Trevithick's Dredger boiler

[iszczyg]

Hi,
I have just finished Trevithick's Dredger model engine. It perfectly runs on compressed air, only paintings is to do. The last thing I have started to do is gas burner. I 've decided to use propane-butane gas delivered in small containers. I have constructed burner in a form of brass tube (inner diameter 8mm) with a set of small holes (~1 mm dia) along the tube. I have selected the appropriate nozzle and I' got nice flame along the tube. Everything is OK until I put the tube into the fire tube. When it is inside, the flame disappears, some stochastic flames appears before the fire tube and in the end of chimney. It does not work at all.
Could you advise me how to solve the problem? Maybe ceramic burner?
Please find attached pictures of the engine, burner and the diagram of burner.

Thanks in advance,
Irek,
Poland

 

[Diversion900]

Sounds like a basic air / fuel mix problem to me.
You may need to fan force air into the chamber to get it to temp, then maybe it might " self draw" it's own air.

Cheers Neil

 

[iszczyg]

I've tried to heat up the chimney with external gas burner but it didn't work

 

[Diversion900]

Well the way I look at the problem is that you need to correct the mixture imbalance to get flame !
Either more air or less fuel will solve the issue.
As you have explained, you only got a small amount of flame from your burner once positioned inside the combustion chamber. That means not enough air for the amount of flame you are trying to produce.
Try gently blowing into the chamber to see if your flame gets better.

 

[Diversion900]

Alternatively you may get better results from a torch type flame, directed into the combustion tube.

Cheers Neil

 

[iszczyg]

I've tried torch type flame, but when I put the outlet of burner to the tube the flame goes out. It behaves in the same way like my burner.

Cheers
Irek

 

[vederstein]

I love the story of Trevithick. He was willing to push steam technology much further and much faster than anyone else during his time. It's a shame he died penniless and is a relative obscure historical figure.

I believe he could have been more successful if the Crown hadn't extended Watt's patent to 1800. He had the ideas, but the patent prevented him from exploiting them until the patents expired.

If you don't know much about Trevithick, a quick Wikipedia read is a good place to start...
https://en.wikipedia.org/wiki/Richard_Trevithick
https://en.wikipedia.org/wiki/Richard_Trevithick

Here's a picture of a Trevithick engine on display at the British Science Museum I took in 2014. For something built around 1815, it's beautiful to the right individual. If I remember correctly, it was discovered in a scrap heap in the 1880s and some enterprising fellow recognized it for the treasure it was and rescued it.

 

[Diversion900]

It might be worth your time to read the previous thread on the small gas burner. It may answer all your problems.
Tony has done all the work for you.

Cheers Neil

 

[iszczyg]

Neil: thanks a lot - I haven't noticed Tony's thread. Basing on the infos from Tony's thread I have changed the size of holes to 1.2 mm - it has started to behave a little bit better. Finally I've replaced nozzle from 0.6mm to 0.15 mm. Now it works perfectly! The gas velocity out of the nozzle increased and, a s a result, the pressure drop is greater which makes that much more air is mixed with gas. Thank you for your prompts!!!

Vederstein: the engine you have shown is exactly the same I have built! I also appreciate Richard Trevithick a lot! It was very interesting person. I have a book describing his life: Richard Trevithick - Giant of Steam by Anthony Burton. I'm sure you know this book.

Once again: thank you for your answers!

Cheers Irek

 

[Diversion900]

No problems Irek, we are all here to help.
I hadn't noticed Tony's post until after I offered my own advice.
After refreshing my memory by reading the next forum subject, I realised it was just what you needed.

Great job on the engine too, it looks good.

Cheers Neil

 

[Charles Lamont]

That looks a very nice model.

I have been working an a similar one for the last 10 years, but at 12" to the foot scale:

www.catchmewhocan.org.uk

See the news pages for the build log.

 

[dkwflight]

You might be able to copy/ adapt a bernsomatic torch design. They used to have a large torch head, about 1: in diameter.
Keith Appleton on you tube has a number of vids about making, adapting gas burners in small boilers.
He uses torch types and ceramics depending.
His is a good source of info.
Nice work

 

[oliomio]

Hi,
I have just finished Trevithick's Dredger model engine. It perfectly runs on compressed air, only paintings is to do. The last thing I have started to do is gas burner. I 've decided to use propane-butane gas delivered in small containers. I have constructed burner in a form of brass tube (inner diameter 8mm) with a set of small holes (~1 mm dia) along the tube. I have selected the appropriate nozzle and I' got nice flame along the tube. Everything is OK until I put the tube into the fire tube. When it is inside, the flame disappears, some stochastic flames appears before the fire tube and in the end of chimney. It does not work at all.
Could you advise me how to solve the problem? Maybe ceramic burner?
Please find attached pictures of the engine, burner and the diagram of burner.

Thanks in advance,
Irek,
PolandView attachment 110646 View attachment 110647 View attachment 110648 View attachment 110649

 

[oliomio]

Hi Irek, I have recently finished a 1:8 Trevithick dredger engine, and had similar problems with the gas burner. The main problem is that it is an inefficient steam engine, made even more inefficient by being a 1:8 model. I solved the problem eventually by using a very large capacity burner, extending the chimney, and lagging the boiler. Rather than detailing the changes I suggest that you visit my blog johnsmachines.com and go back to the posts from early 2019. Happy to communicate further if you wish. John V. johnsmachines.com

 

[Charles Lamont]

Here's a picture of a Trevithick engine on display at the British Science Museum I took in 2014. For something built around 1815, it's beautiful to the right individual. If I remember correctly, it was discovered in a scrap heap in the 1880s and some enterprising fellow recognized it for the treasure it was and rescued it.

Indeed so. Francis Webb, Chief Mechanical Engineer of the LNWR, spotted it from a passing train. He had it restored at Crewe works.

 

[Jennifer Edwards]

Irek,

A good friend of mine in Australia just completed the same dredge engine/boiler and documented his build on his blog at:

https://johnsmachines.com/category/trevithic-dredger-engine/

I thought you may like to see it,
Jenny

 

[Jennifer Edwards]

Here is another John wrote about about the history of Trevithick. He even traveled to London from Australia go research his work.

https://johnsmachines.com/tag/trevithick/