A Smaller Steam Engine For A Smaller Boat

[apointofview]

Kvom thanks I am going to try the locktite this time, but to show my ignorance how do you use guage blocks to keep it all aligned. I guess i just cant picture it in my head. This time so far i mounted the new slightly oversize brass disks on their respective shaft stubs and then mounted the shaft in the lathe and finished off the final dimensions so those parts spin true. Getting the crank throw correct seems tougher.

fcheslop thanks for that link those are really nice renderings and it helped a lot, it cleared a few questions up I had. I will get them printed out.

Pete

 

[Blogwitch]

Pete,

Julius, who does those plans always does a great job of them and in fact, you are better off not printing them out as if you are using the correct PDF reader, you can select very large views of every component. If you printed each part out, you would end up with about 100 pages.
He puts lots of plans on here, and this is one of his latest, for the beginners amongst us.

http://modelengineeringwebsite.com/Oscillator.html

John

 

[kvom]

Use of gauge blocks works like this. Assume that the disks are flat on both sides. Then I place block(s) equal to the desired separation between them so that they are forced to be parallel and the correct distance apart while the loctite sets. I use Loctite 620.

 

[KBC]

Pete.

Make your discs the exact same dia and drill thro' the centre to suit your shaft ensuring that they are machined parallel.
Make a small piece of your shaft material as a sliding fitting set it up vertical in your bench drill and feed the 2- disc blanks on to it, wind out the "X" or "Y" table to the radius of the stroke ensuring that the discs are held firm and square to the vertical, drill thro' to suit the journal dia.
Make another piece of round material to suit the big end journal and slip it thro' the journal hole, you now have the journal parallel to the main shaft.

I use Loctite 603 now think of doing one side at a time by putting some Loctite on the main shaft and slip a disc onto it's position, leave for 30 mins and then put the big end journal in with Loctite and leave for 30 mins, you can then slide the other disc into position with Loctite and a smear of Loctite on the journal and press both into position.

Leave the assembly over night to cure and then drill a 1/16" di hole in each of the discs, thro' the journal and main shaft with the ends sticking out both sides, use a piece of mild steel rod or a piece of brass rod making sure that you have the Loctite going right thro' before pushing the rod thro', leave overnight to cure , flush of the ends , cut out the central piece of the main shaft and.

Do a few practise runs before glueing up as the Loctite goes off quite fast.

Here are 2- pics of a Launch engine shaft with 4- discs with the journal holes and main shaft holes drilled and kept in position before assembly.

I hope this will help you.

George.

 

[apointofview]

Thanks guys I can see what I need to do now, those replays are a lot of help. It seemed simple just to look at the drawings but looks were deceiving!

I do have another question, the disks are just round, most of the time crankshafts are cut to counter weight the piston and connecting rod. Should I remove some material from the crank pin side of the disks or does this design run fine as is ?

 

[KBC]

Thanks guys I can see what I need to do now, those replays are a lot of help. It seemed simple just to look at the drawings but looks were deceiving!

I do have another question, the disks are just round, most of the time crankshafts are cut to counter weight the piston and connecting rod. Should I remove some material from the crank pin side of the disks or does this design run fine as is ?

Pete ,
It makes no difference to the engine performance, stick with the designers discs.

I have in the past made the crank webs with the balanced cut outs and some with just strips of mild steel and I find no difference to performance.
At this size it's purely aesthetic.

George.

 

[apointofview]

Ok thanks George that's less work !!

So for my next attempt I carved up two more webs to replace the ones I destroyed and then drilled them up for set screws to pinch the shafts. I shy away from permanent attachments because it seems everything I own needs fixing at some point. I positioned the set screws for the throw in such a way to allow for carving the web for balancing, that was before George let me know there is no need to do it. I am going to set it all with locktite 242 the blue removable stuff. If that doesn't hold up then pinning and serious locktite will be in order. At least this time everything is nice and straight if I have to lock it all down forever. Next up is the cam.

Pete

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A bit of video just to see it spin

[ame]https://www.youtube.com/watch?v=y7bILYRpRxM&feature=share[/ame]

 

[KBC]

Pete,
Nice runner, you shouldn't have any trouble with the socket grubs it's a well supported shaft, if you do don't use the 243 Loctite it's only for thread lock.
If you have to, be brave and use Loctite 603 or 620. and it will never move.

Keep up the good work.

George

 

[apointofview]

Time for the valve cam. I didn't get as many pictures for this one but here's what I got.
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The brass was rough cut to size and then I drilled the offset hole. I mounted it on a hunk of drill rod and tried to put it in my 4 jaw chuck to get to the final dimensions. Problem was the jaws wouldn't close on the rod in the offset position it needed. I ended up having to put a second piece of rod in the jaws to allow them to be tightened to the 1.3mm offset called for.
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This is the retaining ring

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The securing of the ring is supposed to be a couple of tiny countersunk screws that I don't have. I ended up modifying the cap screws to lower the profile to flush out on the thin ring.
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This is where it will live. Timing it will come later

Looks like cylinder parts are next

Pete

 

[apointofview]

Cylinder end covers are next. They seem simple enough and here is what I got done
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So the two of the covers need work on the back side of them for o-rings and two have a raised area for clearing the nut inside the cylinder, and all of them need a bit of thinning down.. I left them a little thicker because I can't part off pieces right at perfect dimensions with nice finishes. So here is where I need help from you guys...

How do I shave down the back of these tiny disks?

