Thursday, June 13, 2013

Dana Hall's oversized Farmboy

Got this e-mail from Dana on June 13th, 2013:


Hi Allen...
Dana Hall here from Florida...
I hope this letter finds you well...
Been a while since I've talked with you...

I just finished the Farm Boy engine from your fathers plans... I made the engine 25% larger than what is called for... Instead of 6 inch flywheels, now they are close to 8 inches in diameter... I recalculated and increased each dimension on the plans by 25%...

I decided to try running the engine on propane instead of liquid fuel, and after a little tweaking, it ran so well that I just left it that way...

Enclosed are 3 photos of the engine... I thought you might like to see them...

Talk with you later,

Sunday, June 2, 2013

Graphite piston size issue (builders, please note!) (4IN1)

Here's an e-mail I received from Wayne Linfield on June 1, 2013:


At Christmas I received a 4 in 1 engine kit with the Graphite & Bearings kit. I am now getting around to building the engine. I find that the graphite piston is too small. The data sheet specifies the diameter as 1.045" but the part I received is only 0.997".Having already bored the cylinder out to 1.000" it is too small to fit properly.Is it possible to send me one the correct diameter?


And my reply:



Hmmm - never noticed that before.  That must be a typo, because the data sheet for the "Duplex" engine kit shows 1.000", which is the same stock.  I'll have to fix that on the 4-in-1 kit packing slip.

Looking at page 10, it shows the cyl diameter is 1.000".

We do not offer graphite larger than 1".

Although I am not a machinist, I would think it would be wise/prudent to make your parts around any pre-manufactured parts.

Sometimes, bearings are slightly smaller by a thousandth or two from what the plans anticipate.  Once or twice a customer has also complained about that.  Of course, I have no control over manufacturers to make bearings the exact size as the plans specify.   You must allow for generally accepted mass-production size tolerances.  Not unlike 2x4 lumber is actually 1.5" x 3.5"?

Since your cyl is now oversize, I suppose you could insert a stainless steel sleeve like Dad did on his.  Then you won't have to make another cyl.

Sorry about that!