my first build: brompton at 30 mph

[joe tomten]

cwah,

Any possibility of finding a friend who has an oxy welding rig? I really doubt if mapp gas will get it hot enough to allow the steel to form to new shapes easily.

I'll still lobby for the threaded rod and hot heat approach. And i worry that the length of the stays beingso short that the generalized bending approach of the lever or jack might not produce results that you are hoping to avoid.

With the threaded rod - You can work slowly and with lots of control. And you can thus tailor the shape of the assembly so that it is not necessarily symetrical from side to side (which it looks like you will need here in order to deal with the chain line issues.). You could use those big holes just to the side of the axle dropouts, get 1/2" threaded rod, some nuts and some big bearing washers.

If it were me doing this job, i'd go ahead and lace up the wheel and have it standing by while i was doing the job so i could constantly fit and refit it, and explore all the issues that presented themselves. Chainline, brake fitting, & for 25+ mph I'd certainly want an 11t sproket on there.

Patience will be rewarded. Impatience may be punished.

Good luck.

[cwah]

I definitely agree with you Joe. But I don't have a friend with oxy welding rig. And I don't know if there are workshop in london able to do that.

My solution for now is to use butane torch and car scissor jack. It's steel so it should be ok.

I've seen some butane torch at 1300C. It's quite hot. How hot should that be to bent the metal?

[joe tomten]

1300 Farenheight is all you need for heat relief.

Do the threaded rod for more control over the bending process.

[cwah]

Can I use this one?
http://www.ebay.co.uk/itm/Jet-2000-C-Butane-Torch-Dual-Flame-Keychain-NEW-/170777055708?pt=UK_Collectables_Tobacciana_Smoking_LE&hash=item27c31b11dc#ht_500wt_1413

It says 2000C but seems to be a bit small for the job

[Ykick]

Can I use this one?
http://www.ebay.co.uk/itm/Jet-2000-C-Butane-Torch-Dual-Flame-Keychain-NEW-/170777055708?pt=UK_Collectables_Tobacciana_Smoking_LE&hash=item27c31b11dc#ht_500wt_1413

It says 2000C but seems to be a bit small for the job

Ridiculous... You need hands on help for this!

[cwah]

Ykick, can you provide a link to a butane torch that worth it but is still cheap? I'll only use it once.

[Ykick]

Ykick, can you provide a link to a butane torch that worth it but is still cheap? I'll only use it once.

You don't need a torch any more than you need that spreader contraption from your pics. You need to find somebody with a torch who knows how to use it and who's willing to let you watch and learn how to work metal.

I've found small auto and muffler shops to be approachable with my eBike metal work needs. Much more receptive and genuinely interested than most LBS. That's my advice, do with it what you will...

[d8veh]

Cwah. This is a tricky job. You need the frame to bend evenly on both sides and in the right places. If I were you, I'd get the wheel built, and then take the frame and the wheel to a local fabrication company. Explain to them that you want the dropouts parallel, wide enough to fit the motor, and the rim central by applying heat. They'll know how to do it. Look in your yellow pages, Thomson directory or internet search to find local fabrication companies. There's always loads of them. They should charge about £30 to £50. If you're really lucky, they'll do it for a drink. Car bodywork repair shops should be able to do it as well.

[cwah]

What is a local fabrication company?

I've seen this site as you told me: http://www.thomsonlocal.com/BusinessFin ... &2Box=true
Not sure if the results are relevant?

Or I can go to any car repair shop?


For 30-50£ it's a perfectly good price. If the price range is around that it's much better to ask them for help.

[wesnewell]

I'm soo impatient to have my motor fitted... Do you think I can do it with my wood bar or shall I go buy the torch and the car jack?

Well, I've done 3 bikes using wood. Don't see why someone else couldn't do it too. Only takes a minute or two. It will spring back some, so you probably want to go to at least 150mm before knocking the wood out.

[d8veh]

I'm soo impatient to have my motor fitted... Do you think I can do it with my wood bar or shall I go buy the torch and the car jack?

Well, I've done 3 bikes using wood. Don't see why someone else couldn't do it too. Only takes a minute or two. It will spring back some, so you probably want to go to at least 150mm before knocking the wood out.

This one's a small wheeled folding bike .The frame is relatively more stiff - not as easy as a normal bike.

[d8veh]

What is a local fabrication company?

I've seen this site as you told me: http://www.thomsonlocal.com/BusinessFin ... &2Box=true
Not sure if the results are relevant?

Or I can go to any car repair shop?


For 30-50£ it's a perfectly good price. If the price range is around that it's much better to ask them for help.

