101 replies to this topic

[edmontonguy]

Last year i built a kyak out of wood and it is coated with fiberglass fabric. Instead of a resin I used a two part epoxy which sets in a similar fashion but does not smell as bad as resin and has more flexibility when dried. Resin coated fiberglass sticks to most things though if using duct tape i would worry like you said about the tape deteriorating after time. If you have a mixture of base surfaces and strips of duct tape that should avoid the problem of the duct tape deteriorating. Depending on have durable you want your gunto be i would recomend two layers for strength. Before each layer sand the surfaces(including the base surfaces) to make the surface rough enough for the fiberglass to stick. It will just sheer clean off smooth surfaces. For a final coat i recomend a coating of resin or a thick varnish to make a solid seal. Curved areas are no different than flat areas but on critical strength points add strips of fiberglass to act as bracing for the parts. Finally when working in large sheets lay out the fabric and coat it in resin making sure it penetrates the surface don't worry about excess fabric that can be cut/sanded off after the resin has set. For smaller peices wet each down so it is saturated with resin before placing it then add a small amont on after to ensure it sticks.


Hope that helps!
Ask for more help as i have done over 60hrs of fiberglass if you need it

[snowboardguy]

you can find the angle of elevation and the lenght from point A to point B on the lift line and then use law of Sines. That will give you vertical feet and you wont have to spend 100 bux

[CAski]

The problem is that it can be difficult to get an accurate angle measurement, at least using just a standard protractor and weighted string.

[CAski]

I know. You can check for errors by taking two angle measurements, about 20 or so feet apart (or more; a larger distance between should allow for higher accuracy). Through the distance between the measurements and through the angles themselves, you would be able to form both the height, horizontal length, and inclined length of the slope through some relatively simple algebra and trigonometry. If your inclined length agrees with your measured length, you should have an accurate reading.

Of course, this all depends on how accurate this whole job needs to be.

This post has been edited by CAski: 27 July 2004 - 08:11 PM

[snowboardguy]

oh maybe...I was hoping something I learned in geometry would pay off!

[CAski]

Yeah, my entire Integrated Geometry/Algebra IIA class was just about practical applications of math. One assignment was to find the height of a bell tower on campus. This is how I learned that angle measurements can be tricky. Needless to say, my group's value was pretty far off due to improper angle measurements.

[snowboardguy]

once you get the angle it's super easy, just a bunch of proportions. Just need the angle!!!!

[book]

If you can get your hands on a GPS you will find it invaluable. Its handy for taking various measurements including horizontal and vertical, and it'll be great for surveying and marking the site.

[Kelly]

Items of consideration for a rope tow-
Horsepower needed is based on rider capacity.
It is often cheaper to build a few taller towers than many shorter towers.
Clearance from track and riders is more important for short towers.
Tension and carriage requirements might be needed for short towers.
With tall towers the large span will absorb tension differences, but due to your suggested length its fairly certain that some kind of adjustable system will be needed.
¾" rope is pretty small to grip, consider using a larger diameter (think gym class).
The cost of buying shorter sections of rope is often offset by the amount of splicing being done.
Consider a safety circuit for the top and bottom stations.
Yes my resume would include rope tows.

Ryan B

[Alexvb222000]

liftmech:

I got those numbers for ya! :D

The vertical is 150' and the length of the rope tow is 500' (give or take a few feet of course)

Thanks for doing this.


Ryan B:

I took into account about what you said and it make a lot of sense. I think I should use about 10 Tall poles (about 15-20 ft) because 2 ft of it will be in the ground, then in mid to late winter it will be under about 2 ft or more of snow.
So that will leave about 11-16 ft poles sticking out of the snow. I think that that should be enough to hold the rope up above the skiiers heads because there is going to be 10 poles on a 500 ft slope. Thats a pole every 50 ft. or less depending on the ends.

The horsepower thing, I want it to be able to withstand the weight of about 10-15 riders maxium at any given time. I know that it is hard to tell what hp I'll need but Do you know? or could you tell how to find out?

I was think about going to an electric motor again. My only problem being that I don't know how well it will do. I was thinking that a 15 hp 230/460 volt could do it?
I have the amps available to power it at 230 volts so that may be a possibility.
What do you think?

I would then have to slow the rpms down some how. I was thinking that maybe some custom gears? Or belts? I would need to have an 8:1 ratio because (these are est) the motor spins at 1100 rpm. With an 8:1 ratio That would slow the rpms to 137.5 rpm. With a 15 in. rim spining at 137.5 rpm, that makes the rope move at 538.5 ft per min. thats about 8 ft a sec. I think.

Is this TOO fast to have a rope tow moving? What is a resonable speed for a rope tow?

