Trevithicks Dredger Engine

[John MillisParticipant @johnmillis57685]

I have purchased the kit from Brunell and at long last received most of it and about to start manufacture.

As the kit uses castings in lieu of fabrication which is the basis of the original ME article which come as build instructions.

I am looking for any advice that anybody who has built the engine can give me also where can one obtain the square nuts and bolts as the supplier in the article does not do them any more

All suggestions and advice would be appreciated as this is my first attempt into building a working model since my apprenticeship 50 years ago

[John MillisParticipant @johnmillis57685]

[JasonBModerator @jasonb]

Welcome John, I've not built one myself though quite fancy doing it at a larger size. I was talking with a chap who has a very nice one and he said there is a problem with the valve gear as drawn but I'm not sure what.

As for square fixings its really a case of making them yourself. One of the German ME suppliers does do square ones but I'm not over keen on the size of the chamfers and they will also be metric not BA as per the drawings.

 

EDIT, these look OK but no photo

 

J

Edited By JasonB on 19/03/2015 18:39:54

[SaxalbyParticipant @saxalby]

I built mine from the original ME article. It turned out a nice little engine. I do not remember any problem with the valve gear. The only problem I had was in getting the two crosshead columns parallel. Once that was sorted out it ran very smoothly.

I made all my own square nuts and bolts from a suitable square bar. Drill and tap as deep as I could and then chamfer and part off the nuts. Did not take long.

Like Jason, have always fancied doing a larger (2X) version.

[steamdaveParticipant @steamdave]

Posted by JasonB on 19/03/2015 17:36:52:

Welcome John, I've not built one myself though quite fancy doing it at a larger size. I was talking with a chap who has a very nice one and he said there is a problem with the valve gear as drawn but I'm not sure what.

As for square fixings its really a case of making them yourself. One of the German ME suppliers does do square ones but I'm not over keen on the size of the chamfers and they will also be metric not BA as per the drawings.

EDIT, these look OK but no photo

J

The 1/8 boiler is a fair ol' lump. (part of THE list you know about, JB)

Dave
The Emerald Isle

[Paul HorthParticipant @paulhorth66944]

Hello,

I haven't used the forum for a while, just found this thread. I thought I would mention that I have nearly completed a Trevithick engine, it has been running well on air for some months now, there is no problem with the valve gear. I fabricated the boiler and the crosshead as decribed by Tubal Cain. I bought a range of square nuts from the German supplier, with matching metric bolts, I have made square headed bolts by silver soldering the nuts on the other ends. I also have made various square nuts in BA sizes as needed so I have a mixture, I have to keep notes to remember where they all go.

I have made a working water pump, piping and check valve, and I am approaching making a gas burner. I am making a functioning level gauge, I imagine this to have been retrofitted by an engine room foreman in the 1820s. I am perhaps over optimistic that all these little bits will function in steam under pressure.

Paul

[OldMetallerParticipant @oldmetaller]

Paul, I'd love to see some pictures. I've got the build article somewhere, I've always fancied doing one of these.

Regards,

John.

[Paul HorthParticipant @paulhorth66944]

John,

Thanks for your interest. I have tried to upload some photos but they won't go, the connection keeps timing out. So I have an album which is empty. I will try again later.

Paul

[Neil WyattModerator @neilwyatt]

Posted by Paul Horth on 24/01/2016 21:39:25:

John,

Thanks for your interest. I have tried to upload some photos but they won't go, the connection keeps timing out. So I have an album which is empty. I will try again later.

Paul

That probably means the total size is too great

Try uploading one at a time.

Neil

[Paul HorthParticipant @paulhorth66944]

Thanks for the tip, Neil – it worked. I have now uploaded some photos into the album titled "Paul's Trevithick Engine".

I resized my photos down from about 2 MB to about 300kB, and then I could upload them one at a time. As you can tell, I am new to this photo uploading game, being stranded in the technology of 200 years ago.

Paul

[Neil WyattModerator @neilwyatt]

You can upload 2 meg photos one at a time – they will be resized to 1024 pixels along the longest edge.

You could upload 5 300kb images, but 5 2megs at once will be bigger than the maximum uploiad.

Neil

[OldMetallerParticipant @oldmetaller]

Thanks for uploading the photos Paul, that looks like a very nice engine.

I think I especially like the Trevithick engine as I have a very early memory of being taken to the Science Museum in London and seeing this engine in profile as we entered the gallery where it was kept- it was the first historical engine I'd ever seen and I still get a frisson every time I see it!

Regards,

John.

[Paul HorthParticipant @paulhorth66944]

Hello John,

I am retired, and live only a half hour tube ride from the Science Museum, so I visit there often, usually staying on the ground floor. I have looked carefully at the Trevithick engine there, and have a lot of photos, unfortunately they are not very good because the engine is black,and is poorly illuminated. To see the works on top, you have to go up to a balcony where a couple of spotlights are aimed directly into the camera, making the details come out dark.

