Making a Bowman chimney cap

Steve_S · Making a Bowman chimney cap

The chimneys of Bowman 101, 122, amd 135 engines are plain brass tubes of one inch outside diameter topped by a cap pressed from sheet metal. As the cap is held in place only by being a more-or-less tight fit in the chimney, its not surprising that after 75 years or so they're often missing. I needed one for my M122... and the chimney too for that matter... and so began my experiments to find a way of making a reasonable copy of a Bowman chimney cap. I already had a real one on my E135, so I knew what to aim for, but for such a peripheral and almost incidental component part, it's proved to be quite a job to get a result that I am happy with. Originally they would have been made using a press with a suitable punch and die, and with these it would have been easy. Without these it's tricky to persuade sheet metal to deform in three dimentions in the way that you would like it to. I have made several unsuccessful prototypes using metal cut from a biscuit tin lid, but when I thought I was getting close I decided to use thin sheet brass so that there would be no corrosion problems in future. Here's how I made the latest version, which I think is good enough to use on the M122.

First I made a wooden die from a scrap of beech. I hollowed out the hole on my woodturning lathe, but it could be done using a hole saw in an electric drill followed by a chisel to clear out the wood in the middle.

After anealing the brass I began to gently hammer it into shape, until it was a good fit for the depression in the wood.

Next, I soldered a strip of brass into a ring that was a good fit for my chimney tube.

After drilling and filing a hole of the right size in the centre of the hammered part, I soldered the ring in place.

The secret weapon in the next phase is this:

It may look like the top off an old cold water tap, but in fact it's a perfect jig with which to form the curled lip of the cap. The E135 cap fits it exactly.

Any piece of pipe of the right diameter would do for this... it's just a case of hunting around to find something suitable.

The lip of the cap its made by lots of light taps with a small hammer... this is the easiest bit to do!

When the lip is done, the edges can be tidied up with a file and some wire wool.

Here it is next to the real one.

Now it just needs a coat or two of paint, and its done.

johnreid

Oh my that is super! I can not put into words how impresse3d I am with that, I am lucky that mine has the cap, as I would have a hard time finding the right size faucet lever, but that is so ingenious.

Mamodman123

That is just brilliant Steve!

Perfect replacement part for your 122!

I wish I could work that well with metal

Les

That is very clever, do you fancy making three more.

flywheel61

, Another masterpiece from the house of steves', your enginuity is remarkable.

Cheers

Chris

IndianaRog

Steve,

That is amazing. Now you have the hang of it, I bet you could make a dozen, put them on eBay and make it well worth your effort and be a service to the Bowman owners missing their chimney cap. If they all sell, make a dozen more.

I loved the faucet handle for getting that curl to the edge...very ingenious!!!

Rog

alan2525

Great Workmanship there! Thanks for showing the construction process too, finished result looks terrific.

Reid

A finer instructable I've not seen.
Superb teaching/showing!

tmuir

Nicely done.
Another thread destined for the library for sure!

Sandman

MooseMan

Brilliant Steve - I'm sure Old Man Jenkins would approve!

Wallace

Wow steve. That is a top job. Great work

Steve_S

Thanks all for your comments! It was fun to do and turned out well, but it's not an economically viable method... it's too labour intensive and takes too long. If someone could make a proper punch and die, and had a suitable press, then they could churn them out like shelling peas. However, I'd encourage anyone to have a go at making one (or more!) for themselves using methods like mine... it's very satisfying when it works!

johnreid

I have a small Arbor Press, I bet that part would work. I dont have the Brass and the gumption to follow through with the experiment, plus my Bowman has a cap.

IndianaRog

John, I bet you could set yourself up to bang out a dozen of these, list them on eBay and get a nice return on your time and investment in minimal material. The K&S brass sheet sold at Michaels and Hobby Lobby is like $5 a sheet and you could get 6-8 out of such a sheet. I bet fellow Bowmanites missing their chimney caps would pay a fair price for a proper fitting one. You have the chimney, you have a genuine cap...I would go for it!!!

Rog

Andy

well done mate a great use of resources

mogogear

A hammer and a mind -what a wonderful thing!!

oldstuff

Wonderful job, Steve. Your "enginuity" is an inspiration!

IndianaRog

NOT to hijack a great thread, but seeing Oldstuff posting again is worth the risk. Welcome back Chuck, we've missed you buddy.

Rog

xlchainsaw

great job ill give it ago. thanks for the idea.

Steve_S

Thanks again all.

Chuck! Good to hear from you!

Have you made any more engines?

oldstuff

Hey Steve!

Yes, I'm making another twin like the one in my signature only larger.

I remember Cedge making an awesome radial engine. Has anyone else done a
homemade while I was away?

James

Bloody hell! That's amazing

mc_mc

steamyjim

Looks great Steve!

Atticman

Matybe the first use of this sort of tap for metalworking

so ingenious. well done.

Are the Bowman caps glossy?

Our M122s is matt, but me brother got to it so he may have painted it, he cant remember

Les

Steve_S

My E135 cap is dull but not quite matt. It looks like it might have been glossier once. I'll leave the new one as it is until I've done all of painting on the rest of the engine, then see how it looks. If it's unrealistically shiney it'll be adjusted.

James

Steve, could I commision you to knock up one more??

Atticman