Author Topic: Farm Boy #876 - Mike's Build  (Read 3693 times)

Offline mikehinz

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Farm Boy #876 - Mike's Build
« on: September 18, 2022, 10:29:16 PM »
I've long admired the Jerry Howell designed Farm Boy.  Last year i completed an Upshur hit-n-miss engine and got that to run so I thought I might possibly have enough skill to get this engine built, even though it's more complicated in many respects.  So I ordered the plans and started going through them carefully. 

The front and rear frames and the water hopper weren't completely clear to me so i decided to start by modeling those pieces in Fusion 360.  That helps me to visualize how everything should go together and also starts to clarify in my mind, the Order of Operations, work holding, etc.  The JE Howell plans are excellent and I found almost no mistakes or omissions.  Any CAD modeling I did was really not necessary except to enhance my understanding of a particular part and/or to develop a drawing with ordinate dimension which I generally prefer. 

I THOUGHT I had some scrap bit of AL laying around that would be big enough for the major frame elements, but I was wrong.   So the first step was to get some material.  That will be in the next post.

I do want to explain something.  I've already gotten through most of the build, so I'll post the built log and photos fairly quickly until I catch up with where I'm actually at now.  So don't take the pace of posting as how fast I work!  I'm actually quite slow!   

I'll post fairly detailed photos and descriptions of what I found to be tricky so hopefully this build log will help others should they decide to tackle this very interesting engine.

Enjoy!

Mike. 
« Last Edit: September 22, 2022, 12:35:54 AM by mikehinz »
MIke
Wichita, KS, USA

Offline mikehinz

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Re: Farm Boy #876 - Mike's Build
« Reply #1 on: September 18, 2022, 10:57:47 PM »
Since I needed some larger aluminum bar stock than anything I had on hand, and I live on the outskirts of Wichita, KS I took a trip to the famous Yard Store and spent an hour or so with measuring tape in hand, to find a suitable chunk of Al.  Here's a picture of just a small part of this metal supplier.



Surely there's a Farm Boy lurking in there somewhere! 

The Yard does stock some new material, mostly round bar stock, but the majority of the material is Al drops and off cuts from the local aircraft industry.  I think the cost of the drops is around $2/lb, so it's by far the cheapest place to purchase stock.  Most of it is 6061 with some 7075 and 2024 thrown in occasionally.  The only downside of purchasing the cheap stuff is that it's almost never square or to standard dimension or it even has a clean face. 

After some searching I selected this piece, somewhere around 2 1/4 x 4 1/2 x 30".  Plenty for this engine plus some left for future projects. 



Then over to the horizontal bandsaw to cut off 3 slightly oversize chunks.



Starting to square up and bring to size one of the chunks.  I think I was using a 3/4" 2 flute end mill along with running my Unist mql system to avoid chips welding to the cutter.



I used a fly cutter for the final finishing passes in order to leave a good finishing on all sides.



And after a considerable amount of time and a lot of chips produced, I ended up with 3 properly sized blocks of Al that will become the front frame, the rear frame and the water hopper.



That's it for today's posting.  Next will be starting to machine the frame and water hopper. 

Enjoy!

Mike
MIke
Wichita, KS, USA

Offline Bearcar1

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Re: Farm Boy #876 - Mike's Build
« Reply #2 on: September 18, 2022, 11:07:12 PM »
Mike, I just recently took ownership of a set of drawings for that engine and will be following along with great interest. That yard store looks like someplace I could spend an afternoon browsing around in. Good luck...


BC1
Jim

Offline RReid

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Re: Farm Boy #876 - Mike's Build
« Reply #3 on: September 19, 2022, 03:27:36 AM »
Looking forward to seeing this one come together, Mike.  :ThumbsUp:
Regards,
Ron

Offline mikehinz

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Re: Farm Boy #876 - Mike's Build
« Reply #4 on: September 19, 2022, 10:03:53 PM »
So on to some further work on the front and rear frames and the water hopper.  There's a LOT of work in these 3 pieces so I'll probably post this across several entries.  You'll also see some skipping around between pieces as I tend to do whatever work I can whenever I have a particular setup.  For example, if I have my 4 jaw chuck installed on my lathe, I'll do as much work as possible before I change over to collets or the 3J. 

I'm terrible at marking out, so I tend to use my mill to do whatever marking out I need to do.  Here I'm putting a small center hole in one of the pieces.  DRO's, edge finders, and DTI's are wonderful thing to achieve some pretty high accuracy!



