NANO motor)

3. I am sourcing the motor, controller and other bits from China.

4. I am building the battery myself using A123 cells, see other posts above.

5. Using this motor is not unique. I am certainly not the first or I suspect the last to try the DIY approach.

This motor has been well proven in this application. Tony Castles of the EWC was probably one of the first to do it. EWC has been taken over and you can buy kits from them or get them to do it for you. The new business seems well run and at the time of writing this post they seem to respond promptly to email, calls and enquiries. They told me last week that now they hope to have a turn round time of one week, from when a kit is ordered. Lets hope I don't regret not going down this route. If this is the case my loss will be your gain after you watch this project.

Also at the time of writing this post Freedom E have recently released a kit with a light weight battery.

I am on a steep learning curve when it comes to wheel building so I will be looking for input from some of the experts at it and I know there are a few on this forum.

It could all go horribly wrong but this post will hopefully help people to decide if to do it themselves, or just go for a ready made kit. My gut feeling is the latter is probably easier and certainly envoles less risk. But, I like the DIY challenge and if I have any problems in the future, I will hopefully know enough through this exercise to fit a new motor into a wheel.

First as per this post I purchased myself a truing stand. Not essential as you can do it in your forks using your brake blocks as reference. This one was going cheap from here so I purchased it for my project.

Note the graffiti on my worshop wall was added by my wife and kids, as I have spent some time in it over the years and its their reminder not to forget about them indoors lol

The Truing Stannd

Its a pretty basic stand but certainly functional. For the money I think it was worth getting. Notice the aligning pins either side of the rim for lateral truing. The other gauge I am pretty sure is for vertical truing (cirlcular truing ?) as it shows when the wheel is out of circular (see pic below). The final adjustment is dishing of the center hub which I guess means it moving side to side ? Again I am not sure but hopefully someone will chip in to confirm this. This needs another tool one of these though I have not seen them used in the videos ? Maybe this can be done by eye ?

Rear Cytronex wheel in the stand

As I have a puncture in my Cyrtonex back wheel and have the tyre off I thought I would pop it in to see how true it was. It was out a little so I starting turning "nipples" lol. After ten minutes it was even worse! I really started to panic but took a deep breadth, went and watched some of the videos below and realised I had been turning the nipples the wrong way. Looking down, clockwise loosens the spokes and anti clockwise tightens them up. I had been doing it the wrong way! Basically you tighten or loosen spokes on different side (tighten one one side loosen one the other side) to pull the rim left or right. The key is small 1/4 turns loosening and tightening either side to make the rim move in the direction you want. Depending on the length of out of true you may need to work on 3 or 4 nipples either side to get it true. Slow, taking your time and methodical is the way forward. See the links posted below for more info. Another 30 mins and I had it trued up well.

One thing I noticed is that the freewheel (cassette) side the spokes seem to be tighter (they have a higher pitch when plucked, the fourth and final measurement for truing) than the none freewheel side which are looser, lower pitch when plucked. Perhaps someone can advise ??

Close up of the pins that give you a reference for lateral truing of the rim.

Hopefully these post with give a little back to this forum which has given me so much help. I have made some good friends here, had some fun and its become a place I visit and read most days. There are some very experienced people here, so I will be looking for lots of feedback, encourgament and constructive critism when I make mistakes.


Regards

Jerry

 

[jerrysimon]

Before we start here are a few usefull links to read and watch for some intial insight into the whole process of wheel building and truing. Its all been done before and there is loads of info out there, so I am not going to go into great detail here on wheel building but just provide snap shots of my project.

Sheldon Brown's Web site

A great general resource for all things Bike. The above link takes you through wheel building from scratch.

Loads of videos on Youtube. This is a series I like, in a few videos it take you through the whole process from scratch. He also throws in some philosophy for good measure lol

YouTube - How to build a bicycle wheel - Part 1 36 Spoke

Regards

Jerry

 

[jerrysimon]

It seems that getting 36 hole Brompton sized rims is very hard. The only place that seem to sell them is St John Street Cycles here . They are getting some more 36 hole ones but not until mid Jan 2010!

**
NOTE : Read this, blank Brompton rims drilled with 36 holes are IMHO a much better option than using the Sun CR18 rims, especially if you are planning to fit Marahton Plus tyres.

