Need speed switch for DIY funicular/hillside elevator

Here are links to the two operating inclines in Pittsburgh.

The problem with the second solution is that a mechanical failure causes the brake to release. There is a chance of this with version 1 but fewer.

A second item that should be considered is that a fault should shut off the drive motor and not allow it to be restarted by the standard controls at the ends. This is similar to automated machinery controls.

Since you have controls at each end, there should be wires in the circuit that can be opened to shut down the system. The mousetrap (I like that analogy better) opens the circuit until it is mechanically reset. Your control switches should be wired so that they have to be pressed AFTER the mouse trap is reset before the car can move again. DO NOT reset the mouse trap until after the cable is back on the capstan and/or have a way to lock out the power to the circuits at the capstan end. If this was an industrial control, the lock out would be mandatory. At home it depends on where the mouse trap is and how safe you want to be. I recommend having it.

Another part of the circuit should be a timer that shuts off the system if the motor is running past the time the car should be at the other end. This will shut down the system if the cable comes loose at a time when anything prevents the car from making the trip or a limit switch at the end fails. This control should also not be overridden by the normal start buttons.

Bill Fuhrmann

I looked at your pictures from which it seems that the diameter of the spool of the remaining cables would vary significantly with amount of cable played out. So to keep the signal linear with respect to revolutions per minute, one could mount the magnet(s)on idler pulley(s).

... Marc Marc_F_Hult

This has all be a fun exercise of the grey matter. Which needs exercised to maintain some functionality in life. Well then it hit me. Why re-invent the wheel. Since these funiculars have been in operation all over the world for quite some time, I thought that it would be good to look at what the big guys are doing. My hope is that Jeff has already looked into this at some point in time. It might prove beneficial if some of the companies were contacted to get some input of what safety system they use on their equipment.

This link is for a number of manufactures

Les

I had the same thought but about smaller operations I've seen. Most here know that I have a second home in Brazil. In our city there is a wealthy neighborhood with deluxe condos overlooking the Bahia do Todos os Santos (Bay of All Saints). The condos are all situated on a high bluff, some 30 meters above the bay. Most have funiculars or trams for the residents to get down to their yachts (it's the nicest part of town:)).

When I go back next February we will be visiting family in the area. I'll find an opportunity to take some pictures if I can. Even if the OP's project is done by then it might be interesting to see what (if any) safety measures have been implemented.

Good idea.

Thanks for all the good ideas guys, sorry I haven't responded to all of them yet.

Les, yes, I tried to check, even looked at some of the others that sold kits for hillside lifts and they only wanted to sell the whole package, not their speed regulators.

Bill has a good point about shutting the system down if the "mousetrap" is triggered. This is very possible because there is an emergency cutoff switch near the spool (not shown, recently added) and if that circuit is opened, the whole system shuts down. A jumper in series with the switch could shut it down if pulled.

Someone on another board made an interesting suggestion. He mentioned a go cart clutch. When I looked into it, the go cart clutch (GCC) activates when the rotational speed gets up using a centrifugal setup.

See:

In your initial post you said, "I am trying to figure out some kind of simple safety mechanism in the event that the spools break loose from the gearbox or shaft and start rotating freely". Now you indicate that's a minor concern.

I'm c>So here's what I'm thinking. On the end of the spool, have a large

The spring clamp would work fine, as long as you lock it open when you leave the cart. You don't need much of a safety when the cart is empty, only when people are inside, and then it would be a 'deadman' clamp.

Elevators often have a brake that is held off by the cable tension where it attaches to the cab. you can do the same thing, the cable attachment holds open a brake that would grab the rails. If the cable breaks or loses all tension the brakes grab. Even if the cable slacks, there should still be tension at the cart attachment point. This is totally automatic, no user input.

Sorry, now I'm confused. I'm not sure where I indicated a freespool condition is a minor concern, but I'm sure its possible may have implied that by accident. I quickly scanned earlier posts and missed it. If its the quoted text below I must be missing it. In any event here is what I probably meant: The system itself is way oversized for what it does. I think the likelihood of a freespool condition is minor, but its the one remaining possibility that could result in the cart running out of control, so in that sense its the major concern.

