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

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

Dave
The Emerald Isle

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.

That probably means the total size is too great

Try uploading one at a time.

Neil

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

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

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

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

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

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

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

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

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