Here's the water hopper and front frame with the center holes positioned for reference for the next ops.  For the stock for the water hopper you can see a center hole on the front and on the top.  You can no doubt visualize what's coming next. 



Over to the lathe with the 4j chuck installed.  You can see the general way i center an offset feature in the 4J.  The device in the tail stock is home made.  It's a thin rod about 14" long with a 60 degree point on the end and is held in a spring loaded base that's secured in the tail stock drill chuck.  Then I use a dial indicator to get the rod to run true near the stock.  I find that this method works well.



Once the center of the feature is found, I drilled thru up to 1"



Then I switched to a boring bar and bored all the way thru to 1.202" as per the drawing and then counter-bored to 1.50" ID to the depth spec'd on the drawing.  This is all done from the 'rear' of the front frame and this creates the first feature required.  The CAD model I built was really helpful as I added dims from whatever surface(s) that I used for reference 



And here's the part with the lathe work done laid on the drawing.  You can see what the just created feature is when comparing to the isometric view on the drawing I made of the part.



MIke
Wichita, KS, USA

Offline mikehinz

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Re: Farm Boy #876 - Mike's Build
« Reply #5 on: September 19, 2022, 11:15:22 PM »
Next up is the water hopper top.  I wanted to make this now as I want to check the fit on the water hopper whenever I make that vs the other way around. 

I had some 2' "Al bar stock so I chucked a bit of it up and turned the OD to 1.782" as per the drawing.  I also drilled a .750 hole thru the center of the stock and here I've set the compound to 20 degrees and am starting to form the internal taper of the top.



Next I switched to a 3mm carbide round grooving tool and started forming the outside taper.  The compound angle stayed the same and simply progressed the cut until I got to the specified wall thickness of .100".  This tool also left a nice radius at the root of the cut very much like JE Howell's drawing. 



Parting the hopper top off using a 2mm carbide parting/grooving tool.



And here's the finished hopper top on the drawing.



Then back to the body of the water hopper.  I centered on the previously made center hole and then using a 1" drill to remove as much material as I could from the block.  Here I'm finishing up with a boring bar, creating a 1.720" hole and then putting in a slight counter bore of 1.780" to .170" depth. 



Here's the top feature of the part laid on the drawing next to the isometric view.  You can see the other center hole on the front of the part which will be used to reference the thru hole and counter bore(s) for the cylinder sleeve. 



And lastly showing the top fitted into the water hopper body.  Fit was good and I'll end up fastening it using JB welding, but that will come much later.



That's it for today's postings.

Enjoy!

Mike
MIke
Wichita, KS, USA

Offline cnr6400

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Re: Farm Boy #876 - Mike's Build
« Reply #6 on: September 20, 2022, 02:52:54 AM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
"I've cut that stock three times, and it's still too short!"

Offline mikehinz

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Re: Farm Boy #876 - Mike's Build
« Reply #7 on: September 20, 2022, 08:10:36 PM »
Before drilling and boring the hole for the cylinder liner in the water hopper, I wanted to make the cylinder line first in order to be able to test fit it to the hopper.   

I started with some 1.5" cast iron stock that I'd ordered some time back from Hobby Metal Kits (highly recommended!).  After centering it the 4j chuck, I turned the 1.200" OD and the 1.355" 'ring' near what will become the top of the liner.  Then i center drilled and drilled just just under 1".   I think that's a 7/8" drill that I'm increasing the ID with. 



Then I switched to a boring bar and carefully brought the ID to just under 1.000"  I do like machining cast iron as it always cuts easily with small chips.  I don't mind the carbon that gets everywhere either!



Next I put a small chamfer to make installing the piston a bit easier.  That's just a HSS tool that I think I'd ground or threading, but it works fine to put a mild chamfer on a part also.



Next I used a 2mm carbide parting tool to create the ring at the top of the liner and then to part it off from the stub stock. 



And here's the cylinder liner on the drawing compared to the isometric view and the bottom view.



There's a hole oil that needs to be drilled at an exact distance from the front of the liner.  I VERY lightly clamped the cylinder in the mill vise, found the center and the right edge of the liner and then moved x to the spec'd distance and drilled with a #40 as spec'd.    I also very lightly scored the very front edge of the liner at the top center with a small center drill in order to create an index mark which is needed when installing the liner in the hopper.



