One other thought - on over-revving the motor:
We don't usually see that happen except at steep incline angles, but even then, flywheel inertia tends to prevent "spikes." You tend to see reduction in load to the motor, and ultimately motor over-speed errors. Yes, you need to deal with back-EMF...
Hi 43st,
A couple of thoughts (from an engineer at an exercise equipment manufacturer):
1. Most commercial and consumer-grade treadmills don't use synchronous drive belts. Ours use Micro-V, and others I've seen use similar. You're thus slip-limited in the torque that the motor can see. Also...
So here's a question: Does the robot have a length limitation? If not, rotary actuation may work very well.
For example, if the 50mm diameter "body" of the robot is in the middle, and there are relatively long "arms" (say 250mm long) in front and behind, a simple pivot joint could move each...
Does it have to be purely linear? A rotary actuator with a lever arm can achieve an extension approaching 2x the initial size.
Can it be a tension-only actuator? A winch system can easily achieve very high extensions for the initial size.
What's the application?
Thanks for the valuable input!
I've heard back from the harmonic drive people, and it appears that polymer-based harmonic drives exhibit some torque ripple when used in a speed-increasing configuration, and the life isn't very good yet.
It looks like perhaps Ikona might be a better solution...
Hey all,
I'm looking at an idea for a step-up transmission with a ratio around 30:1 - 50:1. The input speed (the low-speed side) is slow, about 100 RPM. The torque required is about 500 inch-pounds, fluctuating (and reversing). Because of the reversing torque, the transmission would need to...
Thanks, MJR2 for the analysis! It sounds like the magnet-backplate approach is the way to go. I agree that the safety factor is important, even if I do have mechanical backups. It's looking to me like this is quite feasible, even with conservative factors of safety.
Well, if your way of...
Looks like some more good info this morning!
OK, at 1 m/s you'll be far from the holding force being equal to the repulsive one. This should occur at about 10 m/s for a 3 mm thick Al 99,5 conductor in the gap...At so low speeds you should use copper instead of the aluminum...
Thanks for the...
Who knew this discussion would be so lively?
A. The 40 lbs assumes a safety factor and includes the weight of magnets in the carriage. I'll also have a mechanical backup (for accidental overload, etc).
C. I know that the eddy current effect will tend to counter the holding force. I don't know...
Thanks for your quick replies!
Here are some more particulars:
A. You didn't tell us what kind of force the magnets should develop.
That's because I'm not 100% sure of the exact value. I'm hoping to optimize the force generated per unit length of array. I suppose for estimation purposes, 35-40...
Hello all,
I'm working on a new design (for my company, that is) of a small wheeled carriage that rolls along the bottom of a 1018 steel bar. I would like to use magnets to hold the carriage to the bar.
The bar is 1" wide, .1875" thick, and several feet long.
I need to maintain an air gap of...
I'd consider submitting this problem to INA/FAG, but my company doesn't buy ball bearings from them, just roller clutches. That's not likely to change anytime soon, and even if I could, I'm not comfortable taking advantage of their "free" service for a product I don't buy.
I am perfectly...
The TK-Solver based software looks pretty comparable to the COBRA-AHS "baseline" package. (price and features) Pretty good, but maybe more than I need for my application. COBRA-EHL might be a better fit for me.
It's interesting that FAG/INA has decided to provide their Bearinx software as an...
Ideally 2 ball bearings would be used to take out the moment, but as I mentioned, the axial space is limited, and the moment is quite small. I've seen competitive designs use a similar arrangement with good results.
I'm still waiting to hear back from the manufacturer. The problem was too...
Sorry, perhaps I wasn't too clear. If there were two bearings, I could resolve the moment into two radial loads. But in my application there's just a single bearing under load. Thus, that bearing must support the small-but-nonzero moment load.
To my knowledge, moment loads on single bearings...
