Author Topic: Muncaster Grasshopper - Work in Progress  (Read 22412 times)

Offline Craig DeShong

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Re: Muncaster Grasshopper - Work in Progress
« Reply #195 on: January 30, 2019, 12:38:19 AM »
Nice  :ThumbsUp: :ThumbsUp: :ThumbsUp:
Craig

Offline Admiral_dk

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Re: Muncaster Grasshopper - Work in Progress
« Reply #196 on: January 30, 2019, 11:19:34 AM »
You have really made some nice parts using the CNC mill the best possible way Kirk  :ThumbsUp: and showing that planning the work sequence is just as important as with manual tools too.

 :cheers:    :popcorn:

Offline Dave Otto

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Re: Muncaster Grasshopper - Work in Progress
« Reply #197 on: January 31, 2019, 01:00:26 AM »
Nice work Kirk!

Dave

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #198 on: February 02, 2019, 06:08:51 PM »
Next governor parts are the lower arms, rather small finicky things.  After some thinking, I decided to use a technique learned from Terry Mayhugh on the other forum.  Using a piece of 1" square brass bar, the profile is machined into each end of the bar.  The vise stop means I can turn the bar over and reuse the same tool change.



Next, the cavities around the part are filled with epoxy, in this case "Devcon 5" purchased at Lowes.  This was allowed to cure overnight.  Note that for future machining the epoxy must be constrained by metal on at least two sides.



After curing, I did a skim to ensure that the surface would be flat for mounting in the vise.  Then I cut off each end leaving a good margin for safety with the horizontal bandsaw,  Then mounted one in the Bridgeport vise and used a face mill to gradually reveal the part's outline.



The parts were then placed in the oven at 500F for an hour.  I seem to remember now that Terry put them in boiling water, but in any case the epoxy releases with a bit of effort with needle nose pliers.


« Last Edit: February 02, 2019, 06:16:53 PM by kvom »

Offline fumopuc

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Re: Muncaster Grasshopper - Work in Progress
« Reply #199 on: February 03, 2019, 07:36:02 AM »
Hi Kirk, I think I have to file this process away for future issues also. Thanks for showing it.
Kind Regards
Achim

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #200 on: February 03, 2019, 11:27:19 PM »
Today I made a start on the upper arms of the governor, those that connect to the balls.  Because I have a good deal of 3/16" square brass bar, I decided to redraw the part in Solidworks using imperial units.  After cutting two pieces over length at 1.75", I used a 3/16 square collet to drill .07" holes 0.2" deep in one end.  These will be tapped 2-56.



Next each bar was reduced to 1/8" thickness by milling 1/32" off of each side.  The first cut was easy, but the reverse side had the vise holding onto a tiny fraction of the bar.



To drill the mounting holes for the governor's upper section and lower arms, I mounted the vise stop and zeroed the DRO on the corner of the small vise's fixed jaw.



Then with the small vise on the surface plate, I used a 123 block to fix the drilled end of the part level with the side of the vise jaws.  Then I could replace the vise on the large Bridgeport vise and locate the holes accurately.



For the balls themselves, I tried some chromed balls I had on hand.  Mounted on the lathe and faced a flat area to mate the arm.  However, the ball was too hard for my HSS spotting drill to penetrate (drill tip was dulled).  So I've ordered some brass balls from McMaster and I'll try those later in the week.



Last op for the day was to tap the ends of the arms on my tapping stand.



There's still some more work to do on the arms, but I need to solve some workholding dilemmas first.

Offline crueby

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Re: Muncaster Grasshopper - Work in Progress
« Reply #201 on: February 04, 2019, 12:26:26 AM »
Nicely done. The brass balls will be easy to drill, also a little more mass to them.


 :popcorn: :popcorn: :popcorn:

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #202 on: February 05, 2019, 09:13:56 PM »
The brass balls arrived this afternoon earlier than usual for UPS.  Not as easy to drill as Chris imagines as the first attempt resulted in a broken .070" drill in the hole, but cutting the peck size to .03", feed 3 ipm, and 4000 rpm did the trick.  Here's the setup:



Using the v-groove in the vise's moveable jaw along with the vise stop meant that I could retain my XY zero after removing the small vise to change balls.  The process I used was to mill a flat on the ball with a 3/16" endmill, then spot drill, and finally peck drill .200" deep.  Then I could take the vise and ball to the tapping stand, so that the hole was still vertical with regard to the base.

