Author Topic: My First Grasshopper  (Read 15658 times)


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My First Grasshopper
« on: November 12, 2005, 01:15:20 PM »
I am having some engineering problems with my first Grasshopper escapement on a clock I call "Swoopy", and thought I might run them by you.

The Swoopy runs just fine if I hang 26oz of weight on one of the spokes of the Center Wheel, but she takes wayyy to much weight if I hang the weight where it is supposed to be hung - on the Great Wheel.  So much it's snapping glue joints (two so far).  That's not good.  

The Great Wheel only had a 1:4 reduction - a 64 wheel pushing a 16 pinion.  From there it is 64 Center Wheel pushing 8, 60 Third Wheel pushing 8 and 30 escape = 3600.

The problem seems to be upon lifting the entrance pallet - that big one on the left side.  The smaller exit pallet seems to work just fine, but that may be an illusion.

The Swoopy also does NOT have a 3 degree swing to the pendulum as I had calculated it should.  The escape wheel is a 30 tooth with a 4" diameter, and the distance from centers of the pallet arbor and the escape is 6".  3 degrees arc for the second's pendulum would be 2 1/8" from side to side.  This one is swinging 6 1/2" and that's a big arc.

To fix that I have tried shortening the Crutch Rod's length.  Right now it is 3 1/2" from its pivot on the arbor to the pendulum pin.  I tried shortening it first by 1/2" and then 1" but it seemed to make no difference at all.

Now that I think of it, the only change from Aydlett's article that I made was that I rotated the escapement 16 degrees into the side of the entrance pallet so that the escape arbor and the pallet arbor would be vertical.  Still...I don't think that should have done it.  

The Swoopy runs just great when I put a little weight (26 ounces) onto one of the the arms of the Center Wheel. But I loaded 12 POUNDS on the Great Wheel wind pulley with its 4:1 ratio and still
couldn't get her to move.

Well, that's not exactly true.  She moves, and swings her pendulum, and will
run by the exit pallet, but without lifting the entrance pallet.  But if, at that point, I then
apply a little finger pressure on the Center Wheel she lifts that entrance
pallet right up.

Sure is a pretty thing to watch - for the few minutes that the weights stay on that Center Wheel strut.  Someday this may be a pretty clock.

The pallets seem to release just fine, the problem seems to be the amount of force
required to lift that long (entrance) pallet.

I made a new entrance pallet that is narrower and lighter and has a larger area of
cut-out at the top, to lighten everything up, but it didn't seem to make any
difference on the amount of force needed to lift it.  The new entrance pallet weighs 0.6 oz and the exit pallet weighs 0.1 oz.

I then changed the 4:1 ratio Great wheel and put on a new 2:1 Great wheel and kept hanging weight onto it until it finally lifted the entrance pallet and then counted up the weight - 12 Pounds!

I thought it might be a problem with the going train gears so I took off the Grasshopper, blew on the Center wheel, and everything turned just great.  

Last night I went back to Aydlett's article and started over from scratch.  I re-drew the escapement, and then overlayed it onto my existing escapement, and everything looks fine to me. I wish there was a way to post a picture of it.  That might make it simpler to diagnose my problem.

Anyway, I can't figure this out, and any suggestions would be appreciated.

Thanks.  Clayton

Offline jrbeall

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My First Grasshopper
« Reply #1 on: November 13, 2005, 06:02:21 AM »
The three GH clocks I have made have all required surprisingly little weight to run.  They are all 30 hour clocks and have light pendulums.  The compound pendulum ones don't even need to be started, they just start themselves when wound.  I am afraid I can't help you with your problem without seeing your clock.  I am pretty much an "eyeball" mechanic and avoid the numbers . Email me a picture if you can.


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My First Grasshopper
« Reply #2 on: November 14, 2005, 10:07:57 PM »
I just wanted to update my above request for information on the Grasshopper for my Swoopy, and let everyone know what the problem actually turned out to be.

I ran the problem by Rabbit.  He cogitated on it a couple of days, and had me try a few things, but what he finally came up with had really nothing to do with the Grasshopper escapement itself.  

What it had to do with is the alignment of the Crutch Arm with the Pendulum shaft.  

Because of the various curves built into this clock (the 'swoops'), the push of the Crutch was not parallel with the Pendulum.  Instead of pushing a parallelogram (as is normal) the clock was having to push a trapezoid arrangement.  This made the pendulum push harder one way than the other.

I have redesigned the Crutch Arm and Connector Link to alleviate the trapezoidal problem and she's been running great ever since.

Thanks All, and a special thanks to Rabbit.

Aloha.  Clayton


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My First Grasshopper
« Reply #3 on: March 06, 2006, 01:38:14 PM »
Your problem is friction, somewhere along the line you are losing power that should be for the escapement. A classic sign of underpower is the lack of kick to the entry pallet, is your pendulum too heavy, a common cause, regards Dave