Author Topic: Muncaster Grasshopper - Work in Progress  (Read 22456 times)

Offline Gas_mantle

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Re: Muncaster Grasshopper - Work in Progress
« Reply #225 on: March 28, 2019, 05:35:52 PM »
Its looking great Kvom, not long till it's finished  :)

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #226 on: March 28, 2019, 08:24:17 PM »

I have a problem with some nuts, esp. 2-56 working loose during running.  I suspect blue thread locker is needed unless members have better ideas.

Offline crueby

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Re: Muncaster Grasshopper - Work in Progress
« Reply #227 on: March 28, 2019, 08:29:12 PM »
The blue is good - keeps vibration from loosening things, but you can adjust/remove them as needed without heating. I learned the hard way to remember to shake the tube to remix the components of the blue/red versions.

Great action and sound on the model!!

Offline Craig DeShong

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Re: Muncaster Grasshopper - Work in Progress
« Reply #228 on: March 29, 2019, 02:29:25 AM »
As Spock would say.... "Fascinating!"  :ThumbsUp: :ThumbsUp: :ThumbsUp:
Craig

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #229 on: March 29, 2019, 07:08:47 PM »
Loctite now supplies blue threadlocker in a red tube.  wtf!   :headscratch: :shrug:

Offline crueby

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Re: Muncaster Grasshopper - Work in Progress
« Reply #230 on: March 29, 2019, 09:02:24 PM »
Loctite now supplies blue threadlocker in a red tube.  wtf!   :headscratch: :shrug:
They have been doing that for a long time - the tubes/bottles I have are all red on the outside, for the blue, green, red loctites... They seem to just use the numbers and names to differentiate them now. Low strength blue, high strength red, etc. I think the company got bought/sold a couple times and every owner changed things.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #231 on: March 29, 2019, 10:41:54 PM »
After applying the thread locker to the most suspect threads, I've run the engine for a while until it eventually bogged down.  I found that the motion was quite stiff and couldn't figure it our got a while until I notices that the eccentric strap was loose.  Thread locker on those loosened it back up.

That said, I think a basic engineering issue is that the eccentric rod transmits its motion to the valve lifters by a horizontal rod, and this rod flexes back and forth on each rotation. (pic attached).

I believe a solution will be to make a part similar to the part that connects the rod to the valve lifter and position it to the other side of the lifter and the mounting bracket.  That will result in both a shorter horizontal rod and a more rigid connection to the lifter.
« Last Edit: March 30, 2019, 12:04:51 PM by kvom »

Offline Jasonb

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Re: Muncaster Grasshopper - Work in Progress
« Reply #232 on: March 30, 2019, 07:12:37 AM »
Yes, longer rod with an arm mounted outside the bracket so you can have the arm and rod join side by side and keep the lever to the vertical rod on the inside. This is how both my Stuart and Easton & Anderson are done. Ideally these linkage arms should be fixed with taper pins to the cross shaft so there is no risk of then slipping.

More importantly that's how Muncasters original drawings show it.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #233 on: April 02, 2019, 12:46:30 AM »
Started first side of the rocker.  After drilling the holes for the connecting rods, I milled the profile 10mm deep using trochoicdal paths.



Then pocketed to reveal the boss that will connect to the eccentric rod, followed by a finishing pass on the profile.



Finally, filled the cavity with epoxy gel that will hold the part after machining from the opposite side.  I am leaving to to cure overnight.



The machining for both sides has 0,0 as the center of the stock; and since I positioned it using a vise stop, it suffices to flip along the Y axis for the next ops.  The "drawing" for the back obviously needs to be mirrored on Y as well.


Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #234 on: April 02, 2019, 11:05:25 PM »
Machining the opposite face; the epoxy keeps the work from moving.



Afterwards I placed the piece in a pan of boiling water for about 30 minutes total.  Still took some effort to release and then clean up.  Then trial fit on the engine.



It needs a bit of adjustment followed by powder coat to match the two other pieces.  And two cross shafts need to be remade longer.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #235 on: April 06, 2019, 03:31:24 PM »
After remaking the cross shafts and getting all the fasteners on, the amount of flex in the horizontal rod is much reduced, and appears only in the the rod end of the eccentric rod, where the fit is fairly loose.  I ran it sitting on the Bridgeport table, and it has a tendency to walk.

Offline kvom

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Re: Muncaster Grasshopper - Work in Progress
« Reply #236 on: April 10, 2019, 08:19:06 PM »
I'm declaring this engine finished.  No good place for photos in the shop, so here she in on the dining room table.




Offline cheepo45

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Re: Muncaster Grasshopper - Work in Progress
« Reply #237 on: April 10, 2019, 08:22:11 PM »
Very Nice!

Offline Admiral_dk

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Re: Muncaster Grasshopper - Work in Progress
« Reply #238 on: April 10, 2019, 10:10:04 PM »
She looks fantastic Kirk  :praise2:  any chance of a video  :thinking:

Offline Johnmcc69

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Re: Muncaster Grasshopper - Work in Progress
« Reply #239 on: April 10, 2019, 10:26:59 PM »
She's a beauty KVOM. Really nice work.  :ThumbsUp:

 Would love to see it running!  :stickpoke:

 John