Farm Boy 651

[Rudy from Norway]

I have started to plan my next build, a Farm Boy hit’n miss engine. Plans are purchased and the serial number is 651. Looks like a fun machine to build. Lot of machining.
I am wondering about how to source the material for the flywheels. They are some substantial chunks of iron. 1x6” blanks are needed. Cutting these out of a plate is an industrial sized task. I have tried to come up with an idea to use something easier to get, like a weight or even a car fly wheel. However, most such things have a large hole in the middle.
Would appreciate some inputs on this.

 

[perko7]

Perhaps look at blank flanges for pressure pipework? They will have a ring of holes around the perimeter but just go up a couple of sizes until the bit in the middle is the size you want. 1 inch thick might be a challenge but in the larger sizes and for high pressure pipe it could be possible.

 

[DavidLloyd2]

I have started to plan my next build, a Farm Boy hit’n miss engine. Plans are purchased and the serial number is 651. Looks like a fun machine to build. Lot of machining.
I am wondering about how to source the material for the flywheels. They are some substantial chunks of iron. 1x6” blanks are needed. Cutting these out of a plate is an industrial sized task. I have tried to come up with an idea to use something easier to get, like a weight or even a car fly wheel. However, most such things have a large hole in the middle.
Would appreciate some inputs on this.

Rudy
You can use mild steel for the flywheels

I have lots of 20mm mild steel so I will be using that for my flywheels and I will be making the spokes a little bit bigger to add weight,

DavidLloyd

 

[Rudy from Norway]

David, pity we are on the very opposite side of this globe.., otherwise I would be on your doorstep begging for some steel . However, hope you will make a thread of your build too. I could need someone to seek advice from.
20mm steel is of cause ok. Do you plan to make the flywheels heavier than original? Or just to compensate for the difference in the original 20,32mm to whatever you can get from a 200 steel plate after turning? The center is 24,64mm, but it should be no problem modifying that to less.
Like the idea of heavier flywheels if that would make the engine turn longer between ignitions.

 

[kuhncw]

Rudy,

Gary Martin of Martin Model and Pattern sells flywheel castings in a number of styles and sizes. www.martinmodel.com
Gary is near Portland, Oregon. I see you are in Norway. If shipping is not an issue, this might be a source of flywheels for your Farmboy.

Chuck

 

[Brian Rupnow]

Just about anything will work for flywheels, as long as it's weight is comparable to steel, which weighs 0.283 pounds per cubic inch. Cast iron, mild steel, bronze, brass, or even a two part flywheel with the central portion turned from aluminum and the outer rim of heavier material (think heavy wall steel pipe or tubing) Loctited to the aluminum center.

 

[Rudy from Norway]

Brian, cutting a piece from a steel tube and make a center of aluminium was a nice idea..
Getting castings from US over here is costly..
However, the task is about to be solved. A friend of mine shal cut some pieces for me.

 

[TonyM]

If you did have a mind to buy castings there are some really good ones here http://www.ateliermb.ch Free EU delivery on orders over 80Euro

 

[Rudy from Norway]

While I'm waiting for the materials for the frame I started with the cylinder.
It started as a 75mm lump of leaded steel.

After a lot of cutting and turning I finally got a nice cylinder. I made a split wooden stick in the lathe for lapping.
Did the piston in the lathe well over final dimension. Then placed it in the mill and did the inside milling and drilling. Note the flat on the bar stock. It serves as reference when I lay the work down to drill the pin hole 90 degree to the slot inside of the piston. I trued the piston to the quill with a dial indicator for each operation.
I should have done the cylinder finished before I made the piston, but I had to take the piston work out of the lathe to make the lapping stick. However, when I put the piston back in the lathe I managed to get it in without any measurable run out (wouldn’t been very important). Then I did the final cut to dimension. Polished with Autosol fine polish compound.

 

[Rudy from Norway]

Made the con rod while waiting for frame material. This piece is actually both easy and difficult to make. Easy to get accurate in terms of function. Difficult to make look right. I found a setup that worked fine to me. Drilling holes to make radiuses and then support it with drill bits to align it for milling. I used screws not threaded all the way in order to get support between the rod and end cap, just like a real car engine. I had to make my own reamer to get the fit tight, moveable but no play.

 

[Rudy from Norway]

Got the frame material! Some lump of aluminum! Nearly an hour in the band saw to cut it. Looking forward to many happy hours in the mill. This stuff machines like butter.

