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MG Midget and Sprite Technical - Laser cut manifold plates

I'm not doing this as a business, just a hobby. I've been making exhaust and inlet manifolds for various friends who don't have welding facilities and have needed to get the flanges cut for each end of the manifolds for Weber, H1 and HS2 carbs plus loads of different engine block faces in different sizes.
I had to learn how to use this CAD thingy (I'm not very computer literate) but have now got a stock of CAD files for having the flanges cut. I get a local company to take the files via E-mail and I then collect and pay.
No charge, although I'd like anyone who uses the files to treat them as 'mine' and not to sell them on to third parties.

Sidevalve 1932 Morris shown below.

I'm away for a few days so don't expect a prompt reply.

Rob


r thomas

The pic below is showing the quality of the lazer cutting. The hole is 0.5mm diameter and perfectly straight. 8mm steel.


r thomas

Very nice
good work!
Dan Cusworth

Rob
Do you have one for an M type in the files?
I'd love 2 flanges for an OHC MG with AA head.

As a CAD draughtsmen I could make a CAD file to add to the collection.
Just don't have a helpfull (affordable) company near to have them cut
Onno K

Hi Rob,

Loving your work on the Morris.

Could you make up an exhaust manifold for a 1500? Or is it just the CAD files and/or manifold plates you are offering?

Considering options re: exhausts for my rebuild. I know I want to replace the cast manifold but not 'wowed' in terms of price/quality of the off the shelf items from the usual places.

How hard would it be to make up the exhaust if I had the plate I wonder...

Malcolm
Malcolm Le Chevalier

Thanks, guys.

I don't have files for the 1500 or the M type and ideally I'd need both a head and a manifold to get the dimensions perfect. I have been asked for a D-type MG manifold (they need all the power they can muster) but am unsure how I can get the dimensions since there don't seem to be any spare engine blocks.

Onno. I get them cut for £30 which is maybe 40 euros? Stainless costs slightly more, obviously. The pipes I get mandrel bent for about £150 (E$200) per set. With all the bits and the cost of the gas it works out at about £250 for a complete manifold for the Morris.

This is how I started. Dirty fingers rubbed over the manifold and then over the block to show the mismatch of port sizes. All done with a Cornflakes box and a knife...


r thomas

....and then 'sized' so that each pipe, when flattened from round to the correct shape, would fit the hole in the backplate to perfectly match the size of the hole in the block without having any step. 28mm OD for the inlet pipes, 30 for the outer exhausts and 31.75mm for the inner exhaust.

There is a small mismatch shown here but I used an average set of dimensions from 3 different Morris engine blocks since the new owner lives a long way from me and I couldn't nip over to check my dimensions accurately against his car.







Still waiting for a car to pick me up and transport me over the border to England for a few days. He is already an hour late! Grrrrrrr.


r thomas

PS Onno. They need to .dxf or .dwg

Had this problem last time in that they don't do .cad files.



More pics here.
http://s82.beta.photobucket.com/user/foggythomas/library/?fromLegacy=true#/user/foggythomas/library/?fromLegacy=true&_suid=1360850476234030101325833246123
r thomas

Rob,

I would be more than happy to receive a copy of your files for the a-series.

I will of course keep you up to date with any developments that come from it too.

Regards

Pete
PeterJMoore

Rob,

Would you be interested in helping me out with drawing up and getting a manifold plate cut if I measured up my head? Would be happy to pay you some beer money for your help. (You are also more than welcome to say no, if you can't be bothered, I would fully understand).

Need to do some drawings and price things up but I am having a Prop moment and very tempted to make my own manifold... maybe lambda and pressure sensors in each header... all linked to seperate dials in the dash... ha ha ha!

Malcolm
Malcolm Le Chevalier

Rob I can deliver any file you want.
I'll take some dimensions over the weekend and draw up a file next week.
I'd be interested in just the flange as I can get pipes.
Onno K

Hello Rob,
The fella that made my exhaust didn't have a mandrel although my exhaust is made of steel and not s/s. He used wooden blocks to block the end of the pipe off, filled it with sand and then blocked the other end off. He then applied heat and got the most perfect bends. He was a metal wizard. He used to make exhaust systems for Formula 1 cars. I loved watching him work.
Neil
Neil T

Neil,

Was the heat applied with a torch or was the pipe put into a fire box or forge? And, when I say torch, I don't mean a flashlight. I don't know what you guys call a torch since you use that term for what we call a flashlight. I also would have loved to watch that.

Charley
C R Huff

Charley-
Depends on how long an area you want to bend, and what sort of torch tips you have, Two torches with rosebud heating tips is better. A fire is probably easier. Small tubing is done by filling with type metal, but it costs too much for big stuff. Another approach is to fill the pipe with water and freeze it, then bend as a solid bar, before it melts. Honda did the double wall pipes for the small bore multicylinder bikes this way. The small pipes the engine wanted were not acceptable to Sales, so they just put fat pipes over them, and bent them together.

