Simple oscillator tensioning

[modeng2000]

Paul, the cheese head screw thing is the reverser - it switches the inlet and exhaust connections, well sort of.

I have tried to post a picture of the proposed boiler but don't know if it will work for me this time.



John

[steammadman]

At those prices i would call them damned expensie not simple
some suppliers just dont know how much to charge
still if your a cheque book model engineer you might be foolish
enough to pay these rob dogs and keep them in their mansions

[paul]

Hmmm, that doesn't look like a normal loco boiler or a typical stationary engine boiler - why the intersecting tubes?? Sorry for all the daft questions!

PS Looks like you've sorted the image problem

[modeng2000]

My aim was to build a Shay and a T boiler is often used for this type of loco. However I now realise what I have taken on and I'll see how the project developes but may change to something simpler.

This link has some pictures of a scratch built Shay :-
www.steamup.com/sitgonline/forum/articles/ottohadornshay/ottohadornshay.html

Unfortunately it is no longer a live link.

John

[modeng2000]

Paul, you have a personal message.

John

[paul]

Well I decided not to put the cylinders on the same pillar so I'm going for a 'normal' oscillator (with pivot in the middle of the cylinder) with the cylinders each mounted on their own steam block.

Progress has been ok so far - here's the cylinders as of today each with the finished bore, steam port and pivot holes and the holes (yet to be threaded) for the cylinder covers.

[modeng2000]

Paul,
You wanted to see the parts for my double acting oscillator. It is possible to see some of the pairing dots on the bearings and cylinders, not visible when assembled.

Now I've got to put it together again.

John

[paul]

That's a useful reference photo John, many thanks! Good job you marked the items that need pairing eh?

[paul]

Did a little more on mine - here's the state of play with lots of temporary fasteners for the covers/pivots and a bit of any-old for a temporary piston rod on piston #1.



John, what are you using for piston rings?

[modeng2000]

Paul,

I thought I would try shallow grooves that should pick up the steam oil and possibly provide an adequate seal. If that fails I might try graphited yarn or ask for advice from our learned forum members.
Just out of interest I try to use metric threads where possible as I'm not building miniature replicas but when it comes to things like boiler fittings I use the Model Engineer threads so I can buy off the shelf if need be.

John

[paul]

Hmmm, I'm not sure what constitutes a 'good fit' for pistons on these little engines; all I can say is that the piston I've just made is a better fit than the first engine I built from a kit where the piston/cylinder was pre-machined so it should run ok on steam at least

I like the 'oil groove' idea, I'll try that next time!

[havoc]

Paul, I don't often come this part of the forum but I have used without any problem a flat spring for my oscilator. This is nothing more than a strip of phosphor bronze with a hole in the middle. Looks like this: _/ \_ (I cannot put a line at the top). It isn't more than 2mm high. Lenght about 30mm, 0.3mm thick. Had to do this because otherwise I needed a blind bus inside the boiler for the helical spring. Works just as well. By bending the "legs" you can adjust the force.

[paul]

Cheers Havoc, that's another idea for me to remember!

[havoc]

Found a pic of it:

[paul]

Yeah that's how I imagined it - like a Belleville washer without most of the disc!

[lancelot]

Hello Paul,
If you check out this site, the front axle tension spring is just what you need, just requires a hole drilled...

www.forest-classics.co.uk/mamod.htm

All the best for now,
John.

[paul]

lancelot said:

If you check out this site, the front axle tension spring is just what you need, just requires a hole drilled...

Buy one??!! Never!

Thanks John... I might just