Hello and a part-built blowfly

[stevep]

Lisa,

To make sure the piston never unscrews from the piston rod, put a couple of deep centre pops on the front face of the piston at the junction of the rod and the piston itself.

[David]

Where do you buy piston rings from?

[Lisa]

I got mine from Hobby Mechanics ( www.hobbymechanics.com.au/piston-rings-cast-iron/ ), but I'm pretty sure EJ Winter sell them too.

[Lisa]

Getting there, bit by bit.
Both pistons are done, both valves are done, the valve spindles are threaded, the valve nuts are made. I still need to make a couple of nuts for the piston rods, where they screw into the crossheads, and also make the gudgeon pins for the crossheads.

A slight problem is a misalignment in the slidebar on the right cylinder; I'm going to drill out the mounting hole in the bar at the cylinder end and make an eccentric bush to solve the issue.

[David]

Great progress and really looks the business!

[Lisa]

TODO:
1. add O-rings to steam pipe tee
2. make gudgeon pins for crossheads
3. make crosshead locknuts for piston rods
4. drill slidebar oil holes in crossheads
5. drill & tap chassis for cylinders & motion brackets
6. make adaptor to connect air compressor
7. assemble it all
8. test on air
9. pray it works

[runner42]

Hi Lisa,

don't want to add to your todo list and it maybe covered under item 7 assemble it all, but setting the valve gear is a necessary pre-requisite to assembling the valve chest covers and fixing the position of the eccentrics, I am sure that you have it in hand, but inside valve chests are difficult to see the valve position even with a mirror. I had a protracted time in getting it right for my Rob Roy, but eventually was provided some very useful information which should you require it I can pass on. Good luck.

Brian

[Lisa]

Yeah, mostly that's under 'assemble it all'. I think I can fit one cylinder, set the vale for it, then remove that cylinder and set the other, without upsetting the timing. Maybe. Otherwise I'll poke about with a mirror.

I once had the valve nuts come loose on one of dad's loco's while at a job running commercially; there's nothing quite like the pressure of resetting valves with paying passengers waiting.

[stevep]

As your cylinders are all iron, don't forget the lubrication - especially on air!

[Lisa]

The pistons are swimming in oil at the moment, I wasn't shy with it; I'll probably cop a face full of oil out the exhaust when I connect air to it!

[David]

It sounds like you know plenty about setting up and running a steam engine so I don't think praying will be necessary! I think it will tick over pretty nicely. It's interesting reading your list of jobs - my Blowfly was built by Barry in 1987 for a guy in Bathurst. It's such an early one it has the short firebox, and there is a photo of it in the construction book. It doesn't have oil holes in the tops of the crossheads that I've ever noticed and I'm pretty sure the piston rods are not screwed into the cross heads or I'd have noticed the lock nuts. The outside plates of the crossheads are made from 1.6mm zinc anneal, unpainted.

[Lisa]

Thanks David. The piston rods being screwed into the crossheads is a change by me, as I wasn't keen on Barry's idea of a plain rod held by a cross pin. Also my frames are built for the original short firebox (I started Blowfly ages ago, then put it away to build a Heidi II, and rebuild one of dad's loco's), I could modify them to take the mid-length design (extra ½" at the back, but same tube length), but by all accounts the original firebox size isn't an issue. I'm regularly finding rust on steel parts, so the zinc crosshead plates are probably a good idea!

[delaplume]

Hello Lisa....I don't have any knowledge of Blowfly itself but can comment on general topics from over 40 years in ME and on BR and the SVR.....The plain rod into the crosshead is generally ok...A taper fit of rod into crosshead can be held firm by an oval sectioned, taper pin fitting into an oval hole in the piston rod and crosshead....This has the effect of drawing the rod into the crosshead when force is applied to the pin's head..................What lead do you intend to apply when valve setting ??...........A piece of cloth over the exhaust pipe will catch that surplus oil when first run up on air.....So you would like to build a Bullied light Pacific eh ??....Please consider the original design with that chain operated valve gear and tinplate oil bath....I lost both Mum and Dad through Dementia...Dad loved the Clipper ships etc. but never got round to building a model.......Do cherish what time you two have together, no matter what the quality might be............Alan

[Lisa]

If it was a taper fit with a taper pin that'd probably be alright, pretty sure that's what (most) full size loco's have; but the design is just a parallel rod in a parallel hole with a parallel pin, which I didn't like. With slip eccentrics there's no great calculation for the lead, the ports should just start to crack open on dead centre. I've vague plans to fit proper valve gear at some point, so will get a little more scientific with that.

Yep, definitely an unrebuilt spamcan, not sure chain driven valvegear would work so well in 3½" gauge, but it'd certainly be an adventure. Regular inside stevensons might be more achievable though.

Dementia is a real shit; dad's not really there anymore, but any day I can get a laugh out of him I still count as a good day.

[Jim]

Caring for your Dad with his dementia is a great tribute to you and the sacrifices you make every day to see that he gets the proper care and love he needs from a daughter who is near and dear to him. I just cannot imagine what it must be like but I certainly admire you and all you are you doing for him Lisa.

Don't forget to take care of yourself too.

Jim

[delaplume]

Nov 26, 2018 6:39:28 GMT Jim said:

Caring for your Dad with his dementia is a great tribute to you and the sacrifices you make every day to see that he gets the proper care and love he needs from a daughter who is near and dear to him. I just cannot imagine what it must be like but I certainly admire you and all you are you doing for him Lisa.

Don't forget to take care of yourself too.

Jim

Thanks Jim---that's absolutely right, especially the last sentiment.......Because of our distances apart my Sister did most of the caring and steadfastly refused to claim for her "Carer's allowance" from the Govmn't that she was entitled to....They are both at rest now.....Lisa, do take time out to re-charge your batteries or you won't be of help to Dad....

Alan 

[David]

Another advantage of screwing the piston rod into the crosshead is being able to tune the length. We use high strength loctite and a pin and the stuff sets so fast you need to be lucky to push the rod in just the right amount as fast as possible. I had to heat one side up to remove it and try again because the loctite obscured the scribed line on the rod.

The shorter firebox is no problem. After giving my boiler a thorough clean inside and out, and realigning the blastpipe, mine has no lack of steam.

[Lisa]

Silver steel is about as fun to work with as stainless, though at least it doesn't work harden as you machine it!
Anyway, gudgeon (little end) pins done this morning:

[Lisa]

I dropped the wheels out of the frames this morning, and mounted the frames on the mill for drilling the cylinder bolting holes.



Something's misaligned somewhere though (a check shows the cylinder is at the correct angle, and the piston rod is pointing straight at the axle centre, so not sure what's happened here.

[delaplume]

Hi Lisa,

Sorry this is a bit late but have  you given Clupet rings any thought ??










maryport.cylex-uk.co.uk/company/clupet-piston-ring---gauge-co-14288401.html