I can hold them to drill the three holes 120degrees apart and get the o-ring grove cut in the three jaw chuck but the chuck is in the way for thinning down the part
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[apointofview]

Oops here is the other drawing showing the dome I need to cut
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[Cogsy]

You could bore a hole in a piece of bar for the 10mm 'boss' to be a slight interference fit into but it's tricky to get right. Otherwise, make it a nice slip fit and use a bit of superglue to hold the part in the end of a bar, then use a bit of heat to remove it after machining and some nail polish remover (acetone) to clean up the residue.

It might not work for large and heavy parts but for light machining on small pieces it should work fine.

 

[Cymro77]

Try using the shellac glue with a small spigot mounted on the lathe. See the article by Tony Bird on this site.

 

[KBC]

Cylinder end covers are next. They seem simple enough and here is what I got done
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So the two of the covers need work on the back side of them for o-rings and two have a raised area for clearing the nut inside the cylinder, and all of them need a bit of thinning down.. I left them a little thicker because I can't part off pieces right at perfect dimensions with nice finishes. So here is where I need help from you guys...

How do I shave down the back of these tiny disks?

I can hold them to drill the three holes 120degrees apart and get the o-ring grove cut in the three jaw chuck but the chuck is in the way for thinning down the part
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Pete .Another method that I use is to machine up a collet as shown about 1/2" long and bore out to leave a ledge the thickness of the cover and cut a saw drift thro' to allow the cover to be clamped, the wall thickness is about 3/16" max. Use any material that you have, the big one is mild steel and the smaller one is Ali.

The big one in the pick is for the Stuart range of engines , D10 & others at 3/4" bore, the other is for an engine that I am working on at present with a 7/16"" bore.
When completed they go into my Jigs and Fixture box for future use.

George.

 

[fcheslop]

I simply made a jig from a wee bit of bar drilling a hole right through 6mm counter bore with a slot drill to fit the cover and super glued them in as super glue doesnt have a great sheer strength a sharp whack released them.Put a small center pop next to number1 jaw so the mandrel can be refitted to the chuck in the correct orientation .Failing that what George said.
I do use shellac chucks when required but now tend to glue them on its just easier I find.Shellac chucks are very useful but unless youve got some shellac some elcheopo super glue will work fine.
Once finished with keep as it may come in again oneday thats why Iv a pile of junk hiding under the bench with the spiders
When making the bottom covers I made the counter bore for the O ring a few thou deeper and then polished them down to get a nice slide fit and also gave the piston rods a light polish as the radial grind marks wear the O rings quickly
Nice Marcher George

 

[KBC]

I simply made a jig from a wee bit of bar drilling a hole right through 6mm counter bore with a slot drill to fit the cover and super glued them in as super glue doesnt have a great sheer strength a sharp whack released them.Put a small center pop next to number1 jaw so the mandrel can be refitted to the chuck in the correct orientation .Failing that what George said.
I do use shellac chucks when required but now tend to glue them on its just easier I find.Shellac chucks are very useful but unless youve got some shellac some elcheopo super glue will work fine.
Once finished with keep as it may come in again oneday thats why Iv a pile of junk hiding under the bench with the spiders
When making the bottom covers I made the counter bore for the O ring a few thou deeper and then polished them down to get a nice slide fit and also gave the piston rods a light polish as the radial grind marks wear the O rings quickly
Nice Marcher George

Drat and double drat, Frazer you have found me out so I suppose I should post a pic of the little engine to date.
It's a Marcher engine from A.J.Reeves and can be made either piston valve or Stevenson reverse linkage, I am making it with the Stevenson gear. It stands about 3.25" high x 3" long, a bit longer when a boiler feed pump is fitted.
The casting were given to me by an old friend who no longer has the eyesight to see what he is doing so I took on the machining of the engine.
It'a a twin cylinder double acting engine of 7/16" bore x 7/16" stroke , each piston contrary to opinions of members on this forum are fitted with Silicone "O" rings and before an argument starts I would ask the question , " why do model engineer suppliers state that black Nitrile or Viton rings are not suitable for steam pistons" and excuse themselves from supplying them for steam pistons.

George.

 

[apointofview]

Hey these are all great ideas!! Thanks everyone for taking the time to help me out. I have started working with the ends of the cylinders using Cogsy's suggestion for an interference fit on the 10mm boss. I have started on the first cover but life has gotten in the way so not much progress but it looks like it's going to work... Great thing about all the answers is it gives me plenty of great ideas on how to deal with tasks like this... I would have never though of superglue or shellac or even a custom fixture, I was stuck. This is what is so great about this group, lots of friendly knowledge that is shared to a bumbling hobbyist like me 😀
THANKS everyone!
Pete
Oh ya here is a pick of the tiny progress. I cut the aluminum round stock to fit the 10mm boss and reduced the dia to allow me to get calipers on the part and be able to knock it off the holder
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[bmac2]

It’s looking good Pete.
I use superglue more than I probably should when machining. If you put a little heat on the part (heat gun, small torch, BBQ lighter) the glue will let go. Saves accidentally putting a ding in the part by knocking it off.

 

[Blogwitch]

It is times like that when a set of soft jaws come into their own.

They are cheap and if looked after will last for many years and you will get perfect accuracy because the jaws are bored to take the part.

John

 

[apointofview]

soft jaws sound great but a web search for those that fit my chinese mini lathe gives no results. I'll keep looking but that also does not line up with my cheapskate lifestyle !

Pete