Farm Boy #876 - Mike's Build

[Kim]

Very nice work on some intricate parts! 

Kim

[Roger B]

Glad to see you back on this build   

[Dalboy]

Going back to September last year you took the cam boss down to size. I am starting to do this part now but the drawings I have show the height of this as two different measurments the rearward view when looking at the drawing works out at 0.075" yet the Bottom view shows it at 0.105 which size did you follow.

And finally I used a 1/2" end mill to reduce the height of what will be the cam boss to the height spec'd in the drawing.





Mike

Many Thanks Derek

[mikehinz]

Going back to September last year you took the cam boss down to size. I am starting to do this part now but the drawings I have show the height of this as two different measurments the rearward view when looking at the drawing works out at 0.075" yet the Bottom view shows it at 0.105 which size did you follow.

And finally I used a 1/2" end mill to reduce the height of what will be the cam boss to the height spec'd in the drawing.


Mike

Many Thanks Derek

Derek, I did see exactly the same discrepancy regarding the boss height that you noted.  I modeled the frame assembly, gears, and cam in Fusion360 and after a bit of playing around I made that height .105"  That ended up working fine as there was about a .025" gap between the cam and the boss that I ended up filling in with a thin SAE660 bronze washer that I made.  I don't think going lower in height hurts anything but you might end making a thicker spacer to take up any excessive slack.  You really can't tell what you need until you get it all assembled.

The other critical point that you should note is to make sure that the distance between the C/L of the crankshaft and the C/L of the camshaft mounting hole is correct to give your gears the proper engagement when assembled.  I had to modify that distance a bit as compared with JEH's original drawings.  I think I documented that in my build so take a look at that detail.  Also note my caution with the gear selection.  I used 32DP gears vs he 48DP gears that JEH spec'd.  The PD can be made the same BUT the OD of the 32DP gears is slightly larger than the 48DP gears, which I didn't realize at the time.  That caused me to make some mods to the catch lever during the installation phase.

In any case, I hope this info is helpful and good luck on your build!

Mike

[Dalboy]

Thank you for that, I was thinking that I would go for the 0.105 and at least if it was the smaller one I could remove material. But as you say at that measurement everything is fine.

 Luckily I have the correct gear cutters that are on the plans.

I do sit and go over the plans many times before committing cutter to metal in the hope that I do not make mistakes(That still does not stop making the odd mistake and not always down to miss reading the plans)

Derek

[mikehinz]

Ok, back to today's posting.  This is the built for what I consider to be the trickiest of the tricky bits for this engine, that being the Exhaust Valve Arm Bracket.  I think there's 2 ways to do this part, one way is to start with some round stock and the other is to start with square stock.  I decided to try the square stock as a starting point and I did have some 1/2" key stock on hand so that's the material that I started with.  I also modeled the part as I wanted to add a few reference dimensions that the JEH drawing didn't have plus modeling parts help me think through the order of operations necessary. 

In any case, here's the drawing that I worked from.



I scribed some reference lines on the stock and after locating the end and edges, I drilled and reamed 1/8" hole in the spec'd location. 



Next was reorienting the stock in the mill vise and milling the sides of the stock to the required dimension.



Orienting the stock again to create the specified 21 degree angle.  I was just using a 1/2" HSS end mill.  The tricky bit is knowing how far down in Z to go to stick to the spec'd dimensions.  This isn't completely obvious once you start contemplating the drawing.



Then over to the lathe to create the round section of the part.  I have some square 5c collets so this makes it quite easy to hold such stock.  Note also that left the stock long enough to have a handling stub.  Note that since it's necessary to get close to the 'top' of the part, I used a parting tool turn the round portion.



And here's the part with the lathe operation almost completed.



And here's a handy tip.  JEH's original drawing calls for a flat to land a set screw on that should be at a 14 degree angle from the horizontal axis.  I couldn't figure out how to accurately place that feature, so I decided to just turn a reduced diameter right where the set screw will land.  This turned out to be much easier and actually better when installing the part, as you can orient it exactly as required. 



And here's the part after parting off the handling stub.



You'll note that there was some leftover material right at the base of the rectangular section, so I used an end mill to remove the excessive material on each side.  This was mostly done visually as there was really no way to establish Z zero.