**

Anyway I managed to get a made up one with a hub which I shall dismantle. Infact I plan to dismantle it and make it up again to get some experience before the Tongxin arrives and I have to do it for real.

Anyway here it is, in the truing stand.

As you can see the truing stand although speced for 16" wheels does not really work. The pins are not high enough to go against the rim. There are only two smaller holes at the bottom to fit them too. Anyway I am sure with a little fiddling I an rig something up. Annoying though

Anyway enough for today. More later. Tomorrow I will start another post on my A123 battery build.

Regards

Jerry

 

[jerrysimon]

Wheel rim dismantled and spokes and nipples which arrived from Taiwan.

 

[jerrysimon]

Meant to add these a week or so ago. Brompton finally turned up. I purchased it on our works cycle to work scheme which actually took an age to process. Anyway as you can see its a black M3L. I also got a C Bag as well which goes on the front mounting block shown.

Small Box

What's Inside

One of the few folds

In all its glory

Its a lovely bike and I have been out a few times on it vanilla. Its probably gonna be after Christmas before the Tongxin Ebike convervion is completed

Regards

Jerry

 

[Fecn]

Here's what I did when I made laced my wheel.

That wheel's done about 1500 miles so far without a single problem.

The green slab of MDF is for vertical truing, and the two hardwood sticks (in between the metal clamps) let me do lateral truing. Push the sticks up to the rim, spin the wheel, and if the sticks move, it's not true... and it's easy to see which stick moves out as the wheel spins.

When I first built the wheel, I had the dishing badly wrong for the bike, so I had to then re-true it all over again after I got it right. If I'd test-fitted on the bike once I'd got the vertical truing sorted, I could have got the dishing right first time.

 

[emissions-free]

Good work Jerry,

I will try to find a source for 36 hole 16" rims also, but I think they're like rocking horse do do I was ignorant of the fact that the smaller rims use less spokes because of the lack of space. Went to the Dahon shop which is quite close to me and am now much better informed They all seem to have 75mm forks and 28 hole rims....

Regarding the tension on the cassette side of the wheel that you noted. I believe that is quite common on dished wheels but don't know if it can be adjusted out. I had to dish the last wheel (sounds like I've built hundreds, actually only the 3rd....) I built as the motor is offset. What I did was to rue it as best I could at first. Then just added half a turn of tension on the side I wished to move the rim towards and removed half turn of tension on the other side. Doing each spoke in turn, starting and ending at the valve hole.

After each revolution see where your rim has moved to and continue the process until the rim is where you want it. If quite a lot of dishing is required you may need to repeat the process several times. Also you'll likely find that the spokes that you have been releasing tension from will likely need a little more tension adding to them. If you try to do this systematically by adding tension by eaqual amounts, starting and ending at the valve, hopefully it will not have gone too far out of true. After dishing you'll probably need to true it again and also once you've used it for a fey days, it'll probably need a little tensioning as the spokes settle down. I'm sure an expert wheel builder can just do it once and it doesn't need to be touched again, but I'm no expert

Good idea to break down the rim you have there and rebuild it a couple of times. Practise makes perfect and you'll quickly start to get a bit of a feel for it. I don't feel a dishing tool is strictly necessary, you should be able to get it close enough just using the truing stand and seeing where it fits in the fork IMO.

Please take everything I've said with a pinch of salt as I'm not an expert wheel builder.

Keep up the good work I'll be watching your progress.

 

[JamesC]

Jerry

Roger Musson's book on wheel building is very good - costs £9 and can be downloaded immediately in pdf form, then printed.

James

 

[andyh2]

I'll second Mussons' book. It includes how to make a dishing tool out of corrugated card and how to easily make a nipple driver which helps get all the spokes and nipples to the same starting point.

I found that and the Sheldon info a good combination for my first build.

 

[jerrysimon]

Wow just got up and you have all replied. Thanks very much guys, certainly gives me plenty to think about. I will take a look at that book.

Its Sunday morning and its p...ing down outside. Off to take my wife to the gardening center for our weekly morning coffee and browse. You have to keep her indoors sweet

I will start the A123 battery build thread shortly.

