small gas engine

[Ian S C]

Wound my own coil, and run it with a buz box, get a better spark with that than I do with a 12V ignition coil.  I'v got the start for the hot tube, an old spark plug body, I just want to know what size of tube to use.     Ian S C

[mhirst121]

Ian, I think if it were mine, I would start with a tube of 3/8" dia with a 1/8" hole bored almost full depth on a tube 4" long. If it does not fire with this and the burner half way up the tube to start with, try moving the burner closer to the engine if it seems very retarded. the hot tube should only need to be dull red at the hot spot. If still no joy try opening the hole out by 1/64" at a time. This is the way I have managed to get some full size engines sorted on hot tube. Hope this is some help. I have a little Villiers converted to run gas with hot tube and the tube is just larger than the one I said to try.

Cheers,
MartinH

[NickG]

The hot bulb interests me more as don't like the idea of needing a flame on there constantly. Thanks for the descriptions.

[mhirst121]

Well I guess its time for another little update. The full build pics of the parts that were on my blown up hard drive have not been recoverable, so I will post some pics of the finished parts and continue from there with the new parts. Shame as I had taken hundreds of pics of the build, lesson learned.

This is the valve housings, made from two parts brazed together


The bearing caps were machined from solid, just one of the smaller items but seemed to take an age to make with alot of rotary table work.


The big end bearing was machined from a solid piece of phosphor bronze


The con rod was machined with the offset tailstock method from the solid. Piston, con rod and big end bearing.


Bushes mounted in support brackets and gearing fit to shafts.


The cams shown on the drawing were individual items but I decided to work out the angles and machined them as one unit.


General view of crank.


That sort of brings the project up to date, from now on I will try and do a better build log for each piece manufactured.

Cheers,
MartinH

[mhirst121]

Next part up was the valve arm pivots

Piece of bar turned to 10mm dia


Threaded M10


Off to the indexer to mill the square on the end


Cut off to length and mounted back on the lathe to spigot the other end, notice the piece of 1.5mm plate behind one of the chuck jaws. This was to give me an eccentric shaft for adjustment when fit to the engine.


The completed pin, two of these were required.


They will be cross drilled and split pins fitted on final assembly.

Cheers,
MartinH

[mhirst121]

Heres a general view of the burner tube holder. It was machined from a solid steel block and has a 6mm hole up the centre for the gas to be pushed up and into the tube. The tube is made from 8mm stainless stell bar and has a 3mm hole drilled blind up the middle, the thread is M8 fine pitch. The size of the hole may need adjusting depending on where the engine fires at first start up.





Next up was the chimney and burner holder.

A piece of 1" BSP tube was used for this.


Faced off and outside dia cleaned up.


Off to the mill and a 12mm hole for the burner holder was put in. At 90deg to this a 10mm flat with a 6mm hole in the centre for the hieght adjuster.


The burner holder boss was machined to fit and parted off.


view of the part prior to silver soldering




And silver soldered


A length of 5mm silver steel was threaded and cut to length for the adjusting rod, then the tube holder was drilled and tapped to accept it.

View of the chimney on the engine


Cheers,
MartinH

[mhirst121]

The mixer is another part I have lost the pics for, so a general view of it will have to do. The mixer has a valve in itto stop the gas flow when not required. In the picture of the brass valve seat, you can see where the valve sits over the small holes therefore stopping the gas flow till the valve is lifted again.

Valve seat


Parts for the mixer.


Assembled mixer


Mixer and hot tube assembly fit to the engine


General view so far.


Cheers,
MartinH

[smfr]

Some nice parts here, and this engine is really starting to come together!

Simon

[Roger B]

What gas are you intending to use? I was told at uni that 'old' town gas had plenty of hydrogen and worked well with hot tube ignition. Natural gas did not contain much and they were forced to convert their hot tube demonstration engine to spark ignition (this was somewhat bigger around 5" bore 5" stroke.

[Dave Otto]

Hi Martin

Somehow I missed the updates to your engine back in May; just got caught up and I must say that it is looking real nice.

Dave

[NickG]

looks very nice that Martin 

[mhirst121]

Well firstly sorry for the delay in posting back on this thread, but I have been restoring another motorbike so progress on the models has been slow. Anyway I thought you might like to see its first proper run. I am running it with a cdi ignition module and a small plug in the back of the hot tube holder, this was always the plan as if it is too windy to run outside on the hot tube I can switch to using the HT ignition.
So here it is, just need to tidy up a few bits and pieces and design and make a trolley for it.

<a href="https://www.youtube.com/watch?v=BHPm9bj9x6c" target="_blank">http://www.youtube.com/watch?v=BHPm9bj9x6c</a>

Cheers for now,
MartinH

[Jo]

Don't know why but it claims the video is private...

How did you time the engine? I have a CDI ignition unit on my R&B and for the life of me cannot get it to fire the engine 

Jo

[mhirst121]

Hello Jo, I have always set them to about 5 degrees before TDC and if I get kickback retard them a little.
Can you see the video now ????

Cheers,
MartinH

[gmac]

Martin;
Thanks for posting the build. Nice running engine! I can view the video no problem. Google Chrome.
Cheers Garry