tiny four cycle

[Krown Kustoms]

Well here goes, I have been working on this one for a couple of weeks now, I wasn't sure if I shold post one of my builds after seeing some of the high quality machine work as I have seen here.
It is simple, I got bored at work and started designing a small overhead valve single.
I have been working on an inline twin 2 stroke, I ended up making 3 cylinders so I decided to use the extra for a different build.
I put the 2 stroke on hold due to design issues.
I have been taking pics here and there to post.
I am not used to documenting work, so most of the parts are nearly complete before the first pic.
I have a 9 week old daughter so this build might take some time to complete.
So I like my board and paper before I go to cad

 

[Krown Kustoms]

here is the cylinder, and starting to turn the crank case out of 6061

 

[GailInNM]

Looks good KK.
How about posting some basic specifications such as bore & stroke so we can start getting a feel for this engine as we follow along.
Gail in NM,USA

 

[Krown Kustoms]

Oh yeah, I guess that would help.
Bore and stroke are both .4375"
cylinder outside diameter is .750"
cylinder hight is 1"
crank case is 1"D x .750"H

here are more pics of the crank case

 

[Krown Kustoms]

ok here are more
I am almost up to the current state of the motor, posting pics that is.

first is boring the crank case, I had a good bit of chatter using a brand new end mill, I later found the problem-lead screws are getting worn-

second is the rough hole finished ( notice the chatter )

third is the mock up

fourth is tapping the 2-56 holes that hold the cylinder in place

 

[RobWilson]

Very nice KK , interesting build,your design too Thm:
Regards Rob

 

[Krown Kustoms]

thanks, I came up with this a while back when someone asked me how small an ohv 4 cycle can be before it is too dificult to build.
So far it hasnt been bad but I havent got to the cam or valves yet.
I should have done more research, im not sure if fuel can atomize in a combustion chamber that small, or if a carb can actually atomize it.
I may be making a shiny paper weight.

 

[GailInNM]

KK,
Just so you know it can be done, one of the masters of small 4 stroke engines is George Luhrs. He has built numerous small 4 stroke OHV engines down to the 1/4 inch bore and stroke range. I have seen them run and they run very well. There are numerous articles on him and his engines, but the place to start is his web site.

http://minimodelengines.com/index2.htm

Gail in NM,USA

 

[mu38&Bg#]

Engines burn fuel just fine as they get smaller. They become less and less efficient though. A little engine like this will blow a lot of unburnt fuel out the pipe. They still make a decent amount of power proportional to displacement.

Cool project. I'll be working on a smaller four stroke for flying RC sometime soon. Maybe 3-4CC displacement.

 

[Krown Kustoms]

Thank you guys for the confidence boost.
After seeing some of Luhrs engines it dosent seem so far fetched.
Here are some more pics all the way up to current.
After I mounted the cylinder and a couple of the head being hacked on.

 

[PhiberOptix]

I may be making a shiny paper weight.

No Way - that's far too good looking to a weight
It looks amazing, and i have every confidence it will be a good runner
but please keep the pic's coming I for one want to see more as this beaut progresses

regards
Andy

 

[Krown Kustoms]

Thanks andy I have been keeping up with your build as well.
It looks nice, by the way im not sure if all phones have it but my phone has a button in the camera settings that looks like a flower, it is for focusing on close up things.
I would be making chips now but the baby is sleeping and she likes to do that if you know what I mean. (the more interuptions now the less I sleep later)
My garage is under the room she is in.

 

[Maryak]

KK,

Looking good and coming along very very nicely. :bow: :bow:

Best Regards
Bob

 

[Krown Kustoms]

The spark plug is posing to be a nice challenge.
I am using an 8-32 stainless cap head bolt for the shank.
Im not sure what kind of heat I will be dealing with but I have a bunch of different plastics for an insulator.
I think teflon will be the best bet.
I also have delrin and PTFE, I will put them all to a heat test.
The problem with PTFE and teflon is it is flexible especially when you have it on a lathe.
For that matter acetal is too.

 

[PhiberOptix]

Thanks andy I have been keeping up with your build as well.
It looks nice, by the way im not sure if all phones have it but my phone has a button in the camera settings that looks like a flower, it is for focusing on close up things.
I would be making chips now but the baby is sleeping and she likes to do that if you know what I mean. (the more interuptions now the less I sleep later)
My garage is under the room she is in.

Unfortunately my phone does not have a macro option i really wish it did, or if i could find my SD card for the camera, I also have a problem with babies, my 'workshop' is an upstairs spare bedroom, alas nextdoor's little girls room is adjacent to my workshop so no late night work for me

The spark plug is posing to be a nice challenge.
I am using an 8-32 stainless cap head bolt for the shank.
I'm not sure what kind of heat I will be dealing with but I have a bunch of different plastics for an insulator.
I think teflon will be the best bet.
I also have delrin and PTFE, I will put them all to a heat test.
The problem with PTFE and teflon is it is flexible especially when you have it on a lathe.
For that matter acetal is too.

what about 'tufnol' we used to use that at work, it mills/turns great, and we used it in the food industry where heat was a factor, its LIKE a fiberglass material with layers of fabric in it, very resilient, i don't know whether you can get hold of any or whether it would be any good in a sparkplug but would be worth looking into.

Regards
Andy

 

[Deanofid]

This is looking good, KK. Small engines have a lot of appeal, don't they?

BTW, check out George Britnell's tutorial on spark plugs on the forum. Should give you some good pointers for making the tiny one you will need for this little beauty.
http://www.homemodelenginemachinist.com/index.php?topic=5653.0

Dean

 

[Krown Kustoms]

thanks Dean, that post is what inspired me to build a plug. After reading I see he used teflon.
I have a sheet of teflon .5 x 24 about 6 feet long.
A friend gave it to me he was going to throw it out.
I use it for a lot of rc car parts.
I will also look into tufnol Phiber.
thanks for the info.
by using the 8-32 bolt I will skip a couple of steps. kinda cheating.

 

[gmac]

KK;

A number of builders are using Dupont "Corian" for their spark plug insulators. The stuff they make countertops out of. Most towns have someone custom fabricating counters, try a few of them though. The first place I went into asking for scraps tried to charge me $20 for a piece the size of the palm of my hand. At the second place I told them what I was building and the guy gave me enough for my lifetime for nothing - "come show me a plug when it's done!"

Info here:
http://www2.dupont.com/Surfaces_Commercial/en_US/tech_info/index.html

Can't tell you how it works - haven't built the plugs yet.

Cheers
Garry

 

[Krown Kustoms]

I didnt know you could get corian thicker than a laminate sheet.
I know someone who makes custom cabinets I will ask him he would probably hook me up.
thanks
-B-

 

[Speedy]

I love this build so far! looks like it can be done on a taig
do you think you will have any plans?