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A Marine Condensing Engine

Some ocasional comments on a new build

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Ramon Wilson07/02/2021 17:22:52
1283 forum posts
367 photos


For a few weeks now I've been nibbling away at pieces of cast iron bar to make the basic 'castings' for a marine condensing compound, the drawings for which were first published in a series in Model Engineer May 1923 and found on the John Tom free plans site.

A fairly large engine with an LP cylnder of 3" dia. it is not a scale model per se but one based on full size practices. Though the size was too big to contemplate the drawings were very alluring so the series was downloaded and printed off. It printed at the size of the original ME format so the three major drawings were then done at 'fit to page' and there lay the answer - as printed it approximated 5/8ths of the original.

marine compound (15).jpg

The drawings dimensions, all in fractions, were scaled by .625 and converted to metric - the drawings being annotated in red ink and the dimensions as such being worked to and not rounded up or down.

Work began by roughing out all the cast to basic shape before finish milling

marine compound (14).jpg

The condenser body was made from two parts slip jointed and bonded with JB Weld. This was left while the base was machined - the longer left the better the adhesion and machining qualities.

marine compound  (5).jpg

marine compound  (6).jpg

The base began as a substantial slab of cast from College Supplies the majority milled away

marine compound  (8).jpg

The well pump, integral on the drawing was machined as a separate component

marine compound (22).jpg

then using a c'sunk screw for correct positioning it was well bonded in place with JB Weld

marine compound (25).jpg

Hope that's of interest - any questions or comments most welcome.

Regards - Tug

Steviegtr07/02/2021 17:37:44
2422 forum posts
336 photos

You keep them pictures coming. Looks great what you have done so far. yes.


Roderick Jenkins07/02/2021 20:00:37
2176 forum posts
608 photos


This look like a really interesting project. You must have had a big bucket of filthy swarf! Looking forward to regular updates.

Stay well,


Former Member07/02/2021 20:09:08
1085 forum posts

[This posting has been removed]

DrDave07/02/2021 20:55:28
240 forum posts
47 photos

Hi Tug,

You lost me at “slip jointed”, I am afraid. Could you explain that in a little more detail, please?

It looks like it will be an interesting engine when finished. I will be following your progress keenly.



Colin Heseltine07/02/2021 21:09:02
654 forum posts
227 photos


That's a lot of cast iron. Does the cast iron de-stress after its basic machining or is there some other reason why you have done all basic machining first. Other than maybe getting rid of the majority of casting swarf at an early stage.


Ramon Wilson07/02/2021 21:37:07
1283 forum posts
367 photos

Thanks for the interest guys - just to say this won't be a build log as such but just updates on progress as it goes along so if you do have any questions just jump straight in and ask.

Swarf - Yes very black and very dusty despite constant vacuuming but whilst the majority has been dealt with now, theres still a fair bit left to go!.

Colin - Most cast iron of this quality - meehanite - has very little, if any, stresses locked within it so the roughing was just to get rid of the major waste to leave between a mil and two to finish machine.

Dave - the condenser is just on 100 mm long so drilling and milling the internal profile was out even from each end. It was split in two along its length and the inside milled to section with the angle created by step milling.

marine compound  (5).jpg

The sides were then relieved (blue marked areas) for half the thickness and the two parts slipped over each other with a generous application of JB Weld between the two - I've cropped the previous pic - you should see it better here

marine compound  (6a).jpg

As said this was left until the base was finished before machining to allow the JBW to fully cure and harden.

Some may note the two drawings - one with red ink the other without. The annotated ones are the dimensions being worked to the unmarked ones are just for reference to establish any missing dimensions. So far have only found one error but there are a few dimensions that need to be sourced from other parts.

Thanks to all for taking an interest and good to see you looking in Rod - I hope you and Sally are staying safe and keeping well.

Regards - Tug

Ramon Wilson17/02/2021 22:48:17
1283 forum posts
367 photos

Just a small update - work has been ongoing on the condenser parts which are now all together

marine compound (33).jpg

Last op on this component this afternoon. The JB Weld is not P38 filler though it looks like it. That's all been filed and smoothed which creates this light grey colour.

marine compound (36).jpg

The slide bars are from cast - the slide will be steel. The bearing caps are two pieces JB'd together with a brass tube oil wick tube loctited in

marine compound (37).jpg

marine compound (38).jpg

All those holes in the end are 8 BA and yes I did break a tap cleaning out the last hole. I was able to drill it out oversize with a carbide drill, Loctite a cast plug in and redrill and tap it - phew!

Cylinder head parts next - 14 parts to do before bringing them all together to create the one piece. It will be really pleasant to finish this cast though!

Hope that's of interest

Regards - Tug

Edited By Ramon Wilson on 17/02/2021 22:50:08

Nigel Graham 217/02/2021 22:54:26
2039 forum posts
28 photos

Definitely of interest! Impressive work, and we look forwards to seeing it progress.

Jeff Dayman17/02/2021 23:01:29
2223 forum posts
47 photos

Top notch work Tug! Thanks for sharing it. Glad to see another member of the BFCIMC (black fingers CI machining club).

PatJ18/02/2021 01:29:11
332 forum posts
407 photos

That is some nice work indeed !!!