Rob-
Don't waste a lot of time "matching ports" It is a waste, and there are arguments that stepped ports are better anyway. Just be sure the flow does not stumble going in the normal direction - ie, the downstream hole should be bigger than the upstream. This is certainly a LOT easier, especially if you are making interchangeable pieces, or for unavailable mating doodads.

FRM
FR Millmore

FRM,

Well, that trick with the ice in the pipe is a new one on me. Pretty nice low tech approach. Have you ever tried it yourself? Am I correct that "type metal" is a low melt point alloy like type set letters for printing?

Charley
C R Huff

Charley-
Haven't tried it, since I always need it in warm weather, and my freezer isn't long enough! Meaning to do tests in winter.

Yes, type metal. It has a low melting point AND it expands slightly as it cools, which gives a tight fit in the tube. There are other, more expensive alloys, which melt at boiling water temps. Super for small parts;
I've made gorgeous bends in 5/16" and smaller brass tubing. Also used to fixture goofy shapes so you can machine them. You can get by with lead (if the enviros and fear mongers let you find any!). A 10 foot piece of 2 1/2" pipe full of lead is pretty heavy though!

Have had good success with sand, using rubber expansion core plugs at the ends.

Meaning to try just filling the pipe with water and those plugs, but I expect it will just blow the plugs out. Then have to weld closer plates on one end, and threaded pipe fittings on the other to hold the hydraulic pressure.

FRM
FR Millmore

FRM,

For smaller tubes like your 5/16" and somewhat larger I've had good success using nylon rod as a filler. A bit of lubricant aids removal by clamping a free end of the nylon in a vice and twisting until the rod is free. All the times I've done this I have had a piece of nylon rod handy which was a nice fit in the tube requiring bending. I wouldn't want to try it on exhaust sized tubing unless I was prepared to melt the nylon to remove it. I have some cerrobend but so far haven't had a need to actually use it. A mate used to work at an agricultural equipment maker where they used the likes of cerrobend to cleanly bend large tubing but I guess they could justify the investment.
David Billington

Yup, the ice trick would be a lot more convenient in the winter.

Once the pipe is packed with ice, sand, or whatever, does it take less force to bend it similar to the way a solid bar is easier to bend than a tube?

Charley
C R Huff

David-
Sounds like work getting that nylon out, esp on tight bends; part damage on thin wall stuff seems likely. And not cheap melting big stuff out! Worth doing a test with the Cerrobend - totally cool stuff.

FRM
FR Millmore

Charley,

A solid bar is more difficult to bend than a tube of the same OD. It's a basic engineering property see http://en.wikipedia.org/wiki/Section_modulus
David Billington

Cerrobend:
http://www.hitechalloys.com/hitechalloys_005.htm
Guy Weller

David

Sorry to correct you, but that is not always the case. It depends upon the wall thickness of the hollow tube. The section modulus of a 50mm dia tube with 10mm wall thickness is greater than a solid tube of the same overall diameter. That's why circular structural elements are generally tubular rather than solid - they are not only "stronger" but material content is less.

Besides which, exhaust gasses don't flow very well through a solid pipe!

Peter
Peter B

Peter B,

Are you sure about that because your example doesn't work as the section modulus of the 50mm tube 10mm wall is less than the solid 50mm bar, easy enough to work it out or look it up. There are many reasons why a structure would use a hollow section such as weight and efficient use of materials. In bending the material nearer the centre contributes much less than that at the outside of the section so doing away with it as in a hollow section saves weight without sacrificing much strength.
David Billington

Rob, I can get both mild and stainless exhaust tube manipulated very reasonably by a local company.
This 2" St/st over axle length was done last week perfect with no rippling or stretching.


J L HEAP

Hey! Is that MY Minor that you're working on?? If the current owner finds he can't pay for the job to be finished I'd still be interested in it now I'm back on my feet. Would your 'bender bloke' be willing to supply 90 degree bends in varios sizes? I can send files if he might be interested in giving a quote.

Malcolm. If you can measure the locations of all of the holes and the exact sizes you need then it would be possible to convert it to a file. Not as easy as having the whole thing here on a bench, though.

Onno. I'm going over to see the laser cutters this week for some other bits. Once you have a file I can pass it on to them, if you want me to. I can ask them for a postage price or get an idea of the cost for me to send it to you.

Pete. Sure. Would you like the flanges with exact sizes for the holes or enlarged so you can slide pipes into them (OD of the tube rather than ID of the carb hole)?

Neil. How did he get it to bend? Pipe bender machine after heating or something more 'home workshop'?




