Scott vacuum engine (flame gulper)

[Sanjay F]

As some of you may remember I had a little accident some time ago with an ICE engine and I'm still building up my confidence to take on another.

In the meantime, on that journey, I'm going to try something different which is this Scott vacuum engine or flame gulper (which sounds terrific!). It looks interesting and has some challenges for me as I build up my knowledge and skills.

[crueby]

Oooh, this should be fun! I picked up a kit for a flame gulper at cabin fever years ago, it has not made it to the top of my list yet. 

[PaulR]

I was thinking about a bar stock version of one of these, I think I have a plan saved somewhere. Will be following along, it doesn't look too complicated (or dangerous!) 

[Sanjay F]

I was thinking about a bar stock version of one of these, I think I have a plan saved somewhere. Will be following along, it doesn't look too complicated (or dangerous!) 

I'm still deciding which degree of danger; either the meths burner or gas version!   

[Jasonb]

You don't see many of them about so it will be interesting to follow along.

Keeping friction to a minimum will be key to getting it running along with a very good lapped fit between liner and piston that does not leak but also is not too tight and creates friction.

[uuu]

I made one of those a while ago.  By luck I got the fit of piston and cylinder just right.  It ran well.  Good fun.

Until some idiot said "These run backwards as well, you know" and gave the flywheel a mighty heave.  It screwed up the valve timing and I put it in a box where it remains.

Wilf

[Sanjay F]

I made one of those a while ago.  By luck I got the fit of piston and cylinder just right.  It ran well.  Good fun.

Until some idiot said "These run backwards as well, you know" and gave the flywheel a mighty heave.  It screwed up the valve timing and I put it in a box where it remains.

Wilf

Sounds like from what you have both said that piston/cylinder fit is critical, I'll bear that in mind ......

I have just read an excellent build on MEM by Bogstandard and he used a jig plate to machine the base and accuratley drill all holes from a datum. I think I'm going to do the same and have ordered a piece of Ali so there's going to be a delay.

I also realised that my good vice will not open up sufficiently to accomodate the base so will have to use the not so good one to mount the base with the jig on it.

I think there's going to have to be an investment in a decent size and quality vice sometime in the future!

[Jasonb]

Can't you clamp the jig plate to the mill table as that will be a lot more solid than using a vice.

[Alyn Foundry]

As far as I’m concerned this engine has a serious design flaw. The flame port shutter is way too complicated and very heavy. Both aspects almost make sure of definite failure.

Pay particular attention to the fit and finish of the piston and cylinder. I also recommend the use of ball races for the crankshaft.

I recently spotted a near complete engine on Facebook marketplace. At just over £100.00 it was a bargain considering the extras like the complete gas tank and burner. The builder must have been worried about the flywheel as there were stacks of old Pennies, hole drilled through the centre and clamped between the spokes. I believe the design calls for a Graphite shutter?

I’m working from memory here but the shutter assembly reminds me of the Watt parallel motion system. It also calls for a tension return spring…. What I did iwas ditch everything apart from the single arm and pin. On the pin I made a shutter from Shim Steel. The final assembly being so light that the lever would return to the rest position by its own weight. ( no need for a spring )

I will try and process a couple of videos for you folks later as I think it will be almost self explanatory.

One further point, the design of the flame producer at the port face is critical. The entire opening needs to be covered by the flame. Any cold air entering has a major impact on good running.

   Graham.

[Sanjay F]

Can't you clamp the jig plate to the mill table as that will be a lot more solid than using a vice.

Thanks Jason

Yes I was thinking that clamping to the mill maybe the best option too

The base is a little 'banana' shaped in all axis, so getting a good underside will be important. I guess I'm just going to have to be patient ............. ho hum

I'm puzzled by the the 2 measurements on the drawing below, 0.525 & 1.450 on the RHS which are the ctrs for the bearings. Is the 'datum' line the surface where it has been milled to take the hopper? The way its drawn it looks like it under that?

[Sanjay F]

As far as I’m concerned this engine has a serious design flaw. The flame port shutter is way too complicated and very heavy. Both aspects almost make sure of definite failure.

Pay particular attention to the fit and finish of the piston and cylinder. I also recommend the use of ball races for the crankshaft.

I recently spotted a near complete engine on Facebook marketplace. At just over £100.00 it was a bargain considering the extras like the complete gas tank and burner. The builder must have been worried about the flywheel as there were stacks of old Pennies, hole drilled through the centre and clamped between the spokes. I believe the design calls for a Graphite shutter?

I’m working from memory here but the shutter assembly reminds me of the Watt parallel motion system. It also calls for a tension return spring…. What I did iwas ditch everything apart from the single arm and pin. On the pin I made a shutter from Shim Steel. The final assembly being so light that the lever would return to the rest position by its own weight. ( no need for a spring )

I will try and process a couple of videos for you folks later as I think it will be almost self explanatory.

One further point, the design of the flame producer at the port face is critical. The entire opening needs to be covered by the flame. Any cold air entering has a major impact on good running.

   Graham.

Hi Graham

That all sounds a bit ominous especially around the shutter mechanism - I'm a long way from that, but will take heed of what you have said and make those mods when needed. Funnily enough the text that came with the casting mentions the strength of the springs maybe excessive and require 'easing' off.

The shutter which came with the castings is a piece of carbon/graphite (see photo) - odd looking stuff and light

I also just noticed the hub of the flywheel is 'interesting' will have to sse how that pans out 

If you have some videos that would be great, thank you

[Alyn Foundry]

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.

<a href="https://www.youtube.com/watch?v=g3ALFqWu6U4" target="_blank">http://www.youtube.com/watch?v=g3ALFqWu6U4</a>

   Graham.

<a href="https://www.youtube.com/watch?v=_Z7GB7lq738" target="_blank">http://www.youtube.com/watch?v=_Z7GB7lq738</a>

[Jasonb]

Graham. That's one of the wonkest flywheels I have seen for some time

Yes the two measurements are from that flat area that needs to be milled to level the base. Odd way to do it as most castings have a raised area that just needs flattening. Bore that flywheel to size a sany drill or reamer may wander if the void is deep.

Must be the season for poor flywheels, I've just taken on a commission to make a new one as the casting supplied was very poor, pattern shift of 3mm, bad hub location, aluminium not iron and over thick spokes which were probably to compensate you the lighter ali flywheel. Shame as a Bremen Calorific deserves a nice flywheel.

[Alyn Foundry]

Graham. That's one of the wonkest flywheels I have seen for some time

Oh….. you noticed a little runout then ? 

The crankshaft, for want of a better description was bent in several directions when I received the engine via a third party.

I did wonder about how nice a Nattie flywheel would look?

   Graham.

[Jasonb]

I'd be wanting to change the crank not the flywheel even the Nattie one won't look good with a wobble like that.

But you know me I like to have a "casting" without flaws and nice quality iron, there is a flywheel inside every bit Two Raabs and a Breman