There needs to be a .158" slot milled through the center of the part, so I put the part in a 5c collet in a collet block and oriented it visually with a square.  I figured this would be plenty close enough.



Shown is milling the slot after securing the collet block in the mill vise and making sure it was vertical.



And finally, I rounded the end on my belt grinder and polished it up a bit on a Scotch Brite wheel. 

View 1



View 2



And finally, the first trial fit on the engine.  Luckily it all fit!!



Enjoy!


Mike

[RReid]

Nice job on that tricky part, Mike. Looking good!

[mikehinz]

First, thanks to everyone following along.  I really appreciate it!

Next up, a few more simple parts.

First up, the Governor Shaft Spool.  This is a simple piece of 3/4" steel and I did have a bit of mystery metal on hand, so that's what I used.  I think it was just some 1018 cold rolled based on how it turned.  The only trick to this is the slots.  I simply used a square collet block and mounted it in the mill vise as shown, found the end and C/L and milled out the two slots.  With the collet block, I could simply turn it 180 degrees, position it to the edge of the mill jaws and mill the other side.



I'm not showing the lathe work as it's pretty basic, just drilling and reaming the center hole then turning the groove and parting the part off.  Here's how it looks when test fit to the crankshaft.



Next parts are simple, yet tedious.  I needed to make 5 small pins for the various joints on the engine.  The best way to do this, at least IMO, is to start with drill rod with the diameter equal to the head on the pin required.  And since this is all thin rod, sawing isn't terribly good so I tend to use my Foredom handpiece with a cutoff blade and then cut the required number of pieces, leaving them long so I can grip them in a collet to turn down the small OD.  My tool is actually a hybrid, that being an actual Foredom handpiece but driven by a Harbor Freight motor and flex-shaft. 



And here's the pins with the small diameter turned to the required diameter.  All simple, yet tedious lathe work, taking very light cuts.



Each of the pins needed a hole for a retainer so i mounted each in a collet block and drilled thru with a #64 drill.  I first lightly touched each pin with a center drill so I could get the bit started straight.



Next each pin was parted off to give the spec'd head height and then cleaned up/trimmed using a sharp insert.



And finally, the collection of completed pins.



Here's another simple part, the rocker arm roller.   I don't show any of the operations as they're dead simple lathe work.  I just started took a piece of 1/4" drill rod, drilled and reamed the center hole and parted it off to length. 



Here's the roller mounted on the rocker arm using the pin that I previously made.



Next is the Governor Catch Lever Roller.  Again no pix of the lathe operations as it was simply taking some drill rod, drilling and reaming a center hole and parting it off.  The mounting pin is just a piece of 1/16" drill rod cut to length using a parting wheel on my handpiece and gently smoothing the end. 



Here's the catch lever roller mounted on the arm.  The pin was simply pressed into place since it was a light interference fit.



Here's the catch lever mounted to the engine and this is where I realized that I'd made a mistake in using 32DP gears vs the 48DP gears that JEH spec'd.  Even though I had matched the PDs, the OD of the gears is slightly larger so the catch lever interfered with the cam gear as it moved in and out.  What I ended up doing was filing away the interfering surface on the lever until I could move it freely through it's entire range.  Luckily there was enough material on the lever that I could do so.  But I would advise others to use the gears as JEH specified. 



There's one more small part to finish the catch lever, the Speed Adjust Screw Body.  I only had some .156" brass rod, so I put a piece in a collet and turned down the OD to .125 and drill and tapped the 2-56 hole as spec'd.  I use a spring loaded tap follower and a very small tap handle for these small taps.  This makes it MUCH less likely to break a tap off!



And here's the speed adjuster mounted in the lever.  It was a close fit and it added just a small drop of Loctite 638 to secure it. 



And I'll wind up this post here as it's probably getting a bit long.

Enjoy!

Mike

[mikehinz]

I'll post the build for one more part/assembly for today, but it's a big one, the governor assembly with the weights, pivots, arms, fingers, etc. 

First are the weight arms.  I don't show any of the operations as this was simply cutting a couple of bits of 1/8" brass rod to length and threading one end of each to 5-40.  Here are the finished parts.



