Good metal worker in london?

[eddieo]

Johnc seems like best plan if he is up for it......get it resprayed as well though.

can you remove rear fork frame? is it bolted through near crank as it looks like it is......

 

[jerrysimon]

A heavy rear mounted hub motor will make swinging the rear frame under cumbersome. In addition widening the rear frame will almost certainly compromise the fold.

I have been riding my Brompton for nearly two years and 3000 miles and have a little play in the back hinge, with that setup the rear hinge will also be under a lot of extra load.

The rear frame can be removed but re-assembly requires a special tool to tap out the frame tube to put new bushes back in. There is a cheaper DIY work round using a generic tap on either side, but quite a percision job.


Regards

Jerry

 

[cwah]

It seems there is something I can unscrew. But not sure.

Anyway, it's better to work with the entire bike to make sure it can still fold correctly with the wider dropout.

 

[jerrysimon]

It seems there is something I can unscrew. But not sure.

I wouldn't advise even attempting to loosen the flush allen bolts on either side, unless you want to remove the frame. The bolts are done up and sealed with a locking compound. If you disturb them the bushes will become loose and the whole back frame will develop side to side play.

Regards

Jerry

 

[cwah]

I would advise even attempting to loosen the flush allen bolts on either side, unless you want to remove the frame. The bolts are done up and sealed with a locking compound. If you disturb them the bushes will become loose and the whole back frame will develop side to side play.

Reghards

Jerry

Thanks Jerry.

My project seems complicated. Not sure how it will fold afterward with a heavy motor.. but first, get it sorted lol.

 

[jerrysimon]

NP. BTW that should have read "I wouldn't advise". That typo changed the whole meaning

Regards

Jerry

 

[Scottyf]

Never short of Fabricators in Birmingham. But then the city is quite industrial and fully of working class brummies that are happy to get a Ham sandwich for and a pint.

I really hope you do get this sorted Cwah. Your poor posts are nothing but a struggle from one problem to the next.
It was never going to be a simple task to get a bromton to do that speed, be light, have lots of torque and the rest of it.

It simply does not mean its possible but it puts alot of modification into the process of the project. To the point where people that have the engineering skills only do these sort of changes.

I'm really suprised there's no one local but I guess its London and untill you move further outside you don't get much on the manufacturing front.

Might even be worth finding some colleges or uni's that specialise in enginnering and welding... Its an option anyway.

I really hope its worth the toil and you get what you wanted but I guess thats why its not been attempted by many.


I personally poop myself at 30mph+ on a 700c Hybrid with good wheels / tires and a stronger not modified frame. The brakes at that speed need to be good with the weight and momentum.
My 160mm disks are very very hot after a few fast stops. They even steam water when in the rain.

 

[cwah]

Jerry that's fine, I've noticed the typo

Scottyf, I wouldn't mind sending the bike to Birmingham if I can get it sorted that way. It's not that far from London. But I'm still trying some london metal shop first.

 

[neptune]

I would guess there is a metal worker living within five miles of you . Ask around back street garages to find someone who can weld a car chassis . Pick an old grey haired guy who can use oxy-acetylene equipment as well as MIG . I knew such a guy , my best buddy , but sadly he is no longer with us . I would cut the bridge piece centrally , and then sleeve it with sheet metal welded into place . By the way , is an oxymoron a really bad welder ?

 

[johnc461165]

Still following this thread cwah seems you still need some thinking time, however I am still here and have MIG welder plus 50 years experience in engineering, only proviso is that the forks are steel not alloy. John

 

[jerrysimon]

only proviso is that the forks are steel not alloy. John

The whole Brompton frame, rear and front forks are steel.

Regards

Jerry

 

[Deleted member 4366]

Cwah, if you can remove the whole front of the bike at the folding point, then remove the pedals, You wouldn't need a very big box to send it to John.