Steel fabrication means making stuff out of steel: cutting, welding, bending, etc.
Go down to the railway arches: There's sure to be someone there that can do it. Normally they all know each other, so someone should be able to point you in the right direction. Here's a list from Thomson, but some of them will only do big industrial work, others might do some other specialist stuff. You need to try and find a one-man type outfit. I think the first one in the list could be a good bet.
http://www.thomsonlocal.com/BusinessFin ... &2Box=true
These people should be able to make new drop-outs for you as well. they can cut off the old ones and make new ones how you want (thicker. longer, more supported) as long as you explain to them clearly what you want.

[cwah]

Thanks dave. Will check with them. Maybe I won't need torque arm if then can make the dropout forend more beefy!

[d8veh]

Thanks dave. Will check with them. Maybe I won't need torque arm if then can make the dropout forend more beefy!

Your drop-outs are very simple - just a small flat plate welded on. It would be a small job to grind off the welds, make new longer/deeper/thicker ones and weld them on.

[Scottyf]

Indeed Dave is correct. As the bike is steel you can find lots of local places that will be very good at making and welding new joints.
This will make the bromton very strong.

But you need to know what your asking.

Even if your not i've always found new projects and things that are quirky really inspire engineers to work their best.
They like doing things that are out of the ordinary.

Take the hub laced in a wheel and just say I need this to fit in here. But I would need the srop out to be thicker to stand the rotational force from the axel. It will put put xx nm torque and they will cook you up something on the cheap.

I'd almost weld a complete new drop out thats wider than the frame. Making it the 130mm width thats needed.

[cwah]

I just went to the steel shop recommended by Dave (thanks ), they said they can do it. I have to meet them with my bike this monday.. I almost want to find another place to get it welded during the weekend lol.

I can't go directly with my wheel because it has not been laced yet. I have to contact alan to lace it. I'll just meet them with the motor.

And I'm not sure to keep this motor anyway, I'll just ask them to provide 135mm dropout symetrical on both side. So it will be easy for me to change motor if I want to.

So my request will be:
- 135 mm dropout wide
- Stronger forkend able to handle 150 nm torque
- Forkend alignment to handle the motor
- Symetrical alignment to the bike frame

The rim would probably not be central because my wheel is not laced yet.. is it a big deal or shall I get it laced first (send it to alan and get it back will take some time)?

[cwah]

I'm soo impatient to have my motor fitted... Do you think I can do it with my wood bar or shall I go buy the torch and the car jack?

Well, I've done 3 bikes using wood. Don't see why someone else couldn't do it too. Only takes a minute or two. It will spring back some, so you probably want to go to at least 150mm before knocking the wood out.

I'm not sure wood would work with my bike. The leverage area is not good:


There is a central steel bar on the middle of the fork as main support. With the wood I'll mostly bend on the area with screws and not the fork itself.

[joe tomten]

Things to think about:

How big of a tire do you want to run?

Do you want that multispeed freewheel? and how will that affect the chainline?

[cwah]

As biiig tire as possible lol. But I think I'm going to be limited by the brakes.

And single speed freewheel is enough. Don't know how that can affect the chainline.

[joe tomten]

I have a Brompton front fork here, and the 16" * 1.95” hookworm won’t fit. A 1.5” Schwalbe marathon winter fits in there with room to spare.

If you want a fattie tire in there the flaring you have done will need to start far out from the axle - which might introduce it's own complexities. Probably best to stick with the least complicated bending and be happy with 1.5 to 1.75 tires.

[cwah]

Ok, will stick to the inital tire then.

I just noticed that my motor dropout is 145mm and not 135mm as advertised for single speed:


Shall I ask for 145 mm dropout or shall I shave the motor dropout shoulder?

[Ykick]

Your method of measurement looks suspect to me so I'd go with the engineering drawings and request 135mm. Leave the file and axle alone. If you can take an absolute accurate measurement and it's indeed 145mm then maybe request 140mm and man handle it with a pry bar while installing.

I'm only looking at cut-off pictures but my eyes question if the body of that motor is gonna fit inside the frame dropout without some serious reshaping?

[cwah]

I don't know either. If it need serious reshaping so be it.

I'll ask them to go for 135mm or 140 mm. I can still shave the dropout anyway.

[wesnewell]

I'm not sure wood would work with my bike. The leverage area is not good:
There is a central steel bar on the middle of the fork as main support. With the wood I'll mostly bend on the area with screws and not the fork itself.

Well, rethink how you are going to use the wood. And not like in your photo. Stand the wood on end on the ground. Put it between the insides of the *forks* sideways. Take a sledge hammer and pound the wood into the forks spreading them apart. If you don't understand, I'll try and draw a picture, but I'm a lousy artist.

[cwah]

I don't know if I'll do it correctly with a wood bar. It's quite a lot to be widened. I'll see tomorrow with the metal guy.