how to use bicycle wheels as pulleys for an exercise device

[johnlvs2run]

I'm designing a rowing machine to ski machine device for training, to focus on abs, hips and legs.
My idea is to attach the fan part of the rowing machine to the wall, loop two cords over pulleys at ceiling level, and use regular ski handles.

I'd like to use bicycle wheels because their size and efficiency is much greater than small pulleys.
The problem is how to attach the wheels to the ceiling.

This will be in the garage where the beams are 8 feet from the floor.

Ideas are much appreciated. Thanks.

 

[jhuskey]

The quickest way that I visualize doing this, without totally fabricating something, is to use a couple of old steel front forks. I would imagine you could cut and weld them as needed.
This is of course a guess without actually seeing a diagram of what you have in mind.

 

[daveryanwyoming]

...Ideas are much appreciated. Thanks.

You can use a roof top bike rack front wheel carrier like this: https://www.1stnissanparts.com/images/NEW PICS.jpg just bolt it to the ceiling but be sure to tighten the wheel nuts or quick releases real tight if there's gonna be a lot of force pulling on your wheel pulleys as there's no retainers on this kind of wheel holder.

-Dave

 

[frenchyge]

Sketch?

I'm visualizing a rowing machine fan and two cables over pulleys at ceiling level, but can't figure out how one could do anything related to skiing on such a contraption.... especially for legs, hips, ab work.

I, too, was thinking of a roof rack wheel holder, but maybe would have other ideas if I could visualize the layout. Be sure to get some home video of the maiden voyage.

 

[johnlvs2run]

Thank you for the helpful suggestions so far.
Perhaps photos will be better than my attempting a sketch.

D/ck Taylor's device

Concept 2 trying his patented device
http://www.concept2.com/us/images/skierg/skierghx3.jpg

Then coming out with their own
http://i2.photobucket.com/albums/y41/johnlvs2run/skierg1b.jpg

Taylor's device has the advantage of direct drive with the chain (no additional pulleys), but the disadvantage of height the way it's set up, and that the chain comes down right in front of the face. C2's device has 4 small pulleys at the top, imo a terrible loss of efficiency. Also it is not tall enough, people keep hitting the bottom (see video), and they don't have a conversion kit from their rowing machine.

My idea has the fan cage of a rowing ergometer on the bottom, two cords (or one split into a V) attached to the chain at the cage, the cords going directly upward to the pulleys. The cords continue over and down to grips, where the athlete does the exercise. The advantage compared to c2's design, is the 2 large pulleys at the top, no bottoming out at the bottom, and a rowing machine can be converted to a ski erg with minimal expenditure.

[ame="http://www.youtube.com/watch?v=OQJBgY82qfo&feature=PlayList&p=E0F71CA39FDF8AD3&index=1"]Video of a skierg competition[/ame]

[ame="http://www.youtube.com/watch?v=bUlRz0oebvI&feature=PlayList&p=E0F71CA39FDF8AD3&index=0"]Video of double poling technique[/ame]

 

[frenchyge]

Does the angle from the pulley to the person matter? In the video the guy furthest from camera looks like he's pulling straight down in front of his body at the end rather than really pulling back through the hips. Seems like the lats + deltoids wouldn't get the full work if you're not pulling at the right angle.

Pulleys: I don't think you'd want pulleys as big and narrow as bicycle wheels, since it'd be easy for the rope/cable to come off the rim if the rider didn't maintain just the right angle. There are plenty of mid-sized wheels with axles and ball bearings which might work better and be easier to attach to a rafter. Going even further, a quality caster wouldn't add too much resistance, would self-align with the cable as it was pulled through, and would come pre-assembled with a 4-bolt mounting plate ready-made.

 

[johnlvs2run]

Does the angle from the pulley to the person matter?

Yes, it can, as the bottom of the V on the back (fan) side could get within a foot of the top. The grips will be 16 to 18 inches apart at the bottom, but could be close at the top. Maybe the wheels could be angled to reflect this, i.e. 4 inches apart on the fan site, and 10 to 12 inches apart in the front (grip side), or else 4 to 6 inches apart and parallel. I'm not really sure and this might take some experimentation though I'm hoping to click on the jackpot the first time.

