Parksy's single cylinder four stroke

[Parksy]

Gday all

I have started a new project and would like to document it here for future reference and others to see.
I want to build a single cylinder air cooled four stroke engine which I could one day convert to hit and miss.
I don't have any plans so will be working with my own thoughts and copy a few things I've seen.
First thing made is the crankshaft. After having a crank that was made in sections fail I decided to try and make a one piece crankshaft. This wasn't as difficult as I thought and I'm happy with how it turned out. Made from 4140 rod.
The shafts and throw are 10mm in diameter with a 28mm stroke. Haven't decided on bore size yet, this will depend on material availability. The crank will run in ball bearings.



That's it for now. Next will be a base to mount it and the cylinder. Plan to make the cylinder out of cast iron then nickel plate it for corrosion protection.

Cheers

 

[Herbiev]

Are you planning on doing your own nickel plating ?

 

[Parksy]

Yes. I have made my own nickel acetate using vinegar, nickel and a 12v power source and have plated a number of things with good success. My previous project (v8 nitro engine) I've plated the rocker arms and cylinder liners.

 

[gbritnell]

That's a really nice looking crankshaft! I'm glad the 4140 worked out for you.
gbritnell

 

[Parksy]

Thanks George.

Made the cylinder this arvo out of cast iron. 50mm outer diameter, 26mm bore. Was able to achieve nice even fins. The new DRO that I fitted to the lathe is just wonderful. Was getting sick of counting the hand control rotations. Bore looks good too. Will mount the cylinder on the mill and drill the required mounting holes, then nickel plate it. I want to avoid plating the bore, does anyone have any suggestions on how I could do this?



Cheers

Andy

 

[Parksy]

Working on the housing at the moment. Machined from a solid block of 6061. Chosen to use large bearings to support the crankshaft. One thing that is apparent is that I may not have made the crankshaft long enough to add the hit and miss components at a later stage. I will have to work something out.

Soon I'll make the conrod and piston. Have got some 7075 aluminium which I intend to use for the piston.
I'm curious about the gudgen pin location. Have seen some drill in the centre (in relation to the height) vs some drill at the bottom. Is there any significance to this?

Cheers

Andy

 

[gbritnell]

Hi Andy,
If worse comes to worse you could set the crank back up in the lathe and turn down a section of it then make an extension and press and Loctite it in place. If you go that route I would make the extension shaft a little larger than the finished diameter of the crank and drill a center hole in the end. Once pressed in place you could use the center and then turn the shaft to the finished diameter.
gbritnell

 

[Parksy]

Thanks George. I like that idea.

Made the piston today. Have worked a lot with 7075 sheet metal on aircraft but have never machined it before and it is just wonderful stuff. Pity about the price tag.

Two ring groves which I'll soon make some cast iron rings.

 

[Parksy]

Ringed it. Made heaps of spares which I never needed. It so easy when it's only one cylinder.


Currently working on the conrod. Found some 431 stainless. This stuff isn't that bad to machine and has very good strength characteristics.

 

[Parksy]

Conrod is well under way. Just a few small milling operations to do then will clean it up and polish it.

 

[10K Pete]

Looks really good! At this rate it should be running soon.

Pete

 

[Parksy]

Thanks Pete. That's the plan.
Loosely put together for a quick pic. I need to make some split bushes for the big end. I have heard how people cut the material in half then soldier it together and turn on the lathe to required dimensions. Does this method present issues with regards to having both halves of equal size?

 

[10K Pete]

I don't think it matters how the two halves are held together and it's my experience that if the split is within 10 or 15 thou of actual center it's good.

Solder, glue or in some configurations nothing but holding the pieces in the chuck
or collet, whatever gets it done.

That's a great looking engine!

Pete

 

[petertha]

I need to make some split bushes for the big end. I have heard how people cut the material in half then soldier it together and turn on the lathe to required dimensions. Does this method present issues with regards to having both halves of equal size?

