"Topsy" 0.375c.c. compression ignition engine

[ozzie46]

Bob, Is this just done on non ringed pistons or is it needed on ringed pistons as well?
I'm hoping to get into IC engines eventually.

Ron

 

[Maryak]

Ron,

IMHO this mating process is not required where rings are used. The piston and cylinder are not in contact, only the rings and cylinder, (a much smaller surface area). The rings are compressed to fit the cylinder and have a specified clearance across the ring gap when compressed into the cylinder via the ring grooves in the piston. This in turn exerts pressure between the ring and cylinder which for a model SI or steam engine should be around 6 to 8 psi and for a CI around 12 to 18 psi, providing the necessary seal for compression and preventing blowby into the crankcase.

As an aside I did some research into piston ring tribology and when I compared this to an 1890 fitting and machining book the difference in the results from the boffin formula in the tribology to offset by X/64" in the old machinists book was infinitesimal. Our ancestors new more than we sometimes give them credit for.

For a good result piston rings should be made from spun cast iron, irrespective of cold formed or heat treated.

Hope this explains a little more about a very fascinating aspect of pistons and cylinders. Many thanks to Mr Ramsbottom and Mr Lanchester pioneers who ran rings around their contemporaries. :

Best Regards
Bob

 

[roadrage17]

Here some more pics for yous...

Had some time to put the hole in where the cylinder going to be screwed on ...

The reason this was done on the lathe is theres a small step on the inside.

Centering it on four jaw chuck (took some time)

Slooooooooooowly getting there.

And it finished, with some cleaning up to do on it.

Thought i would share some other projects on the go...

My flintlock.

My Lathe.

Think I've got to many projects on the go for an apprenticed haha

Best Regards

RR17

 

[ozzie46]

Thanks Bob.

RR17
Good work, I cant believe how small this is.


ROn

 

[roadrage17]

Yeah ROn lol it will sound like a bee in a tin can if it starts.

RR17

 

[Maryak]

RR17,

Nice job on threading the crankcase. :bow: :bow:

Best Regards
Bob

 

[roadrage17]

AARRRRRRRRRRRRR

The first mistake has happenned , misread the drawing and the hole thing rong because of it :

Oo well , the fun is in building it.

So ill have to make anouther one ill update u guys once i get back to where i was .

Best reagards

RR17

 

[Maryak]

RR17,

Think of it as a test piece to determine the possible ways of going wrong. My come in handy box has a large collection of these test pieces.

Best Regards
Bob

 

[Seanol]

RR,
As you saw in my WIP post, I made some mistakes too. What helps is having more stock sized and ready to go! With the lessons I learned from the first I should have netter luck next time around.

Sorry to hear about your misfortune and look forward to seeing this little beast run!

Sean

 

[roadrage17]

Yes bob thats what i will call it a test piece the first of many im sure.



As you can see from one of my first photos ive got enought for bout 5 more of these crankcases haha :big:

cheers Sean looking forward to seeign your beeing put together think i might do i bigger one next time.

Best regards

RR17

 

[roadrage17]

i Am glad to say the crankcase and also the fuel tank are nearly done so new pics on the way

Best regards RR17

 

[90LX_Notch]

Looking foward to seeing them RR17.

 

[roadrage17]

Right guys back to where i was and a bit further.

As you can see the new crankcase has been made with a near finshed fuel tank. Also i have finished the carbaretor off on the Crankcase.

Best regards

 

[Seanol]

Roadrage,
Looking good!

I have had some setbacks but I am still forging ahead.

Can't wait to see it together!

Sean

 

[roadrage17]

Thxs for the interest guys.

Sean ive been following yours aswell and i think i should of made two aswell lol.

Best regards RR17

 

[Seanol]

RR17,
I am making 4!
I started on a second crankcase and was side milling for the mounting tabs. As i kept feeding the mill in I noticed the mounting tab getting lower and lower...

The Ti pulled the endmill down out of the collet!

So on to #3...

Sean

 

[roadrage17]

Owch that sucks but at least you wont have that happening again on your third.

I look at it this way if you make a mistake, and then remake it but make a different mistake than last time, you've made progress.
And eventual you will finish it but with loads of lessons learnt in the progress.

Do you all your machineing at home, cause at the moment i do all mine at work when i have spare time.
Any machines you would recommend for me to buy. Also at work we have DRO ( digital read out) which i have always used . i no most machines out there dont have them is it hard to get as accurate without it or am i just being stupid.

Best regards

RR17

 

[Seanol]

RR17,
All my stuff is at home. I lucked into an older 13x40 lathe and I have a 6x26 grizzly mini bridgeport.

As I am biased I would recommend the bigger stuff as even on the 6x26 heavy cuts are out!

Without a DRO you will do a lot of measuring. They make it easier and you won't get bit with backlash issues. On the other hand, $600 and up will buy a lot of material/tooling! ;D

I have more time on my hands then money (read none of either) but I believe that when I am good enough at measuring I will look into the DRO as a way to go beyond where I am at now. My learning curve is so steep I need to get speeds and feeds down so I am not buying endmills all the time :big:

Here is my stuff from the "show us your lathe thread":

Here is my lathe and mill:

Still learning not to make scrap and making slow headway but loving every minute of it!

Good luck with your decision and share it with the board,
Sean

 

[roadrage17]

Thanks for the quick reply sean. Gave me some ideas . Nice lathe and mill you have .

Best regards RR17

 

[roadrage17]

A questions for you guys out there is it nesscary to lap the main bearing and the crankshaft together. Or can i get away with a good finish and nice fit?

Any comments would be helpful.

Best regards RR17