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WW1 Thornycroft restoration

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I should be very surprised if they had deliberately cut the down pipe to a tuned length. My experience of Thornycrofts is that they are pretty 'agricultural' in their engineering and not nearly as refined as the Dennis.

Thanks for the Cast Iron Welding Services tip-off, Tomo. I actually worked in the factory right next door for seven years making rock crushing machines and could have walked there in my lunch hour! I hadn't found a job for them until now!

 

Steve    :) 

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Rather than weld  on your little lug, it might be easier and stronger to build up a lump with weld and then post-machine that. 

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The techs from the local industry museum did weld a big broken clamp of my drillpress with brass. But they had to warm up the cast iron to red hot first. It still works fine since.

Edited by Citroman

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16 minutes ago, Citroman said:

The techs from the local industry museum did weld a big broken clamp of my drillpress with brass

Braze repairs are quite common with cast-iron parts, which is why I suggested silver-solder. 

I don't think that the following  is the solution here, but I have also had good results repairing the arm of a mechanical hacksaw using stainless-steel MIG wire. The reason to use stainless is that it won't turn into a super-hard martensite due to carbon migration from the cast iron.  I guess that bronze MIG wire might be even better. 

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Is it possible to weld thin cast iron sheet?

I have an old railway stove and the side sheets are about 1/8th inch and cracked.

It is not the normal rounded version but more square.

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I am sure that it is possible to weld but it would take a skilled man to do it. I suspect that it would have to be done with the lot hot as well. Good luck with that!

Dad has been to the foundry today and picked up the body mount brackets and also the radiator water outlet.

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We are very pleased with the results but the patterns suffered a bit this time. The foundrymen said that they could have done wih a bit more draft on them and that MDF is not so good for deep patterns as it is difficult to get the screw to bite in very well when trying to pull them out Another lesson for the future!

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The water elbow is fine too but does show my limitations as a pattern maker. I have used far too much metal!

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Good job we are only doing one!

More homework for Dad now.

Steve :)

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Those body mount brackets look great. You should have had an extra box type one to keep on your desk to cheer yourself up with.

David

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4 hours ago, ploughman said:

Is it possible to weld thin cast iron sheet?

I have an old railway stove and the side sheets are about 1/8th inch and cracked.

It is not the normal rounded version but more square.

Iron welds beautifully...but there's rules to abide by 

For a start it's difficult to know what grade of iron you have...particularly with older items...or items from minor foundries and obscure manufacturers that often just threw any old crap into the cupola... 

Secondly the long term effects of hot & cold...hot & cold effects iron on the molecular level...this can make it difficult to weld with an argon set... 

Thirdly is the issue of thermoshock... Iron generally only allows for about 5% movement during heating & cooling...which can manifest itself with cracking on large surfaces... 

 

In your case a good move would be to prep the area to be welded first by identifying points where cracks end...and drilling at a point just beyond (this prevents the crack from creeping)...a narrow Vee prep to cracks (both sides)...and the usual support during welding...  

You need a DC stick welder and a pack of 2.5mm nickel rods... 

Go DC electrode negative for welding the root...and then put the welding plant into DC electrode positive for capping the root weld... 

You'll need a bucket large enough to put the welded part in...and some kiln dried sand... 

If you have access to a coke forge you can get an even pre-heat on the part to be welded...and also give it a post-heat after welding before chucking it in the bucket and covering it with the dry sand... 

An alternative to covering it in sand would be to keep it in the forge and gradually reduce the heat over a given time...

Or tell her indoors you've allocated her £100 pocket money allowance to go buy herself summat fancy with...once she's out of sight you can use the oven in her kitchen to gradually pre then post heat the casting... 

Edited by flandersflyer

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I brazed a new steel flange onto the cast iron exhaust manifold of my 1927 Vauxhall 14/40 a decade ago. Has done over 10,000 miles of hard, fast driving without coming apart. Done with 1/16 brazing rod dipped in sif-bronze flux after a gentle pre-heat with a propane torch.

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18 hours ago, flandersflyer said:

Iron welds beautifully...but there's rules to abide by 

For a start it's difficult to know what grade of iron you have...particularly with older items...or items from minor foundries and obscure manufacturers that often just threw any old crap into the cupola... 

Secondly the long term effects of hot & cold...hot & cold effects iron on the molecular level...this can make it difficult to weld with an argon set... 

Thirdly is the issue of thermoshock... Iron generally only allows for about 5% movement during heating & cooling...which can manifest itself with cracking on large surfaces... 

 

In your case a good move would be to prep the area to be welded first by identifying points where cracks end...and drilling at a point just beyond (this prevents the crack from creeping)...a narrow Vee prep to cracks (both sides)...and the usual support during welding...  

You need a DC stick welder and a pack of 2.5mm nickel rods... 

Go DC electrode negative for welding the root...and then put the welding plant into DC electrode positive for capping the root weld... 

