Over Crank Engine

[SBWHART]

Some time ago I spotted an interesting engine at Quarry Bank Mill Style, I didn't recognise the type but after asking around I found out it was an Reverse Crank or Over Crank engine, this particular was quite small no bigger than a suite case, mounted vertically from a beam and was being used to power a small workshop. Here's a few pics of the particular engine.

The cold weather we've bin having in the UK has driven me out of the shop, so I've bin keeping myself warm in doors on domestic duties and to keep me sane I've started drawing up the engine 1/3 scale as a project to start as soon as things warm up.

I've attached the drawing as PDF files to give you an idea of the design, my plan is to make the engine from bar stock with the exception of the fly wheel which will be cast iron you can get these quite easily from trade, for the cylinder I'm going to fabricate this up from brass.

If things work out OK I'm planning to fit a governor to the engine, and mount it vertically on a board (painted to look like brick) with some line shafting on the back that the engine will drive, but we'll see how things work out first.

I've only skeemed out the governor drawing I'm planning to adjust the spring tension so that i can vary the speed of the engine through the governor, which brings me to a ?. How do you adjust the speed a governor controls an engine a can think of:-

Adjust the weight of the balls

Adjust the spring tension.

Vary the drive pully ratios driving the governor.

Can you can add to this ?

Any comment you guys have will be much appreciated.

Stew

View attachment Side View Assy-Model.pdf

View attachment Plan View Assembly-Model.pdf

View attachment Connecting Rods-Model.pdf

View attachment Crank Shaft Bearing Housing-Model.pdf

 

[SBWHART]

The rest of the drawings

View attachment Cylinder.pdf

View attachment Cylinder-Model.pdf

View attachment excenrtric asy -Model.pdf

View attachment Fly Wheel and crank Shaft-Model.pdf

 

[SBWHART]

And finaly the governor

View attachment Governor-Model.pdf

 

[cidrontmg]

"How do you adjust the speed a governor controls an engine a can think of:-
Adjust the weight of the balls"

That won´t work. If you see a carousel, with seats on chains, the empty and occupied seats hang at the same angle.

Many thanks for the drawings!
:bow:

 

[SBWHART]

Stew-

That is an interesting engine.
I have seen a few engravings similar to that.
I am not sure what the correct term for this engine is.

I will post a link to a few engravings in a minute.

http://www.homemodelenginemachinist.com/index.php?topic=12062.0

Pat J

Edit: Nice drawings!

Thanks for your interest guys.

Another name for this type of engine is a Reverse Crank Engine

Stew

 

[hammers-n-nails]

the weight of the balls will effect the speed because hevier balls will have more power to compress the spring more, closing the valve and slowing the engine. at the low speed of a carosel the difference may be so small that to the observer they may seem the same.

also the ratios and configuration of the arms will have an effect.

i would suggest this book http://books.google.com/books?id=v1...governing+of+prime+movers#v=onepage&q&f=false

im sure you can find more free reading on the subject

 

[Mrinventworld]

This is an interesting design. Thanks for the plans, I can't wait to get started on it.

 

[MachineTom]

Is that name due to the position of the crankshaft, or to the job it does ie: Barring Engine

 

[steamer]

I've seen steam fire pumpers set up that way....interesting.

Thanks for posting


Dave

 

[Cedge]

Stew
Having recently designed and built a 2 and a 3 ball governor, I can attest to all the mentioned factors having a part to play. The interplay between ball weight, arm length and spring tension had me sweating for a little while. I didn't have to deal with the added factor of pulley combinations since mine mounted concentrically on the crank shaft. Getting the spring tension just right proved, for the most part, to be an exercise in trial and error. Let's just say I can now disassemble the front of the engine, remove the governor, swap springs and reassemble it all in about 5 - 7 minutes....LOL

Steve

 

[SBWHART]

Thaks for your replies Chaps

Steve I never considered the arm lengths but I can see that it will have an effect, I built a governor for my beam engine my first engine build, but I don't think the governor controlled anything it was linked to a butterfly valve and I think the air pressure just kept the valve open.

I liked Bryans design but its a bit big for this engine and would look out of proportion, but I did like his shutter valve he used in his design and aim to do something symilar, I think getting a governor to work properly in a model is very dificult, I think the bigest problem is for the governor to have enough engergy to work the valve properly, and for it to still keep its proporsions, what you would call issues of scale.

Thanks again

Stew

 

[tel]

My understanding is that that type of engine is known as a 'wall engine' ('cos it is usually mounted on a wall) - there have been a couple of models described over the years.