Jenny Wren - a tiny steam steam engine

[optima21]

the second vertical boiler was made slightly differently to the first, this time I decided to do it with 2 lots of silver soldering, so the first thing was to turn a step on the end of the bottom of the chimney , the tube is 8mm o/d

and the completed parts for the vertical boiler, the steel tube on the left isnt part of the boiler, its just a spacer

so the bottom of the boiler was silver soldered first, and upside down, with the steel spacer going around the chimney. the step on the bottom of the chimney was to stop the bottom of the boiler sliding down the boiler tube as it would expand during heating so would be a loser fit on boiler base. once again I used solder rings, here seen coated in flux and ready to go (the top was also soldered on now with the solder ring inside the tube)

and turned over and the filler / safety valve bush was soldered in place with the top of the chimney, all fluxed up and ready to be heated

and the completed boiler after soldering and pickling

this was then pressure tested to 60psi, so is all ready to go.

Very nice work there, one quick question is how do you clean the solder from the outside of the boiler?

polishing is something that I dont really know anything about so bought some rubber mounter points

https://www.ebay.co.uk/itm/282638917495

now I dont know if they are supposed to be used as they are but found that they cut well when loaded with the blue polishing compound from this (it was £3 for a 100g bar on its own so getting all 3 for £0.65 more made sense

https://www.ebay.co.uk/itm/292023061115

I also used some autosol metal polish for final polishing on a cloth and it ended up looking like this, so Im happy with that (jsut for scale the thread is M4)

 

[optima21]

next were the brackets to mount the engines to the boilers, and while the engines are identical the brackets arn't. with the vertical boiler, the mounting bracket is just screwed to the firebox part of the boiler, which makes sense as you can remove the engine by unsoldering the steam pipe. On the lilliput horizontal boiler, the engine mounting is soldered to the boiler, which I didnt want to do so decided to ,make a mounting to silver solder to the boiler, so the engine bracket can then be screwed to that.

so the mounting was made from a peice of 5/8" x 1/4" brass, with 5 holes in the end, the centre one is conterbored so that it can be screwed to the boiler with a 10ba screw before silver soldering it in place (that way you know its not going to move when heated. the holes either side of it are just to reduce the mass of it, which is means that there is less metal to heat up when the boiler is steaming). the tow outside holes and threaded 10ba to mount then engine bracket to. the hole being centre drilled is the distance to the centre of the boiler.

this hole is then clocked up with the brass block being mounted on a faceplate, I use my small faceplate in a 4 jaw chuck as it doesn't mount on my faceplate anymore

this was then bored out to the diameter of the boiler tube to a depth of of just over 5mm.

the finished mounting needs to be 3/16" thick, so by doing it this way meant I could then mill the excess metal off and end up with the final part (shown part way though the milling)

to end up with this

unfortunately one of the threads stripped, so I ended up using the part I was going to throw away, but ended up using a smaller vice in my normal vice on my milling machine to drill the holes. I've still got to silver this to the boiler, but I need to complete the engine first to get the mounting position

the brackets for the engine are made from 0.6mm thick brass and the one for the horizontal boiler is basically a piece of channel with 4 holes drilled in it. the first one I drilled the holes first and bent the bracket but they end up out of line (not by much but on this scale that's a huge difference), so on the one I used I bent it to shape then used a surface gauge on my milling machine to mark it it. this was the first scarp one and the bracket is being bent round some 5'8" wide brass

that was easy compared to the bracket for the vertical boiler, and the springiness of the brass didn't help, but an option was to anneal the brass, but I didnt want to do that. to do this I started with a 5/8" wide channel similar to the one for the horizontal boiler. then to get the correct curve for the the boiler (which is roughly 25mm diameter, I used a 14mm socket to bend the brass channel arrond around. this was done my removing the spring from a market stall clamp and modifying the end slightly so the sides of the bracket could then be bent back to parallel. the stall clamp was clamped to the socket with the brass channel between them

and the final shape before drilling the holes in the sided of the channel. the two holes shown were drilled before any bending was done

 