You'll need a bucket large enough to put the welded part in...and some kiln dried sand... 

If you have access to a coke forge you can get an even pre-heat on the part to be welded...and also give it a post-heat after welding before chucking it in the bucket and covering it with the dry sand... 

An alternative to covering it in sand would be to keep it in the forge and gradually reduce the heat over a given time...

Or tell her indoors you've allocated her £100 pocket money allowance to go buy herself summat fancy with...once she's out of sight you can use the oven in her kitchen to gradually pre then post heat the casting... 

Thanks for that.

The stove is actually a bit big to fit in her oven, so that options out.

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Very impressed with your pattern making and as always the result look very professional. 

On the subject of  cast ironwelding I have used these rods for gas welding with good results . As already mentioned plenty of pre heating and very slow cooling down .I usually bury parts in cement dust after welding. Our cooker is regularly used to temper springs and pins etc  .King pins and spring pins about gas mark 7 and springs anything up to gas mark 9

  

 

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Thanks Smiffy. You are very kind but my patterns can only be classed as 'adequate'. I get what I want but I use far too much metal and they are not very robust. To see some real works of art, have a look at Tharper's patterns elsewhere on this forum. They are gorgeous!

We now have 25 patterns completed and five left to do. One of those is for the propshaft spider.

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As you can see, this is a cussing awkward shape and would certainly test my wood-turning skills. Fortunately, Barry came to the rescue and very kindly offered to 3-d print the pattern for us on his amazing machine, an offer we accepted with alacrity!

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The very thin structure in the middle is temporary to support a horizontal face which is not on the base as the machine cannot lay down the fibres in mid air! They are broken off on completion.

!cid_X_MA1_1509393070@aol.thumb.jpg.a7adce19dbe9b42de566eccb01b47747.jpg

The model is not solid but has a honeycomb structure internally.

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Bingo! And there you have it! The boss on the end is a core print as it would be a waste to have to machine a 3" hole through the centre.

!cid_X_MA1_1509619311@aol.thumb.jpg.cfb6484df2202191e3c6d16990409cb6.jpg

The foundry told us last time that a good surface finish is essential to get the sand to release. Printed objects have a natural surface finish rather like an old 78 record and the sand can get a really good grip of it. I could see this when the silencer end patterns came back as where I had not painted the outsides of the core boxes, there were still lumps of sand attached. On Barry's recommendation, I applied two coats of 'Patterncoat' epoxy paint and rubbed back well after each. A horrible job but the surface is now very smooth.

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Today I am making the core box to go with it. Then that will be number 26!

Many thanks Barry!

Steve    :)

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Is the change to black because the red filament ran out, or to indicate the core print in the conventional way? 

I can see a use for pattern-coat on other parts, as it goes on like paint but then doesn't shrink on curing/drying like paint does. 

So would work well for smoothing rusted surfaces too. 

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I think the colour change is because the filament ran out. It is certainly not critical in this application!

The Patterncoat is a heavily loaded primer so there is a significant thickness to rub off which is great for giving a finish. You have to apply it briskly though as it goes off pretty quickly. Might be worth a try on other things.

Steve    :)

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I have to ask, how do cope with approximate 2% reduction in size when you have pieces cast. I had several brackets cast and I had to enlarge, ever so slightly, the hole where a piece of round stock had to got thru. For a pattern, the foundry used an original bracket as a core.

 

John G

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58 minutes ago, 42 chevy said:

I have to ask, how do cope with approximate 2% reduction in size when you have pieces cast.

It's absolutely trivial if using CAD / CAM or 3D printing, you just model it the size you want then scale by 1.02.

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Hi John.

To be honest, I have not taken much notice of shrinkage as most of my castings are quite small and the reduction is less than the accuracy of my pattern making! I do have a shrinkage rule, however, which has inch scales oversize depending on the material for which they were intended and I have used that. A good pattern maker uses the minimum amount of metal to achieve the desired result so there is no spare available for machining back. I am just not that good!

Steve    :)

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On 11/11/2017 at 8:54 AM, Old Bill said:

Thanks Smiffy. You are very kind but my patterns can only be classed as 'adequate'. I get what I want but I use far too much metal and they are not very robust. To see some real works of art, have a look at Tharper's patterns elsewhere on this forum. They are gorgeous!

We now have 25 patterns completed and five left to do. One of those is for the propshaft spider.

DSCN0434.thumb.JPG.bdffd41e72ebdea5509d9d7b9e48055b.JPG

As you can see, this is a cussing awkward shape and would certainly test my wood-turning skills. Fortunately, Barry came to the rescue and very kindly offered to 3-d print the pattern for us on his amazing machine, an offer we accepted with alacrity!

