Weaver Ransom 1cc CI engine

[Streamer]

 Hi Ramon,
If you get it from their own website you may do even better!

This is the last part to be completed for the engine, the venturi and fuel tanks.
The venturi is as I have made before, the only pics I have included are of drilling the main intake hole and of the home made tapered reamer I made from silver steel. This reamer is double ended as the intake taper is different to the taper from the needle to the engine. This worked alright on aluminium but I wouldn’t like to try it on steel – maybe it would work better if the hole was step drilled.

The interesting part was the fuel tanks – I didn’t want these to be too big for the engine but needed to be big enough to be useful. I couldn’t find any plastic containers suitable so bought some glass test tubes on ebay thinking that I could cut them down to size.

This is more difficult than I expected – I had seen that my hobby tool came with diamond coated disks - amongst the uses it said were for glass. Great I thought, that should be straightforward – they do cut glass but as soon as I broke through in one place the test tube would disintegrate. I expect this released internal stresses or something.  Anyway I eventually managed to find a way to reduce the length, using a very fine diamond file (triangular) I etched very lightly all the way round the circumference slowly etching deeper and deeper until almost all the way through – then pulled the two parts away from each other. Once this is done filing the glass to achieve a flat edge is straightforward.

The first design really is over complicated but does work. The aluminium lid has a groove machined on the internal diameter at the top (I used the same tool as for the groove in the piston). There is a matching lip on the aluminium rim which is epoxied to the glass. I have filed away three equal sections of the lip, and machined away three matching sections of the internal diameter of the lid. So slot the base into the lid and turn one third and the two parts stay together – told you it was over complicated!
The second one is much simpler and easier – I had loads of time to think about it as I was making the first one. The lid internal diameter is machined with a small taper, wider at the top. The diameter at the top matches the diameter of the glass tube. File away four equal sections all the way round and the small amount of spring in the remaining thin  ‘leaves’ very firmly hold the glass. It is very easy to pull out if needed but will not come out on it’s own. This one works very well and will use it again if I need a similar tank in future.

That is all the components complete, I will report soon on whether these run or not.

Steve

PS. Usually by this time in a project I know what I am going to be doing next, but I don’t this time. I would like to try something larger (machining through a magnifying glass is a bit trying) before my next small diesel, maybe a Mills. If anyone has any suggestions for something larger, maybe a two stroke glow engine that I can get plans for I would be grateful.

Steve

[Streamer]

Hi,
Here is a pic of the completed engines, hopefully will be back soon with some video.
Steve

[Ramon Wilson]

Those have come out really well Steve  If they run as well as they look you should be well pleased indeed.

Now, how about scaling one up to 5cc  (you could even convert it to Glow too )

Regards - Ramon

[Admiral_dk]

They look fantastic 

Plastic tank is possible - Jason got some ideas if I remember correctly .... 

[Streamer]

Hi all,

Very pleased to say that below should be a couple of videos of the two engines running

As much as the fact that they are running I am pleased that now I have sorted out the settings for each they are easy starters. The engines I have made before have run but have been very unpredictable to start. Another interesting thing, now that I have written down the starting and running instructions for each they both start and run with the same prime, compression etc and both run best with very similar settings.

The performance is about the same as well - at the moment running at about 8,000 to 8,500 rpm with 7 x 3 props. Maximum 8,900 with the red one having the edge at the moment.

Ramon, I genuinely don't think I would be confident scaling anything up. I have thought about it a bit, would I start by scaling the bore and stroke (keeping them in proportion) and work all other dimensions back from there? For a glow conversion would I need to know the ideal compression ratio for a glow and adjust the free space at the top of the cylinder? The other options from my own research at the moment are a Jones .605 or possibly (less likely) a Vega Twin four stroke.

Anyway, I have to finish running these in and give my workshop (telephone box) an end of project spring clean so I have got some time to decide.