In the model series, Tubal Cain said that when the engine was rescued from a Victorian scrapyard, various mistakes were made in the restoration. Over 100 engines were built under licence, and I'm sure that each was slightly different,according to the builder's judgment and what the client specified, so I'm relaxed about making a few changes of my own.

The Science Museum is for me a wonderful temple of engineering and design, so much to see there.

Regards

Paul

[OldMetallerParticipant @oldmetaller]

I sometimes get an hour or two in London: last year I managed a whopping 14 minutes in the Science Museum! Time enough to walk round the Trevithick engine, watch them start the big mill engine and pay my respects to the Rocket- I even managed a surreptitious touch on the left hand cylinder as the security guards were distracted by the thousands of children milling about!

I don't remember being allowed to run about screaming when I was taken there as a child..? At least, I think I'd have remembered the resultant thick ear that I would have collected!

Regards,

John.

[Paul HorthParticipant @paulhorth66944]

I have now fitted a level gauge to the boiler, see my photo album. I hope that it will eventually function. The tube is 3 mm biro tube – very readily available and unbreakable, but it is rather cloudy. If I can find some 3mm glass I will use that.

I discovered to my surprise that not all biro tube is the same size! Seems to range from 0.125 down to 0.109 or so. I have reamed the firttings to take 0.117 (3mm) with end seals.

Paul

[John MillisParticipant @johnmillis57685]

Just an update to my original post. Progress is slow but 2 months in Australia don't help. I'm currently machining the boiler end casting and having to invent ways to hold the casting on my mini lathe and mill. Picking up on a comment in the posts I believe Brunnel are considering a X2 version of the kit.

John

[Paul HorthParticipant @paulhorth66944]

Hello all,

A year later – and at last I have raised steam on the Trevithick engine. Progress was slowed down by various factors including medical ones. I had two goes at making a burner, then a little fan to keep it alight inside the boiler tube. I spent a lot of time fiddling with the pump valves to get reliable pumping, with only partial success. But now it has run on steam, in a frantic burst of about two minutes, Difficult to throttle between rhe clappers and stop. There now follows a period of debugging, and making the finished deck to go on the plinth, with all the piping and water tank below the deck.

I've put up a few new photos in my album.

Paul

[Neil WyattModerator @neilwyatt]

Excellent news!

I look forward to seeing it on wheels.

Neil

[Paul HorthParticipant @paulhorth66944]

Yeah right………that sounds like what Mrs Trevithick would have said to Richard.

then he did it – and the result was totally bonkers!

[Neil WyattModerator @neilwyatt]

Doh!

Apologies – I have the Airfix model of Trevethick's Pen-y-Darren loco and of course the engine part is almost identical!

Neil

[Paul HorthParticipant @paulhorth66944]

Hi Neil,

I had forgotten about Pen-y-Darren, I was thinking of the "Puffing Devil" , the crazy road engine which Trevithick drove up Camborne Hill in about 1801. It's basically just the dredger engine on wheels, vertical connecting rods linked directly to a pair of wooden cartwheels. A replica has been built which is run on Trevithick Day, with operaors desperately clinging on while trying to steer and avoid being burnt by the chimney or pulped by the moving parts. I've put up a photo of it, but no. I'm not going to build that.

Paul

[KWILParticipant @kwil]

Try this one **LINK** for a Trevithick

Edited By Neil Wyatt on 30/04/2017 15:45:33

[Paul HorthParticipant @paulhorth66944]

Thanks for the link,KWIL. Some questions – the engine shown has the piston at the same end as the chimney, coming backwards towards the driver. So where is the firedoor? If it's at the front, where does the fireman stand? and is there only a single pass furnace inside?

The replica Pen-y-Darren is different, it has the piston at the front, opposite end from the chimney, so the firedoor can be next to the chimney accessible to the driver, with a return flue, just like the dredger engine. Except that with a horizontal cylinder inside the boiler, there isn't much room for a return flue. Trevithick must have been trying out several different layouts.

Paul

[Tim StevensParticipant @timstevens64731]

The Puffing Devil was a very significant device. It was the first mechanically propelled vehicle in the UK, it suffered the first motoring breakdown, and the first property fire caused by a motor vehicle. And quite possibly, the first motor insurance claim.

Cheers, Tim

[Paul HorthParticipant @paulhorth66944]

An update on progress with the Trevithick engine….

I have re-made the regulator valve to get a tighter fit, and the engine now can run in steam continuously for about 25 minutes, until the gas in the tank runs out. It is still too fast though at about 200 rpm. Closing the regulator valve by the smallest movement that I can manage, can cause it to stop. I have fitted a restriction orifice 1/32 inch dia in the steam port of the throttle valve, but even this will pass more steam at 10 psig than the engine needs, about 3.1 gram/minute. The pressure is sustained by the burner, at 10 psi, which stays alight without any additional draught. The pump works, I have ended a run with more water in the boiler than I started with. .

I now have to try to slow the engine to a more respectable speed, I might have to make an even smaller orifice, or try putting on a driven load in the form of a little motor driven off the flywheel rim, running a LED light. That would be nice.

Paul

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