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Discussion Starter · #1 ·
I am interested in designing a rope tow to pull 500 lb up a 22 degree slope. I am thinking of using an SEW-Eurodrive or similar electric gear motor capable of pulling at a rate of approximately 250-300 peet per minute uphill. There are similar designs such as: http://www.sgeise.com/lift-td.htm and even detailed design diagrams --> http://www.sgeise.com/services-sd.htm#lift . I am looking to assemble a simplified version of this on my property creating a rope tow on an adjustable 'trolley' to accommodate rope stretch and load. I plan on using readily available (Internet or local stores) materials. I need to specifically know how to translate the gear drive into an appropriately geared tow system to pull 3/4 inch line. Simple scanned pencil drawings and details are fine. Compensation will align with experience and includes the opportunity to remarket this. (Note: I don't expect this to take an experienced practitioner more than a few hours)

I have already looked at Capstan and similar industrial winches but they don't pull at the right rate which is why I'll need some type of geared motor and appropriate gearing system.

Example drive
http://cgi.ebay.com/ws/eBayISAPI.dl...ea56f1c&itemid=110638159061&ff4=263602_304652

Thanks!
 

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carpe mañana
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Could you use an off the shelf winch and pull via a set of pulley wheels to adjust the rate to what you want?

_MK
 

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22 degrees? That's pretty steep for a "hand" tow. The one's I've seen that are hands only are on seriously mellow grades. The steeper ones are all the sit types, making use of the stronger thigh muscles to grip the t-bar...more like a frisby.
 

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Discussion Starter · #4 ·
Pau11y -- I agree -- it's maybe more like 20% but I was thinking I'd use a climbing ascender to lock onto the rope & bike. Then do an emergency stop mechanism at the top to unclip. That's why I need a mechanical engineer to help me design and think through this thing so I don't build a system that is unusuable.

MK -- yes I looked at off the shelf winches, but by the time I customize and re-gear it so it's not pulling me at 20 feet per minute, I will have spent more than a properly geared motor. I also looked at boating capstans and windlasses like this one --> http://www.powerwinch.com/powerwinch/controller?action=product&c=3&p=19 but by the time I get an AC/DC converter and build a proper installation platform I haven't saved much and it would probably wear out with repeated usage of lugging my butt up the hill on my DH rig.
 

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Yeah... I'm electrical - power specialty, and starting/stopping motors like that is not ideal AT ALL! You might want to consider some sort of a VFD so you don't have to stop it, altho it'll cost you. In most industrial/critical load situations, you can only do a full start/dead stop a motor maybe twice an hour because of the inrush current during starting (typically 6x the full load current, as a rough est). That sucker (mtr) becomes a heating element during starting.
 

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xcguy said:
A bunch of hamsters in a cage wheel should do the trick. Cheap to operate, too.
You might need to feed them crack to get enough torque, but then we go back to that "inrush" problem...in this case, exploding hamster hearts :D
 

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Stiff yet compliant
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I'm not an engineer but I play one on the internet.

Looking at the drive from the Ebay auction you listed. With an output of 164 RPM you would want a pulley wheel with a diameter of .5822 ft to achieve 300 feet per minute pull speed.
Assuming the 1153 lb-in torque is the actual output and not a maximum rating, this equals 96 lb-ft. Divide by pulley radius to get 330 pounds of straight line pull.

I'm not sure how to calculate for the 22 deg slope. You will need to retain the services of another armchair engineer for that one.
 

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someone has to say it

pedal up to the top?

:D

(be sure to post pix once this feat of ingenuity is complete)
 

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Discussion Starter · #12 ·
Moustache rider said:
I'm not an engineer but I play one on the internet.

Looking at the drive from the Ebay auction you listed. With an output of 164 RPM you would want a pulley wheel with a diameter of .5822 ft to achieve 300 feet per minute pull speed.
Assuming the 1153 lb-in torque is the actual output and not a maximum rating, this equals 96 lb-ft. Divide by pulley radius to get 330 pounds of straight line pull.
.
Moustache - impressive. thx! I of course am accepting all armchair engineering and real world advice. Someone else advised me that the pull multipler is 2 to 1 for a 22 degree slope...or a 100 lb of pull can handle 200 lb bike/rider.

Blueallah - emailed your friend.

GotDirt, I'm working the xc trail too but it's not ridable on a 45lb DH rig.
 

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Moustache rider said:
I'm not an engineer but I play one on the internet.

Looking at the drive from the Ebay auction you listed. With an output of 164 RPM you would want a pulley wheel with a diameter of .5822 ft to achieve 300 feet per minute pull speed.
Assuming the 1153 lb-in torque is the actual output and not a maximum rating, this equals 96 lb-ft. Divide by pulley radius to get 330 pounds of straight line pull.

I'm not sure how to calculate for the 22 deg slope. You will need to retain the services of another armchair engineer for that one.
I didn't check your work, but assuming it's right ;) a .58' diameter wheel may be too small to grip the rope... IDK, but something to check into, usually the pulley wheels for surface lifts are much larger.

For the 22 deg slope, the sine of 22 deg is about .375, which is the multiplier for the acceleration of gravity on a body on a 22 deg slope, so 9.8 M/s^2 * .375. This will be the constant load on the motor once the load gets up to speed plus friction. However, the largest load the motor sees will be when the motor accelerates the load from rest, so you will need to calculate the maximum allowable acceleration and figure out how not to exceed it... maybe a bungee could be used to control acceleration? F=Ma is a good start :p
 

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davec113 said:
...the constant load on the motor once the load gets up to speed plus friction.
I'm thinking the friction might be negligible if the rider/bike is going to be dragged up there on its wheels.

davec113 said:
However, the largest load the motor sees will be when the motor accelerates the load from rest, so you will need to calculate the maximum allowable acceleration and figure out how not to exceed it...
There are mtrs out there to deal w/ the requisite starting torque. But these types of mtrs are typically not meant to be ran at high rpms as they generate larger torques on starting and their performance drop off significantly beyond...say about 50% of its max rpm. But again, I don't think this will be much of an issue if you let your system spin up to speed first, unloaded. If you do this, then you can use standard issue motors w/ its peak efficiencies at ~80% of its max rpm.

DaveC's also right about the cbl drive wheel diameter...they're typically pretty big to provide enough friction to the cbl (check those pics of the links you included). If you gear it right w/ the proper drive (mtr), you can use the stretch/sag of the cbl like the bungee effect. But w/o some sort of a variable frequency drive (VFD) to modulate your cbl spd, you're limited to a fixed cbl speed and it'll be kind of slow so you don't rip the arm out of anyone trying to grab on. Those kiddie rope tows crawl up the hill.
 

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edenger said:
Pau11y -- I agree -- it's maybe more like 20% but I was thinking I'd use a climbing ascender to lock onto the rope & bike. Then do an emergency stop mechanism at the top to unclip. That's why I need a mechanical engineer to help me design and think through this thing so I don't build a system that is unusuable.
Here you go, just order one of these up from NZ:

http://www.powderhounds.com/NewZealand/Nutcracker-Ropetows.aspx

:D
 
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