foundry pattern

[miken]

My tank project has a cast turret which I would like to reproduce in iron (If i cant, they were also made with an octagonal version made from flat plates riveted together).
Unfortunately I dont know how to go about this, so I have a few questions I hope someone can answer for me.
First off,
Can someone recommend a foundry near Sussex?
If not, does anyone know a foundry I can post my pattern to? I'm happy to drive maybe 100 miles to deliver.
Next,
Ive never had anything cast, or made a pattern.
Below is a sketch of the rough shape I require, Its sort of bucket shaped.
I can work out how to make the top disc bit but I dont know how to make the tapered cylindrical part.
Should I Cut a series of wooden discs maybe 20-25mm thick and glue them in a stack? With the grain at 90 deg to each other. Finish turn on the lathe. Ive got some old oak shelves I can use.
Or can you suggest a better method of construction.
Thanks
Mike
Finished pattern needs to look like this: upload.wikimedia.org/wikipedia/commons/thumb/6/66/Renault_FT-17_turret%2C_Paris.jpg/800px-Renault_FT-17_turret%2C_Paris.jpg?20120616134830

[mbrown]

Some years ago, Blackgates made some wheel castings in iron to my patterns - very nicely done, fairly quick turnaround and not too expensive.

I don't know if they still offer this service but it may be worth an enquiry.

Malcolm

[ilvaporista]

I'll be called a heretic, but do you need a casting? I have found that for one offs like that it's cheaper to machine from solid.

[chrisb]

You could use a disc of wood for the “roof” of the turret and then use tapered pieces like barrel staves for the sides of the turret. You might need to use cable ties or big jubilee clips as temporary hoops whilst you assemble and glue the side up then you can turn it to round it off. Not forgetting that the roof disc will need a slight taper on its edges 2-3 degrees draft angle to allow it to be withdrawn from the sand.

[andyhigham]

I'd have thought the full size turret would be fabricated. Cast would be too weak to stand the impact from ordnance

[SteveW]

Miken, it occurs to suggest using MDF for your pattern. Agreed horrible stuff given the dust but a far more consistent material and loads cheaper than tree wood an no end grain to knacker it up.

If I read your measurements correctly its going to be flippin heavy and a bit tricky to machine unless you get very creative.

Another point is going to be shrinkage so some deep research on how much bigger to make the pattern.

Keep us posted. Fascinating project, just recalling the nonsense with Model Engineer when some clever person successfully complained about scaled plans/drawing being advertised for the famous Gatling Gun because it was gun related, not steam and it could shoot someone. Duh!. The image of some little old model engineer, fed up with locos, building a magnificent Gatling Gun purely to go hold up a Post Office or similar wasn't within my range. It occurs to ask what your plans for your little tank are when finished. Perhaps world dominance. We certainly need a change.

[miken]

Nov 26, 2023 21:35:13 GMT andyhigham said:

I'd have thought the full size turret would be fabricated. Cast would be too weak to stand the impact from ordnance

They weren't made from cast iron , they were made from CHSA or cast homogenous steel armour.
I don't need that, so CI will do.

[miken]

Nov 26, 2023 20:48:18 GMT ilvaporista said:

I'll be called a heretic, but do you need a casting? I have found that for one offs like that it's cheaper to machine from solid.

I agree, I've made quite a few loco cylinders, domes and chimneys myself over the years from solid, however,
I've just seen the price for 200 mm dia. Black round bar. It's just over £2000.00 a metre plus carriage.
Admittedly I only want a length of 100 mm but I think my lathe would struggle a bit chewing that out.
I think I might struggle lifting it too.

[ettingtonliam]

I made quite a few wooden patterns some years ago, and if I was doing your turret, I'd use a core to form the inside. Its difficult to explain, but if you get a basic book on pattern making, and have it as your bedside reader, all should become clear.

Finding a foundry that will work with one off loose wooden patterns is getting harder and harder, though.

Maybe go for the rivetted steel version?

[miken]

Nov 26, 2023 20:46:59 GMT mbrown said:

Some years ago, Blackgates made some wheel castings in iron to my patterns - very nicely done, fairly quick turnaround and not too expensive.

I don't know if they still offer this service but it may be worth an enquiry.

Malcolm

Thanks for the suggestion Malcolm , I shall give them a call.

[miken]

Nov 26, 2023 22:34:34 GMT SteveW said:

Miken, it occurs to suggest using MDF for your pattern. Agreed horrible stuff given the dust but a far more consistent material and loads cheaper than tree wood an no end grain to knacker it up.

If I read your measurements correctly its going to be flippin heavy and a bit tricky to machine unless you get very creative.

Another point is going to be shrinkage so some deep research on how much bigger to make the pattern.

