Tuesday, January 26, 2010

Farmboy Gear dimension problem?

I received this e-mail from Curtis Strong:

"My name is Curtis Strong. I purchased the plans and started biulding my Farm Boy engine almost a year ago. I just finished it resently and it looks and runs very well. I did run into one problem on sheet 3 the rear frame. The dimension of 1.026 from the center of the crankshaft to the center of the camshaft may be too short.Although this is the first time I have made gears, I did folow the plans and did end up with very nice looking gears but when I tried to assemble them to the frame they were to tight to assemble. I took a long hard look at the plans and did some figuring which led me to believe that the plans actualy put the gears at apox. .003 interference. after doing the math using trig I figured the dimension on sheet 3 should be aprox 1.034. The fix was fairly simple. I just enlarged the cam shaft bore in the frame and changed the center of the larger bore to 1.034 then installed a press fit alluminum bushing. This dimension has produced a clearance that has resulted in the proper gear engagment. If there is somthing I may have over looked please let me know.
Thank you, Curtis."

If anyone can shed some light here, it would be appreciated.




Hi Curtis, I built serial #3 (Finished it March 19, 2009) and went by the plans and everything came out just fine. I did the math also and by my calculations the distance between the crankshaft C/L and the C/L of the camshaft hole is 1.1203 " and doing the pitch diameters the distance between the centers of the gears the distance is 1.1220" . That's a difference of .0017". When I run the numbers with 1.034" I come up with the gears being .0056" too wide? I think the numbers on the drawings are well within tolerance.

Jim G

Saturday, January 16, 2010

Ralph Ervolino's cast Farmboy

From an e-mail sent to me:

"... Here is a picture of my farm boy. I made patterns and casted the frame and cylinder. Also casted a base under frame to get flywheels off the wood base.
         Sorry for your loss (Jerry). I learn a lot from his work, and look forward to building the other engines from plans I got from him. I built a inline 4cyl., it runs great, but it's not pretty. Your father's plans showed me how to make them look good too.  The farm boy is like a sewing machine. I can't wait to hear it run. Thanks so much. Ralph"

Thursday, January 7, 2010

Farmboy Ring Groove Question

I had a caller a few weeks ago who stated the plans said to make a piston ring groove .105" wide by .110" deep for a .094" section by 1" diameter Buna-N "O" ring.  Sure enough, I checked the plans (Sheet #5), and this is what it shows.  The callers question was how could this seal the cylinder?

Does anyone have an answer for this, or is there an error in the plans?

Please advise.




Yep, the sizes are correct. I thought they were incorrect also. But after making the groove to size everything works just fine. I have noticed that the "o" ring swells when in contact with acetone or alcohol.
I wouldn't change a thing on the plans as there correct.
Jim G


Jim - I wondered if the perhaps the "O" ring would swell up to make the seal.  Now I (and future builders) will know!



Wednesday, January 6, 2010

Dana Hall's Super-Duper Fan! (SUPERFAN)

From an e-mail he sent me:


My name is Dana Hall and I am in Florida...

I would like to pass on my condolences as to the passing of Jerry...
I never met him, but we exchanged a number of emails, and he was always very prompt with his replies back to me... And his knowledge on the engines he designed is very impressive...

A while back I built Jerry's Super stirling engine and it works beautifully... Then I thought I would build another fan but doubling all of the engine dimensions times 2...

The pictures are deceiving as to the size of the fan... The blade diameter is 18 inches and from the bottom to the top of the fan blades is 31.5 inches... It has a maximum rpm of 245 and runs quite nicely on a .5 inch tall flame... The base stand for the engine is my own design...

Enclosed are 2 pictures of the fan...
I thought you might like to see them...

I would like to thank you for keeping Jerry's web site and business going...
His plans and engine designs are by far the best on the Internet market...

Dana Hall