[optima21]

the brackets need to have a piece of tubing soft soldered to them made from 1/8" brass , and the crankshaft runs in this, the finished brackets before soldering and polishing look like this for the horizontal boiler

and the vertical boiler

and the the standard (which the cylinder mounts to) needs to be press fitted to the tube. a 1.7mm drill was held in the collet chuck to locate the tube and the standard was then press fitted into place using a chuck in the tailstock.

the face that the cylinder mounts on was first lapped on a glass plate using metal autosol metal polish and wd40. the cylinder faces were done in a similar way too.

and on to the crankshaft, this is just under 30mm long, the main part of it is 1.7mm diameter, the crank pin is 1.0mm diameter, and the stroke is 5mm....ohh and I wanted to make it in one piece. and it was made from 8mm dia stainless steel. the main part is turned along its length a few mm at a time , as turning this to size in one pass would result in failure as I wouldnt try and take a 3mm cut to do it in one pass. so the end was first threaded 10ba and here the next 8mm are being turned down to 1.7mm as this is a bearing surface in the brass tube and the bore of the flywheel goes over it (and you dont want a wonky flywheel do you)

the next section was turned down in 3 stages, with the final part near the chuck being 2mm diameter as it is another bearing surface in the brass tube

hold the crankshaft to turn the crankpin, I decided to use a collet chuck to hold the large diameter of the crankshaft (7.3mm in this case), but wasn't sure if this would hold properly and the chances of holding it accurately were slim, so I ended up making a 7.3mm diameter brass spacer to thread onto the end of the crankshaft blank. (both shown with a completed crankshaft)

this was mounted in a collet chuck which was then mounted in a 4 jaw chuck, offset 2.5mm to give the stroke of 5mm

and a close up of the crankpin being turned.

I was dreading making the crankshaft but it ended up being fairly easy once I'd workout out how to do it, its not rocket science, its just adapting what you already know.

 

[optima21]

I then made a couple of flyweels, which are straightforward turning jobs, this is the larger on and 24mm diameter, and was polished before parting off and the other side turned. I've decided that plain ones like this dont look right and after a day volunteering in the engineering section of the local industrial museum, have decided the flywheels need spokes in them (and will have once I work out how to do them)

and the completed engine ready for mounting on a boiler (this is the vertical one). it runs nicely on 8psi of air, so as long as the boiler can produce steam they should run well.

and with a £1 coin for scale

so thats me up to date with this, hopefully some of you guys who have lathes and milling machines and havn't used them much can see from this that its not that you cant make things, its just working out how to do it. we all make mistakes but thats part of the fun and its good when it works out well.

if anyone likes toy steam engines, they've got a display at leeds industrial museum tomorrow

and how Wilesco make steam engines in a production environment

I really need to get these finished now as Ive had a new R-Tec AC/DC tig for over a month now and have only plugged it in to make sure it works

 

[Mick Annick]

Brilliant, proper engineering, thanks for sharing it

 

[optima21]

ohh time for another update...

the horizontal boiler has had the mounting for the engine silver soldered to it, it was screwed to the boiler barrel to stop it moving while doing the soldering. I also decided to add a bush to the top of the boiler to solder the steam pipe to, as it would be easier to do it this way rather than directly to the boiler as the veneer cladding would have to be glued to it first. the existing silver soldered joints were also refluxed before doing the soldering

next I made the firebox for the horizontal boiler I decided to do this with soft solder and to have a base that would be screwed to it. the firebox is simple sheet metalwork, the only thing making it complicated is the size.

