Trying to make an Andy Ross B20

[AAMS]

Hello forum members,

We are a group of students from Denmark that are trying to build a B20 model for a workshop project. We have a BIG question, that we hope that someone can help us with.
We also have been in contact with Andy Ross, but thought we will give the forum a go to.

How do we work out the weight of the counter weight that the yoke turns, for it to be balaced. Is there a way we can calculate it with with our piston and rod size.

Thank you in advance for any help, and look forward to hearing back from the forum!

Cheers from Denmark

[TheGermanDude]

Hi,

"How do we work out the weight of the counter weight that the yoke turns, for it to be balaced. Is there a way we can calculate it with with our piston and rod size."

Yes.

You must know the mass and center of mass of all rotating parts.

Look at this:
http://en.wikipedia.org/wiki/Lever
http://en.wikipedia.org/wiki/Center_of_mass

Lever must be balanced.
Hope it helps.

Greetings

[Ian S C]

AAMS, If you look in my gallery there are some photos of my Ross Yoke motor, it is unpressurised, and doesn't have the balancer.
I,v got an article from "Model Engineer" by Andy Ross", titled "35 cc Rider Stirling Engine", it's contained in three issues of the magazine, 17 July 1981, 21 st August 1981, 18 th September 1981. This is the engine that preceded the B 20.
Did you manage to get one of the kits that Andy produced, or are you building it from plans, I think the kits a quite rare.
Have you down loaded the book "Making Stirling Engines" Andy has allowed free down load, about 68 pages.
Ian S C

[Chriske]

Hi,

I had contact to with Andy. Last year he sent me plans of that B-20.
They were all imperial, with his kind permission I redrew these plans to metric. I can send you a copy.
I started working on that B-20 but did not finish it yet. Most of the parts are done. Still, a few more to make.
This B-20 is not what I would call a 'first to build engine choice'. I would go for a simpler engine if you never made a stirling before.
Here's an animation I made of that engine :

https://www.youtube.com/watch?v=8lqoEAU ... y3_0bYbC9Q


Chris

[ooos]

can you please send me these plans.

[Ian S C]

ooos, You might have to Email Chris, I don't know how often he looks in on the forum.
My engine, 30 mm bore, 20 mm stroke is still going strong, about 5 to 10 Watts unpressurized, and unbalanced, with no regenerator.
Ian S C

[joweizbrot]

are the plans still available? from the video it looks like there are CAD drawings of this engine, I would love to see them in CAD, thanks Jo

[Chriske]

Been 'out' for a while due to health issues.
Still need those(metric) plans..?

[Aviator168]

My engine, 30 mm bore, 20 mm stroke is still going strong, about 5 to 10 Watts unpressurized, and unbalanced, with no regenerator.
Ian S C

That's a respectable output Ian for such an engine. At what rpm do you get that power? If contact area allows, you should be able to 15 - 20 watts per cc with a regenerator. Can you upload a pix of that engine?

[Ian S C]

Chriske, good to have you back, hope you are better than you were.
Aviator 168, we'll see what we can do about a photo. The motor has changed a bit, the water jackets have been removed, and replaced with aluminium fins, and the steel cylinder head has been replaced with aluminium. The little power hacksaw uses a Junior Hacksaw blade, and will cut through a bit of 1/2" steel bar in 20/30 minutes, sort of like watching the grass grow, but it works!
Ian S C
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[Trevor]

HI Ian - I noticed the fins on your cooling tubes. Was this an afterthought due to not working with the water cooler idea. It sort of looked like the same as I had made on the diaphragm engine.
Another question for you Ian on the hot piston area. Is the piston made of cast iron and is it lubricated? It also looks as if your original was pressurised as can be seen from the font box. Did you get more HP out of it when it was pressurised? Sorry for all the questions but your engine looks a million dollars.
Trev

[Aviator168]

Did you get more HP out of it when it was pressurised?

In general. Pressurisation increases output proportionally if the outside heat transfer area is sufficient until the drag of the working fluid takes over.

[Aviator168]

Ian, it looks like you can move the heater a bit lower.

[Trevor]

Thanks Aviator. A lot of people do not realise that air is a fluid pursue and when pressurised becomes a lot denser.
Trev

[Aviator168]

Trevor, I don't want to get into calculations of aerodynamics forces and heat exchanger here, but the main force blocking working fluid transfer has to do with the size of the cross section area. One thing though, the kinematic viscosity gets smaller with increase of density. (https://en.wikipedia.org/wiki/Viscosity)