The new Stuart model - no7 V twin.

[Jo]

I think if we keep talking about it long enough Jo's casting fetish will get the better of her and she will build one in the forum. 

 

[ChuckKey]

Well my first thought was "that was not an engineer who designed it".

No one would ever have designed the trunk guide like this in big size.
Well my first thought was "that was not an engineer who designed it".

No one would ever have designed the trunk guide like this in big size. The mounting surface to the base is way to small for being mounted only on one side of the guide.
 
That will of course work in the model but in big scale it would have been pretty unstable and I guess not up to the forces which are being produces by the steam cylinder.
I also doubt that in big size they would have chosen to keep the trunk guide mounting surfaces at a right angle to the cylinder, I would have rather expected them to be parallel to the ground (in order to have the two mounting surfaces in one plane on the base.

I wonder if anyone thought the same things about this design?
Cheers Florian

My thoughts exactly.  Because it offends against sound engineering it looks just wrong. Anyone unclear about the stability should try imagining just one half of the thing.

[Jasonb]

It is strange that you say its all wrong when that link to the Sturgess and Tolston I posted earlier is an almost identical full size design eg a trunk guide with one sided cast standard and a flimsy looking brace to the other cylinder.

If we imagine this as one half then we basically have a stuart No1 or the old No7 which is a single legged standard and a brace, just a different method of guiding the crosshead. many "open frame" engines like this exist in full size. You even find them without the brace like this Tangye https://collection.maas.museum/object/208092#&gid=1&pid=2

Having said that I still don't like the Stuart offering.

[Jo]

Quick Jason: Stuarts are looking for someone to make one of these  engines and it will be free if the build is written up 

Jo

[Jasonb]

Well give them my name

[Jo]

You will have to find someone going to the Doncaster show then... rumour (from a reliable source    ) is that whoever says yes will be given a casting set to take home with them 

Jo

[Jasonb]

Think my friend Neil is going tomorrow, do you think he would put in a good word for me?

[Jo]

Think my friend Neil is going tomorrow, do you think he would put in a good word for me?

If Neil is who I think he is I've seen his excellent editorial ability so I couldn't guarantee he would remember to put a good word in for you 

The sales pitch should be that you might be able to do something with their initial concept for a Vee engine to make it more marketable

Jo

[Jasonb]

Now that's a thought that would let me earn from a few more pages "pimp my 7V" I had already thought of that as most of the mechanicals could be stripped off the basic engine and put into a fabricated frame like that Steeper Vee one I posted the other day plus a nice bit of wood cylinder cleading etc. Only problem is they might want me to paint it dark green and you know I like my colours

[Florian Eberhard]

It is strange that you say its all wrong when that link to the Sturgess and Tolston I posted earlier is an almost identical full size design eg a trunk guide with one sided cast standard and a flimsy looking brace to the other cylinder.

Hey Jason

Its not about the pricipal design of a one-side supported trunk guide but about the relations of the mounting surfaces. That real size engine is far more rigid where the trunk guide and the base connect and therefore a "good design". By the way, that flimsy brace is probably not to increase stability but for something like controlling drain cocks or so.
he stuart instead has a very small surface between trunk guide and base. That would have worked if the two trunk were connected through a massive beam but not with that small bar.

I have added a modified picture of the No. 7 to show make it clear what I am talking about.
The green beam would be one solution, the purple "modification" to the trunk guide the other one.
The red line shows the "problem" which is the very short side of the mounting surface.

Cheers Florian

[Admiral_dk]

I will have to agree with Florian as the Sturgess and Tolston is very substantial where it meets the bottom "triangle" engine mount and the Stuart is flimsy .... 

[ChuckKey]

If we imagine this as one half then we basically have a stuart No1 or the old No7 which is a single legged standard and a brace

Its not that simple. In the No1 the brace is attached to something rigid, the bed, and it is subject to loading along its axis. In the case of the 7-V the point is that attaching one unsteady half to another equally unsteady half achieves little when the means of attachment relies on friction at the single bolted joint to provide any additional stiffness. Florian's annotations illustrate the point admirably.
Trying to make the best of the 'design' as presented, I note that the bolts at the feet of the standards are towards the outside. Ensuring that the tie-bar is a few thou short to ensure it is always in a little tension would help to keep the feet as firmly in contact with the bed as can be expected - but it is still 'orrible.   

[Gas_mantle]

I took a couple of photos today at the Doncaster show - they aren't great but they may be of interest so I may as well show them.

I thought it was a bit of a let down  It's a lot smaller than you expect. I would say it is about as tall as a 10v

[steam guy willy]

So ,Looking at the eccentric rods  (Noun/Verb) because the right hand one is mounted on the left hand one with a bearing in the slot does this mean that there is less /more valve travel and is this accommodated in the port faces ?  the geometry may need looking at ?? Discuss...

willy...........

[Craig DeShong]

Not meaning to hijack this thread but.... I have fallen in love  with the de Havilland Gipsy Major Mk I.  But at nearly $1000 US and metric to boot, I'm gonna pass.