!cid_X_MA1_1509199179@aol.thumb.jpg.f981f8fb8f6b5a81092a146a944205d8.jpg

The very thin structure in the middle is temporary to support a horizontal face which is not on the base as the machine cannot lay down the fibres in mid air! They are broken off on completion.

!cid_X_MA1_1509393070@aol.thumb.jpg.a7adce19dbe9b42de566eccb01b47747.jpg

The model is not solid but has a honeycomb structure internally.

update.thumb.JPG.1e649f4d723b71b835d3de7c92b00754.JPG

Bingo! And there you have it! The boss on the end is a core print as it would be a waste to have to machine a 3" hole through the centre.

!cid_X_MA1_1509619311@aol.thumb.jpg.cfb6484df2202191e3c6d16990409cb6.jpg

The foundry told us last time that a good surface finish is essential to get the sand to release. Printed objects have a natural surface finish rather like an old 78 record and the sand can get a really good grip of it. I could see this when the silencer end patterns came back as where I had not painted the outsides of the core boxes, there were still lumps of sand attached. On Barry's recommendation, I applied two coats of 'Patterncoat' epoxy paint and rubbed back well after each. A horrible job but the surface is now very smooth.

DSCN7141.JPG.c52ef26300e7ba2d43d3e031209380bb.JPG

DSCN7143.JPG.0ead66fbcc58b324b9d78088019b0ffc.JPG

DSCN7144.JPG.86a21d5842453f1159949eddc9f39338.JPG

Today I am making the core box to go with it. Then that will be number 26!

Many thanks Barry!

Steve    :)

I'm sorry steve but I'd be forging that mate... 

 

Cut out the wastes afterwards with the bottles...

Cold chisel to knock off any fluff...

Die grinder to brighten it up... 

(if your burning gear is set rite)... 

Edited by flandersflyer

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I think you have to remember that the load applied to this spider is transmitted through some pieces of leather sewn together.  I would put my money on a quite substantial SG iron casting not failing rather than the hide of a bovine.

Edited by Asciidv

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I think the original was a steel casting but whilst not impossible to get, steel is a lot more difficult. Our local foundry does SG iron as a matter of course so we will opt for that. Thornycrofts did not have that option of course as the stuff hadn't been invented then! I am confident that it will be OK but time will tell.

Steve :)

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Getting bored with all of this woodwork so I have cut out the exhaust flange as a brief interlude!

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The elbow is away being welded so, with a bit of luck, we will be putting the whole system together very shortly.

Now back to pattern making!

Steve  :)

Edited by Old Bill

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How do you scan the object to be 3-D printed? Is it drawn on Autocad or similar first, or is there a simpler way? Ian

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Ian, for Steve's printed parts they have always been produced from a 3D model derived from a pencil and paper drawing from Steve and then translated into a 3D drawing. The drawing for the spider is shown below. 3D scanning to engineering accuracy is something usually reserved for bureaux offering scanning, who can afford expensive  laser based machines. 

If you ever wanted to try drawing parts in 3D for printing there is a free professional programme called ONSHAPE. ( www.onshape.com  ) which is very good once you get the hang of it.

Barry.

 

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Edited by Asciidv
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Thanks for that Barry. I hadn't heard of that software so I must give it a try. Always something new to learn!

The bonnet is on order but we won't see it until the Spring now. In the mean time, Dad has made up the bonnet catches. They are a slightly odd arrangement as the pegs are mounted on curved brass strips. These do give a handhold for lifting the bonnet but are really too small as I can only just get two ungloved fingers behind them. Never mind. That is how Thornycrofts did it!

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Dad curved the strips by putting them through our small bench rollers until they matched his template.

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They were then clamped in the jig and the ends bent over to match.

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The rivet holes  were drilled.

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The pegs were turned up and silver soldered in place before cleaning up and a final polish.

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They have since been painted green, as per prototype!

Steve    :)

 

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3 hours ago, Asciidv said:

If you ever wanted to try drawing parts in 3D for printing there is a free professional programme called ONSHAPE. ( www.onshape.com  ) which is very good once you get the hang of it.

Onshape seems to be the Solidworks version of Autodesk's "Fusion 360". Both appear to be Cloud-based but free for hobby use. 

I didn't look in detail at the Onshape conditions, but Fusion is free for Hobby, education of "Startup" which they define as making < $100,000 per year. 

I actually use Autodesk Inventor in the main, as I get a free home license through my job. But Fusion does seem to have all the features of Inventor that I use, just with the slight inconvenience of having to upload any files not in the native format to the "Cloud" to get then converted into the Fusion native format (You can, however, work offline with native-format files)

I switch from Inventor to Fusion when I need fancy CAM (G-code generation for CNC machines). The 3D CAM in Fusion is way ahead of the Free module in Inventor (pretty much equivalent to the Pro module). A nice example is here, engraving text on a cylindrical part using a rotary axis. (Normally a hard thing to do).

I imagine that there are similar Onshape tutorials on YouTube. 

 

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