Wheel Building - Tongxin in Brompton wheel

[jerrysimon]

Hi Jerry, Daniel et al.
Freedom Ebikes has been a bit quiet on this forum while we've been busy growing the business and getting large amounts of stock to avoid the problems others have had with supply.

I have a few comments on Daniel's build given that he's done for himself quite similar what we supply as a complete kit.

Hi Andrew its good to see you back posting on the board.

1) Re the spoke lacing of tonxgin into 16" Brompton rim: Freedom Ebikes started out radial, moved to cross and then moved back to radial after Ian Sims of Greenspeed (a world expert in small wheels) confirmed in A to B magazine that a radial build was the best option for a 250watt hub motor in a 16" wheel.
A lot of people have done a cross because of what is written on Sheldon Brown's site but it seems clear that he was talking about larger wheels and (importantly) the more powerful (500 - 750 watt) motors allowed in the US.

I am still not convinced I would use radial spoking on this Tongxin hub, though your points do have merit.

2) The Sun Ringle rims are excellent but difficult to get some tyres onto. The solution is just good quality metal tyre levers.

Getting them off and on is possible (I can even get the tyres on without levers). The real issue is getting them off (Marathon plus at least) without damagining the bead which in my view after a few times is not possible.

3) We have large supplies of tonxgin motors, controllers, throttles and 36 hole 349mm (16") rims and high quality A123 battery packs direct from A123 itself for do-it yourselfers

That is great news! There are quite a few of us DIYers that would would like to buy these parts especially motors and controllers from you. Could you post some prices maybe in the for sale area ?


Regards

Jerry

 

[mj8765]

Radial v Cross wheel lacing

Hi Andrew - could you post the advice from A to B re radial spokes - I didn't see that article. For the Nano Brompton - we took some advice from a pro bike shop that the way to go to deal with the torque generated by the motor was a cross pattern but with the cross not "laced" ie spokes not crossed over each other as there was not really enough room. We were also advised that the outside facing spoke (which apparently can carry the most load) should be angled backwards on the rim so that it was this set of spokes under tension when the motor was pulling.

Martin
the electric wheel company

 

[Pedalo]

Hi Martin,

I spotted a reference to it on page 9 (letters page) of issue 76 (Feb 10).
It was a letter about small wheel spoke breakage.

I remain to be convinced either way but it would be intersting to know if anyone has experienced spoke breakage on a 16 inch wheel fitted with a motor? If so what spoke pattern was used?

 

[daniel.weck]

For the Nano Brompton - we took some advice from a pro bike shop that the way to go to deal with the torque generated by the motor was a cross pattern but with the cross not "laced" ie spokes not crossed over each other as there was not really enough room.

That's how I laced my 16" motorized rims too. Otherwise the spokes would bend too much at the crossing points, which would generate stress in the steel structure (...and that's potentially more damaging than when spokes are screwed-in with left-over twisting/rotating force, apparently).

A note for readers who are new to wheel-building: spokes should normally "touch" each other at the interlaced point (last crossing), as this helps distributing the tension. The only way to interlace the spokes is to bend them gently, but in the case of small wheels with large diameter hubs, the spokes are so short that this would likely bend them beyond the steel rebound threshold.

More info online from Sheldon Brown, and from Jerry Simon's recommended book:

Wheelbuilding

We were also advised that the outside facing spoke (which apparently can carry the most load) should be angled backwards on the rim so that it was this set of spokes under tension when the motor was pulling.

Yes, it is generally recommended that trailing spokes (the ones that seem to "pull" the rim due to drive torque originating from the hub) are located on the inside of the hub flange (heads facing out). The rationale is based on the fact that trailing spokes are under more stress than leading ones, but bearing in mind that there are actually cases where the aforementioned recommendation is inverted ! (depending on the type of gears, brakes, etc.) Everyone seems to agree that this is not the most critical part of wheel-building: good wheels can be built using either side of the flange for trailing spokes.

 

[daniel.weck]

it would be intersting to know if anyone has experienced spoke breakage on a 16 inch wheel fitted with a motor? If so what spoke pattern was used?

I fear there is a misleading emphasis on hub motors in this discussion: human power applied to the cranks can generate a considerable amount of torque in the drive hub (normally at the rear, although there are front-wheel-drive recumbent bikes...but I digress). Whether it is a front or rear wheel, the wheel-building principles are exactly the same (bar dishing/asymmetry requirements to accommodate drive sprockets / disc brakes): in other words, a badly-laced rim will be prone to breakage, regardless of whether human power or an electric motor is driving the wheel.

The most common factor leading to spoke breakage is actually not so much the lacing pattern, but the uneven tension (often lower than required) in the spokes. Decent Local Bike Shops normally check spoke tension before delivery, but that is often not the case with online-purchased bikes, poorly-assembled Halfords ones, and I'm afraid to say...even Brompton bikes have had the reputation to be sold with loose spokes. Professional wheel builders take their time to not only lace the rims and make them true, but also to relieve tension, etc. (all the finishing touches that make a wheel last). Mass-produced bikes don't get that level of attention, thus why the LBS usually check these things out before delivery to the customer.

Cheers, Dan

 

[Pedalo]

Hi Dan,

Yes I agree totally. There is a subtle difference when a hub motor is used though because of the larger diameter hub, shorter spokes and less than ideal angles of spokes entering the rim when cross patterns are used. I just wanted to know if there is any evidence of higher than normal incidence of spoke breakage when this is the case. The implication from the letter in A to B is that there might be.