I have admired those drawings for many years, but I am not sure I will ever gain enough skills to make something that complex.


Ramon Wilson18/02/2021 10:45:26
1283 forum posts
367 photos

Thanks for your comments guys. Yes 'Black Hand' gang indeed it is Jeff - love machining the stuff but hate the 'side effects'. All the cast used so far has been superb to machine.

Despite very careful checking of dimensions I find there's a slight anomaly on alignment of centre lines of standards to bearing position. Probably an error on my part it will be easier to put this right first rather than try to make due allowances on build up of parts so some tweaking is required.

Pat J - It was the quality of the drawing that attracted me to this engine. so far I have only found one distinct dimensional error but there are quite a few missing which require looking at other parts to establish a dimension.

Regards - Tug

Roderick Jenkins18/02/2021 11:28:23
2176 forum posts
608 photos


That's terrific fabrication work.

I think Jason may have to up his game wink

Stay well,


JasonB18/02/2021 12:09:00
22588 forum posts
2641 photos
1 articles

No, that's all simple stuff with straight lines and edges Rod, it's once you get into the stuff with compound curves when you really start playing. Plus with the right machines you can do it from solid, none of this sticking it together lark.wink 2

Looking good as always Ramon.

Ramon Wilson18/02/2021 13:21:10
1283 forum posts
367 photos

Maybe so Jason but it's still done with traditional handle swinging - none of that fancy computer driven stuff that's so easy create complex shapes with. Isn't that right Rod wink

Besides the right machines cost money - didn't you get a free hand out laugh

All beyond my old brain cells now even if I had the finance - I'll stick to what I know for what times left.

Cured the error - result of accumulation of many dimensions I think but back on stream and made a start on the cylinder head

Regards to all

Ramon Wilson19/02/2021 09:13:48
1283 forum posts
367 photos

That was tongue in cheek Jason - hope you weren't offended smiley

The cast iron calls - one cylinder done so far


ChrisH19/02/2021 10:38:41
1018 forum posts
30 photos

Tug - brilliant, what a good find, now you have me looking at them and downloading the same pdf, a marine steam engine has always been on my "to do" , it's just my snails pace speed of working has held me back as I struggle to finish and aero engine.

Will be following this build along Tug yes


ChrisH19/02/2021 14:29:22
1018 forum posts
30 photos

Having now had the time to take a very close and long look at the thread so far, what a lovely bit or workmanship there Tug, it's all looking just so good. Not seen the slip joint done before so always good to learn a new trick, but how did you clean up the JB Weld that (must have) squirted out on the inside, or did you just scrape it off with a long implement like a chisel while it was still soft?

It's blowing a hoolie here and lashing it down so I guess an afternoon studying the pdf download is well on the cards. Scaled to 0.625 you say...........


Ramon Wilson19/02/2021 15:29:20
1283 forum posts
367 photos

Hello Chris, thanks for commenting and taking an interest.

My very first model engineering project was the Stuart Compound Launch Engine !

It was way, way beyond my knowledge and skill set at that time and doomed to failure from the outset - needless to say but it never made it beyond the shelf of doom. I've always wanted to have another go at one but never quite got round to it. After finishing my last engine I discovered this article and was very attracted to the quality of the drawing itself. I didn't check dimensions one to another but something said that there would be little to fault. As designed it was far to big to comtemplate but as said once printing to fill an A4 sheet the answer was in front of me - .625 fiting the bill nicely. I prefer to work in metric so converted all the dimensions first before making anything. No rounding up or down as such just working to the results eg 15/16ths x .625 x 25.4 = 14.88 mm - 14.9 at most

I think it would make a very good project if done at exactly half scale though and still make for an imposing model. It would probably ease the making of the condenser from one piece too as well as reducing the material cost.

I've used (Standard) JB Weld for many years - well before using it to simulate castings and from the outset was impressed not only by it's strength but its ability to withstand heat to a fairly high degree - and still remain functional.

Though some may doubt it's usage I have every confidence in it for the type of application as on this build. This engine will only be run on air (for me) but it will certainly withstand steam temperatures of around 60psi with a considerable safety margin. The 'one piece' cylinder head on the modified Double Ten fitted to the Wide a Wake steam launch was made from seven individual parts JBW'd together with minimal fastening and runs on 60 psi dried, but not superheated steam without any issues.

There was very little to clean inside the condenser and was done as you say. I always place the bonded parts on an ali plate sat atop an oil filled radiator to cure overnight and fettle any fillets the next day. The longer it's left the better it is if it's going to be machined but filing fillets is best done as soon as cured.

It would be nice to think someone else was inspired enough to give it a go.

Any comments on JBW or anything else please ask


Regards - Tug


Edited By Ramon Wilson on 19/02/2021 15:32:30

JasonB19/02/2021 16:15:37
22588 forum posts
2641 photos
1 articles

The 0.625 or 5/8 scale is also very close to the ratio you get if you use 1mm = 1/16" which makes for nice round metric numbers for those that like to work in metric.

For those that want an easier round condenser there is also a similar engine in the 1924 ME which again are about on the net


PS Ramon, did you not know Rod also has a CNCdevil

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