I decided that the base for this engine should match the base for the vertical boiler, so it would need to have a stepped and fluted edge (one day I'll decide to do something simple). the stepped edge was first milled around the base

then the pockets for the flanges that the firebox will be screwed to were milled

the holes for the mounting screws were then marked and drilled (using the firebox as as guide) and the base was then turned over and the counterbores cut with a 1/8" wide slot drill

the flute was then cut with a 3/32" ball nosed slot drill

and the finished base

then it was time to solder the firebox to the boiler, I decided to use high temperature soft solder (300C melting point) although I'd probably have been fine using normal soft solder (185C melting point). I used prepared sections of solder inside the firebox and fluxed it before assembly. The mounting for the engine was screwed to a piece of scrap sheet steel and this was placed of some steel chunks from the scrap box. the boiler was upside down with the firebox on top. the firebox was held in place with another chunk of metal out of the scrap box

and checking the alignment with a pair of squares

 

[optima21]

so then it was time to get them ready for finishing, some parts are polished and the rest needs to be keyed for paint and gluing veneer planks to the boiler. I decided to do the polishing first and then masked the boilers up for grit blasting. I used electrical insulation tape for the masking, and screw holes were plugged.

and after grit blasting using a pressure of 30psi as I needed to be gentle to leave the insulation tape intact shown below with the bases in place

just need a tiny bit of JB weld to fill the edges of the horizontal boiler where the tabs are for mounting the base.

in amongst this I was also thinking about burner and wicks, so here is me testing an 2mm silica wick for an e-cigarette, which seems to work well enough for the vertical boiler, it was tested with 5ml of hot water in it, but without the filler plug/safety valve being fitted, it steamed fairly quicky which is good, sign as a boiler that cant steam is a bad sign for a steam engine. the meths is in a milk bottle top

 

[Parm]

so then it was time to get them ready for finishing, some parts are polished and the rest needs to be keyed for paint and gluing veneer planks to the boiler. I decided to do the polishing first and then masked the boilers up for grit blasting. I used electrical insulation tape for the masking, and screw holes were plugged.

View attachment 149294

and after grit blasting using a pressure of 30psi as I needed to be gentle to leave the insulation tape intact shown below with the bases in place

View attachment 149295

just need a tiny bit of JB weld to fill the edges of the horizontal boiler where the tabs are for mounting the base.

in amongst this I was also thinking about burner and wicks, so here is me testing an 2mm silica wick for an e-cigarette, which seems to work well enough for the vertical boiler, it was tested with 5ml of hot water in it, but without the filler plug/safety valve being fitted, it steamed fairly quicky which is good, sign as a boiler that cant steam is a bad sign for a steam engine. the meths is in a milk bottle top

View attachment 149296

Absolutely top notch engineering

 

[Ton-up]

Superb work. Love the blasted/polished contrasting finishes!!

 

[bletchmonster]

Stunning engineering and a really well compiled thread!!
My hats off to that job. Takes an engineer of stature to achieve such tiny work.

 

[optima21]

the firebox parts of the boiler have been painted with bbq paint, and seems to be able to withstand the heat from the burner, but since a lighter has a bigger flame I dont think that will be an issue

I've also been testing a few design tweaks on the meths burner

I also needed some flanged 10ba nuts to adjust the spring that holds the cylinder in place as using a normal nut ad spanner will be almost impossible due to the space arround it on the assembled engine. I also needed to make a driver for use with the nuts so its made from a M3 cap head screw, and the hexagon body is made from an annealed 4mm Allen key (so that it can be used with s screwdriver handle if necessary.

for the wooden cladding I used some veneer, Im not sure what it is but I've had it years and though it would be best to seal the surface before cutting it into planks, so I used about 6 or 7 coats of danish oil as is soaks into the wood and wont chip like varnish.

the planks are cut to length first by cutting a strip of veneer the length of the boiler and the using a square on a cutting board to cut the side square to the end

I decided to use 4mm wide planks so used a 4mm square hss tool blank as a guide for cutting

the cutouts for the chimney and safety valve on the horizontal boiler ended up being a bit more complicated to do. what worked for me was to stick some masking tape to the back of the veneer and then superglue the masking take to a large lolly stick. the cutouts were then filed to shape, with the lolly stick being thick enough to give support while filing

the plank is then cut to width and peeled off the masking tape

for glueing the veneer to the boiler I was originally going to use epoxy resin and when looking at a steam temperature vs pressure chart

from here

https://www.valvesonline.com.au/references/steam-tables/

my boilers have both been pressure tested to 60psi so will both happily run at 30psi (2 bar) so the temperature would get upto 135C so I got some mannol 9905 epoxy resin at it can operate upto 150C

https://mannol.de/en/?action=accessory_chemical_preview&name=9905 Epoxy-Metal

but then decided that I would use superglue instead as it would annoy me having to mix epoxy resin adhesive for each piece of veneer and waiting for it to set. It appears that superglues loose strength rapidy at about 100C and it you want some that is suitable for 150C, you'll need deep pockets. so after looking at specs of superglue I ended up using loctite 454, which can be used up to 120C, but as I dont think strength will be an issue, you can use it at a higher temperature.

