Scimitar Run Times - how to increase

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djlunt
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Scimitar Run Times - how to increase

Post by djlunt »

A bit late to the Scimitar construction. Read a few posts and looked at a few videos way too many times and still have some questions. I think it should run longer than I am able to get it to run.
With 10 lbs of weight:
5-6 back rotations with no vanes - seems pretty good
2 back rotations with 1/2 inch thick vanes
2-3 back rotations with 1/8 inch thick vanes. I expected more as the vanes are much lighter
When the ratchet releases there is about 1/2 inch gap from the ratchet to the impulse pallet. I have played around with moving the trigger to change this gap and the 1/2 inch gives the most push to the impulse pallet. I have also played around with rotating the vane arms on the shaft and adding weights on the vane arms to get the most rotation and still have enough momentum on the reverse rotation to trigger the escapement. Still only getting the rotations as noted above.

What weight are most people using to get the rotations (more than 2-3) that appear in you tube videos?

With the 10 lbs of weight, the force on a ratchet tooth is about 1 lb. Seem to be loosing a lot of energy between the drive pulley and the ratchet. All bearings have been degreased and spin freely. The shafts (8mm) were threaded into the base plate using T-Nuts on the backside and a nut and washer on the front side - the shafts are solid with no discernable movement. As with all kinetic sculptures the holy grail is to make them run longer. Any suggestions to get more spins other than adding more weight?
Thank you all in advance for any hints and suggestions.
Doug
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ArtF
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Re: Scimitar Run Times - how to increase

Post by ArtF »

Hi Doug:

I cant tell you weights, I kinda just add small chunks of metal till I get the results I want, but for me the secret was not the weight of the main drive,
though of course that's important, but the moment of inertia of the vanes. (That small offset that makes it come back to trigger point. I spun my vanes and times how long I could spin them with the same approximate push.. the better balanced they are they longer they spin. It is a balance for sure..
Its been awhile since I've driven mine, it sits as a wall decoration at the moment.. with the vane shaft glue needing resetting..

Art
djlunt
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Re: Scimitar Run Times - how to increase

Post by djlunt »

Hi Art,

Thank you for the reply. I will work on balancing the vanes. Right now I have them all balanced slightly different to get varied spins on them when the direction of rotation changes.

Doug
djlunt
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Re: Scimitar Run Times - how to increase

Post by djlunt »

Hi Art,

Did some more work on Scimitar and got it to run fairly well - 5-7 back rotations with the vanes. Worked on the timing and "unbalancing" the vane arms to get the the vanes to reverse to the trigger point. Also used one ceramic skateboard bearing in each vane. The vanes spin very freely and produce quite a chaotic pattern as they spin on their shafts as they are rotating around the main vane shaft. Due to the clicking it has been relegated to the shop wall!
Thank you for the plans and videos.
Doug
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ArtF
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Re: Scimitar Run Times - how to increase

Post by ArtF »

Nice to hear Doug:

( Yeah, can be noisy, I added felt to the hit spots..

Art
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