In the video the guy furthest from camera looks like he's pulling straight down in front of his body at the end rather than really pulling back through the hips.

Yes, which is okay with me. It would be more difficult to pull back at an angle, at say 45 degrees, due to balance and leverage. My aim is to do this for the exercise.

Seems like the lats + deltoids wouldn't get the full work if you're not pulling at the right angle.

I think the lats, abs and hips would, yes? Because the resistance is pulled down by the lats, not the arms. If delts are not worked, that's okay, but I think they are as I've been feeling the exercise in various places this week while doing it without the resistance.

Pulleys: I don't think you'd want pulleys as big and narrow as bicycle wheels, since it'd be easy for the rope/cable to come off the rim if the rider didn't maintain just the right angle.

This I don't know. I've got a pair of old nashbar racing wheels in the garage that could be used, but smaller wheels would be easier to handle (and wider). By mid-sized do you mean bmx type of wheels? Yes, the smaller wheels would probably also be deeper. Good points.

There are plenty of mid-sized wheels with axles and ball bearings which might work better and be easier to attach to a rafter.

This would be great.

Going even further, a quality caster wouldn't add too much resistance, would self-align with the cable as it was pulled through, and would come pre-assembled with a 4-bolt mounting plate ready-made.

This would be fabulous, except they have a hard wheel and no rim? Two important points are that the pulley needs to have (1) bearings, and (2) the sheve size (outside diameter of the wheel) should be as large as possible. I think the C2 pulleys are 2 inches. Anything significantly bigger is a plus.

 

[frenchyge]

This would be great.

This would be fabulous, except they have a hard wheel and no rim? Two important points are that the pulley needs to have (1) bearings, and (2) the sheve size (outside diameter of the wheel) should be as large as possible. I think the C2 pulleys are 2 inches. Anything significantly bigger is a plus.

Here's a 5" plate-mounted caster which looks to have a rim of sorts: Caster City - Casters - Swivel Caster - Polyurethane on Aluminum Wheel - Model N3 Kinda pricey, maybe.

Otherwise I would think you could find a swivel pulley in that size which would also be suitable. For $7 I might give this 4" one a try: [ame="http://www.amazon.com/gp/product/B000AY2TBO/ref=noref?ie=UTF8&s=hi"]Amazon.com: National Hardware V7633 Garage Door Pulleys with Fork, Axle Bolt and Nut, Galvanized, 4-Inch: Home Improvement[/ame]


Edit: for the smaller wheels I was thinking of the little ones like on the back of a tricycle (6" or so) or kids' wagon. A 12-16" bike wheel would be okay, but then you're back to figuring out how to attach it to something so that it can swivel + spin freely.

 

[johnlvs2run]

I would think you could find a swivel pulley in that size which would also be suitable. For $7 I might give this 4" one a try: Amazon.com: National Hardware V7633 Garage Door Pulleys with Fork, Axle Bolt and Nut, Galvanized, 4-Inch: Home Improvement

That could work. How would it be attached?

for the smaller wheels I was thinking of the little ones like on the back of a tricycle (6" or so) or kids' wagon. A 12-16" bike wheel would be okay, but then you're back to figuring out how to attach it to something so that it can swivel + spin freely.

Either of these would be fine, with some way to attach them.

 

[frenchyge]

That could work. How would it be attached?

The garage door spring pulley would be tied with 1/8" steel cable looped around the top of a rafter in your garage, or tied through an eyelet screwed into the bottom of a rafter. If you look at that link, the cable is shown as part of a combo deal just below the picture of the pulley.

Come to think of it, a small wheel could also be attached to an eyelet or hook using a loop of steel cable.

 

[johnlvs2run]

The garage door spring pulley would be tied with 1/8" steel cable looped around the top of a rafter in your garage, or tied through an eyelet screwed into the bottom of a rafter. If you look at that link, the cable is shown as part of a combo deal just below the picture of the pulley.

Come to think of it, a small wheel could also be attached to an eyelet or hook using a loop of steel cable.

That sounds good, though I'd rather have a fixed base for the wheel/pulley.

My reason for thinking larger bicycle wheels might be better is due to the larger diameter and less resistance to a cord. For example, I have spun bicycle wheels that continue around 30 to 80 times on their own. I doubt that a pulley would be able to do that. Plus considering the much greater circumference, it seems to me that bicycle wheels would have much less resistance.

