Scott vacuum engine (flame gulper)

[uuu]

I've used graphite for the valve, as per drawing.  It doesn't have much friction, and the shape of the top surface tends to encourage the flame towards the port as the valve drops.  I run mine on a spirit burner, so it needs all the help it can get.

There are no piston rings.  If you get the fit of the piston right you should be able to hold the cylinder vertically with your finger over the port and the piston won't drop out - until you remove your finger.

Wilf

[Sanjay F]

Hi Sanjay.

I have a penchant for Vacuum engines, the family call it more of an obsession…. I acquired my first antique engine over 30 years ago now.  An Ernst Planck made in Nuremberg around the turn of the nineteenth century. This engine became the basis of several designs affectionately known as the ‘ CHUK family ‘

The key to success is friction reduction. The engines develop such little power that even strong springs will hamper their performance.

As promised here’s a slomo video taken at the front face.  Hopefully you can see the simple lightweight shutter in action?  It is designed to pivot on the pin to both open and shut the port but also allow the exhaust outwards and upwards so as not to sully the flame.

The key to the excellent running of my CHUK engines is that there’s a separate exhaust pathway available which would otherwise hamper running.

Thanks for the videos the slo mo really captures what's going on during the cycle. This being my first vacuum engine, I need all help I can get. Clearly there are nuances with these type of engines which I'm going to have to find out as I progress through the build. The trouble is knowing when to deviate from the plan or is better to follow the plan then modify after?

I understand what you mean about exhaust gas needing to flow up and away rather than into the flame itself. Seems like I'm starting on a bit of an adventure with this one!

I wasn't going to say anything about the flywheel, but as Jason has done so already, it definitely gets the award for the 'wonkiest flywheel' 

[Michael S.]

Hello Sanjay,
I'm excited to see how the engine construction progresses. I also built a flamethrower two years ago. It wouldn't move, and after a year, I put it back on the workbench and checked everything again. Then it worked.

Michael

[Alyn Foundry]

I can only pass on what information I have learned over many years of experience. The WWW is crammed with many dissatisfied builders of this particular model. It all boils down to the balance achieved with the port face shutter.

I would suggest you proceed by following the instructions and see what happens. They do run very nicely after careful and patient management.

As has been mentioned a good parallel cylinder bore with near mirror shine is an absolute must. The piston should hold its own weight until the port is opened. ( preferably dry )

As for the flywheel…. Well I’m glad the membership had a good laugh….

   Graham.

Here’s my latest acquisition built around the mid Victorian era.

<a href="https://www.youtube.com/watch?v=E5hjyPixo6Q" target="_blank">http://www.youtube.com/watch?v=E5hjyPixo6Q</a>

[Jasonb]

A very wonky mamod funnel to go with it. The motto is to keep plastic funnels away from flames.

Yes I have heard a lot of people had problems with the Scott, the springs supplied look very heavy. A bit like reducing friction, as these engines don't make a lot of power you want to avoid them having to stretch excessively strong springs every time they go round as it will sap what power they do have.

[Sanjay F]

Shock, horror, the piece of metal I've been waiting for finally arrived after a week! Clearly there must've been a rip in the Space Time continuum as the parcel has a Next Day Delivery sticker on it 

Anyway the start on this engine will have to wait while I finish up the Stuart 10h

[crueby]

The next day they deliver it to the next truck not going to your house...   

[Sanjay F]

There are also the planets which take longer than 24 hours to rotate to consider 

[Sanjay F]

After a few little distractions with some other engine restorations which are nearly finished I'm back to this build. In the thread from username Bogstandard it says:

"If anyone is interested in a little more detail, here is a set of build articles that came from the public domain. I downloaded them and turned it into a PDF to keep it all together.

File name: Scott vacuum engine.pdf File size: 4.52 MB"

I can't seem to locate this - I don't suppose anyone out there has this? I have a feeling it will be really useful for this build?

[Sanjay F]

So a new journey begins.......started making the holding plate from Ali and I drilled the four mounting holes in the base casting which will be used to secure it to holding plate during machining.

I finally invested in a new (2nd hand from eBay) milling vice, a Warco D10 which can be configured in several different interesting ways and hopefully will be a good investment for the future .......let's see

[Jasonb]

I've sent yoy the pdf but if anyone else is interested it was in issue 6 of "World of Model Engineering" these can be found on Model Engineer website under magazine reprints.

Part 2 at the bottom has the Scott article

https://www.model-engineer.co.uk/759/world-of-model-engineering-issue-6-parts-1-and-2/

[Sanjay F]

Brilliant thank you! 

[Sanjay F]

Finished make the jig and base casting is in place inverted and ready for milling to get a nice flat base datum. I'm thinking light cuts

I have a set of fly cutters which came with some other workshop stuff but have never use them and really ought to try it on a bit of scrap first - what's the reason for using a fly cutter over an end mill?

[Jasonb]

You can cover a reasonable area in one pass and they work out to be cheap to run. A piece of HSS is not that expensive and can be sharpened 100s of times.

I have had a similar set for years and they got a lot of use until a few years ago when I went over to insert face mills but not as cheap to run as  a flycutter.

[crueby]

Yup, time saved over lots more passes with an end mill. And it can leave a smoother finish over a wide area than an end mill. Though an end mill can take a deeper cut. And the flycutter does make a bigger divot in the part if it comes loose in the vise!  I still have the fly cutter for my mill, can't remember the last time I used it, I'd rather swat flies than cut them!