And last operation on this part was lapping the ID.  I used a 1" Acrolap and Timesavers lapping compounds, mixed with just a few drops of oil.  I progressed thru the 3 grades of the Timesavers and when finished, the ID of the liner was very smooth and close to a fully polished finish.  I turned the lap with my lathe set to the lowest speed of 90 rpm and then held the cylinder liner by hand while running the lathe with the jog button.  I did it that way as I could instantly release the button should something go wrong.  It's always interesting when lapping that you can feel the process progressing.  It starts out rather 'lumpy' feeling and the lap needs to be tightened quite often.  As things progress the feel gets much smoother and very little tightening has to be done. 



So that's one more part completed. 

Enjoy!

Mike
MIke
Wichita, KS, USA

Offline mikehinz

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Re: Farm Boy #876 - Mike's Build
« Reply #8 on: September 22, 2022, 12:35:06 AM »
In this post I'll show the rest of the work that i did to complete the hopper.  This part ends up with a LOT of labor to get it completed!

I decided to go against the Howell's suggestion on the drawing and did the thru drilling from the front side, mostly to eliminate one additional setup step.  Here I'm using an extended length drill to drill thru in 3 locs as per the drawing.  I actually generated my own drawing for this as I used the technique of centering up on the bore and then using the DRO stepping over in x and y to the required locations.  I did center drill each location and when drilling, I backed the drill out quite often as it's very easy to get the chips packed in tightly and end up breaking a drill. 



Then I made the counter-bores at each location using a 1/4" 4 flute end mill.  I know the bottom of the hole isn't perfectly flat using this technique, but it's plenty good enough, as long as the head of the screw doesn't protrude from the hole.



There were 4 additional holes to be drilled and tapped on the front so I again just located each position using xy coordinates on the DRO.  I spot drilled, then drilled tapping size and here I'm tapping using a spring loaded tap follower and a small tap wrench.  Plus I'm using a spiral fluted tap as it's a blind hole and I find the spiral flute taps work well in this situation.  I always try to use a tap follower as these smallish taps were way to easy to break if you're not careful!



The next operation was to flip the hopper over and drill the oil access hole on the back side of the hopper.  Again I centered the body using a DTI mounted on the spindle referencing the cylinder liner bore.  Positioned using the DRO, spot drilled, drilled #42 .475" deep.  Shown is putting in a .060 deep counter bore with a 1/4" end mill.  All that went well.  You can also see the thru holes drilled from the front came out in the correction locations on this back side. 



Now comes the tricky operation of drilling an intersecting hole from the cylinder bore to the hole just created.  This is to create a path for the oil to flow from the drip oiler to the cylinder.  The first issue is locating exactly where to start the hole.  The drawing specifies the location from the front of the hopper, but since I know the OAL, I decided to locate from the back side.  So while the hopper is still oriented with the cylinder hole vertical, I decided to use a boring bar to mark a mark on the ID, indexing from the rear surface and measuring the depth via the quill DRO.

Here I'm locating the surface and setting the quill DRO to zero.



Then I lowered the quill to the spec'd depth, moved the table until the tip of the insert just touched the cylinder hole ID and then lightly scratched a mark at that location.



Next I tilted the hopper to 18 degrees using some angle blocks (angle was suggested on the drawing by Howell) and then visually aligned the center of the end mill to the mark using x movement only.  I didn't move y at all as the part was already located in y from the previous step.  I used an extra long 1/8" end mill to mill a flat surface for the subsequent drilling operation.  This actually went shockingly well but I barely had enough room even with the extended length end mill.



Then i center drilled with an extended length center drill.



And finally drilled the intersecting hole with a #42 aircraft drill.  Luckily I'm located near Wichita, KS so aircraft drills are easy to find here!  I could feel when the drill broke thru into the previously drilled hole. 



Here's a pretty good picture of the two holes after both operations were completed.



You might reasonably ask, are you completely sure have intersecting holes here?   We'll there's  a quick and easy way to prove that!  I'm just shining a light thru hole drilled through the face and observing the light that appears at the hole in the cylinder bore ID.  The camera actually shows it more clearly than I could see it with the naked eye. 



So the next operation was to round the bottom of the hopper.  I'll comment more after the pix, but I don't think that this was the best way to do this.

I used my 6" rotary table and made an alignment system consisting of a small steel pin that fit in the rotary table bore on one end with the other end fitting into an Al rod machined to fit the hopper cylinder bore as closely as possible. 



I centered the rotary table under the spindle and secured the hopper to the RT using the alignment jig I made and 2 step clamps.  I offset the mill table in y only and walked in with a 1/2" extended length end mill.  As you'll note, this wasn't long enough to completely round the bottom. 



