Model Engine Maker

Engines => Restoration of Model Engines => Topic started by: BeaverBoy on February 01, 2018, 03:50:18 PM

Title: Whatizit?
Post by: BeaverBoy on February 01, 2018, 03:50:18 PM
A relative newcomer to the forum, my introduction post said that I would put up some pics of this engine - inherited from my late uncle. I have little idea about it, so can someone help?
Some idea of what the brass attachments are for would be a start - some kind of pump?
Also, there is quite a bit of free play when the crank is at both bottom and top dead centre - obvious when you see how the big end connects to the crankpin.
All comments will be greatly appreciated. Hopefully the pics will appear - or will they? YES! they did.
Title: Re: Whatizit?
Post by: Stuart on February 01, 2018, 03:54:04 PM
Looks like a rotary boiler feed pump with a type of scotch yoke crank

But I could be wrong


Title: Re: Whatizit?
Post by: Roger B on February 01, 2018, 07:18:04 PM
I agree with Stuart that it is a pumping engine with a scotch yoke crank. As the power is transferred from the steam cylinder to the pumping cylinder directly and the crankshaft and flywheel keep it going past the dead centers it might be quite an efficient setup  :headscratch:
Title: Re: Whatizit?
Post by: BeaverBoy on February 01, 2018, 07:48:06 PM
Thanks for the answers so far - the fog is beginning to lift a little!
Title: Re: Whatizit?
Post by: crueby on February 01, 2018, 07:54:35 PM
Do those big rods at the sides on the bottom pivot? Not sure what those are, unless they are shutoff valves? Don't look like they are pipes...
Title: Re: Whatizit?
Post by: b.lindsey on February 01, 2018, 08:01:16 PM
MY guess is that they are air chambers to reduce water hammer, though probably not an issue in a model this size. Could be replicating a full size set-up though. Now if they do pivot, then my guess is likely out the window.

Title: Re: Whatizit?
Post by: BeaverBoy on February 01, 2018, 08:11:56 PM
I don't think they pivot as such - although they will move radially, as the ends are screwed (at right-angles) into the block. The position they are in is where they tighten up.
I'm with b.lindsay on this, thinking like him that they are air chambers.
As for replicating a full-size example - who knows? I didn't even know my uncle had this engine or where he got it from until after his death. He definitely didn't make it himself.
Title: Re: Whatizit?
Post by: crueby on February 01, 2018, 08:14:35 PM
If you hold a fingertip over the holes in the bottom pipes, do you feel it alternately sucking in on one and blowing out on the other as you turn the flywheel? If so, definitely a pump. Looks neat, whatever it is.
Title: Re: Whatizit?
Post by: ChuckKey on February 01, 2018, 10:08:26 PM
The air chambers, assuming that is what they are, should be pointing vertically upwards so that air pockets can be held in them.

It looks pretty old, and the design has interesting contrasts, with an elegant standard supporting the clumsy great lugs on the cylinder.

Slack around the slipper might be due to one of the scotch yoke bolts apparently having its nut loose. I would prefer to see spacer collars between the two halves of the yoke.

For a slide valve, it would seem to have an air inlet hose connection fitted to the exhaust port. Could it perhaps have an inside admission valve?

Again, the hose connections on the pump mean it could not have been actually used for boiler feed. A fire pump, perhaps?   
Title: Re: Whatizit?
Post by: Ramon on February 02, 2018, 10:14:06 AM
Hi Beaver

I would agree with all that it's a pump - I happened to find this this morning .....


....but I have to say I think your version has so much more character. I would agree they are likely to be air reservoirs and if so should be vertical as said. I find the steam inlet connection a tad strange with its 'reverse' taper given that the water pipes are parallel but these are small things that could easily be improved - like adding spacers between the yoke as 'ChuckKey' suggests too. I really like the standard and how it's bent over to support the cylinder - all the hallmarks for replication at some stage.

I can't quite get my head around the water delivery internals though - does that deliver on the upstroke or down and how is the valve arrangement done. If you strip it down at some stage Beaver, could you share those details with us?

Thanks for posting - certainly a very nice and interesting little inheritance :ThumbsUp:

Regards - Tug

Title: Re: Whatizit?
Post by: Jasonb on February 02, 2018, 10:27:38 AM
Probably going to have a couple of balls in there as valves, if the top cover were taken off you should be able to see them, Ramon s photo has the balls under the two plugs in the top surface of the pump.

The Scotch Yoke arrangement is quite common on pumps, along with the Banjo type.
Title: Re: Whatizit?
Post by: BeaverBoy on February 02, 2018, 01:26:05 PM
Thanks to all for the informative replies - much appreciated.
I've not got round to checking the 'suck & blow' yet and the eventual strip-down will have to wait for a short while, although it will happen. Fitting spacers to the yoke bolts sounds like a good idea. However… I have a 4-foot glider to finish building for a competition at the beginning of March, so the engine/pump is now on the pending list.

As an addition to this post - I also have a complete set of dyeline drawings for a Burrel Thetford Chase road engine. These also come with a college-produced illustrated parts list. The drawings are in good condition (not folded) and as I am unlikely to ever make a start on building the engine, they are up for grabs if anyone's interested. I haven't seen them since we moved house a couple of years ago - I just have to find them first! Not certain on who the designer is/was, or the scale, but 1":1ft rings a bell. A message to me will probably encourage me to dig them out.
Title: Re: Whatizit?
Post by: ChuckKey on February 04, 2018, 09:16:40 AM
The pump may well be double acting. This one seems to follow the common practice of having the suction a larger bore than the delivery.
Title: Re: Whatizit?
Post by: tinkerer on February 04, 2018, 05:02:47 PM
There could well be a simple diaphragm/flapper between the upper & lower chambers of the pump. Much like in a bicycle pump.