And another BIG factor that I don't know to much about is about the speed of the electric motor. It will slow down with the added resistence against it. with an engine this does not much matter, but with a motor (electric) I am afraid that is could OVER HEAT . It will also end up draw many more amps then it usually would to try to keep up. What do you think? (and anyone else that knows about any of this)

The problem I have is that with an engine, I have to refuel it every day and I'll need to maintain it much more, also the noise it produces. Theres the fact that I will have gas laying in the 'shack'/'shed' that could catch on fire do to a spark for an electrical panel witch has to go out there for the fan gun a few lights (maybe).
Ok so maybe that was a lot of problems with it.

If you can help, please do.

Thanks,
Alex

[edmontonguy]

In response to the speed of the rope abou 8ft per second sounds about right. That'll make for a quick ride but will not wear the grips of your gloves.

[Alexvb222000]

Cool,

So an 8:1 gear ratio will be good for that speed motor. Now All I need to do is find a gear box to do it. ($$$) thanks for the reply.

[ISMrider]

hey i am thinking of building a tow like your small tow and i was thinking could I deflate my tractor's tire and add alot of tension.Would this work as a bottom wheel?

[Allan]

I think the electric motor would be a good idea - way easier to maintain. To put it into perspective for HP requirements... Our 2000 foot t-bar, with 466ft of rise, and a one way capacity of 66 people only has a 75 horsepower 550VAC three phase electric motor. 15 hp should be good. You could probably find a cheap little set of pre-made gears somewhere with a ratio close to what you want(check ebay!) to reduce the speed to a manageable level. If you have a 538fpm tow, and a 500ft slope, it'll be less than a minute ride! Which will mean lots of runs :)

[phild]

Hi Alex,
I've been following your posts on the snowmaking board but did not know this board existed. We built a rope tow a few years ago about the same size as yours. I have not taken any recent pictures but would be glad to go out and shoot some updated ones. Below is a link to a temp web page with some older shots (4-5 years) and some useful (and useless) info.

Some quick thoughts... 1" polypropylene rope is great. Very little stretch, light, will not absorb water, cheap, and fairly UV stable (though we take ours down at the end of the season). Make sure you use a long splice to join the ends. A "regular" splice will leave you with too large a mass. There is a picture of one on the webpage.

If at all possible put the power at the top. It may mean a walk up, but when you think about the physics involved... it is much easier to pull a rider directly up. The return rope has almost no friction and therefore puts very little pull on the bottom bull wheel. If you power from the bottom you are having to tension the top (return) rope and pull the riders via the top bull wheel...lot of extra stress on various parts and you will definitely need a counter weight. We used no counter weight on ours...just the sag between towers was enought. When we checked out some of the "lost areas" that had rope tows the majority were top driven and the bottom driven had some very creative counter weighting.

We used 5 main tower (poles) and that was plenty. Tall ones should be set well into the ground (4-5 feet).

Check out the picts on the webpage and feel free to ask any questions. I will be away for a cople of days but will try to check in.

http://www.vermontel...ild/ropetow.htm

-PhilD

[liftmech]

Alex- re your concern about overheating the motor- install an industrial cooling fan so that it will blow directly on the motor from the side. That way you're cooling both ends. I'll get your tension for you in the next day or so after I bring my engineering stuff home from work. I can also email you a simple safety circuit diagram as Ryan B suggests.

[Alexvb222000]

That is an alsome lift (phild). You can bet that I'll be looking pretty hard at that. I will probably have a few quesions for you soon but for now it is too late for me (tired).

o and the lift will be powered from the top (I live up top)

Liftmech:

Thanks alot for doing this for me. For the Email on the simple safety circuit diagram, you can reach me at Avb22@direcway.com .

Now I need to find out how much this is going to cost to run all this wire. AHH!!!

Thanks,
Alex

[liftmech]

For the safety circuit you won't need much more than #24 phone wire. If your lift was any longer I'd suggest #22 or even #20, but at 500' you won't have that much voltage loss.

[Alexvb222000]

No,

I'm talking about runing the wire for a 15 hp motor (electric).
I live about 1000' from the top of the slope (I actually live right next to the top so its a 1000' across to the top not up) I know that a wire just for that will be $$$ but then theres the lighting wire (maybe) and the snow guns wiring and that runs off of a 50 Amp 230 volt circuit alone. Also I need to power a pump that I have. So its a little more then just 1 wire (although I do want to run a main power supply cable out there and just have a 200 amp @ 230 volt box, and a 200 amp @ 115-120 volt box.)

I really have not even considered a safty wire yet. Won't I have to run like a 230 @ (whatever the amprage of the 15 hp motor would be) wire across in order for someone to knock out the wire and shut off the motor? How does this work? Like a shut off switch?

Thanks,
Alex

[ISMrider]

Hey everyone I went to the dump yesterday and picked up some stuff for my rope tow inspired by all this knowledge. I am going to take some photos of my slope and wheels that I have. The rope tow I plan will be 150' feet long(well that all I have). All this talk is getting me so pumped for winter!!! Well it is time for some Warren Miller movies. :D