If > In your initial post you said, "I am trying to figure out some kind of

Nick, I undestand what you are saying. I suppose you just have to be there to see it, but the cable is quarter inch aircraft cable and is pretty stiff. It is long too, over 150 feet. When that cart goes down in a freespool condition (drums rotating freely) it will be dragging that cable down with it. As it drags it down there is going to be some tension there because the drums/spools have some inherent resistance until they build up speed. Even when the cart goes down, the cable sags in between the supports some. I guess what I'm trying to say is that I don't know an easy way to indicate that tension drop.

In the event that both the cables snap, this would work beautifully, but both would have to break at the same time, and each one is rated for about 7,000 lbs. Thanks!

That would work, but I would have to depend on my kids to set the clamp when they get off and hope they remember to unset it when they get on. I would be afraid that it would get set open and not thought about, or even worse, locked at the bottom (brake on) and someone at top hits the recall button and has the cart connection point ripped out. Or on the opposite situation where its locked at the top and the cart is called down and the cable unspools up top.

Researching this I'm not sure it would work. Most of those clutches activate at around 3500 RPM, and by my calculations the drums are moving at 23 rpm (2 minute trip for 142 feet on a 12 inch drum) and perhaps as fast as 30-50 RPM when I increase the VFD motor speed. The largest gear I can find has 112 teeth, and the clutch has 10 (drum clutch ration of 11.2) That would give me a max "regular" RPM of 560 RPM on the clutch. By the time the thing got up to full speed it would be going too fast.

Additional gears could be added to multiply this, but I'm wondering if it would put too much torque on the gear to increase the drum/clutch ratio to 60, but I don't know gears that well.

Since the brakes will be on the car, its the weight of the car "pulling against" the cable that will hold the brakes off, it doesn't matter if the cable is sagging in the middle, its still holding the car and the brakes will be held off.

It could be as simple as the cable passing through a correctly rated coil spring at the car and attached to a lever that will hold off the brake, when the cable is attached to the spools and the spools are winding or unwinding normally the weight of the car will compress the spring and release the brake, if the spools are unwinding uncontrollably or the cable is broken then there will be nothing for the car to "pull against" and the spring would expand and the brakes will no longer be held off.

Doug

What you need to do is rent yourself a "cable load meter". Attach to one of the cables right at the cart. Go "up" and "down" a couple of times and then move it to the second cable. Repeat the process. You should be able to confirm that there is tension in the cables regardless of whether you perceive they're going "slack". If this is the case, using Doug's idea would be the simplest solution for you.

A little background first: Each cable attaches to a cable eyelet that attaches to a large U-bolt on the respective side near the low side of the cart. On that there is an individual 6 foot stretch of cable that connects near the uphill side of each cable and is joined by 2 pulleys that are connected to the lowside U-bolts mentioned. They "eyelet" portion of the cable is slack (by about 6") in between the where the pulley cable connects. This allows the tension to be spread evenly, and by keeping the eyelets there, they act as a buffer if one of the cables break. Before, I didn't have the pulley section and the cable tension varied, and it was difficult to adjust. Adding the 6 foot section distributed the load.

So, for both cables there is a common tension point which is anywhere along that pulley'd section. I suppose I could add a spring oriented solution that applied pressure to a brake caliper (go karts have these) to a fixed cable. Initially there wouldn't be much friction to slow the cart down, but as the cart did start to slow and removed tension from the main cables, the spring would be more dominant and would apply full force to it. Even if it doesn't stop it but slows that might be sufficient. And I could always add more calipers like this:

snipped-for-privacy@earthlink.net wrote: they'd be much better off in the long run if they just walked up and down the hill. then you could spend your time on something important.

I think you should look at a motorized winch with a single cable to raise/lower the tram. I'm sure the manufacturers have seen similar applications and have addressed the safety aspects. In any event, it should be much easier to slow and stop the rotating drum of the winch than it will be to design and maintain any of the Goldbergian suggestions you've gotten here.