Author Topic: Muncaster Grasshopper - Work in Progress  (Read 16064 times)

Offline Craig DeShong

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Re: Muncaster Grasshopper - Work in Progress
« Reply #210 on: February 26, 2019, 12:56:25 PM »
The powder coat looks great!

"Little disasters" are just part of the game.
Craig

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #211 on: February 26, 2019, 09:54:09 PM »
Having received 3' of 5/8" 1144 steel rod, I proceeded to attempt to duplicate the broken vertical stay.  What followed was success followed by  other disaster.  That said, I think I have found a sound way forward to replace all 8 of the stays with steel.

After cutting and facing to length, I mounted the rod in a collet block, clamped in the vise against a vise stop, and zeroed the mill.



Then milled the two sides of the rod to 7mm thickness.



The vise stop allowed me to turn the collet block 90 degrees and refasten without losing my zero.  The same endmill then profiled the head.



After drilling a reaming a .251" hole through the head:



Moving to the lathe, the base is turned to .375" allowing holding from this end.  Drilled and tapped 8-32.



I reversed the work in the lathe and center drilled the head with a #1 center drill.  When I started to turn the shaft, it became clear that then live center wasn't turning.  After examination, I discovered that the sharp point of the live center had become dulled somewhere or other and didn't fit the hole.  Rather it had broken the thin wall between the hole and the edge of the head.   :facepalm:

I managed without using a center to turn the shaft down to just over 6mm by progressively exposing about 10mm of shaft from the collett.  Once I had done the entire length, I used a parting blade to try to even up the diameter, cutting about .002" deep each pass.  Then after some sandpaper and scotch brite, the shaft looked decent but not perfect.

So now the goal was to machine away the top of the head with the ugly hole.  To hold the piece, I tried clamping in a V block using a height gauge to ensure the head was horizontal.  Then clamped in the Vise and used a wiggler center  finder to zero on the center of the hole.



Then came disaster #2.  The clamp isn't strong enough to resist machining forces, so the first endmill contact caused the piece to both slide back and rotate.




Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #212 on: February 26, 2019, 09:56:20 PM »
Going forward, my intention now is that each stay will have separate heads made as above, connected by some 7/32" diameter drill rod for the shafts.  They will be assembled with loctite using a jig for proper spacing.

Probably no shop time until Thursday.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #213 on: March 01, 2019, 11:12:15 PM »
Started on the "separate head" idea and discovered that with a 6mm width, the 7/32 shaft is too close to the walls.  So now the head will be 7mm thick , and the neck 7mm wide.  Did a trial single that seems to work.

Workflow for each:

Op1:  mill sides to get 7mm thickness
Op2:  turn 90 degrees and mill head profile
Op3:  spot drill
Op4:  drill 11/64 through
Op5:  ream .251
Op6:  Move to lathe and part off leaving .2" of rod attached for holding in the collet
Op6:  Insert head into the collett and face
Op7:  spot drill

Next on the mill mount the collet chuck and center.  The collet will have a collet stop so that the target depth of the 7/32 drill is constant regardless of the amount of material on the base of the head.

Op8:  Insert head first into the collet against the stop and tighten.  Peck drill 7/32.
Op9:  Back to lathe to part off the completed head.

Tedious because of tool changes, but I got 5 of the necessary 14 complete through Op7.


Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #214 on: March 09, 2019, 12:45:06 AM »
Got the stays finished after several short shop sessions during the past week.  Here's the result of swapping ends in the collet block and machining the other end:



Part in two, drill 7/32 hole in the end, and then part at the "neck".  I did these two to verify the process.



Here's the rest waiting to be drilled.  I spet drilled the ends on the lathe after parting and facing.



To get a consistent depth drilling, I used this setup with a collet stop in the collet.  I measured the first piece to determine how deep to go from the exposed end, then set that at Z0.  Thus, none of them risked the drill breaking into the cross hole.



Each pair of stays have different lengths than the other pairs.  This fixture allow assembly.  I used a 1/14" endmill to drill properly spaced holes that accept some 1/4" drill rod in a tight fit.  Then cut some 7/32 drill rod to fit tightly in each end while the ends are held by the pins.  Basically started with each rod a bit long and whittled down on the lathe until a good fit was attained.  Then Loctite 620 on the ends and back onto the fixture to cure.



Here are the 4 pairs:



To fit the single ended (vertical) ones, I scribed a line along the Y axis at X0, the drilled a hole at X 90 mm.  Then adjusted the length of the rod until the bottom lined up with the line.

Since I made the heads 1mm wider than the old ones, I'll need to adjust the spacers on the cross rods when I reinstall them.

Offline crueby

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Re: Muncaster Grasshopper - Work in Progress
« Reply #215 on: March 09, 2019, 12:59:24 AM »
Very nice!

I have never seen a collet holder like that - looks like a wheel hub? What is the black ring, and why does the holder flare out like that?

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #216 on: March 09, 2019, 02:14:39 AM »
It's a Hardinge collet chuck that mounts on my lathe with a d1-3 spindle.  The black ring is turned to tighten/loosen the collet.  I have a repurposed d1-3 spindle nose clamped in the vise that allows me to mount lathe chucks on the mill.

In the past its main used was holding round stock for thread milling studs.  Very handy for the Jpy engine build.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #217 on: March 13, 2019, 02:20:22 AM »
An afternoon in the shop allowed some decent progress.  After installing the steel stays, which went fairly well with only some trimming on a few spacers, I wanted to fabricate a way to attach the bottom of the engine to the brickwork.  To do this, I squared up two pieces of 1/2" aluminum that are attached to the end walls with 8-32 screws. 



The lower base of the engine was separated by removing the 6 screws, and I drilled and countersunk holes on each end for 8-32 screws.  Then after placing the base onto the brickwork, I used a transfer punch to mark the blocks on the walls.  Then the blocks were drilled and tapped, so that the base could be attached firmly.  Since the base and brickwork can be separated easily from the engine, it will make transporting it more easily separately.



The engine as it now sits:



The major pieces left to do are those for connecting the governor collar to the dummy valve.


Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #218 on: March 14, 2019, 01:57:53 AM »
Notice how I emulated George Britnell and show a penny for scale.   ;)

Online yogi

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Re: Muncaster Grasshopper - Work in Progress
« Reply #219 on: March 14, 2019, 02:34:15 AM »
Beautiful engine Kirk! Coming together nicely.  :popcorn: :popcorn: :popcorn:

Are you sure thatís the same penny George is using?  :stickpoke:

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #220 on: March 14, 2019, 10:52:55 AM »
George uses an older, more elegant, wheat cent reverse.

Offline Craig DeShong

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Re: Muncaster Grasshopper - Work in Progress
« Reply #221 on: March 14, 2019, 06:21:16 PM »
Very nice Kirk.  Looks grsat.

George uses an older, more elegant, wheat cent reverse.

I'm STILL convinced George has a 'special' penny he uses for scale.  :lolb:
Craig

Offline crueby

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Re: Muncaster Grasshopper - Work in Progress
« Reply #222 on: March 14, 2019, 06:55:19 PM »
Very nice Kirk.  Looks grsat.

George uses an older, more elegant, wheat cent reverse.

I'm STILL convinced George has a 'special' penny he uses for scale.  :lolb:
Nah, he has that shrinking machine from Fantastic Voyage!