Writing from the view of a true pessimist, a ramp mechanism by any other name is still just that and (in this corner) tried and discarded in all its manifestations.
True for prime movers.
But cams can be useful control mechanisms.
In the case of a chiming clock, the power of the chime
comes from the hanging weight, but the timing/control
is from the snail shaped (ramp shaped) cam.
Took me a while to post these photos of the drawing,i'm disappointed the compression effect shrunk the image never the less....004 shows the spokes and weights from the drum side at 12 o'clock....this is the position the bullet shaped weights and guide pins must be in to give motion...which i will detail the problems later.......003 shows approx.position of guide pins in the fixed slotted guide plate at 12 o'clock ......006 shows the fixed slotted guide plate on its own...please remember this is a sketch not to scale and for simplicity i have not included the simple structure to carry and support the wheel(which would cloud the details of the wheel with pencil lines.i'll post the problems in my next post in casa this computer throws me out......i'm really slow at typing.Thanks for bearing with me.
Rasselas busied himself so intensely in visionary bustle he forgot his solitude
I propose a linear fixed cam(rigid) fixed to a stanchion which would fit very close to the guide pins(these pins would have small roller bearings to reduce friction)and position the linear cam round the axle but not touching it(not rubbing etc.)....I had thought of a box cam(grooved track)but the acute angles needed might cause lockup of the turning wheel this brings on the next problem,the acme quick screw spokes could possibly induce lockup too so maybe just a rattling fit so to speak weight sliding up and down a plain spoke....another problem is the weight at 9 o'clock may have to be positioned further to the spoke centre because of the close proximity of the weight guide pin at 6 o'clock(which i would prefer not to do as it would reduce the turning torque)i would also prefer the acme quick thread spoke for controlled movement......looking at fig 003 we can see what the fixed pins and weights have do to complete a 360 degree turn ....i welcome any advice or constructive criticism but to me i must build the model/contraption.....before i can decide on the fixed cam or type required...thanks to all who assisted in helping me to post the sketches..you are very helpful people.
Rasselas busied himself so intensely in visionary bustle he forgot his solitude
Tarsier79 i appreciate the links(food for thought)and Wubbly i found that link very interesting......Over here its been bitter cold and i have no heat in my workshop,hopefully the cold snap which is unseasonable for here will cease in the next few days and i can make this contraption.If i bring anything into the house that does not resemble a household fixing i get the Medusa stare from" her indoors "which believe me stops most folk in their tracks.........I remember many years ago before he was famous attending a lecture by Stephen Hawkins at Manchester University,anyway after the lecture he asked for questions and one of the under graduates present asked the age old question which bore no relation to any part of the lecture ,he said "Which would hit the ground first if a ton of lead and a ton of feathers was dropped at exactly the same time from a height of 100 feet", Hawkins was obviously somewhat taken aback but after a moment or two said, "I can give you 2 or 3 variable formulas for the answer,but the best solution is to try it and see"......i am very much "a try it and see "type of person and if it does not work i will continue to try.....thats what i like about this forum the enthusism from the bloggers is contageous and encouraging no matter what the outcome of our endeavours...
Rasselas busied himself so intensely in visionary bustle he forgot his solitude
Its still bitter cold here,yesterday the wife was out so i made a start to the model(in the kitchen!!)just the fixed guide plate,the linear cams to make and acquire the guide pin bearings.... two photos...
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Rasselas busied himself so intensely in visionary bustle he forgot his solitude
Sketch with linear cam template below the axle and snail cam template above the axle to show how little of "nudge" required to comlete one revolution....also photo of "rig"with mods.to adjust height should a larger wheel be made........i ran it at 100 r.p.m.attached to drill m/c for 10 minutes to loosen tight spots.......if it does not "run"as expected i could connect it to a timer and simple motor to frighten the birds from my seeds in the springtime!(joke)
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Rasselas busied himself so intensely in visionary bustle he forgot his solitude
A rough sketch of a m/c i made a few years back(which i am sure has been done before on this Forum)...i had some success using differing "pulls"of magnets and lighter/heavier pendulum weights to drive a simple "clock train".....the problem was the pendulum "shake"which i controlled to some degree in a slotted wooden track....i dismissed the contraption because although it would "run" for weeks driving the clock train/hands etc......i could not make it do "work"(lifting weights etc.)....since joining this Forum and reading others and their theories on pendulum activity....i shall look at this again....PS....the time keeping was erratic to say the least.
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Rasselas busied himself so intensely in visionary bustle he forgot his solitude
