Building a 31/2" Gauge Locomotive Engine

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sbwhart:
Hi Chaps next instalment

Up to now my postings have covered work done over the past 18 months, this posting bring you up to date. The cylinder is more or less finished, I wont fit it between the frame until I've completed the motion works so that it goes in the correct position. Also the front covers need machining to take the slide bars, but again i'll wait until the motion works are complete, it being easyer to make the covers fit the slide valve than the slide valve fit the cover.

OK lets do it

Front and Back Covers

The covers and made from phosphor bronze casting, the stuffing gland being integral with the front covers, the casting come with a chucking piece.

The casting was set up in the three jaw, and the chucking piece diameter and the face skimmed up. Gripping by the chucking piece the outside diameter was turned up and the small stepped diameter turned to a nice snug fit in the cylinder.

The chucking piece was cut off, and to grip the cover a split bush was turned up.

The covers were stamped L and R.
The front covers were set up on the rotary table and the lozenge shape stuffing gland machined.

The position for the clamping holes were carefully measured and marked out, taking care not to drill into the steam ways, this is the reason for the uneven spacing, Tip:- drill with the tapping drill first then when the cylinder has been drilled off the cover open out to clearance size, this way the holes will line up spot on. When I made my Beam Engine I drilled the clamp holes over the steam ways, so I had to hide this by having a dummy bolt, shhh don’t tell any one that’s my secret.

To fit the covers onto the cylinders, they were gripped onto the cylinder and the surplus material marked, and filed off.

It is called for the clamping holes of the front covers to be countersunk. This was done using a little tungsten countersinking tool I bought from an exhibition, on a whim, as they looked handy and the price was right.

To transfer the holes to the cylinder the covers were fixed into position using two way tape, the cylinder drilled through the cover 5mm deep, I held the cylinder by hand on the base of the vice, the jaws were opened up out of the way. The cover removed and the holes carefully tapped 7BA. What’s the best way to remove the sticky left by the tape, I tried:- Meths, WD40 and Terpintine substitute, which I found the best. (you chaps may use something different)

Finishing off the Slide Valves

Cross bar:- The cross bar is made from 1/4” square mild steel. The two were made on one bar. Position marked and the hole centered and then drilled and tapped. Tip:- to ensure that the tap starts square: lightly grip the shank of the tap in the chuck, just enough to keep it square yet allowing it turn.

For the slide valve to work efficiently the surfaces need to be good and dead flat. To achieve this rub on progressively finer emery paper on a flat surface I use a square cube I rescued from a scrap skip, but a piece of plate glass or mirror will do.

Divided he ad:
Looking good Stew :thumbup:

Accuracy.... That's where it's at..... That's where I need to concentrate!

I would think it woulde be a while before I would attempt such a huge project.... I can barely find the time and patience for the ones I have to do now!!

One question, I've heard the term a few times but never found the time to investigate.... What's a stuffing gland do?

Looking forward to seeing the rest take shape.

Ralph.

rleete:
A stuffing gland seals the rod so the cylinder can be double acting. Thing packing like in an old fashioned faucet valve.

sbwhart:
Hi Ralph Re Stuffing Gland

Simply a stuffing gland is method used to seal a shaft. It consists of a cord impregnated with: Graphite, PTFE, or some form of Wax, the cord is wound around the shaft, you then tighten the Gland nut down onto the cord compressing it and forming the seal.

The cylinder for my loco has four of these glands:- two on the steam chest and one for each cylinder.

Instead of piston rings you can use the cord to seal the pistons, but some people are know using PTFE sealing rings for this job.

The pic hopefull shows this

Have
:wave:
fun

Stew

Divided he ad:
Ahh!! (enter light bulb smiley here!!)

I've got it now. Thank you guys :)

Roger...

--- Quote ---Thing packing like in an old fashioned faucet valve.
--- End quote ---

I'm not old enough to have ever stripped down or possibly even used one of those :lol:

Still, I have a firm grasp on the concept now :thumbup:

Looks like that there chest is very near done Stew?

Ralph.

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