Farm Boy 651

[BIGTREV]

Seriously impressive work

 

[Bob44]

 

[Bob44]

Made these for my Farm Boy about 3-4 years ago. I bought 1.5"x6" solid cast disks from Speedy Metals and cut them out on my mill using the measurements in the Howell plans. It took a while but they seem to do the job.

 

[Rudy from Norway]

I had an issue with the flywheels getting them to run straight. I did everything possible to make the crank straight and the hole in the flywheel in line with the wheel. Despite all the effort the flywheels ran visibly wobbly. The problem came down to the collets. I had drilled and reamed the center hole. Might be my reamers, but when accuracy has been critical, I have never managed to get a drilled and reamed hole perfectly straight. I had to bore it with a boring bar. Just as I did with the holes in the flywheel. So the second attempt became a lot better. Sidewise runout is now 0,05 - 0,1mm. If I tweak the collets I believe I can cancel it out to neglectable. At least I can sleep again now.
Other than that I have done some trail assembly and started to fine tune the parts. I´m particularly happy with the crank and bearings. No play and the shaft spins freely forever when the flywheels are mounted. This was also a drilling/boring exercise. Drilled and reamed holes in the block did not work. Despite perfect fit on the bearings the shaft locked up when the bearing straps was tightened. Had to line bore the block with a boring bar and taking out all the spring in the bar. Took about 10 minutes for each pass on each bearing. Same with the bronze bearings, turned and bored. It paid off.

Rudy

 

[Rudy from Norway]

Done some progress lately. The "carburetor" and drip oiler is done. The 90 degree bend took a bit to make. Lots of manual grinding and filing. The final buffing is the easy part.
The oiler looks difficult to make, but it wasn´t. The glas is from a test tube. I struggled with cutting it in the first place. It´s very hard glass. The ordinary tube cutter doesn´t make a scratch. Tried the method filing a scratch and warm with a micro torch, but that did´t work at all for me. However, a diamond cutting wheel in the Dremel and spinning the glass in the lathe, the job was done in seconds.
Rudy

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[Rudy from Norway]

Here is a "problem".. (if only all problems was that nice to work with..). The oil from the drip oiler is fed to the cylinder through some drilled passages in the block and through the hole in the cylinder sleeve. However, there is some play between the block and sleeve for the oil to escape in between. I didn´t want to make a tight press fit between the sleeve and block that probably could minimize the problem. I´m trying to find a way to seal the gap. A thin gasket will be pushed out so I´m thinking of making a O-ring seal. The problem is the angled pocket and rounded surface. I plan to make an bigger hole, put in an insert with the right profile, with room for an O-ring.

Rudy

 

[Rudy from Norway]

Help needed!
I´m having an issue getting compression. The valves are sealing well, but the piston ring is not. I have used a smaller O-ring than the plans say so I have the posibility to make a larger groove in the piston for a larger o-ring.
The plans gives dimesnsions on the groove, but not the ring!
Anybody that knows?

Rudy

 

[johnstij]

Hi Rudy.
On sheet 5 showing the piston drawing the note says " make the groove .105" wide and .110" deep for 094" section by 1" diam O ring"
Ian

 

[Rudy from Norway]

Thanks! How could I miss that... lets blame my metric eyes

While we are at it. How important is it to harden the wrist pin? I have made it from dril rod and not bored it out.

Rudy

 

[johnstij]

I did not harden mine but I think the idea of drilling it out is to lighten it a bit.
I build mine a couple of years ago. Here is a short video of it running:-

 

[Rudy from Norway]

Thanks John. I had already found that video. Runs very well!
I´m soon to be starting my own. Very exited, it´s my first IC engine and my second build.
Rudy

 

[Pierkemo]

Knap gemaakt Hanss, fijne modelbouwer!!
Toi, toi!

 

[Rudy from Norway]

Made the O-ring seal between the cylinder sleeve and block, or water hopper as the plans say. Think it will work. As I mentioned I have a small play in the sleeve to block fit. Some of the oil from the drip oiler would be leaking away from the hole in the sleeve and out under the sleeve. Maybe the gap would be filled with oil and stayed there. Anyway, I made a fix for it.
Bored the hole in the block with a 5mm endmill. Made a bushing with the same profile as the diameter of the sleeve outside (+1.5mm). Inserted a tube to make a support for the O-ring. Lock-Tite to hold the parts in place.

Rudy

Here is the finished O-ring seals. I´m using a flexible piece of something to press down the O-ring when I push the cylinder sleeve in place. Works fine.

 

[Rudy from Norway]

Painted the engine block. Started to assemble the finished parts. This is really a big moment, seeing the final stage of the long build. Posting some random pics of the parts so far.
Have yet to make a nice base, tank and ignition.

Rudy

 

[Johno1958]

Rudy you've got to be chuffed. That is "sweet as".
Sorry Rudy in Australian slang that means absolutely beautiful and you have to be happy about it.
Cheers
John

 

[Rudy from Norway]

Thanks John. Yes, I´m happy about it. Also this engine is something I will recommend. The construction is very good. Making engines from bar stock is also a good thing, especially for beginners. I have done several of the parts two-three times. Don´t be put down of the small price for the plans. This is nothing compared to the man hours we spend making an engine.
Rudy

 

[Rudy from Norway]

Have been busy pleasing the wife refurbishing the living room. However, my Farm Boy did it's first puffs. Didn't get hold on any fuel, so I just placed a butane torch in front of the mixer and let it sip some gas into it. Works just perfect! Not to recommend though. There will be some unburned gas in the room.
I soon run into problems with the ignition. The micro controller on the pcb died. Also the hall sensor. Maybe the car coil is to heavy for it? Run it on 7,2V. Made a new electronic ignition of my own construction, same problem. I will deal with it when the house is done and come back with a write up.

The initial run was OK, but after that the compression disappeared. Use an "ordinary" O-ring. Polished the cylinder to a better finish and put in a new O-ring. Seems to be much better now and it ran better, until the ignition quit..

I have plans for a propane demand valve. Think I will go that route. Propane burns so clean and leaves no smell from the exhaust.
Made a ignition circuit similar to the PIC TIM, but with analog circuits (NE555). It makes a series of (approx 6) sparks as long as the hall sensor is engaged. When the rpm increases, the number of sparks decreases. If I get it right I will put up a diagram of it.
Now I try to get hold on a suitable ignition coil.

Rudy

 

[DavidLloyd2]

Rudy - That is absolutely beautiful,

Thanks for that video
DavidLloyd

 

[a41capt]

What a beauty! Excellent running machine and the finish is amazing. Thanks so much for sharing.

John W
Camp Verde, AZ

 

[Rudy from Norway]

Glade you like it. After all, not many around the house understanding what we are doing and the effort we have to put into this hobby.
I like this build. Think I have watched every FarmBoys out there.
There is stil some work. I'll make a stand for it, and a tank (Even if I run it on propane). I will also make new gears. The ones I have are making a bit noise. I made them with a gear cutter grind by eyeballing. I have bought proper gear cutters now.
There are two things I will point out for those wanting to build one (newbies like me). The first is make sure the block is line bored straight. I did't manage to achieve that with drill bit and reamer. Holes didn't line up, at least not with the accuracy I wanted. Had to use a boring head.
The other is the collets on the flywheels. If not machined and bored absolutely true, the flywheel will wobble.
I have described this earlier in this thread.
Rudy