The balls are then attached to the upper arms of the governor using some 2-56 threaded rod.

Here they are in place:



Because the end of the support rod is larger than in the SW model, I need to make the sliding collar spacer longer to avoid the balls hitting the rod end.  The space between the sliding collar and the top of the bracket is close to 5/8" vs. the planned 8mm.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #203 on: February 07, 2019, 11:53:09 PM »
Since the last update I powder coated the upper and lower brackets.  Here is a shot of the governor pre-assembly showing the brackets and rotating parts.



Upon mounting to the engine, it's evident that there are some problems.  At the maximum permitted by the pivot, the balls will contact the conrod.



At the pivot rest position the balls hit the support bar.



I did notice that the balls' arms are  .020" longer than the SW model given how I machined the flat on the balls.  Also, the ball in the photo is not screwed all the way flush with the arm.  While I can make the flat spot on the balls larger and shorten the arms as well, I can also change to .5" balls from the current .625" ones.  Whether the engine can turn fast enough to raise the collar so that the balls will interfere with the conrod is unknown.  If so, a stop ring between the fixed and sliding collars can be added.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #204 on: February 10, 2019, 11:09:59 PM »
After replacing the 5/8" balls with 1/2" ones and some other adjustments, the governor now spins without interference.  It has a vertical travel of only 1/8" as restricted by the pivot.  I could increase it some by filing the pivot arms, but as I like to run engines at slow speed, I doubt the governor will actually move much at all.

Here's current state of the project.  I still need a dummy valve that lies under the steam chest and is connected to the governor's pivot arm.  Other than that not much but little stuff.



Height gauge is set at 12" for comparison.  Highest point of the beam is 14.5".

Offline crueby

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Re: Muncaster Grasshopper - Work in Progress
« Reply #205 on: February 10, 2019, 11:16:28 PM »
Very very well done!!

Offline Admiral_dk

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Re: Muncaster Grasshopper - Work in Progress
« Reply #206 on: February 11, 2019, 12:18:11 PM »
I looks amazing Kirk  :cheers:

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #207 on: February 17, 2019, 03:35:26 PM »
The last major piece needed for this engine is the valve that's regulated by the governor.  As drawn by Julius, here's the head on view:



One can see that the critical size are that its top be below the bottom edge of the steam chest cover and its bottom edge above the cross shaft that links the pushrods.

The side view shows its position relative to the steam chest:



As drawn, the connection is a flanged elbow of just the right dimension, something that's quite difficult to concoct.  When I first assembled the engine for its trial run, I had a brass elbow with a 1/16 NPT male end screwed into the bottom of the steam chest.  As you can see, the female opening is too high to allow the valve or a close approximation thereof to work.



I decided to replace this with a nipple and an elbow.  Since 1/16 NPT fittings aren't available generally in local stored, I made one from some 1/2" hex brass rod.  It's quite difficult to get precise dimensions from such fittings, but this seems close enough.



I'll measure the top and bottom clearance from the center of the pipe, and redraw the valve to fit.

On another front, Eastwoods had a Valentine's day sale with free shipping, so I ordered some "chrome" powder.  If it looks good on a test piece, I'll powdercoat the brass support beams to look more like steel.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #208 on: February 22, 2019, 03:47:12 PM »
I made an initial dummy valve and mounted it with a nipple.  Turns out it sits far enough clear of the steam chest cover that I can make it much closer in size to that drawn by Julius.  So that's a current to do.

In the interim, the chrome powder arrived from Eastwood, so I powder coated a couple of pieces of scrap brass.  Not as shiny as actual chrome plate, but I think a metallic finish for the links is preferable than brass.  So I dismounted the 6 bars at the cylinder and coated them:



I started to reassemble and had a small disaster.



Seems I drilled/tapped the end too deep so that the walls at the joint were too thin.   :(   So I'll need to remake it and its partner, this time in steel.  I ordered a 3' piece of 1144 5/8" diameter rod from McMaster.  It out to arrive tonight.  If things work out I may just remake all 8 bars.  Hopefully I can get a better finish too.

Offline crueby

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Re: Muncaster Grasshopper - Work in Progress
« Reply #209 on: February 22, 2019, 03:51:54 PM »
Ouch on the bars, but at least you know the new powder coat looks good.