Steve

<a href="https://www.youtube.com/watch?v=KF3vIklcTPo" target="_blank">http://www.youtube.com/watch?v=KF3vIklcTPo</a>   

<a href="https://www.youtube.com/watch?v=pavdvDBux5k" target="_blank">http://www.youtube.com/watch?v=pavdvDBux5k</a>

[Ramon Wilson]

Well Steve, you've certainly produced two excellent little engines there - Have you tried opening both videos at once (on the page) - Ahhh - harmony 

Scaling up is relatively straightforward - I do just as you say and find the ratio required to take the bore and stroke from the original to the desired cc. Once I have that then all measurements - either from the drawing or as in the case of the Etas etc from an original engine - are scaled by that ratio. Due to scaling 'the volume' the engines can come out a tad heavier than what would be expected for it's given size but not overly so so I have kept to all scaled dimensions rather than thin things to save weight. This does have a greater effect if the original is smaller - the Super Tigres for instance, scaled from the 1cc original to 5cc are quite beefy compared to the Racers and Etas.

Converting to glow should be relatively straight forward too - you may have to bring the cylinder head down into the liner (rather than shorten the liner if you want to keep the overall appearance)as a lower compression ratio of around 12 to 1 is required rather than the higher ratio for diesel.

The Jones is a nice engine - if I recall correctly the crankcase was designed to be made from a casting but you should be able to create that from block without too much trouble. I stick with 5cc for two reasons - the first is that I've always 'liked' 5cc engines above other capacities but from a making point of view the components make for much easier work holding but without the need for largish blocks of material. that said you will find the blocks involved for a '5' rather large to begin with after your Weaver's

All this talk of engines is having an effect - it's been nearly a year since mine saw light of day but Forncett looms so they'll soon be brought out for their annual run.


Congratulations on a fine result Steve,

Regards Ramon

[Admiral_dk]

  They are great runners Steve 

You can be proud of your achievement 

[Streamer]

Hi Ramon,
What a great idea, I never would have thought of opening both at the same time, they do sound good together.

Thanks for confirming about the scaling up, I had worked it out to be a factor of about 1.73. Shows how daft I am and how I am enamoured of small engines, only an hour later I was working out how to scale one down to 0.5cc!

The Jones casting is available from Hemmingway, although with plans etc it is in the region of £120 so may have to go on the back burner. I don't know what Forncett is, sorry.

Thanks very much Admiral, and thanks to everyone who has followed along this build.
Steve

[GailinNM]

Steve,
I have been following along on your  Weaver Ransom double build.  You have made some real works of  art.  Congratulations. 

Be careful. Small engines can become addictive.  Over the last dozen years I have built 30 successful engines of less than 1cc displacement. Actually 4 of them were greater than 1cc displacement, but they were twins with individual cylinder displacements of less than 1cc so I count them. Built a few others which, although they ran, I did not consider successful. These were compression ignition in the 0.2 cc range.

Breakdown of the under 1 cc engines is:
7    2 stroke singles (3 glow, 4 Compression ignition)
19  4 stroke hit & miss, all spark ignition
2    2 stroke compression ignition twins
2   4 stroke spark ignition opposed piston twins

Of these, 10 of the h&M engines are working for a living in Gauge 1 model locomotives.

So they can be addictive.  If you start scaling things down from existing model engines you will have lots of fun.  If you start designing your own you will have even more fun, of course assuming that you consider troubleshooting to be fun also.

Gail in NM

[Streamer]

Hi Gail,
Nice to hear from you, thanks very much.

I fear it may be far too late for warnings although I have more or less decided that the next project will be a vega twin 9cc four stroke. I am fairly new to model engineering so I like to have projects that teach me new things. I have never cut any gears, made valves, I have only made plain bearings, never cut a cam etc so this project should teach me quite a lot.

Having said that I don't think it will be long before I am back to small diesels, the Mills, Owens Mate, scaled down Weaver, scaled up Weaver, I quite fancy having a go at a Topsy .375 and there is also the small matter of a metric Lobo Pup that has been winking at me from the pages of MEB for a while. I don't know what it is about these little diesels, maybe the fact that they are independent and work 'stand alone' without the need for electric for spark or glow plugs. Anyway, I think the bug has bitten.

Cheers
Steve

[Ramon Wilson]

Anyway, I think the bug has bitten.

That's good to hear Steve - 'go forit' 

Ramon