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WW1 Thornycroft restoration

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19 minutes ago, k2lofty said:

I have achieved success using fine sand, but it is essential to wooden plug one end solid, and use a tapered plug for the other, once filled with fine sand, bang the taper on the floor and continue to drive it in until the tube rings like a bell (solid bar) it is then properly packed,  and if annealed, you wood formers may work. A cheap route worth a try.

   

This is why I'd fill it with water...then freeze it... 

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If you pop over to Ben Hawkins Dennis lorry thread you will see that Ben reached the same point as Steve but a week earlier. Andy suggested packing the tube with monkeys which I thought was a very clever and amusing suggestion!   ( I am sure you can work it out....), Seriously though, mandrel bending  is the only way to achieve tight bends ( 3 x tube diameter) in light wall tube. I made a mandrel bender for one particular application and it was well worth the time spent as there was multiple tight radius bends.

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On ‎13‎/‎01‎/‎2018 at 5:48 PM, flandersflyer said:

This is why I'd fill it with water...then freeze it... 

 

 

Edited by k2lofty

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My goodness, what a response! Thank you everyone for your help and suggestions.

Looking at what I have done so far and what I have around me this is the plan for tomorrow. I have glued up the split press block and that is going off now. I have cut a new length of tube and will braze up one end. I shall then pack it with some dried sand and seal up the other end. I shall put it back between the blocks but support them width-ways with G-clamps. Then, I will have another go. Watch this space!

Steve     :) 

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Another option is take it to an Exhaust Shop who does mandrel bending and let them do it.

Cheaper than a Plumber.

 

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3 hours ago, k2lofty said:

When using sand packed steel tube you can apply heat, I am fairly sure this may effect the ice. 

 

 

I'm Fairly sure it'd affect the copper as well... 

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I know this is of no help, but this photo shows the plumbing on my Foden FD6 marinised engine. There are numerous copper pipes with bends. Those that I added (mainly in primer) are steel stock pieces from the exhaust shop, which in my case were OK as it is for water where I use an anti-corrosion additive.

Ian

Foden plumbing.JPG

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6 hours ago, flandersflyer said:

Come on then pal... 

Show me how your going to bend a 1 3/8 copper tube with a 'spring'.... 

 

The spring is placed inside the tube to keep it circular, then wound out afterwards.

It works with 15mm and 22mm routinely. Why wouldn't it work with 35mm? 

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Well, I have just had another go but cannot claim success yet.

I brazed up the end of the tube after annealing and then packed it with sand, thumping it well down with a rod before the final squeeze which was achieved by hammering in a plug.

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Back in the press, I strengthened up the blocks with G-clamps to hold them together.

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Looking promising.....

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As far as I could go.

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Not quite what I am after......

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As John said earlier, the bending block needs deeper sides which would prevent it spreading and pulling over the edges. Also, I agree that thicker wall tube would be easier to pull around. This is only 18swg as it is what we could get.

Barry. What is 'mandrel bending' and what did your tool look like?

Steve

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Not too sure if you can do this method with copper but old school Sparkies used to bend steel conduit using a length of timber with a hole,  sized to the conduit, through it.

This then had a radius edge put around it so that when bending the tube it wouldn't foul on the former block hole as it is pushed through.

Tube is inserted in hole and bent a little then pushed through hole a little and bent a little more and so on until you have the bend you want.

Mark where you bend so that any adjustments can be made in the same place.

 

 

Edited by super6

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Filling the tube with a soft low melting point metal is one method. The resulting rod maintains its shape but is harder to bend. "Woods Metal" (also known a Cerrobend) was common for this. It melts at 70 deg C and does not shrink on cooling so eaasy to use but as it had 10% Cadmium in the original mix it's now considered a health risk. Roses metal is a non Cadmium option. You could use lead or solder but they tend to shrink on cooling. not a problem if the pipe is long enough. A homemade option is 50% Bismuth 50% tin/lead solder.

Edited by G8RPI
spelling

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Might be a daft question, but are there no pipe and tube benders locally? We have a couple here who are normally quite happy to do small jobs at sensible prices. Appreciate the desire to DIY, but it'd be done and dusted and let you get on with other jobs...

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19 hours ago, andypugh said:

 

The spring is placed inside the tube to keep it circular, then wound out afterwards.

It works with 15mm and 22mm routinely. Why wouldn't it work with 35mm? 