 

[Rudy from Norway]

Some updates on the build. Lots of machining on those big aluminum lumps. Have to be really careful not to overshoot and destroy the whole thing. The DRO is really helpful in this case.

 

[Rudy from Norway]

The engine frame material arrived. Nice lump... Good to have a band saw for this. Tock an hour to eat through.
There is a lot of right ways to setup the work on these parts. I tried several and found my ways. Since it is the first time I do such machining, I have to go slowly.
I got my selves a 16mm rough end mill. This one seems to do good work in this application. Lots of material to remove.

 

[Rudy from Norway]

(Discovered I had posted some pics before).

The crank bearing caps was LockTited (603) on before drilling. This ensured a very good fit when the screws goes in. Had to heat it to separate.
The two-piece frame is screwed together with several screws and LockTite 603 instead of fewer screws and pins in the split. Pretty sure it will hold.
Did the final finish with hand tools. It’s going to be painted and look like castings, so I will have to either roughen the surface or use shrink paint.

 

[deeferdog]

Thanks for posting these pictures Rudy, I'm really enjoying following your build. Cheers, Peter

 

[Rudy from Norway]

Glad you like it guys. I enjoy this project very much. I'm so eager to see this engine running. Being new to Model Engineering it is a very good feeling when you mastering new challenges. Guess it's like when athletes are winning something.
Anyways, what I can say so far, to someone considering this project, it is really a well designed engine. One will really get their machines work. There are many good ways to set up the work and make the parts. Many of the operations are not critical and can be done with just layout lines. However, keep in mind the critical measurements and dimensions. I have DRO (digital readout) on my milling machine and I can hardly imagine doing anything with some accuracy without. Highly recommended.
Next up is the crank. Brian Rupnow encouraged me to make it from silver steel rods, cold rolled steel webs and pinning, so I will do so. A bit reluctant to use silver solder and have a warped shaft.

Rudy

 

[Rudy from Norway]

Made the crankshaft. I went for the pin and rod approach. The shaft is 10mm silver steel (drill rod) and I left it as is. The webs are cold rolled steel. I made them equally sized pieces and Locktited (603) them together and drilled them as one to ensure the two holes being parallel.
I actually could turn the ends in the four-jaw with light interrupted cuts holding just with the Loctite.

 

[Rudy from Norway]

I managed to make the crank absolutely true. No measurable run out.
However, when it was time to fit it in the frame, I had a real fight. I struggled to get the frame line bored straight. First I tried to bore with just a 13mm drill since I have no reamer at this size. I can't believe how crocked a drill bit can make a hole. Discovered that after having made bearings with very close fit. The crank was locked solid when the bearing caps where tightened up.
Then I bored up the hole with the boring head. Made new slightly larger bushings, still no luck. Made another attempt, now with extremely slow feeding when boring. 10 minutes through each bearing (that was actually boring for real..). New bushings with absolutely no play, tightened up the bearing caps, bingo! I can't believe it! The crank falls around by its own weight. The fit is so close that if I loosen a bolt the crank locks up.
This was a major discovery for me. I'm working way beyond the native accuracy of the machines and really have to learn how to work around and understand really what's happening here. The issue was the long thin boring bar. It had to work out the spring force fully and equally through both holes.
Can't remember last time I had such fun!

Below you can see the setup I used to get the line boring 90 degrees to the cylinder. I also made good use of my new center finder. This is actually a very easy and reasonable accurate way to find the center.

 

[Rudy from Norway]

Made my first ever gear today! Can’t remember I had such fun since I got the line bore right. It was not difficult at all. I have to rush in and say, this is not a precision gear. But for a slow turning hit'n miss engine? I recon it will work.
I made the tool to my best ability by copying another gear profile from my model RC car that has the same pitch. I grinded the cutting tool under a magnifying glass. It will of cause never be very accurate this way, but as long as it works, I'm happy. (Haven't tested it yet, but it simply has to work somehow).
As long as the number of degrees between the teeth is whole numbers of degrees, the simple rotating table works. In this case it is 5 and 10 degrees between the teeth, so the dials on the rotating table is more than enough accurate. And it was easy to keep track of the number for the next tooth.
Again, not a precision gear, but I had such a fun time doing it. That's what matters to me. Hope it will work. If not, I will put more effort into grinding the cutting tool.

 

[rlukens]

(that was actually boring for real

I see what you did there...