small steam engine for a model boat.

[optima21]

the flywheels were made from an offcut of 1/8" thick brass plate, the holes for mounting the crankpins and axle were reamed using precision ground stainless steel rod with three flats filed on them, to get the best fit possible.

and a m2 hole was drilled and tapped for a allen screw in one of the flywheels so that it can be mounted to the axle, the other flywheel would be loctited to the axle. this 2mm grub screw was the only part of this engine not made by me.

the flywheels were then clocked up on the centre bore and the outside was machined. The flywheel blank was superglued some aluminium so that I could machine it.

I also needed a couple of tensions springs and a compression spring, so here's me making them using a transfer punch as a mandrel and they are hardened, so that would minimise the flexing as the spring coils get further from the chuck. small compression and tension springs are easy to make and only take a few minutes. heres my way of doing it.

Making Small Compression Springs

today I had a go at making some small compression springs as I wasn't prepared to pay the minimum order quantities for half a dozen so thought I'd have a go at making my own. I need stainless steel springs so got some hard drawn stainless steel. this is available from the far east via ebay etc...

www.mig-welding.co.uk

as this engine was being assembled using loctite, I needed to make some grooves on the shafts for it. this is making the groove on a 2.00mm diameter shaft using a 0.6mm wide parting tool.

then a couple of weeks ago I went to a steam punk event at Leeds Industrial Museum with a stand for a model engineering club. so I though it would be good to take it in pieces in a small container so people could see the parts, and later that day I was given an airbrush and the display box for perfect for doing this. The 5mm squared paper just made it easier for me to position the parts.

the engine was then assembled, using Loctite 648, to hold it together, and ended up using it like superglue, using a wooden cocktail stick to apply it to the grooves, then assembling it. After a couple of minutes the excess Loctite was then wiped off, which gave a very clean finish, and the final engine looks like this (on a pound coin for scale).

and compared to the original engine that its a smaller version of

it runs very nicely on compressed air, just need to get on with trying it out on steam and making a new boiler for it. The drive for a propeller shaft is taken from the extended crank pin. on the propeller shaft there will be a disk the the same size as the flywheels but has a slot in it to take up the drive. this also makes it very easy to remove the steam plant from the boat if required.

 

[Dilkris]

Incredible

 

[optima21]

time for another quick update, and it does run on steam too, although it does run better on air, but after a few run it is getting better. Im using wet steam from the boiler as that should provide some lubrication.

and speaking of boilers, this is the boiler that I was using, which is from a small steam plant. the original engine that it came with will be used as a decoration on a Christmas tree. I'll be using the barrel from this boiler to make a new boiler with. I could have bought some new tubing to make a boiler from but the wall thickness is much thicker (well over twice as thick) and I need to keep the weight down. I'll also be silver soldering the boiler as soft soldered joints seem to disintegrate over time. A new boiler casing will be required that will fully encase the boiler to keep the heat in.

as for fueling, I ran this engine on 50cc of water using 10cc of methylated spirits for 20 minutes just as a benchmark. the twin wick burner is an original one for this boiler. I also tried 50cc of water using 15g of fuel gel using a Mamod car burner. this gave a hotter flame but only 10 minutes running time and left 10cc of water in the boiler, so I think experimenting with burner tray shapes may give a longer burn time.

as Ive just been using wet steam, I can also play about with using a steam dryer (a steam pipe going though the flames) as this will increase the power output of the boiler, but the lubricating properties of the steam may be reduced, so I may also need to fit a lubricator. What has surprised me is how thermally insulting silicone as the silicone tube shown here can be easily held with the steam going through it, and you cant do that with a copper steam pipe.

 

[optima21]

I bent a piece of 3mm copper tube to make a steam drier, it was a bit of a failure though as it went around the wicks rather than though the flames, so didn't pick up any heat. To have any kind of effect, I think it needs to wrap closely round the bottom half of the boiler with as much of it a possible being in the flames of the wicks.

I also made a tiny displacement lubricator, they work by allowing steam into them by a small hole, the steam then condenses into water, this then displaces the water and the oil goes into the steam pipe.

the cross tube was silver soldered to the main body of it, then a 0.4mm hole was drilled though the cross tube. this was then enlarged to 0.5mm

the top for the lubricator was made, Im not a fan of knurling for gripping things, but prefer the feel and look for a fluted grip

and the competed parts for the lubricator, the collar for the body was loctited into place rather than silver soldering.

I got some wick chafing fuel (diethylene glycol (DEG)) and tried to see what it was like for burning, well it burns ok, once you get it lit, but its less viscous than methylated spirts (MS), so needed to use a 6mm diameter wick rather than a 4mm wick (that I would use for MS). if I was trying to burn MS like this, i think the liquid in the container at the bottom would be burning too.

I then needed to make a new burner for the wider wicks. this was made from 0.25mm thick brass. the wick tubes were flared at the ends to stop them falling through the holes when I soft soldered them to the top

and then it time to test how the 3 fuels burn (from left to right) MS, DEG and fuel gel ( some form of alcohol, water calcium acetate). both the DEG and fuel gel are used by restaurants to keep food warm at tables so are readily available.

and one of the fuels under test, there is a probe thermometer at the back to measure the temperature between the wicks to show how hot the burner may get, as I didnt want a soft soldered burner to melt if it got too hot. the pressure gauge was a 0 to 15psi gauge and the engine was run at full speed continiously.

rather that post a lot of figures, 10ml of DEG gives slightly more heat energy than 10ml of MS with 15cc of fuel gel coming in 3rd place.

Diethylene glycol - 10ml ran the engine for 14 minutes with the steam pressure being 2.5psi average and no water left in the boiler

Methylated spirits - 10ml ran the engine for 13 minutes with the steam pressure being 2psi average and 10ml of water left in the boiler

Fuel Gel - 15grams ran the engine for 12 minutes with the steam pressure being 2.25psi average and 15ml of water left in the boiler

so for me thats good news as for fueling a small boiler like this the DEG gives a better performance than the MS, but it works out at being twice the price of MS but for the quantity that I'll be using, its small change still. the DEG is safer as it has a flash point of 124C and a boiling point of 244C when compared MS which has a flash point of 11C and a boiling point of 78C. I guess its a bit like comparing diesel and petrol, both are fuels, but diesel is a lot harder to burn than petrol. I did put some DEG on a teaspoon and try to burn it, but I could not get it to burn. the temperature between the wicks got up to 100c , so soft soldered fuel tank should be ok as the it wont get hot enough to melt the normal soft solder (170 to 180C melting point).

the DEG is also fairly clean burning as this shows the carbon deposits on the bottom of the boiler after about 6 hours total running time

so next I need to make a new boiler using a cut down tube from this boiler. I need to use this tubing as it is thin walled so will save me some weight.

 

[Bullet2012]

I bent a piece of 3mm copper tube to make a steam drier, it was a bit of a failure though

failure ! your work is awesome, if thats a failure !