I know how these springs work... 

They're also a flat profile... 

 

 

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24 minutes ago, flandersflyer said:

I know how these springs work... 

They're also a flat profile... 

 

 

So rather than taunting me with what an idiot I am, and showing off how clever you are, why don’t you explain the problem that I am too dumb to see?

 

 

Edited by andypugh
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Steve,

I can't help feeling that the press is not the tool for this job. The pipe needs to be filled with sand tamped and capped then pulled round by hand with an extension tube to give you the necessary leverage. There are a number of youtube vids showing this method. Obviously, the key is a firm anchorage for this approach. Good luck. T.

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Steady on chaps, this isn't worth falling out over. I appreciate all advice as it is always well intentioned. If I don't take it, it is my look-out.

Thanks Tomo. I have been looking at Youtube this afternoon and I have reached the conclusion that I am asking too much of the press for this one. The radius is too tight and the wall thickness too thin so it will have to be a mandrel bender. Fortunately, I now know what that is!

Sean, you are right in that the best solution is to get someone to do it for me locally. Now the trick is to find someone who has one of this size! Will have to get on the phone tomorrow.

The day has not been a complete washout though. I have finished pattern number 29 which is for the brake lever on the top of the transmission brake. It started with a kit of parts:DSCN7275.JPG.cc083cbcdd4129432fc581f5d2883f24.JPG

Gluing up!

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After some filler and glass paper.

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Two coats of Bondaprime.

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That makes two ready for the foundry. Number 30 is currently on the bench giving me another puzzle. I'll show you why in a day or two!

Steve    :)

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Steve,

I found this supplier for copper tube in a selection of wall thickness. The 1 1/4" tube is available in 6swg, almost 4mm, 10swg, approx 3mm and 13swg, approx 2mm.  I don't know anything about the company and have no connection with them.

http://johnhoodandcompany.co.uk/materials/copper/copper-tube

Hope this may help if you have to go for a heavy wall tube.

John

 

Edited by Barney

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34 minutes ago, flandersflyer said:

 

I'm neither better nor worse than anyone else but I've made my mind up about you pal months ago...

Keep away from me in here... 

Steady please - that isn't the sort of tone we have on HMVF. That sounds like a threat to me, I hope I am wrong.

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Those small little engineer books used to state mandrel radius and also offsets depending on thickness.  I have one of those books at home but I am in the middle of a desert at the moment.

But as you are leaning towards there must be someone who can bend it up exactly the way you want..... maybe motorcycle restoration place..as smaller exhausts....just have to think of something that uses small bore piping... boat plumbing????

 

 

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To me the wall thickness is an issue on this as stated. I have formed 4” copper tube on steam boat engines with no problems using the fine sand method, but that was thicker wall. We have hydraulic pipe benders in the workshop but even doing thin wall steel tube is an issue for us. Pity an internal support spring can’t be sourced, what about a spring suppliers, we have an old time spring manufacturer local who make and spring clip or coils, a lot kept in stock. 

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7 hours ago, fesm_ndt said:

Those small little engineer books used to state mandrel radius and also offsets depending on thickness.  I have one of those books at home but I am in the middle of a desert at the moment.

But as you are leaning towards there must be someone who can bend it up exactly the way you want..... maybe motorcycle restoration place..as smaller exhausts....just have to think of something that uses small bore piping... boat plumbing????

How do the Steam Loco restoration groups bend the copper pipes for Oil lines and Steam pipes?

Maybe worth contacting your nearest large restoration base.

 

 

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10 hours ago, fesm_ndt said:

Those small little engineer books used to state mandrel radius and also offsets depending on thickness.  I have one of those books at home but I am in the middle of a dessert at the moment.

Fesm-ndt, if you have chance when you get back from eating your pudding, I would love to see a scan of the table of offsets and mandrel radii. I made a rudimentary mandrel bender for one size of pipe and just guessed and experimented with the settings until it worked, never thinking that there were tables of such information.

Thanks,

Barry.

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Don't know if this is any help? I once watched large diameter copper pipe for steam locomotive injectors being formed at my local preserved railway. Their technique was to pack the pipe with sand, clamp one end firmly and heat the area where the bend is to be formed to a cherry red colour, then bend freehand before allowing it to cool.  it would probably be possible to bend around a former of suitable material. I don't know if this was a one off or whether it is the usual method, but it certainly seemed to work.

Mike

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