Next were the spring mounts.  I do show a couple of the operations on these parts.  I mounted a piece of 1/8 brass rod in a collet block and milled the flats on 2 sides and then drilled though the flats with a #55 drill.



Here's a bit of a time/material saving trick.  I used a larger piece of brass and made each end as shown.  Then I went to the lathe and parted each end off and ended up with the 2 required parts.



And here are the completed weight spring mounts.



Next was the pair of weight fingers.  Again, a piece of 1/8" brass was mounted in a collet block and created the small radius by moving in from each side equally with a small end mill.  Then each end was parted off in the lathe. 



And here are the completed weight fingers along with the brass rod stock.



Next is the pair of arm pivots.  Starting with a piece of 1/4" brass rod, I drilled thru with a #42 drill leaving a bit extra length for holding.



Then over to the mill with the part mounted in a collet block.  Two holes were created at 90 degrees to each other.  First, each hole was drilled to the center using a#44 dill and then reamed .125" at each location.  The collet block makes it easy to achieve the necessary orientation.



Then each part is parted off back in the lathe and here are the completed pivots.



Next up are the governor weights.  I purchased a few 5/8" brass balls from Amazon as the starting point.  In order to keep the orientation between the top and bottom of the balls, I first center drilled and then drilled all the way through with a #38 drill, which is tapping size for 5-40.  I don't show the operation, but I then tapped that end 5-40 1/2" deep. 



Then to maintain orientation, I ran the drill all the way through the ball from the other side and used that to align it and remounted it in the collet, but of course, turned around.



Then from that side, I enlarged the hole to the spec'd depth with a #31 drill and then reamed 1/8" 



And here's one side of overall assembly after the arm and finger were soldered to the pivot.  I used Harris Stay-Brite 4% lead free solder along with a bit of Oatney tinning flux.  The alignment was a bit tricky and I ended up lightly dimpling the end of each rod so each would stay in place when soldering.  I used solder vs silver braze as I think the solder is sufficiently strong and I didn't think the setup would last thru a much higher temp process.  The spring mount were mounted into the balls using Loctite 638.



And finally here's the entire assembly loosely mounted with the shaft spool on the bench just to make sure that everything roughly fit together.



Not being sure that this assembly would work properly, I made a very basic test jig to try it out.  Here are the basic parts I made, just a bit of drill rod with a hole tapped in one end, and an AL bit with a couple of holes to fulcrum arm assy to it.



And here's the test assembly all setup and ready to go!  I made a spring out of some .015" music wire just guessing at how many turns and how strong it should be.



And just to show it all works, here's a slow-motion video of the test being conducted.  I just spun the test assembly in a variable speed drill motor.  You can see the balls moving in and out and most importantly you can see the governor shaft spool moving in and out as the rpm changes, through, I was guessing, something approximating the actual engine operating range.

<a href="https://www.youtube.com/watch?v=GbtVMunqR-w" target="_blank">http://www.youtube.com/watch?v=GbtVMunqR-w</a>

This all turned out good in the end, but it took some time to get here! 

That's all for today.  I'll try to finish off the build log of this tomorrow.  I'm just a bit tired of copy/pasting for now.

Enjoy!

Mike

[Kim]

You're making great progress!  That's a lot of tiny parts you completed here!   
Kim

[Admiral_dk]

I'll say that you have been very busy in the small detail department lately .... and the reward has been a working Govenor 

Per           

[mikehinz]

After a bit longer of a break between posts than I intended, I'm back to try to document the carburetor build today.  My excuse is that I've helping my brother with the rebuilt of an old house he's going to move into.  We just finished the kitchen cabinets installation.  That turns out to be tricky in an old house!

In any case, on to the carb build!

I followed JEH's drawings exactly and I found them to be completely accurate and clear, so no need to build my own model of the carb.  As he suggested, i started some some PM Research castings.  In this case, I purchased a 5/16" casting tree and here I've just sawn off one of the 90 degree elbows to start working on it.



I fabricated a quick and dirty jig to hold the fitting, but this turned out to be far from optimal.  The biggest issue is that it turned out to be too long so turning it in the mill vise didn't work out so well.  Plus it was just a waste of material.  The pins are 1/8" dowels secured with Loctite in one half of the jig and the holes were a close fit in the other half.   