Keep us posted. Fascinating project, just recalling the nonsense with Model Engineer when some clever person successfully complained about scaled plans/drawing being advertised for the famous Gatling Gun because it was gun related, not steam and it could shoot someone. Duh!. The image of some little old model engineer, fed up with locos, building a magnificent Gatling Gun purely to go hold up a Post Office or similar wasn't within my range. It occurs to ask what your plans for your little tank are when finished. Perhaps world dominance. We certainly need a change.

Steve, MDF, I hadn't thought of that, good idea.
Yes, it will be quite heavy, however, I don't think it will require much machining. There is a hole in the front where the gun pokes out and another at the top where the commanders cupola bolts on. The bottoms just got to be flat.
in a similar vein to the Gatling gun, I was a little concerned myself the other year when I started a thread (on this forum somewhere) about the 1/3 Maxim machine gun I made. Fortunately no-one objected.

[SteveW]

Miken,
Was thinking more about machining or heavy petting you'll need to do on the embryo pattern necessary to get it right and also the bit bigger enough to allow for shrinkage of the final casting.

[peteh]

I wonder if you could weld some thick wall tube to a disc and then turn the taper. No need to buy solid billet.

[Jo]

I would try your local metal merchant. Failing that in my 2020 M-Metal cat 200mm dia was only £17 per 25mm. So about £120 by the time they charged you P&P and double to allow for inflation LOL.

Also try contacting some of the Traction engine companies, the likes of MJ have huge chunks of come in handies lying around - you might get lucky someone might be using it as a door prop.

Jo

[jasonb]

I'd draw in CAD and 3D print or CNC cut the pattern but depends on what your CAD is like and what you have to hand for making the pattern

If you want a more traditional approach then draw it out on paper and put lines through it say every 6mm and work out the contour at the bottom of each of those lines

Transfer the contour to some 6mm MR MDF and cut out.

Glue together and then refine the shape by sanding, planing or whatever to blend the contours together.

It does not look like a core is needed as there is reasonable taper on the inside so you coul ddo what is know as "self-coding" where the pattern ropduces it's own "core" which will just be a protrusion of the sand in one half of the mould. If you do go with that option then I suggest having the wall thickness at the bottom 6mm tapering to 8mm at the top which will give a greater draft angle.

This crankcase was done using the self-coding method with no core or associated core box



The stuff I have been making patterns for lately has been cast this foundry though they are a bit slow at the moment due to health issues, I post the patterns to them
www.facebook.com/thecastingman/?locale=en_GB

Have also had good reports of www.suttoncastings.co.uk/

That part as a casting should cost considerably less than a solid bit of CI, sometimes it's less of a saving but as the volume of iron is quite small compared to overall size it would be worth doing. Can also depend on how a particular foundry charges, some just go by weight, others a set charge plus material and others will just have a minimum charge for small one offs.

[davewoo]

Hi
There is a foundry at Hastings, East Sussex, Harlings. I have used them some time ago, their work is very good, but wasn't cheap and it did take a lot longer than promised for the casting in iron to be done, gunmetal ones I had done were very quick. I know they are still in business but understand there have been some changes in staff recently, and their policy towards one offs has changed. I got this info second hand so it might be worth enquiring before making too many plans to use them.
Nice project by the way, I'd never thought of tacking with TIG before silver soldering fabrications,could prove a real time saver, thanks for the tip.
Dave

[jasonb]

If you are enquiring about prices then there is about 4.5kg of iron in that turret.

[miken]

Thanks for all the replies.
Jason, Thats amazing! Have you just drawn that up or did you already have it. It looks just right.
I have no CAD ability and that looks like witchcraft to me.
Do you mean 4.5kg if its solid or hollow?
I spoke to a model engineering supplier and they recommended Bridport Foundry.
Ive just spoken to them and they said they are happy to do one off castings. Apparently they do castings for Plastow.

[weary]

Hi MIke,

(Pending Jason's response) ..... As & when it suits you may find using this calculator to establish the approx. weight of any components useful.

I think that Jason's 4.5 kg. estimate is 'hollow' as that webpage estimates just under 5 kg for a hollow structure as drawn in your first posting in this thread.

Phil

[jasonb]

Couple of minutes to draw it and then a click of the button to "analyze" the model, which gives a cast weight 4.5kg approx. That is with the 6 to 8mm wall thickness. A 100mm slic eof 200mm bar would be in the region of 22kg

Bridport also own and cast Stuart Models

If you were to hollow out under the cupola then you could get the weight down a bit more. Furher faving scould be had if th e"top" were made with an 8mm wall thickness rather than just doing an angled cut off the 20mm thckness.