spreading rear stays - mixte

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hoogerbooger
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spreading rear stays - mixte

Postby hoogerbooger » 6 Aug 2018, 3:06pm

Any obvious reason why a 531 butted mixte frame can't be spread from 120mm OLN to 126mm ?

(or perhaps 130mm)

I've seen videos on youtube using threaded rod, washers and nuts & was thinking of having a go on an old 531butted mixte frame.

Just wondering if having 3 sets of tubes with 3 fixed points to the seat tube makes it any riskier ? The diagonal down tubes are currently straight as they go from the steering tube to the rear dropouts with attachments either side of the seat tube. So If I spread the frame these thinner tubes will obvious bend at that fixing point to the seat tube. My head is thinking thin tubes are more vulnerable ??

( The inside of frame appears in good condition with little sign of rust. The down tubes are completely sealed. no air holes.

Any experienced frame aligners out their within insight ?

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robgul
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Re: spreading rear stays - mixte

Postby robgul » 6 Aug 2018, 3:53pm

Done it twice with mixte 531 frames (and about 10 other frames) using the threaded rod method, and a bit of string to view alignment.

Warning: You need to wind the dropouts out to quite a bit more than the required OLN as there is spring in the frame stays - may seem alarming but gently does it and keep checking width as you progress.

Sheldon Brown also has a method that's less scientific involving levering with a bit of "lumber" (that's wood to us in the UK)

Rob

Brucey
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Re: spreading rear stays - mixte

Postby Brucey » 6 Aug 2018, 3:54pm

depends on exactly how it has been built. If the joints are fillet-brazed to the seat tube bracket, and there is no brace in the lateral stays, they might just crack as you reset them. In any event the force required will be greater than normal.

cheers
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fossala
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Re: spreading rear stays - mixte

Postby fossala » 6 Aug 2018, 4:29pm

robgul wrote:Done it twice with mixte 531 frames (and about 10 other frames) using the threaded rod method, and a bit of string to view alignment.

Warning: You need to wind the dropouts out to quite a bit more than the required OLN as there is spring in the frame stays - may seem alarming but gently does it and keep checking width as you progress.

Sheldon Brown also has a method that's less scientific involving levering with a bit of "lumber" (that's wood to us in the UK)

Rob

The threaded rod method is worse than using a bit of wood. With the wood method you bend one side then the next. If OP wants to cold set his frame to 126mm this would be 3mm each side. With the threaded rod one side could bend more than the other, especially when you take have bent/pressed chainstays to accommodate chainsets. I tried to use the threaded rod method myself and ran into this problem.

hoogerbooger
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Re: spreading rear stays - mixte

Postby hoogerbooger » 6 Aug 2018, 4:41pm

Here's a picture of the seat tube area. I forgot the additional lateral bracing of the rear brake arch.

Stays are identical either side. lower ones pinched on the insides (both sides) for tyre clearance (but not for chainset)

Anymore views on potential for brazing/tube failure ?
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Brucey
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Re: spreading rear stays - mixte

Postby Brucey » 6 Aug 2018, 4:47pm

it looks no worse than a lot of other frames, I think it should cold-set OK, but there is always a small risk that something unpleasant will happen at the braces.

cheers
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hoogerbooger
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Re: spreading rear stays - mixte

Postby hoogerbooger » 6 Aug 2018, 5:05pm

Any more comments welcome. But at the moment I think I will go for 126mm at the weekend.

I take full responsibility for my actions .... ( there are plenty of past ones I'm still annoyed about, so why not add one more)

( If I turned the frame the other way up you'd see how much surface rust it has ! However inside is sound and the tubes ring nicely)

I've viewed videos on the long piece of wood- lever method. Was not sure it is as easy to do with a mixte frame. However I note the potential to spread unevenly with the threaded rod method. As the 3 sets of tubes look symetrical in construction I'll have a go at the threaded rod method in small steps & check alignment before I get to the full spread. fingers crossed.

Thanks for the comments

resus1uk
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Re: spreading rear stays - mixte

Postby resus1uk » 7 Aug 2018, 9:55pm

I got Jacksons to spread my mixte before they resprayed it. I was worried about the complicated lugs. In the past I have used the metal rod system, very scary to over spread the dropouts and forks. So I got the experts to do it

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Mick F
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Re: spreading rear stays - mixte

Postby Mick F » 8 Aug 2018, 8:12am

I tried the threaded rod method on our Mixte, but it was better IMHO to lie the frame down and stand on the dropout and tug the other one upwards by hand. Trial and error and checking the alignment did it perfectly and easier than the rod method.

126mm to 130mm.
Mick F. Cornwall

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cycleruk
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Re: spreading rear stays - mixte

Postby cycleruk » 8 Aug 2018, 9:43am

Could you cramp the tubes at the brake arch and other places so as not to strain the joints. ?
Also after setting the frame you may have to realign the drop-outs.
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landsurfer
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Re: spreading rear stays - mixte

Postby landsurfer » 8 Aug 2018, 9:55am

How essential is the cold forming?
It's only 2 mm per side and i just spring the dropouts apart on my 531 frame.
It's just like that, it's just the way it is.
The road goes on forever.

Bowedw
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Re: spreading rear stays - mixte

Postby Bowedw » 8 Aug 2018, 10:34am

I tried the threaded rod on a mans 531 frame, took it out to 180mm,removed the rod and it sprung back to within a mm.
Plan B involved securing the bottom bracket in a vice a rag and a piece of 3x2 timber, took one side out 3mm and then the other to arrive at the 130 mm. I also had the frame checked by a local frame builder and being a mid 80's Raleigh was spot on.
Did the same with an identical frame apart from colour and also spot on.
You just need to be positive when going for it and be mindful that a poorly soldered/brazed joint could reveal itself.
If the frame is slightly out now with this method you should not be any worse off.
Maybe check with the string method before starting and factor that into the amounts you spread the stays each side.
My wife also has a Mixte frame Raleigh bike from the same era, whether I would tackle that and suffer the consequences of a failure is not a decision I would like to make.

AM7
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Re: spreading rear stays - mixte

Postby AM7 » 16 Aug 2018, 8:58am

Mick F wrote:I tried the threaded rod method on our Mixte, but it was better IMHO to lie the frame down and stand on the dropout and tug the other one upwards by hand. Trial and error and checking the alignment did it perfectly and easier than the rod method.

126mm to 130mm.

Yep that's exactly how I did my 531 mixte frame - took about 10 minutes.

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Mick F
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Re: spreading rear stays - mixte

Postby Mick F » 16 Aug 2018, 9:22am

Yes.
Simple and quick, and wouldn't hesitate to do the same again if required.
Mick F. Cornwall

hoogerbooger
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Re: spreading rear stays - mixte

Postby hoogerbooger » 16 Aug 2018, 11:34am

I used the threaded rod method and spread it to 126mm then checked alignment with string method ( used dental floss!)

It's actually a tad short of the 126mm, but no problem putting the wheel in.

The 3 sets of stays appeared symetrical in design & the alignment ended up close. about 0.5mm less on nearside. I haven't tried realigning the drop outs. There's nearly 1mm difference between the from and back of the dropout.

I reckon that's close enough so I'm building it up so the missus can try it out and play with the set-up/ fitting.
(If we decided to keep it, it'll need a respray so would try to get all spot on before that and might go for the 130mm. May need the long bit of wood to even things out then)