So I turned the hopper over and started the rounding operation from the other end.  You can see in the pix how I progressed the cut inward using y only and swinging the part around the cylinder axis.  I took pretty light climb cuts as this seemed to keep the chatter to a minimum and gave the best surface finish.



And here's the completed part on the drawing.  If you look closely you'll start to see the problem.  It turns out to be very difficult to start and stop the rotation of the part exactly in the correct position so that the cut progresses neither too little or too much.  Plus even though it's close, you can see the difference between the operations from each end.  There's  a little difference in position from each side and each ends up at a slightly difference place.  My solution is going to be body putty followed by sanding and painting!   



So having done it this way, what would I do differently the next time?  I think that I should have oriented the RT and the hopper so it rotated around the horizontal axis.  Then I would have lowered the spindle and made a series of cuts moving in x and rotating between each cut.  That way there would have been no swapping of ends and I'm of the opinion that it would have been much easier to judge where to start and stop the rotation.  And as an added bonus, i think the cuts would have been smoother with less chatter, since the end of the EM would be engaged vs a long length of the flutes.  If anyone has any suggestions, please feel free to comment.  I'd love to do better next time. 

And the last operation on this part was to round over the edges of the top and ends.  The Howell drawings indicate a .125" radius on the top and a .093 radius down the sides.  I decided to simplify that a bit and use a .125" radius rounding over end mill for all the corners.  Here I'm rounding over the rear surfaces.  I did practice quite a bit on some scrap before doing the actual part.  What I found was that you either have to make some cuts to determine exactly where the radius you're creating will be located at or you have to come up with a process.  What i ended up doing was to look up the nose diameter of the end mill and used that number to determine when that nose would just contact the work.  Then prior to making a cut, I'd move the cutter until it was almost off the edge of the work and lower it until it just scratched the surface of the work.  Then to make the cut, whether in one pass or multiple passes, simply leave the cutter at the previously determined depth and move in x or y as necessary to get to the full depth of the cut.  I also found that climb milling gave a massively better finish than conventional milling. 



And at last, here's the hopper completely finished, well except for securing the top in place and doing the body work on it.  But that won't happen until everything is assembled and tested.  This part is a LOT of work and the further I got into it, the more nervous I got that I'd scrap it and have to start over.  Anyway, it's a relief to get that done!



All for now.

Enjoy!

Mike

« Last Edit: September 22, 2022, 01:09:58 AM by mikehinz »
MIke
Wichita, KS, USA

Offline RReid

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Re: Farm Boy #876 - Mike's Build
« Reply #9 on: September 22, 2022, 01:26:44 AM »
That's a heck of a hopper, Mike. Nice job! I think I would agree with your alternate approach for doing the rounding "next time".
Regards,
Ron

Offline cnr6400

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Re: Farm Boy #876 - Mike's Build
« Reply #10 on: September 22, 2022, 02:55:12 AM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
"I've cut that stock three times, and it's still too short!"

Online Kim

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Re: Farm Boy #876 - Mike's Build
« Reply #11 on: September 22, 2022, 03:01:05 AM »
Wow!  That is some fine whittling there!  Beautiful work  :ThumbsUp: :popcorn:

Kim

Offline Admiral_dk

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Re: Farm Boy #876 - Mike's Build
« Reply #12 on: September 22, 2022, 07:32:59 AM »
Great descriptions and result  :praise2:

Looking forward to see the rest of the journey  :cheers:

Per

Offline Krypto

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Re: Farm Boy #876 - Mike's Build
« Reply #13 on: September 23, 2022, 03:18:02 AM »
Looking forward to this build!
My Workshop Blog:  http://doug.sdf.org/

Offline mikehinz

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Re: Farm Boy #876 - Mike's Build
« Reply #14 on: September 24, 2022, 09:21:26 PM »
First, thanks to all that are watching this build log and making comments.  They are always appreciated, and of course I appreciate any good tips or techniques!

So, on to the next part on this build, the front frame.   

In one of the previous posts, I'd already squared up and brought to size a chuck of Al for this part, plus on the lathe, I'd bored the hole thru the entire block and put the counter bore on the back side, all as per JE Howell's drawings.  The next step in my planned OoO (order of operations) was to create the profile(s) as viewed from the side.  I do all the work using my DRO for positioning, but because this was a fairly complicated series of operations, I blued up one side of the part and marked it out just as a reference.  That way I could double check myself to make sure I wasn't about to make a tragic mistake. 

Here's the part marked out and ready to go into the mill.



That arc on the upper right surface doesn't actually go all the way to the back of the part, so i first milled away that straight portio with the result as show in this pix.