In comparison, the c2 device uses 4 small pulleys, and might be losing losing 8 to 12 percent of the force (due to friction and resistance). If that is so, then large bicycle wheels might lose less than 1 percent of the force. In fact almost any size of reasonably quality bicycle wheels should be better than the 4 small pulleys.

 

[johnlvs2run]

The garage door spring pulley would be tied with 1/8" steel cable looped around the top of a rafter in your garage, or tied through an eyelet screwed into the bottom of a rafter. If you look at that link, the cable is shown as part of a combo deal just below the picture of the pulley.

Come to think of it, a small wheel could also be attached to an eyelet or hook using a loop of steel cable.

That sounds good, though I'd rather have a fixed base for the wheel/pulley.

My reason for thinking larger bicycle wheels might be optimal is due to the larger diameter and therefore low resistance. For example, I have spun bicycle wheels on a stand that have continued around 30 to 80 times on their own. I doubt that a pulley would be able to do that. Plus considering the much greater circumference, it seems to me that bicycle wheels would have much less resistance.

In comparison, the c2 device uses 4 small pulleys, and might be losing losing 8 to 12 percent of the force (due to friction and resistance). If that is so, then large bicycle wheels might lose less than 1 percent of the force. In fact almost any size of reasonably quality bicycle wheels should be better than the 4 small pulleys.

 

[daveryanwyoming]

....I have spun bicycle wheels on a stand that have continued around 30 to 80 times on their own. I doubt that a pulley would be able to do that...

Not a great analogy. The much larger moment of inertia of a bicycle wheel will sustain the spinning much longer even if the bearing losses were identical. Take a bicycle hub that hasn't been built into a wheel and see how long it takes to spin to a stop. Same bearings, very different spin down results...

...Plus considering the much greater circumference, it seems to me that bicycle wheels would have much less resistance... If that is so, then large bicycle wheels might lose less than 1 percent of the force.

Yes, but this is a workout device not a transportation device. Who cares if you dissipate energy into the pulleys vs the rowing load unit? Is it the accuracy of a rowing erg power display you're after?

Here's another approach to the pulleys including some very efficient designs: Ultralight climbing equipment and Climbing Pulleys by CMI, DMM, Petzl, SMC,
Get a couple of these rescue pulleys, clip a climbing caribiner or hardware store quick link through the 'biner hole and clip the whole thing into a screw eye in your garage ceiling. The setup will cradle the poling cords nicely, be free to rotate laterally something like +/- 30 degrees or more to allow cable tracking and have limited losses if that's a concern.

-Dave

 

[johnlvs2run]

Not a great analogy. The much larger moment of inertia of a bicycle wheel will sustain the spinning much longer even if the bearing losses were identical. Take a bicycle hub that hasn't been built into a wheel and see how long it takes to spin to a stop. Same bearings, very different spin down results...
Yes, but this is a workout device not a transportation device.

Good points. The momentum of bicycle wheels could also make reversing direction more difficult.

Who cares if you dissipate energy into the pulleys vs the rowing load unit? Is it the accuracy of a rowing erg power display you're after?

This would affect the force generated on the chain, and the resulting power display on the monitor, as compared with a rowing machine that does not have the 4 additional pulleys.

Here's another approach to the pulleys including some very efficient designs: Ultralight climbing equipment and Climbing Pulleys by CMI, DMM, Petzl, SMC,
Get a couple of these rescue pulleys, clip a climbing caribiner or hardware store quick link through the 'biner hole and clip the whole thing into a screw eye in your garage ceiling. The setup will cradle the poling cords nicely, be free to rotate laterally something like +/- 30 degrees or more to allow cable tracking and have limited losses if that's a concern.

-Dave

Climbing pulleys are nice. I've been wondering about them, as their resistance is quite low. Thanks for the link and explanation of how to connect them. Perhaps climbing rope could be used for the cords.