I just had another thought. I was wondering whether you could modify a front motor rather than use that one. I made an adapter like this from a pressed steel BMX hub. If the motor side plate is thick enough, you could drill some holes in it and bolt the adaptor to the side for a total width of about 120mm.
Bafang Crank drive pictures by d8veh - Photobucket

 

[cwah]

Still following this thread cwah seems you still need some thinking time, however I am still here and have MIG welder plus 50 years experience in engineering, only proviso is that the forks are steel not alloy. John

Today is my lucky day! Thanks a lot John. PM sent.

 

[cwah]

Cwah, if you can remove the whole front of the bike at the folding point, then remove the pedals, You wouldn't need a very big box to send it to John.

I just had another thought. I was wondering whether you could modify a front motor rather than use that one. I made an adapter like this from a pressed steel BMX hub. If the motor side plate is thick enough, you could drill some holes in it and bolt the adaptor to the side for a total width of about 120mm.
Bafang Crank drive pictures by d8veh - Photobucket

That's a good idea Dave.

I have no real experience with a drill and neither about opening a motor. Not sure if I'm good enough to do that yet.

And the brompton rear fork width is 112 mm. Not sure if that may work either.

So maybe for now it's better to extend it to 135mm. So I can also fit other motors later.

 

[wurly]

Why don't you hacksaw down through the crosstube first, then you will be able to prise the forks apart. I also think that the dropouts will need pulling back to align with the hub. If so, cut some reliefs (we call 'em piecuts) in the tubes near the dropouts, then....when the motor is fitted in place you can finally get the frame welded. I've had years of fabricating and thats how i would approach it.

In fact, i'm heading up your way on Sunday. If you can get to the M25 somewhere, i'll take your rear frame with me and i'll do it for you. You can organise a courier to get it back. I have a tig welder also.

Another thought....i have a powerful propane torch so i can also heat the frame instead to align the dropouts. You will have to paint it after of course.

 

[Cyclezee]

What a team you guys are on here, it never ceases to amaze me the way people rally round to help a fellow member with something approaching mission impossible.

I can weld, braze and solder steel, titanium and precious metals, but do not have the capacity to for objects as large as bike frames.

Excuse my ignorance, but are Brompton frames welded or brazed?

 

[jerrysimon]

Excuse my ignorance, but are Brompton frames welded or brazed?

Brazed as per the info published on their web site here.

"The Brompton is brazed rather than the more common practice of welding. Brazing is a highly-skilled and labour-intensive method which introduces less heat to the metal than welding: this maintains a stronger frame with less distortion. This enables Brompton to continue to use high tensile steel alloys which deliver the rigid frame that is at the heart of Brompton's quality ride and longevity."

Interestingly it mentions steel alloys for the frame construction ?

Regards

Jerry

 

[flecc]

Yes, I've watched them brazing the Brompton frames on TV.

 

[Cyclezee]

Brazed as per the info published on their web site here.

Interestingly it mentions steel alloys for the frame construction ?

Regards

Jerry

Sorry Jerry, maybe I dimmer than usual tonight, I know you are not, but steel is an alloy, so I am not sure what you meant?

I know Brompton also produce a model with titanium parts too, but very expensive.

 

[cwah]

Why don't you hacksaw down through the crosstube first, then you will be able to prise the forks apart. I also think that the dropouts will need pulling back to align with the hub. If so, cut some reliefs (we call 'em piecuts) in the tubes near the dropouts, then....when the motor is fitted in place you can finally get the frame welded. I've had years of fabricating and thats how i would approach it.

In fact, i'm heading up your way on Sunday. If you can get to the M25 somewhere, i'll take your rear frame with me and i'll do it for you. You can organise a courier to get it back. I have a tig welder also.

Another thought....i have a powerful propane torch so i can also heat the frame instead to align the dropouts. You will have to paint it after of course.

Thanks Wurly

I just sent a pm to John because he was ok to help too. I can't of course ask the favor to both of you lol. I may contact you before sunday if there is any problem to ship the bike to John location.

This forum and you guys (especially wurly and john) are all amazing!! Thanks