Phew. Been a busy week.
r thomas

JLH-
Maybe I am drunk, but those bends look half closed to me, got any pic from the side of the bend?

FRM
FR Millmore

Rob, yes I'm sure he'd be interested. Convertible now being finished for a new customer. Have an unfinished Minor Pickup if you are interested !!
Really pleased you are on the mend now, hope all is okay.
How about letting me have one of your midgets to trial our modified parts!!:D

FRM
I see what you mean from this angle, but believe me this section is superbly formed. I#ll take a better photo tomorrow.
J L HEAP

Yes. I'm very confident of the theory behind this. z for 50mm solid is 12.27cm3, z for 50mm tube with 5mm wall (40mm id) is 9.06cm3 and z for 50mm tube with 10mm wall (30mm id) is 17.08cm3.

In simple terms 50mm solid rod is stronger in bending than 50mm/5mm wall tube but weaker than 50mm/10mm wall tube.

Hope that helps
Peter B

David

Yes. I'm very confident of the theory behind this. z for 50mm solid is 12.27cm3, z for 50mm tube with 5mm wall (40mm id) is 9.06cm3 and z for 50mm tube with 10mm wall (30mm id) is 17.08cm3.

In simple terms 50mm solid rod is stronger in bending than 50mm/5mm wall tube but weaker than 50mm/10mm wall tube.

Hope that helps
Peter B

Peter,

I think you've made an error somewhere as I agree with the solid but get 7.25cm3 for the 5mm wall value 10.68cm3 for the 10mm wall. http://www.novanumeric.com/samples.php?CalcName=SectionModulus agrees with me and gives the formula involved. I haven't had to know how to derive this for over 25 years but given the formula subtracts the inner radius or diameter from the outer then it is impossible to get a section modulus greater than that of the solid bar by removing material from the centre.
David Billington

Peter,

I just realised what you've done, instead of dividing pi * (OD^4 - ID^4) by (32 * OD) you're dividing by (32 * ID) which gives the answers you get. Same thing for the radius based calculation.
David Billington

David & Peter,

I have a vague memory of being told that a solid bar is easier to bend than a tube/pipe because the solid center acted somewhat like a fulcrum, which gave a mechanical advantage to perform the bending. This assumes all else equal. Though I have noticed this in “field” testing, I don’t think I have ever had the “all else equal” circumstance.

Charley
C R Huff

Thanks, David, You're right - ought to get a speeding ticket for rushing things too much!
Peter B

FRM

As promised ,here are some better photos of the 'over axle' exhaust as shown 'badly' earlier


J L HEAP

Another


J L HEAP

And lastly




J L HEAP

is that done at Woodford Halse?
Nigel Atkins

Agree with David: "I" is the second moment of area which is the measure of stiffness. The value of I for a tube is the I value a solid rod equal in diameter to the outer diameter of the tube less the value of I for a solid rod equal in size to the inner diameter. So a tube can never be as rigid as a solid rod of the same od (material remaining the same of course).
Since I is based on the fourth power of the diameter, outer material has a much greater effect than inner material so weight for weight tube will be stronger.

Ow, that hurt! 1966 Strength of Materials, Mech Eng, Leeds Uni - that's 47 years! Bloody hell!
G Williams (Graeme)

Nigel,

BTB in Woodford H, no, used them for our K series manifolds when we fitted them into Minors. They became just far to expensive. Excellent quality though.
This was bent by a friend of mine who runs a tube manipulation company, both round and square bar/tube at very good rates. The above section was made to our design, then digitised and reproduced in top quality stainless, of a slightly thicker wall than normal.We're talking around £50 for the above part, something not so fussy ,obviously less.
J L HEAP

yes those pipes look very good (another 20hp there :) )

I'd have been round to see you if I'd have known at the time

BTB done my centre pipe, not at all cheap and not really the type of work they take on

I warned them that a Midget was a narrow car which they said was no problem as their lift was adjustable width (what a great idea) and a lad even came out to measure the width of my car to set the lift, he agreed it was narrow, I think they have some vehicles with wider rear tyres that than the width of the Midget
Nigel Atkins

JLH-
Yes, very nice, proves you can't always believe watcha thunk ya saw, see!

FRM
FR Millmore

I've had a price back for 6 or 8mm plates for the carb end of the intakes and they work out at £7 each. Gives everyone an idea of price. Engine end of the manifold with, obviously, 5 holes and the holes for the studs either cut out or just pilot holes costs about £35, depending on lengths of total cuts.

The tube bender company I used charged about £170 to make a total of 8 bends in sizes from 26mm OD to 34mm OD. Not as nice quality as the one shown above but maybe the size has something to do with it.

Added my email address at the top in case anyone wanted to chat directly.

TTFN

Rob.
r thomas

This thread was discussed between 14/02/2013 and 19/02/2013

MG Midget and Sprite Technical index

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