Then back in the mill vise to chew away most the material that needed to be removed in the upper right area.  I stayed well short of the marking lines at this stage.  That's a 1/2" roughing end mill and it does chew away Al fast!



Next I positioned the mill spindle over the center of the arc which is actually not on the surface of the part.  Then I took repeated passes advancing the boring head between each pass. 



And in not much time at all, I ended up with what you see in the pix.  I kept progressing the boring operation until I just met the layout line at the front and the previously milled away horizontal surface at the rear.  A bit of measurement also confirmed that the radius achieved was as per the drawing.  How can also see how this feature intersects the previously bored hole and counter bore to create a good portion of the rear of the part. 



Then back into the mill vise.  I didn't show the operation but i put the mill spindle over the center of the arc that forms the front radius.   Then I drilled thru in steps and ended with a 1" drill.  Then i switched to the boring head and progressed the cut until that arc being cut met the front and bottom layout lines.  I also confirmed the dimensions by measuring. 



Next I reoriented the part in the mill vise and started chewing away everything that didn't look like the front frame.  That roughing end mill works fast so this didn't take long at all.  You can see how this operations is intersecting the previously bored hole. 



Then after I got most of the material removed I switched to a convention 1/2" end mill and brought the piece to dimension. 



There was also a bit more material to remove on the base of the part so i did that with the same end mill, being careful to try to blend this cut and the previous cut as closely as possible to the arc.



And here's a couple of pix of what the part looks like at this stage of the operations.



and



Back into the mill vise in yet another orientation.  This time I milled away the material in order to form the feature that will become the joint between the this front frame and the rear frame.



Next the rest of the material that needed to be removed was done.  Again I started with the 1/2" roughing end mill as shown.



Then i finished it with a conventional 4 flute end mill.



And here's the part laid on the drawing.  I've shown it as compared with the drawing's isometric view.  So far so good!



Back into the mill vise yet again, this time oriented to drill/tap for the drip oiler.  That's a PM Research oiler that's threaded 3/16-40  in what they call their 'UST' thread.  I ended threading the hole 3/16-40 METP, but I've also noted that you thread it 10-40 and that will also work.  I always do use some thread compound prior to final assembly and I've not any problems with leaking either way.



Orienting in the mill vise again and checking to make sure that the part is straight in the vise.



Then centering the spindle over the cylinder hole and setting the DRO to 0/0.



Next drill and tapping 3 holes for 6-32 and drilling a 4th hole to provide a passage for oil from the drip oiler eventually thru to the cylinder liner. 



Next tragedy struck.  I was overconfident and entirely too aggressive trying to tap the 4 2-56 holes in the side of the part.  Of course I managed to snap off the tap on the right off on the very last hole!



And here's the remaining bit of the tap buried in the Al. 



After some weeping and gnashing of teeth, I decided that there's no way that I was going to remake this entire part, so I was determined to at least attempt a repair.  I was pretty convinced that there was no way any sort of removal process was going to work given that there was nothing above the surface, I decided to attempt to mill it out.  So I went after it with a 4 flute 1/8" carbide end mill and slowly progressed it and in fairly short order, I had a clean 1/8" hole through the part. 



Then I enlarged the hole to .1875" with a larger end mill as shown.



I cut off a short plug of 3/16" Al rod and put a very slight chamfer on the leading edge of it just so it would start into the hole.  I applied some Loctite 638 and pressed it into place using a 1/4" pin in the drill chuck, using the quill downfeed lever. 



And here's what it looked like after pressing into place and letting it cure overnight.



This time, being quite careful, I drilled and tapped the repaired hole.  This time successfully!  I used a spring loaded tap follower and a very small tap wrench handle this time. 



And here's the part with all the holes drilled and tapped, with the exception of the holes that will be added where the front and rear frames will be joined at, but those come later.  You can see the repaired hole with the plug, but that will be hidden after painting and assembly. 



Next I rounded the top using the same setup with the rotary table as I did for the water hopper.  I think that this worked better as i could more easily tell where to begin and end the rotation. 



And here's the part on the drawing after the operation to round the top was completed.



And the very last operation was to round the front corners of the base off using a rounding over end mill.  This was a pretty simple thing, but I think it adds to the appearance.



And this part is now entirely done!   This part really turned out to be much easier than I originally though it might be.  There are a a LOT of different operations and setups, but none of them turn out to be that difficult.

I hope this was entertaining and at least a bit helpful!

Enjoy!

Mike


MIke
Wichita, KS, USA