bending & cutting a frame

[stormbird]

Hi all

Here in the UK historically we have never built many bikes with curves in the frames [ unlike the beauties you have access to in the USA & Australia ].

So when it comes to hacking , the frame shapes I get access to are limited in geometry are boring and need some help to look good.

I built a simple chopper with a couple of hacks to a ladies brazed lugged frame , I added 2 foot to the forks and cut rear end from the frame and added 9" and a small curve to the chain stays and then some new seat stays to give cantilever brakes on the rear.


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Now that bike has a few issues and I want to do something different to the next one.

I have an almost identical frame and wondered if this would work ?


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I now have a hydraulic bender so wanted to cut the frame at points B and try to bend the bottom tube between points A to allow the head tube to become more vertical and the forks to be a bit shorter and reduce the trail which on the old bike is about 8"+.

I would then bend a matching [ ] tube to join parts B back together.

One of the other problems with the old bike is inseam length to solve that I will cut the frame at E and add about 4-5" in there then cut the rear end off adding about 10" of tubing at C and attach some new seat stays to give cantilever brakes on the rear again.

So will I be able to bend the tube ? and what will it look like when I do ?

regards paul

 

[OneHorsePower]

that is certainly doable if you have the right tool , but you could also do it much simpler by cutting B and A tubes on both sides 2 inch behind the lugs , and fit new tubing over those 2 inch parts , that way you will be able to bend the tubing alone and even stretch the frame as you wish, i think i am actually gonna try this on one of mine good technique if you can't weld like me , you could just bolt them on

 

[texon]

thems some crazy lines stormbird glad I am not alone in the UK

 

[stormbird]

Hi all

Thanks for your replies.

I wanted to leave the head tube attached to the rest of the frame so it could be cold bent into alignment after I had bent it to shape , however it does limit how close the bender can get to the ends of the down tube.

Still if I make a mess of the bending cutting the frame as you suggest will mean I can still use it and so it won't be wasted !

I don't really want to lengthen the front of the bike , in fact by putting the bends in I hope to shorten the front and then add some length to the back.

The reason being I am not fond of large amounts of tiller in the steering geometry.

Wife is away from Saturday so will get a chance to try this , I will post a picture when done.

Paul

 

[alecw35]

That looks to be a really old Raleigh frame, or one of there other Brands that they put on those frames.
If so it will have there own thread pitch on the fork steerer and headset cups. And the BB shell will be around 70mm wide with there own thread pitch.
Thats ok if your using the original BB axle, cups and axle. But has to be adapted to fit other cranks. I have rettapped the threads on some Twenties and RSWs, and narrowed the shells. But those bikes have a tubular BB shell. that all the tubes are welded too. not Lugged construction
Also the head stock looks to be longer than is usual these days. Thats good as the bearings are further apart, and counter acts the leverage that long forks will have on them. But it might be tricky finding other forks for it.

Im in the UK too.

 

[stormbird]

Alec

Well we can't have the Yanks & Aussies monopolising this forum can we :lol:

You are right it is an old Raleigh frame , it actually had rod brakes ! and the head badge is under the blue paint.

I have the forks , they are the ones with the lock in one side , I am unsure whether I can use them or if it would be easier to get some different ones and as you spotted the head tube is long , it may be necessary to extend the fork head tube to match the frame head tube ? but only as a last resort.

I have the BB cups and hope I can fit a normal axle in to replace the cottered one that came with the frame I have a good selection to try.

regards Paul

 

[alecw35]

The cup and cone Bottom bracket axles with square tapered ends, often have a size code stamped on the centre of the axle. Sheldon Brown has an article on his website, that decodes them.
Also some ebay sellers have a chart.
I think its a 5 that is needed for the Raleighs, cant remember the letter on the code tho

I will be fitting be fitting alloy cranks to my Raleigh Grifter, and my Raleigh Stowaway folder bike. As soon as I get round to ordering the axles. But then I'll have to saw off the stand lug from the Grifter, not to keen on doing that. Dont have an angle grinder anymore

I do have a set of MTB forks with a very long steerer tube, they are from a very old bike tho.

I have heard of people extending fork steerer tubes, by welding on another steerer tube, to whats there. They use 2 lengths of angle iron, clamped together to box in the tubes to be welded, and keep them straight. maybe a cut out in the angle iron where the welding is to be.
Welding would have to be very good, with lots of penetration. And no lumps on the outside that might catch on the inside of the frames headstock. Theres a lot of stress on a regular bikes forks. Theres more on a long forked chopper

 

[texon]

I have just extended the fork tube to fit a french frame called a Roold which I am building a limo bike out of . I used a piece of handle bar stem as a slug for strength clamped it all into a piece of angle with a 5 mm gap between the two fork tubes so I could get plenty of weld onto the slug ,I lightly ground the welds so as not to weaken it and fitted it to the bike JOB DONE .Sorry not very good with a camera so no picks yet .But I intend to do a write up with picks of the bike soon . by the way Im from Doncaster anyone near . 8)

 

[stormbird]

Hi all

I am in North Nottinghamshire , Mansfield to be more accurate so yes I am close.

Whilst I have built the Red chopper I am a novice TIG welder and so am currently shying away from a weld there , although if I can find a fairly long head tube so I can put a sleeve inside it without interfering with the goose neck and can grind a decent bevel on it for good penetration then that is the way I shall go.

Are you building a copy of the Lowlife Limo ? [ seen on this Forum ]
I have a friend who was interested in one , but at 10ft long I can imagine it being a pig to store/transport and ride !

Alec are you close , I have an angle grinder you can come over and use ?

Paul

 

[alecw35]

Im in Scotland. Near Dundee. So not close at all

thanks for the offer tho.

 

[texon]

wow stormbird you are close only about an hour up the A1 .The limo I am on with is for my 11yr old son its just under 7 ft based on a lady`s roold so not to bad for storage .I have made some girder forks for it which are starting to look the part , It will not be long before I put a write up on it .I just wish we could get hold of some of the custom parts our American friends have easy access to .But until then we will just have to make our own parts from scratch .

 

[stormbird]

Hi all

Got a chance to cut & bend today :-


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The masking tape and the pen marks are where each of the bends were made.

This is it mocked up with a 20" front wheel :-


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and if I had the time to add a space saver car wheel to the rear :-


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It seems I am still fighting the geometry of the base bike , whilst doing the bend has reduced the fork length it has also moved the handle bars forward a good piece and I really wanted to move the seat rearwards to get more leg room.

Then my arms will not be long enough grrrr....

You can see my red bike in the back ground for reference.

Paul

ps Texon love to see some pictures of the limo & forks , I will have to build one myself soon