 

[johnlvs2run]

Here's another approach to the pulleys including some very efficient designs: Ultralight climbing equipment and Climbing Pulleys by CMI, DMM, Petzl, SMC,
Get a couple of these rescue pulleys, clip a climbing caribiner or hardware store quick link through the 'biner hole and clip the whole thing into a screw eye in your garage ceiling. The setup will cradle the poling cords nicely, be free to rotate laterally something like +/- 30 degrees or more to allow cable tracking and have limited losses if that's a concern.

-Dave

Wow, they have the efficiency posted for each pulley!

Awesome... woo hoo!

I wonder if 93.3% efficiency means 6.7% of the force would be lost.

 

[daveryanwyoming]

... Perhaps climbing rope could be used for the cords.

Yes and no. Sections of static cord like Perlon: Perlon Accessory Cord (by the foot) would work nicely for your pull cords, I'd avoid the Kevlar cords as they're awfully stiff. But an actual climbing lead rope would be a poor choice as it's both larger diameter than necessary and dynamic meaning that it's designed to stretch quite a bit under load to reduce the impact of climbing falls. You don't want stretchy handle pulls between you and your load unit.

Yeah, accuracy of erg power readings and snappy handle return are the only reasons I can think of for low friction pulleys in your system. FWIW I've set up raising systems with most of the more conventional climbing pulleys shown on the link above and even the low cost versions work very well under load. If they're in your budget the large diameter versions are definitely lower loss but any of them will work really nicely in your system.

-Dave

 

[johnlvs2run]

Yes and no. Sections of static cord like Perlon: Perlon Accessory Cord (by the foot) would work nicely for your pull cords, I'd avoid the Kevlar cords as they're awfully stiff. But an actual climbing lead rope would be a poor choice as it's both larger diameter than necessary and dynamic meaning that it's designed to stretch quite a bit under load to reduce the impact of climbing falls. You don't want stretchy handle pulls between you and your load unit.

Yeah, accuracy of erg power readings and snappy handle return are the only reasons I can think of for low friction pulleys in your system. FWIW I've set up raising systems with most of the more conventional climbing pulleys shown on the link above and even the low cost versions work very well under load. If they're in your budget the large diameter versions are definitely lower loss but any of them will work really nicely in your system.

-Dave

Dave,
Thanks much for your comments.
The 2 3/8 celcon looks like the largest diameter, and lowest resistance that they have.
I will go with your recommendations. Much appreciated.

 

[Felt_Rider]

this place is pretty good for home style fabrication.

Rope Pulleys (look at the menu selection on the left for more variety)

Mounted Pulleys

Rope

 

[frenchyge]

Those climbing pulleys cost an arm and a leg -- well worth it when your life is dangling off the side of a cliff, but for a workout device?

Another reason not to go with a bicycle wheel is that the circumference of a full-sized wheel is about 2m. Judging from the video of those guys poling I'd say the length of a pull is 2m tops, and probably less. This means that the wheel is making less than 1 full revolution each pull (more like rocking back and forth) and that the force is always present on the same side of the wheel instead of being distributed around the wheel as it spins. I would think that could be trouble for the bearings after a while.

Also, keep in mind that the amount of friction on a pulley depends upon the number of degrees that the rope contacts the pulley wheel. Mounting a pulley high overhead is going to create more friction then one out in front of the athlete for any pulley used.

 

[johnlvs2run]

Those climbing pulleys cost an arm and a leg -- well worth it when your life is dangling off the side of a cliff, but for a workout device?

Right, but at $60 to 80 total it's not a bad deal.

I do wonder if the biners would rock back and forth,
and if it might help to fix them to the screw eyes with bolts.

Another reason not to go with a bicycle wheel is that the circumference of a full-sized wheel is about 2m. Judging from the video of those guys poling I'd say the length of a pull is 2m tops, and probably less. This means that the wheel is making less than 1 full revolution each pull (more like rocking back and forth) and that the force is always present on the same side of the wheel instead of being distributed around the wheel as it spins. I would think that could be trouble for the bearings after a while.

Good point.

Also, keep in mind that the amount of friction on a pulley depends upon the number of degrees that the rope contacts the pulley wheel. Mounting a pulley high overhead is going to create more friction then one out in front of the athlete for any pulley used.

Does this mean that 2 pulleys with 90 degree turns would have the same resistance as 1 pulley with a 180 degree turn?

In that case, c2's 4 pulleys would work as well as if they'd used 2 of them.