I didn't even put it together in my head that it was a cam. Seems obvious now...
It's fun following these sort of projects and thinking through the possibilities. Even the ideas that turn out to not be all that good help sort out a good solution. Brainstorming is one of the most fun parts of the process. Please keep on posting updates as the project progresses.
The study of linkages is actually pretty fascinating and very complex. Mechanical engineers (I'm not one...) take entire courses on studying and designing linkages and there is a lot to know. I have a few books around here on that topic, but have never really done more than skim through them. Maybe one day I'll actually try to study my way through one of them.
As for the "cardboard assisted drawing" same here, I've done my share too. And like the saying goes: "If it's dumb and it works, it's NOT dumb!"
I have done a fair amount of computer based design in my job and for my own stuff, but sometimes nothing quite takes the place of actually holding the parts in your hands and moving stuff around.
I guess ya it is ingenious. Irritating for me because I cannot adjust it the way I like! BUT lets talk about reliability.... I mean this wacky thing has been working for what? Gotta be more than 70 years. And you could fix any single part of it pretty dang easy. Even the ratchet mechanism we welded new teeth on when it was broken a few years back.
In the video on the ratchet mechanism at 0.18 just to the left of your finger is the outside ratchet bar. If you leave the existing catch and spring on the existing pin with a couple of spacers you could drill a couple of new holes closer to the centre of the wheel move the levers closer to the centre. This will make the ratchet move over more teeth with each action and increase the speed of the chain. CA$1100 for a hydraulic remote is way over the top. I'm not familiar with your tractor but most have either plugged ports for fitting extra hydraulic controls or a replaceable plate where the existing hydraulic controls get their fluid from to enable extra valving to be fitted or you can bolt on an extra valve block ,(extend), what is there now.
Remotes can be a hassle though. You will want dry-breaks if you go that route and routing the hoses can be a pain.
If you go with an pony engine you have many options. Engine and hydraulic pump driving a small motor coupled by chain would be easy. Engine driving a gearbox,(old motorcycle?),and chain drive to your spreader gives you a number of speeds to vary whatever final drive ratio you decide on.
You could see how much power you need by hooking up a torque wrench,(scale and pointer type works well),and turning the mechanism by hand,(after disconnecting the ratchet of course!),to measure the torque needed.
Handy calculator here: HORSEPOWER TO TORQUE CALCULATOR to help understand the relationship between torque, R.P.M. and horsepower. Just remember to multiply lbs/ft by 12 if you want lbs/inch.
Hope that helps.
Last edited by NortonDommi; Feb 25, 2021 at 01:49 AM.
clavius (Feb 25, 2021)
I like all of this brainstorming.
Measuring the load with a torque wrench is a clever approach. Good thinking.
OK, sounds like adding lobes to the cam is not ideal.
So another random idea:
Alter that cam that it spins freely on the axle and drive it off the wheel through a set of pulleys (or chain and sprockets, or whatever) at a two to one speed increase. It should no be all that difficult to do I don't think and far less complex that adding hydraulics or whatever.
This also is not likely a workable approach, but if you can spare the ground clearance you could change the wheels on the cart to be half as large in diameter. That would double the speed of the cam...
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