16mm IDRIS

Hi Martin.

Gas Tank looks good and fits perfic.

P873 fig 17 and 18.
You call for 2 X 32 DP 30​ tooth gears for the final drive.

The wheels are nominal .750 Radus (Centre to edge)

My gears are .740 dia and together the centres are .700
This places the axle within the wheels.

Ideas / Comments please.

Thanks

Alex

Hmmmm

The Packet says '32DP 30 T .250'

The reality is:
There are 30 Teeth.
The Bore is 1/8"
If they were 32 DP the gears would be about 1" dia.

These are /not/ 32 DP Gears. Great......

Back to the shops again.....

Morning Alex ... if the gears you bought have 30 teeth then I am not sure what size they are ... 48 DP would be a bit small and 40 DP would be a bit larger then the ones you have. ( does anyone use 43 DP ?? )

If they are metric, then 0.5 mod would be a bit small and 0.6 mod would be a bit larger than yours ... maybe there is another system for small gears ?? I know there is a system for much larger gears called CP ( circular pitch )

On page 874 of the same issue I did put that 40 DP would be ok ... the important thing is the outside diameter, so everything will fit in the available space.

Can I ask whether your gas tank and fittings will fit under the burner assembly hung out of the rear of the boiler ?? Does your design alteration include altering the position of the gas tank relative to the burner ??

martin

Hi Martin.

I have ordered new 32DP Drive Gears.

The ones I have don't seem to be anything that I can make sense of....

As for the Gas Tank, It may well cause me issues further down the line. I can drop it fairly low down in the frames but the Bushes will be proud. I can trim a bit off the bushes if need be. I can also cant it either way.
If things get really bad I can cut the top off and add a plate or I have material to make another.

I'm very much learning here and enjoying doing so.
If nothing else my soldering skills have improved no end.

Morning Alex ... good for you ... the only way to learn anything is to experiment ... my scrapbox is always full of my mistakes ... usually the bits come in handy for something ... a quick skim on the lathe or a dab of silver solder and an old "whatsit" is useful to make a new "thingummy"

martin

Made the Valve Bodies tonight. Fairly easy turning / drilling / Tapping job.
Going to use Metric Threa​ds for them (M3)

Started to make the 1st Valve needle. Ground the parallel and point with the dremel. Very easy.
Finished with a flour file.
Ground off .15mm to make the rod 3mm.

What's the secret to threading stainless ? Got it started after a bit of effort. About 1/2 way in it stripped.

Decided that's enough for 1 evening.....

Make it a bit undersize, just as you would drill a hole oversize to tap in stainless.Use lots of cutting fluid.

Neil

Valve needles made tonight.Came out rather well.
Discovered the trick was to turn the die over and use the Back.
Maybe my M3 die is getting past it's best.

I'll make some nice knurled handles for them tomorrow.

You say to Silver Solder the side arms into the valve bodies.
Any reason why I can't soft solder them ? ​

Hi Alex ... yes you could soft solder them, but there is not much area of solder in the middle of the joint ... Silver solder is a lot stronger ... you could always make up a soft-soldered spare and test it to destruction with a spanner ... if it does not need much force to break loose then stick with silver solder ... I have used this type of assembly for many shapes of valve over many decades ... so far, none has ever broken ... maybe I am guilty of over-engineering ?? ( again ) ... let me know what you think after you have done an experiment.

martin

They have all soft soldered rather well. Joints are more than strong enough.
I made the side arms. Turned a 1mm nipple to 4.5mm. Drilled the body 4.5 and soldered them before drilling through to the middle with the .0625 hole.
Gas Valves are complete.
However I can't get all 3 into the tank (something you warned me about)

I will have to re think the discharge valve...... ​

The Gas Tank is complete.

The Valves all seal and it holds gas. (Only put a bit in)
Need to get some 1/4" sealing washers.
The Valve needles are sealed at the top with Teflon Pipe.

Morning Alex ... wow, that is a squeeze for the 3 valves !! can I ask if you have arranged for it to be pressure tested at the Chelmsford club?? same idea as a boiler test, but a bit higher pressure.

I may be a bit of a "thickie" but I still have not worked out how the tank fits under the burner at the rear of the boiler. Any chance of a sketch or a photo please ??

martin.

Hi Martin

CSME are going to Pressure test it for me tomorrow. What do you suggest ? 100 PSI ?
The fit is very tight for the valves. I made the Discharge valve from 7mm hex. The other 2 are made to the drawings.
The longer Bush had to be shortened.

How does it fit with the Burner ?
I am equally unable to answer this one.
You have more information than I do so I guess I will have an issue here.

I may have to cut the Top Off and make a new flat Bush Plate. It'll be fun soldering that on the inside.
I may have to start again. We shall see as things progress.

Hi Alex

For butane I would test at least 300psi and at least 400psi for butane/propane mix.

Roundhouse test their 16mm loco's gas tanks at 490psi for a working pressure of 245psi

.

Dave

Edited By Steambuff on 22/08/2015 10:07:43

Hi Alex ... the question of test pressures always produces different values depending on who you ask ... if you are having it tested at Chelmsford and planning to run it on their track I would be guided by them ... possibly even find the local Chelmsford boat club as they may have a lot more people who use butane/propane gas ... some people have figures which have an enormous safety factor built in ... ask at Chelmsford.

martin

100 psi would be woefully low, below the operating pressure.

The Model Power Boat Association test to 1.9 times the vapour pressure so it varies according to the gas mix used.

mpba.org.uk/PDF/Corrected%20Steam%20Rules%20Leaflet.pdf

These appear to be based on the same 50-centigrade vapour pressure as the aerosols you get in the supermarket (although they are only tested to 1.5 times, presumably as they are single use only so no risk of mis-filling).

Neil

As usual, great info guys.

I'll take it to 377.5 PSI​ so I can run Blowlamp Gas. It comes in nice large cans.

It was only soldered last week so I may well leave it another week as the stay tube will still be soft.

Testing while annealed can make it stronger,as it settles to a shape with lower strain.

Neil

Took the tank down to be pressure tested today.

The advice was: Tube is not suitable for the Stay.
Soft Solder is not suitable for the Valve Arms.

The tester suggested that if we were to test the tank that the tube would more than likely fail.

Overall they were happy with the Soldering and construction. "Could have been tidier in places but it's soldered well"

3/16 Copper rod is on order. I have no idea how I will get the old tube out.....

Just drill it out in stages, but thread something through it from the other end so it doesn't just fall and you can line it up with the hole.

Neil

Edited By Neil Wyatt on 23/08/2015 16:26:17