Model Steam Donkey Engine

[brian Rupnow]

And more---Damn, there's a lot of parts to a Donkey!!!

[brian Rupnow]

And my last bit of Donkey Doo for today---

[Dave S.]

Brian

Here is a scan from the 1925 Willamette Iron and Steel Works catalog of there donkey engines. This scan shows the drum cross section and shows the clutch set up.

Dave

[brian Rupnow]

Thank you Dave S.---That helps.---Brian

[brian Rupnow]

My nice long design contract across town is limping to an end. The design work is all finished and I'm just waiting for all the various machined parts and weldments to be completed and brought "in house" so I can supervise/orchestrate the final assembly of the machine. In the meantime, I get to spend quite a bit of time at home, and consequently get to spend day time hours designing my toys. In a way I am covering new ground here, as I have never completely designed a steam chest and slide valve on my own. On all of my previous steam engines I have copied other peoples designs. This time, using the original Popcorn design by Stew Hart as a starting point, I am changing port sizes and eccentric travels, and a host of other related items. I haven't posted drawings of any of these changed items, because I first have to convince myself that the changes I have made will work properly. I'm off now to the bank to pick up a wheelbarrow full of money to buy brass at my local metal suppliers.

[oil mac]

Brian,
The late Edgar T. Westbury, designed a basic little steam engine called a Theseus, This engine was completely fabricated & his method of building up the cylinder block was most simple & easy to do, A friend of mine is starting up model engineering for the first time, And both he and i are going to have a go at it, We have already started

The series was serialised in the Model Engineer from 1st. November1956 It is a little 3/4" bore cylinder I have looked out the material to make the cylinders In our case cast -iron, But EdgarT W. sweated them up out of brass bar and some brass plate for the valve port face, & 3/8" brass plate for the steam chest
I have noticed recently the costs of Stuart Turners castings are too high at least for anyone retired

[brian Rupnow]

Oil Mac----I have had really good results making all of my engines from "bar stock". I use either brass cylinders and an aluminum piston, or an aluminum cylinder and a brass piston----they seem to run very well together. Of course, I am running my engines on air, not steam. I have been advised against using a brass piston because of the inertial mass, but these small engines rev so slowly that I haven't found it to be a problem.---Brian

[brian Rupnow]

I have been studying Captain Jerry's clutch mechanism which he came up with for his Donkey engine build. It is indeed a clever mechanism, and there are some vitally important parts that simply don't show up or get mentioned in his posts. I have wore my "engineer detective" hat all morning, and I'm pretty sure I have sussed out how Jerry did it. I am going to post a drawing and a few solid models to show how I believe this clutch works.

[brian Rupnow]

These two models show the components inside the clutch. Of course that purple shaft with the round knob on it which I called an "activation pin" is in there only for "show and tell". In reality it will be a short pin operated by a hand lever to engage and disengage the clutch. There will also be a spring under that sliding hub which under normal circumstances will hold the sliding hub away from the winch so that the clutch shoes don't constantly "drag" on the inside of the winch drum. I will post more about that lever as my design progresses.

[brian Rupnow]

Well there!!! Thats another 6 hours out of my life that I won't get back.----Modelling clutches. The models do look great, don't they.--Can't really take credit for the design though. Captain Jerry did a remarkable job on coming up with this clutch in his original Donkey post.--I just had to do a bit of detective work to figure out what he'd done. Thats enough for now. I'm off to my metal supplier with a barrow full of money to buy brass.