First Ever Machining Project (Rupnow H&M)

[wagnmkr]

I made doll house size, miniature turnings for 15 years or so. Building an IC engine has been on my bucket list forever so it is time to try and fix that.

This will not be a quick build, but I'm hoping it will be steady, and my goal is to have it running early in the New Year.

This will be my first ever complete machining project and I have chosen the Rupnow Hit and Miss with flyball. At least if I get in a real pickle, Brian is only about 1 1/2 hours away from me, although he may move soon

I am going to do the air cooled version, with an aluminum cylinder and piston. I do have the material to do the cast iron cylinder if the ali one doesn't work.

The flywheels will be cast iron as I can't afford the hit for brass.

I have most of what I need to get going so I am going to start on the cylinder.

I know everyone loves pics, but all I have at this moment are some vacation snaps of my trip to England, so the machining ones will be along soon.

Edit in ... the first couple of pics ... cylinder turned to size and the cooling fins started. Also the id being bored to size, ready for honing.

Cheers,

Tom

 

[Cogsy]

I'll be following along eagerly. I'm enjoying my build, although it has challenged my abilities quite a few times. Enjoy!

 

[wagnmkr]

Thanks Cogsy, this is definitely going to challenge my abilities as well. Virtually every operation will be new to me.

The one success so far is doing the cooling fins. I had tried several times before with no success at all. After MUCH searching and reading I found that I had the tool ground wrong, and also my tired lathe was a bit loose. I did a mod or two on the lathe, reground the tool, and there ya go! I also used the wd40 lube trick and I managed to getr done.

Cheers,

Tom

 

[Swifty]

I will be following along, it will be interesting to see how the aluminium cylinder and piston combination work. Usually similar materials running in each other is not the way to go, they tend to score and jamb up.

Paul.

 

[wagnmkr]

Swifty, I will be using the Viton o-ring on the piston. I have the material to make a cast iron one if I need it.

I am open to any and all suggestions here.

Cheers,

Tom

 

[wagnmkr]

Not much more got done today. I did get the blanks cut for the flywheels, and I got the blank for the cylinder head cut to size and ready to layout in the morning. I would like to get the head done over the weekend ... I think it is the part that scares me the most.

Cheers,

Tom

 

[Brian Rupnow]

Tom--Just a heads up. The head detail that is in the download package is not the most current rendition. The only difference is with the deep slot in the head where the nose of the sparkplug extends into. I found that with the head machined as per that drawing, the engine flooded very easily and wouldn't clear itself without removing the plug and drying it off. I went back in and opened the bottom of that slot up in an angled configuration, and it solved the problems. The revised drawing is posted near the end of my build thread, but never made it into the download package.---It will be very interesting to see what results you get running an aluminum piston in an aluminum cylinder. There is an extremely high chance that running two pieces of similar metal together like that will cause it to gall and seize up. Since you have already successfully made your cylinder from aluminum, I recommend that you make the piston from cast iron or bronze, or even mild steel.----Brian

 

[Swifty]

I agree with Brian about the piston, you have the cast iron already so you may as well use it.

Paul.

 

[wagnmkr]

I was at our monthly model boat club meeting last night, and the other two lads that play with small engines both told me the same thing about my cylinder. They suggested putting a CI sleeve in, but measuring shows there is not enough meat to do that.

I already have a cast iron blank the size of the piston so I will go that way for now. I can also just put it down to practice, and do another cylinder in cast if I want.


Brian, Thanks for the heads up on the head detail. I have the advanced drawing and will use that.

Cheers,

Tom

 

[wagnmkr]

OK, so not being one to totally disregard information passed on to me, I made a new cylinder out of CI. (Note to self ... use sparingly ... dirty) It took longer to clean the lathe and the chuck than it did to make the part. I did remember to include one small design opportunity.

I have put the aluminum cylinder away for now, and when I get a minute I will try and put a cast iron sleeve in it just to see if I can.

Now ... I was wondering ... would there be any difference in the vibration level of this engine depending on whether a heavy cast piston is used, or a light aluminum one? In my mind it would be better with the aluminum one ... not so much weight going back and forth at high speed. Just curious.


Cheers,

Tom

 

[Brian Rupnow]

This engine is so seriously unbalanced that it probably wouldn't make a big difference. If the engine is not bolted down to a good solid base, it will try and run around the room when its running. However---As a rule of thumb, always go for the lightest material for a piston. One thing to keep in mind though---aluminum has the highest thermal expansion rate of any of the metals we work with. On an i.c engine which is running some kind of rings, that's not a real big deal, because there is about .001 to .002 clearance between the piston diameter and the cylinder diameter. However, on a steam engine or some other types of engines where rings are not used and the piston has to be a really close fit in the bore, aluminum is not a good choice because it expands so much that if you started out with .0002 to .0005 clearance, as soon as the piston heats up it will swell to the point where it starts to seize in the bore.

 

[lennardhme]

Good luck with the build - I'll be watching progress.
Leonard

 

[Philjoe5]

Tom,
Great job on the CI cylinder, nice finish.

Cheers,
Phil

 

[wagnmkr]

Not much new at the moment. The piston is turned to diameter and fits like a glove. I can now see that some recent adjustments I made to the lathe have worked fine.

I will try and finish the piston today. I am also going to try and get the head laid out.

Thanks Leonard. This is a good learning project for me.

Thanks Phil.

Cheers,

Tom

 

[wagnmkr]

Well, I was hoping to show a pic of a finished piston, and I could do that, but it would be a bad one. It was all done except for drilling the hole for the wrist pin ... and then I drilled that off center I am not sure how I did that or if something moved, but the air here was pretty blue for a while.

Piston #2 is turned to size and I will do the milling in the morning.

This engine is going to take a long time if I have to make each part twice.

On a positive note ... I got the Viton o-rings ordered today as well as the bearings for the crank and con rod.

Cheers,

Tom

 

[Brian Rupnow]

Take heart Tom.--Every model engine machinist has a shelf of "fails". This is how we learn.---Brian

 

[wagnmkr]

Well, I think that wee potlicker is done and dusted (he says, fingers crossed). I will know when I go to put it all together.

Don't know what I will tackle next ... She That Allows Me To Play has a few things on the list.

Brian, I am just hoping that I don't end up with more parts on the bad shelf than the good one!

Cheers,

Tom

 

[Brian Rupnow]

Tom---I'm not absolutely sure about the old adage "Practice makes Perfect", but I have seen very few people over my lifetime that got worse with practice!!!

 

[Philjoe5]

Tom,
That piston looks good, see practice makes perfect :hDe:

I can say that 'cause my bin of failures just may make it into the Guiness Book of Records.

Keep up the progress.

This engine is going to take a long time if I have to make each part twice.

Just tell yourself, SOME parts not ALL parts

Cheers,
Phil

 

[wagnmkr]

Today I picked up the o-rings (Viton, 7/8 od x 3/4 id x 1/16 profile ... # 018 from Canadian Bearing ) and the bearings from the same company.

My boring head is ordered and should be here tomorrow.

No pics, or finished pieces taday, but then I have no bad pieces either!

Cheers,

Tom