my first build: brompton at 30 mph

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Re: my first build: brompton at 30 mph

Post by d8veh » Feb 24 2012 5:08am

wesnewell wrote:
cwah wrote: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.

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Re: my first build: brompton at 30 mph

Post by d8veh » Feb 24 2012 5:15am

cwah wrote: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.

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Re: my first build: brompton at 30 mph

Post by cwah » Feb 24 2012 7:05am

Thanks dave. Will check with them. Maybe I won't need torque arm if then can make the dropout forend more beefy!
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by d8veh » Feb 24 2012 8:38am

cwah wrote: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.

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Re: my first build: brompton at 30 mph

Post by Scottyf » Feb 24 2012 11:01am

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.
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Re: my first build: brompton at 30 mph

Post by cwah » Feb 24 2012 11:36am

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)?
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by cwah » Feb 24 2012 11:48am

wesnewell wrote:
cwah wrote: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:
Image

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.
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by joe tomten » Feb 24 2012 12:55pm

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?

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Re: my first build: brompton at 30 mph

Post by cwah » Feb 24 2012 1:18pm

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.
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Re: my first build: brompton at 30 mph

Post by joe tomten » Feb 24 2012 2:34pm

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.

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Re: my first build: brompton at 30 mph

Post by cwah » Feb 25 2012 3:52am

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:
Image

Shall I ask for 145 mm dropout or shall I shave the motor dropout shoulder?
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by Ykick » Feb 25 2012 8:43am

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?
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Re: my first build: brompton at 30 mph

Post by cwah » Feb 25 2012 4:32pm

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.
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by wesnewell » Feb 26 2012 2:09am

cwah wrote: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.
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Re: my first build: brompton at 30 mph

Post by cwah » Feb 26 2012 7:17am

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.
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by cwah » Feb 27 2012 3:12am

Just went to the metal shop. They said they can't do it because of the metal bar in the middle of the fork. The bar in the middle was added at the end.

They said I need to have a new fork with the right size... but there is no way I can have that. :( :( :(
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Re: my first build: brompton at 30 mph

Post by adrian_sm » Feb 27 2012 4:22am

What rear brake are you planning on using?

The reason I ask is that if you don't need a rear disc brake, and you are running single speed on the rear, can't you modify the axle and reduce the required drop out width?
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Re: my first build: brompton at 30 mph

Post by cwah » Feb 27 2012 4:48am

I'm thinking about it. Will check later tonight.

but the hub may be too big for the fork
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by dogman dan » Feb 27 2012 6:37am

Steel right? Cut the crossbar, bend the forks yourself, then have someting put back to restore the crossbar. Perhaps a bolted on piece of angle iron. The metal shop is just covering thier asses, so you are on your own.

Do what you can to the axle, so you just bend the forks enough to clear the motor shell.

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Re: my first build: brompton at 30 mph

Post by cwah » Feb 27 2012 6:44am

Ok, you're right, I'm going to visit another steel shop. It shouldn't be that difficult :x
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by d8veh » Feb 27 2012 12:41pm

I don't see what the problem is. A competent metal-worker, who has a hack-saw and welding set could make the frame do whatever you want. To me, it looks a small job to heat up the stays and bend them to the right shape. You could, like said above, cut that cross-piece and weld in an extension, but I don't believe that it's necessary.

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Re: my first build: brompton at 30 mph

Post by cwah » Feb 27 2012 1:21pm

Just went to a frame builder shop... He said it was possible but may need to change the rear fork... And may cost 200 to 400£ or more :shock:

How come just widening the bike dropout could be that expensive.

I'm about to give up and just buy the Crystalyte G209... Will check other metal shop tomorrow
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by cwah » Apr 05 2012 12:54pm

News from my e-brompton build:
I'm now adding all the torque arms to my bike. I've 2 anti-rotation washer and:
- Conhistmotor torque arm (thinner) on the gear side:
Image
- Cyclezee torque arm (stronger) on the other side:
Image

This configuration should be enough to handle some torque :)

I'm trying to put the chain tensionner on top of the torque arm:
Image

The chain tensioner is not yet aligned with the chain:
Image

I'll have to keep filing the chain tensioner inside to allow it to go closer to the bike..

Now my biggest problem is that I've put too much strenght when I tried to tighten the motor shaft bolt. Now it's getting loose and I may need to change the shaft... but for that I'd probably need to purchase a new motor :(
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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Re: my first build: brompton at 30 mph

Post by d8veh » Apr 06 2012 3:53am

Cwah, I think that chain tensioner's going to cause a lot of problems. The way I understand it, all it does is keep the chain tight when you fold the bike to stop the chain falling off. As an alternative, couldn't you just carry a a bungee strap and hook it round the chain or between the chain and the frame just before you fold, and then remove it after you've unfolded.

I'm looking at your torque arms and the installation isn't the best. The axle will try and turn in the opposite direction to the wheel, so try and imagine what happens if they turn a bit. The one on the opposite side to the tensioner is too straight and the first bolt will slip. Ideally you need a right angle between the first two (from the motor) parts. Alternatively you need to get someone to weld the first joint so that the bolt can't slip.

I'm looking forward to seeing what you can get out of that motor.

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Re: my first build: brompton at 30 mph

Post by cwah » Apr 06 2012 5:44am

The chain tensioner allow me to keep the chain tight when I fold the bike, but also to keep the chain on the gear when I'm pedaling. If I remove the chain tensioner, the chain would just fall off the bike.

I corrected the torque arm angle in the opposite side of the tensionner:
Image

Is it better? :)
Help me find my stolen electric brompton: http://bit.ly/1a0vbBC and Bosch Sinus B3 http://bit.ly/1eV0WQz

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