Fecn, I love you DIY jig very inventive

Regards

Jerry

 

[daniel.weck]

Hi Jerry, thank you for sharing your experience !

Being a keen guitar player, I am used to plucking strings and my ear is very accurate. I use the same technique for building my wheels and for adjusting the tension on a regular basis: "listening" to the spokes is the most efficient way of getting it right, for me anyway. I know people who cannot distinguish sound pitches very easily, so your mileage may vary.

You would have noticed your error immediately (when you first used the nipple wrench the wrong way) had you been plucking each spoke after each 1/4 turn or so.

You can even "play" the wheel like a harp as it is rotating on the stand (with both hands, one on each side). This way, you can spot uneven tension on one given side as well as inappropriate dishing (the Brompton front wheel should have no dishing at all, but I'm not sure about the rear wheel to be honest).

The key to be successful is to keep rotating the rim with nipple quarter-turns (always checking left and right sides for each rotation increment), until the spoke tension stabilizes uniformly.

My Bafang rim is still laterally and vertically true (and of course not dished), but unfortunately my tyre is slightly twisted in the rim well, so it makes the wheel vibrate at speed...that's my next job. I'm ordering new steel-reinforced tyre levers as well as the VAR tool, to avoid cursing on the super-stiff Marathon !

I hope you receive the rest of your kit soon !

Cheers, Daniel

 

[jerrysimon]

Ok now I have had chance to lick my wounds of pride, I can provide an update

The kit arrived quite quickly well packaged in about 10-12 days. I have two full kits, one is shown.

All looks great doesn't it

Read on.......

Jerry

 

[jerrysimon]

Now lets take a close up look at that motor

Oh no what is that!

Well folks its called a bushing for a roller brake. I kinda guessed I had made a mistake after ordering it. As you can imagine I was pretty gutted when I saw this and felt like calling it a day. So I put it all away and thought about it for a day or two. Always good to take a break.

Lets take a closer look with all the shaft fittings removed

Man that is some shaft lol

The first good news is that the flange on the shaft is removable and underneath is a regular one threaded all the way up. So if I put the first space nut back on we have this with the space nut sitting proud of the roller brake bushing/fange.

It gets better the space between the two flange nuts on either side is 80mm so this is going to fit in the Brompton 75mm forks
once they are spread. I weighed the motor as well and its the same wieght as the one Dan has, i.e. just under 2.1kg.

It looks like the roller brake bushing won't hit either. I have measured it all and it seems ok. That said I can easily take a few mm's off it if need be.

These 80mm motors are made to take a roller brake and then the spacer gives you a 100mm motor for standard bike forks.

So its not so bad after all. The only challenge now is that I may have to take off about 20-25mm of that shaft as its pretty long. I would need to put some sort of metal tube around the wire to stop it being damaged whilst I cut round the shaft. Any suggestions ?

I think even if I left it as it is, it would still allow the Brompton to fold as overall its not going to be wider, than the same forks fitted with a 100mm motor.

So the moral of this little exercise is if you thinking of ordering one of these 80mm motors, make sure you speciffy you want one without a roller brake

Interestingly as well is there are no labels on the motors, though the supplier assures me they are 36v 260RPM motors. Not sure how I can test them until I actually run them ?

Regards

Jerry

 

[jerrysimon]

Here is a close up of the controller.

It is not the original Tongxin plastic one as I had hoped. I purchased them because they were cheap ($20) and I had hoped at the very least if they were the Tongxin ones they would provide spares for my Cytronex. Alas they are not. Text on the case indicates they are 36V250W sensorless controllers. L.V cuttoff of 31.5 V. Not sure what the amps cut off is ?

I notice they have a few wires cut off as you can see.

Top - Right to Left

Motor - Green Yellow Blue
Power - Red Black
Thumb Throtte (I think) Black Green Red (Now tested this is the throttle connection)
Cut - Black Red Green ?

Bottom - Right to Left

Cut - can't see color brown I think ? (Its brown see inside controller in later post)
Brake I think - White Black
Cut - Earth Green and Brown

They are pretty easy to take apart so I may do that to check and see if I can find out what brand they are. There is a brand name DiYe on the case. Again comments welcome.