http://www.loctite.co.uk/loctite-4087.htm?nodeid=8802626109441


and since the engine happily run at 8psi of ar pressure I can reduce the safety valve pressure to 15psi (1 bar) and then the steam temperature is 120c.

and they're not looking to bad now with the black firebox and wooden boiler cladding

so with the engines attached I think they're beginning to look pretty impressive, but Im not liking the solid flywheels, so my next part will be to make some spoked flywheels, 4 spoke for the vertical steam engine and 6 spoke for the horizontal steam engine I think will look best.

 

[brightspark]

don't lighten them 2 much or it defeats the object of the flywheel on momentum

 

[Robotstar5]

don't lighten them 2 much or it defeats the object of the flywheel on momentum

Most stationary engine flywheels have quite a thick rim to keep the weight.

 

[brightspark]

4 round holes would look ok that's what some traction engines have

 

[rtbcomp]

Most stationary engine flywheels have quite a thick rim to keep the weight.

...

It's not so much the weight as the distribution of the weight. It's weight x the distance from the centre of the flywheel that gives the moment.

 

[zx9]

I thought this was going to be a great thread @optima21 and you have not disappointed. I am still blown away by how small everything is and the precision to which you work, almost lost for words.

 

[optima21]

don't lighten them 2 much or it defeats the object of the flywheel on momentum

Im thinking that too, but I'll be keeping the ones I've made and making some new ones.

I thought this was going to be a great thread @optima21 and you have not disappointed. I am still blown away by how small everything is and the precision to which you work, almost lost for words.

thanks for the kind words, its definately challenging at times and the small size is the biggest issue, and its been a steep learning curve with some of the items, and the amount of time things take to make. If I knew it would take this much time I would have spent on them. I need to finish them though as dont want another unfinished project

 

[Tinbasherdan]

Beautiful job there mate, I have two of those vertical boiler steam engines, one the same size as yours and the other maybe twice the size, they were pulled out of a skip!!

 

[optima21]

so time for another update, so I made a couple of new flywheels, the first thing to do is face the end of a bar and drill and tap the 10BA hole for the crankshaft and check the endfloat with the crankshaft in place.

and then cut the hub and outer rim using a form tool, this is ground from 1/8" square hss

then turn round, clock up in a 4 jaw chuck and cut the other face

and cut the spokes using a rotary table. Im not going to say much here as I think its worth a thread on its own about how to do simple machining on them (if I can work out how to do it, it cant be that hard)

and the completed flywheels look like this, the large one is 24mm o/d and the small one is 20mm o/d

then its time to fit the copper pipes, which doesnt seem to be too complicated, apart from my electric soldering irons wern't suitable as the contact area is so small to get the solder to melt, so I ended up having to use a blowtorch, which isnt too good with so much wood about, so a bit or ceramic fibre paper should help for a few seconds soldering. the ceramic fibre if good for over 1000C.

and the completed plumbing, the copper tubes are 1/16" thick

and then its time to run it and it didnt work

with the length of copper pipe I was thinking that it might be an issue, and so tried to run it on compressed air, but now it needed just over 20psi to run, which is far too much for a wobbler engine. the only thing that was different to my earlier testing was the exhaust, so this was cut off and would nicely turn over on 6 psi or air pressure with adjustment of the spring tension. this is why I made the flanged nuts as its easier to fit them and compress the spring.

so I tried it again and it still wouldnt run, but it would run if i reduced the spring pressure, so I'm guessing the escaping steam from the port and cylinder face was working as a lubricant and would run for about 5 or 6 seconds and stop.