And here's the fitting secured in the jig after I drilled two intersecting holes just under the fitting body diameter.  No pix of that as that process was straightforward. 



And here's the first process, just milling each end of the fitting flat using a 3/8" end mill.  Here's the problem with this long fixture.  It's too long so that when I tightened the mill vise, it tended to spread the top so I secured the top with a Kant-Twist clamp before tightening the vise.



Then as per the drawing, I drilled each side with a 'K' drill to .410".  This worked fine and came out exactly as per JEH's drawing.



And here's the elbow after a bit of filing and work with a Scotch Brite wheel. 



I don't show the lathe work on the head/pipe elbow as it's simple lathe work.  I secured the pipe into the elbow using some high temp Loctite 620 retaining compound.  Here's the 2 parts prior to securing them together. 



And after Loctiting them together.  Not terribly exciting!



Here's the needle knob.  I don't show the lathe work on this as it's pretty simple.  I started with some 5/16" brass rod, knurled a small section, drilled and tapped the 2-56 hole in the center and turned the small OD and parted it off. 



Here's the first delicate operation, making the fuel needle.  I started with some 2-56 all thread, set the compound to 4 degrees and started taking VERY gentle cuts using a very sharp ccmt insert.  I think I ended up doing a bit of filing on the part when I got close. 



And here's the fuel needle and needle knob assembled.  They were secured together with a drop of Loctite 242 Threadlocker. 



The next few pix are of the process of making the mixer body.  I started with a small piece of 1/2" brass hex bar and chucked it up in a hex 5c collet.  The two OD's were quickly turned with a ccmt tool and then I used a tool holder as shown that holds a ccmt insert so that one of the 40 degree sides can be presented to the work.  That makes as nice rounded feature as shown.



Next was drilling and reaming through the center of the stock and here I'm putting a small chamfer on the ID as per the drawing.



Parted off the work.



I reinserted the part into the collet and using the 40 degree tool and a small radius tool, I formed the end feature, not exactly as JEH's drawing calls for but close enough as this is all for appearance.



Then over to the mill after installing the part into the 1/2" hex collet in a hex collet in the milling vise.  This way I was able to easily index the part to do the operations on the hex faces as per the drawing.  Here I'm reaming 1/8" thru as per the drawing. 



After indexing the part using the hex collet block, I spot faced, drilled #43 and tapped the part as per the drawing.



Finally, here's the finished mixer body with the set screw installed in the tapped hole.  This all came out well.



The last, and most scary part to me, is the mixer spray bar.  It's scary just because of the very small holes to be drilled. 

Just to give everyone a sense of perspective of the drill sizes involved, here's a pix of my 1/2" drill index with my newest drill index laid in the lid.  The small drill index ranges from #61 to #80 (.040" to .135"). 



Here's the brass round stock and drills to be used.  Stock is 1/8" and the drills range from #50 (the largest) to the #76 (the smallest)



I took the approach of drilling the #76 cross hole first as I was scared of drilling each a small hole that would cross the interior hole.  I thought it would be better to drill thru the solid material vs fighting the drill starting on the 2nd interior surface.  I did touch the stock with a small center drill prior to starting the small drill.  Note that I DID use a sensitive drill attachment here, that I'll show in a subsequent pix. 



And here's the sensitive drill attachment that I used.



And here's how it's used in the mill.  It's simply held using a 1/2" R8 collet. 



Then over to the lathe with the work held in a 1/8" collet.  Here I've just drilled #50 and am tapping 2-56 using a spring loaded center and a very small tap holder.  This gives a good feel while tapping so that snapping off the tap can hopefully be avoided!



Then I turned the part around in the collet and first drilled .370" deep with a #55 drill.  Here I'm using the sensitive drill attachment to drill thru the part with a #65 drill.  Luckily the operation worked and the drill didn't snap off!!



And finally, here's the assembled carb!  Everything fit together well but we'll have to wait to see if it actually works!!



So this completes several days of work on one of the more complex parts on this engine. 

Enjoy!

Mike

[Kim]

Nice work on the carb!  Looking forward to the field trials    

Kim

[Dalboy]

Looking great and learning a lot on how to approach these small parts when I get to them

[mikehinz]

Gents, thanks for following along with this build and for this nice comments!

Mike