Hit Miss Engine - second try

[Racer57]

My first try at a hit-miss motor was not 100% successful. It had to go to the small motor whisperer (ChrisH on this forum). We did indeed get it working and stable. I never felt that O-rings were a proper way of sealing a piston. I bought a piston and rings from China a set off on the next adventure. There were some false steps and there are a few "warts" in the final product. But... its runs and runs well.

My biggest issue was learning how to do ball bearing assembly. There is a very small difference between just right and too tight. It took a little "tuning" to get everything where I liked it. It is wonderful what locktite and emery paper can fix. The final displacement is ~30cc.

If the forum does what I expect the link to a video will be below.

Will

The final product link

 

[Eddyde]

Looks and sounds nice! Do you have any pictures of the parts & assembly process?

 

[rdean]

Great job Will
So what is next?

Ray

 

[Chris Hamel]

Sounds great. You can be proud of it.

 

[Racer57]

I have some photos. I will put something together in the next couple of days.

I don't know what is next. There is a Youtube series about making die-filer that is interesting. It would be an expensive project.
We will see,

Will

 

[Racer57]

The flywheels started out as a 1.5"x7" slug from Alro. I had to spit it. As seems to be my normal this was at the limit of my equipment.



After a time and multiple turns of the blank I had two.

I have the best luck on my equipment turning these big diameter pieces is between between centers. It turns out that 7" is my limit,



The next piece was the crankshaft. I made the end plates using a home built mandrel. When I had both plates machined with the mains hole I bolted both on the mandrel centered on the mill and drilled and reamed the journal holes.



There final assembly was drilled and pinned with #2 taper pins and Locktite. After lots of machine work it looks like this. I had a length of precision .5" rod for the mains. In the end it has been strong and true.





That's all for now. If this is not interesting let me know. There are gaps because I was doing the photos to share with my mentor and brother (ChrisH) and not necessarily create a complete story.

Will

 

[rogerl]

Chris:
What piston did you buy? I have a hit miss engine that runs good when you put in a new o ring on the piston. Then it looses compression and does not run.

Roger L

 

[Chris Hamel]

I bought it from ebay. 32 mm which is a little 1 1/4". It came from China so it took a few weeks to arrive.

I have other engines I have built using O-rings and they run pretty well. The first o-ring wears pretty fast but once the cylinder gets polished, the next o-ring lasts a long time. I run 10% wd-40 in my fuel.

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[rogerl]

Chris:
Thanks for the information. I have a 3/4" bore cylinder so I would need a smaller piston. Somthing to look at. I might just need to polish the bore better to get a smoother finish. That might solve the problem.

Thanks Again
Roger L

 

[Racer57]

All of these pistons are for repairing chain saws and like. The smallest that I have found is around an inch.

Will