alos the planks could be easily removed from the boiler which may indicate that it got over 120C, which would suggest that at times it was creating more than 1 bar (14.5psi) of pressure.

so its looks like I've got some testing to do including

1) change the exhaust pipe to 2.0mm o/d tube and enlarge the bore to 1.6mm (if Im lucky)
2) counterbore the back of the port face to allow the 2mm copper tube to fit.
3) see what pressure the boiler generates. you can run oscillator engines without a safety valve as the cylinder is spring loaded as works as one anyway.
4) do the same as 3 with gasket paper between the port face and cylinder face to see if steam is escaping there
5) make a crankshaft with 3mm throw to see if that can reduce steam consumption
6) see of heating the cylinder and pipes with a hot air gun helps.
7) I'll probably think of something else

I also need to replace the planks, but will need to see how hot the boiler gets to see what the adhesive options are

might be a while before I do another update as its time to start playing with cars again.

 

[optima21]

time for an update,

the first thing I did was to make a new crankshaft with a 4mm throw instead of 5mm, seen here being checked for fit on the engine with the flywheel in place

and with the 3mm crank it still wasn't working, even though the engine alignment was checked and everything seemed to work smoothly. you'll also see that the cladding has been removed as it one strip fell off, so Im guessing that the operating temperature of the engine is too close to the temperature limit of the superglue (should have been ok to 120c)

next job was to make some new pipework, the steam pipe from the boiler was 1/16" od and the original bore was 0.85mm but this was drilled out to 1.1mm, which might not seem much bigger, but is 66% bigger in cross sectional area. the exhaust pipe was 2.0mm o/d pipe and the bore was drilled out from 1.1mm to 1.4mm, which is a 170% bigger cross sectional area compared to the original bore of the 1/16" tube. the tube lengths I started off with were 45mm and were drilled from both ends. I had an 80% scrap rate with the tubes, but you have to expect things not working correctly. I did try drilling the 2mm tube to 1.5mm but had issues with the tubes cracking when bending them.

then its a case of counterboring the standard of the engine to accept the 2.0mm exhaust pipe, its not just a case of enlarging the existing hole, as it needs to be offset 0.2mm so that it doesnt break into the counterbore for the steam pipe. this was done with a 2mm end mill. I removed the old pipes by desoldering them, but one of the ports filled up with solder, do I needed to redrill that too.

then it was a case of bending the tubes, they were annealed first, the 1/16" tube would could be formed round a 2mm radius without any issues, the 2.0mm tube was struggling with an 4mm radius without cracking, and the former with the semi circular groove helped the tube to keep its shape.

the tubes were then soldered in place, and the port face was flattened with a fine diamond stone (due to the heat from soldering) then I re-assembled it and ran it on compressed air to just to make sure the the holes in the ports hadn't filled up with solder again, and it worked better than expected compared to previous attempts to run it. it was running on less than 5psi of air.

so next thing to do was try it on steam. with my previous attempts to run it, I had struggled to get it to run for 20 or 30 seconds, so my expectations were pretty low of it being a success. so 5ml of hot water in the boiler and 3.5ml of meths in burner and it was time to play again. so allow it 2 minutes to warm up and then turn the crank, and this time it ran for 11 minutes, which made me a happy person, but I still have no idea what changes have made it work, or it could be a combination of all of them. I guess its just that the engine is so small that small changes can make a big difference.

so I needed to make a new filler plug. I decided to ditch the safety valve as the cylinder is held to the port face with a spring, so if the steam pressure increases it works the same way as a safety valve and allows the steam to escape. The boiler was reclad this time using epoxy adhesive with a 150C operating temperature

so here it is the finished engine and runs well without any issues after about 6 or 7 runs

and once again with a £1 coin for scale

got to say I'm pretty impressed with how well it works, and how it looks, the black firebox and wooden cladding just look so much better than plain brass.

I just need to finish off the horizontal boilered engine and make proper burners for them.

ohh and just for scale I've recreated the first picture in this thread with my box of matches.....is the engine really that small, or have I got a huge box of matches