 

[jerrysimon]

Ok Thumb Throttle

I quite like it, has power indicator built in. Not sure what the red button is for, power on/off ?

Also it has two connectors one Red Black White and another seperate Green one ?

Again a couple of wires snipped off with no connectors on them Yellow and Brown I think ?

Well thats it for now. Bit of a Jigsaw Puzzle but hopefully I will get there.


Regards

Jerry

 

[emissions-free]

Jerry,

that doesn't look so bad. It wasn't as I imagined it would be, at least the shaft is already threaded all the way with flats.

If it's not too much bother opening the motor you could just pull the cable back through the shaft. If the Togxin is anythin like motors I've seen, the shaft with the cable entry is bolted to the motor assembly. Just remove the screws and pull the shaft section back over the cable and do the mods as required. You may need to remove some of the crimps for it to fit through the shaft. However if you're careful they could still be reused if you open up the part clamping the outer insulation, then just solder the wire back onto the crimp.

Some motors have a side cover that is threaded on, so in that case you'll have to knock up a tool that fits over the shaft and can be bolted onto the side cover to get it started, as they can be quite tight. If thats not the case the cover should come off quite easily. First remove the 6 side cover bolts and you'll need to use the same bolt holes to secure the tool onto the motor. It shouldn't be too tight if the motor hasn't been run but once it's been run they can be a bugger. You'll need to turn the cover in the normal direction for forwrd motion of the motor as they thread will typicall tighten as torque is applied by the motor. The tool I made up is just a piece of angle iron with a 40mm hole put in it with a hole saw. I then carefully put 2 holes in the correct position to line up with the side cover bolt holes. Use bolts that will not extend into the motor further than the original bolts. Once the cover is loose, remove the tool and continue doing it by hand.

However, please do not hold me personally responsible if this all goes horribly wrong as I've not opened a tongxin before.

The other option that occurs to me is this:
1. Try to pull the protective spring clear of the shaft.
2. Shape a small piece of metal and force it down 1 side of the entry into the shaft.
3. You could use a dremmel with a cutting disk to then slowly cut the shaft as required, ensuring that the protctive metal is in place to preven the cable getting knicked.
4. Get a needle file to all the edges on the inside of the shaft as best you can.

If you're careful I'm sure you could do the above without damaging the cable.

If you pull the motor apart the brake could be more easily removed. Just don't take too much material off it. There should be some be some bearings that need to be retained. A hack and dremel would do the job whether you pull the motor apart or not.

Best of luck Let us know how you get on.

BTW what do these tongxins weigh?

 

[emissions-free]

Ok Thumb Throttle

I quite like it, has power indicator built in. Not sure what the red button is for, power on/off ?

Also it has two connectors one Red Black White and another seperate Green one ?

Again a couple of wires snipped off with no connectors on them Yellow and Brown I think ?

Well thats it for now. Bit of a Jigsaw Puzzle but hopefully I will get there.


Regards

Jerry

The green is likely the battery supply voltage for the LED power indication. There will likely be a connector on the controller with small cables, probably red and black that has the battery voltage across them. The negative will be taken from the 0V on the throttle signal. I imagine the switch is a power switch if it is a toggle type. As it's likely not used on that controller, they've probably just snipped the connector off.

 

[jerrysimon]

that doesn't look so bad. It wasn't as I imagined it would be, at least the shaft is already threaded all the way with flats.

Thanks Paul,

Yer it appeared much worse when I first got the motors than it actually is.

I have read posts about taking the Tongxin apart and it is not advised

I have had the same thoughts as you about cutting the shaft carefully using protection for the cable as I go. I am going to fit the motor into the forks first anyway and then see how it folds before I cut anything!

The Roller Brake bossing probably won't need anything taking off it and I would only take a mm or two off if it needed it with a simple file.

Weight is as stated just less than 2.1KG

Regards

Jerry

 

[emissions-free]

Weighs the same as the small ananda 108 motor which is 2.05kg. I'm really keen to try the freewheeling on the Tongxin. The Ananda is a great little motor but it has some drag without power.

 

[jerrysimon]

I updated page one to show my new Brompton which finally arrived a week or so ago after a very protracted Cycle To Work process

Regards

Jerry