Cheers,

 

[apshamlton]

Letter from Ian Sims of Greenspeed

Home » A to B » February 2010


Small Wheel Spoke Breakage
I was interested to read in A to B 75, about the possible reasons for spoke breakages in small wheels. Having used small wheels on our recumbent trikes for 20 years, I’d like to suggest that the main reason for any increase in breakages is the fact that because the spokes are shorter, they are stiffer, and will need less fretting for the tension to drop by a given amount.Thus it is easier for the spokes to become loose, be it from the elbow of the spoke elongating the hole in the flange, the spoke head moving in the rim hole, or whatever. And as soon as the spokes drop below a certain safe tension, there will be more flexing at the elbow, which is what causes spoke breakage. Of course this will be exacerbated by the heavier rider, where the spokes will go through a greater range of tensions between the bottom and top of the wheel.

So to go for 13g spokes over 14g spokes seems to be partly self-defeating, as they will be stiffer than 14g spokes, and harder to tension. In my 20 years of building recumbents I have never come across any spokes which have broken at the nipple. Thus in my opinion, the best solution is to use SINGLE butted 13/14g spokes. Spokes made for 700c and 26" wheels often have quite long butts, and the butt is obviously stiffer than the rest of the spoke, so I would suggest the best solution is a spoke with a short single butt at the elbow end.

ABOVE: A single butted spoke - thick at the hub, where most breakages occur, but tapering down to a thinner section all the way to the rim.The smaller the

We have also saved weight by using 14/15g spokes, with no increase in spoke breakage over the 14g spokes. Another problem which can occur with small wheels is some people using the wrong spoke pattern.While a 4-cross pattern may be OK on a 700c wheel with small flanges, such a pattern used on a 16-inch wheel - especially with a small spoke count and a large hub - will result in the spokes bending at the nipple, which will prevent the nipples from being tightened enough to get a safe tension in the spoke. I was pleased to see that the hub motor on the Freedom Brompton on page 26 was laced radially - ie with no spoke crosses. In my opinion this is the correct pattern for a such a large hub in a 16-inch wheel.

gauge number (g), the thicker the spoke: this rather extreme example is a 12/19g BELOW: A very neat lightweight 16-inch wheel built by

Ian Sims using 15/16g spokes

Ian Sims, Greenspeed, Ferntree Gully, Australia A to B magazine, folding bikes, electric bikes, electric motorbikes, trailers, sister publication to Miniature Railway magazine

9

A to B 76 Feb 10
Copyright © 2010 Exact Editions and the publishers of the titles represented

 

[apshamlton]

I tend to think that Ian Sims is a better expert on small wheels because that's been his main business for 20 years and he is considered a legend in the Australian cycling community - and I'm Australian
Also Sheldon Brown is unfortunately no longer with us to be asked the specific question regarding 250 watt hub motors and small wheels.

 

[daniel.weck]

Ian Smith (all due respect to him) expresses his opinion by arguing that the acute angle at which the nipples enter the rim holes may eventually prevent spokes to retain their tension, and as we know, loose spokes is one of the main factor for breakage. However Ian fails to mention the difference between a 36H and a 28H rim, and furthermore his remark may well apply to large motor hubs (direct drive or with internal reduction gear), not necessarily to the small Tongxin. Does Ian have any experience with various types of hub motors ?

My own experience with a 36H rim and the Tongxin motor laced using a cross-1 pattern is that the angle of incidence of spokes at the nipple level is not that much more acute than say, a normal 28H Brompton/Moulton wheel laced with a gear hub. The robustness gained by not using a radial lacing pattern far outweigh the possibility of spokes coming loose, especially considering that spokes should be checked and tightened regularly anyway.

Now, things panned-out totally differently with my 8-Fun motor (Suzhou Bafang): it is larger in all dimensions (which implies a more problematic angle of entry of the spoke into the rim hole) and it was laced into a 36H rim with brass eyelets (which essentially makes the rim holes smaller, essentially generating further stress into the spoke nipple). As a result I must service / check this wheel more often than usual, but there is no way I would use a radial lacing pattern with a torquey hub motor like this one !

Best regards, Dan

 

[apshamlton]

Freedom Ebikes now has parts pricing for DIY enthusiasts on its website Freedom E-Bikes - Home

 

[daniel.weck]

Freedom Ebikes now has parts pricing for DIY enthusiasts on its website Freedom E-Bikes - Home

Thanks for the heads-up on part pricing

One remark: the funky typeface used in the menu on the left is fine for the title of the website, but it makes the text near-unreadable in the menu itself.

Cheers, Dan

 

[jerrysimon]

Liked the video

Freedom E-Bikes - Videos

Regards

Jerry

 

[daniel.weck]

Liked the video

Freedom E-Bikes - Videos

Looks like a hot day

High-res video here:

YouTube - Kanal von FreedomEbikes

 

[daniel.weck]

Fantastic video documentary called "Ride of My Life, The Story of the Bicycle". Wheel builder guy at 5mn40s into the video (weird accent/elocution, but obviously quite good at lacing/truing wheels ):

YouTube - Ride of My Life The Story of the Bicycle Part Four