I made some finicky split lap clamshells using this technique which probably amounts to similar shape you are contemplating. One of the experiments was aluminum so soldering wasn't an option. Crazy glue & Locktite seemed to hold things together. Joint parted with some gentle torch heat. You cant get too aggressive with cuts, but that's probably more a function of how things are being held in the chuck/collet.

ps, some guys are using silver sheet for this application which are clamped between the split rod segments. Silver is apparently available through jewelry making suppliers. I guess this method can yield a very thin bushing equivalent & saves you a separate OD/ID split bushing which might be a finicky little bugger depending on the size. I've also heard of bronze sheet but never really explored this option in terms of stock thickness & cost etc.

 

[deverett]

I made some finicky split lap clamshells using this technique which probably amounts to similar shape you are contemplating. One of the experiments was aluminum so soldering wasn't an option. Crazy glue & Locktite seemed to hold things together. Joint parted with some gentle torch heat. You cant get too aggressive with cuts, but that's probably more a function of how things are being held in the chuck/collet.

ps, some guys are using silver sheet for this application which are clamped between the split rod segments. Silver is apparently available through jewelry making suppliers. I guess this method can yield a very thin bushing equivalent & saves you a separate OD/ID split bushing which might be a finicky little bugger depending on the size. I've also heard of bronze sheet but never really explored this option in terms of stock thickness & cost etc.

Would copper be a substitute for bronze? It is available in 0.1 mm (0.004") thickness from our favourite online auction house. eBay item number:
311450892213.

Dave
The Emerald Isle

 

[Parksy]

Almost completed one flywheel. Need to mount it to the rotary table and drill some holes to remove some mass from the center and make it look nicer. Also had a go at making a taper lock. Not too difficult at all and works very well.
Will make a second one.



The flywheel is 100mm in diameter which is quite large for the mini lathe. Getting a bit of chatter which I'll clean up later.

 

[Parksy]

Half way through another flywheel. The drive belt on the lathe isn't coping too well with the steel and the large diameter so I'll need to replace it before I break it.

Have made big and small end bearings for the rod and have started on the head. The split bearings for the big ends was very straight forward. Ended up soldering two halves of LG2 bronze together and turning it to required dimensions.
Here's a quick pic of what it will eventually look like. The flywheels are not completed nor attached.

Similar to the "tiny" engines but larger.

 

[goldstar31]

I'm not into this now but I would have thought that recovering the bearing metal from scrap car shell bearings would stand up better than silver. Silver really needs to alloyed to get durability.

Bearing metal once recovered, can be 'tinned' onto steel and then machined. I tinned and whatever the worn out feed screw nuts on an old Pools Major lathe and the lead indium bearings came from the worn out shell bearings on my old Mini Cooper. You can do it all in decent baked bean can and then a bit of fireclay as a mould.

Which brings me to my question. I have a rather large stock of silver amalgam. It came out of a lot teeth. The gold platinum alloy, my late wife re-cycled into a jewellery ingot. Any bright ideas about the amalgam recovery?

Regards

N

 

[mayhugh1]

I think if you're going to use silver you want to use pure soft silver. An alloy like Sterling is too hard. You want a metal that is very soft and will easily conform to the shape of the journal. I used silver for the shell bearings in my Merlin, but that was really an exercise in novelty. I machined press dies to form the shells which was a lot more work than the more common method of soldering/unsoldering bronze half shells. The alloys used on the surfaces of automotive bearings are even softer than silver, but their embedding properties (ability to embed grit and reduce journal scratching) are superior and probably one of the reasons silver isn't more commonly used in high performance applications. Ron Colonna used very thin pure silver sheet as an overlay to the bearings in his Offy, and that seems to have worked out well fir him. My advice for a first effort is to stick to one of the common modeler's techniques for making them and to use bearing bronze. Lot's of single cylinder model engines even get along well without separate bearings. - Terry

 

[petertha]

Some silver bearing discussion here.
http://www.modelenginemaker.com/index.php?topic=5123.0

and here post #139 onward
http://www.homemodelenginemachinist.com/showthread.php?t=24153&page=14
George mentions down the thread, Ron's Offy engine apparently uses this method

* you beat me by a nanosecond Terry, thanks for more qualified reply *