Bikes on Mars? - Don't laugh!

quasar777 · 2004-09-29 07:18:56

there should be an Xprize for this. held underwater perhaps, to simulate lesser gravity.

sethmckiness · 2004-10-14 03:44:37

Speaking as someone that worked in a bike shop for 5 years, and used to be an Avid Mountain biked(no pun intended).
1.) Chain is not an issue.. light non stick wax based lubricant. it sheds off when dirt comes in contact with it. put a little on before you go.

2.) 35 PSI on earth is the lowest most people go on front or rear tires. I would guess 20 PSI would be doable in Martian conditions. if you go to low you will pinch flat. When the rim smashed the tube between the bottom of the tire do to underinflation.

3.) With the proper suit materials, rippage would not be an issue, nor would movement. They won't be racing.

4.) a slightly wider tire, say a 3" would be great for rough terrain.

5.) Saying gravity is working against you by not letting you get as much traction is false since everything weighs less. Less moments of Inertian in the wheel, less frame weight, exact same center of gravity, maybe a bit more for the suit. a simple spring/spring fullsuspension would work. maybe a bit boundy, but oil emulsion dampening may be tricky to work out.

6.) no O2 in Atmosphere.. NO Corrosion on steel to worry about for chain or bearings... :-)!

7.) Bikes are incredibly easy to work on other then trueing wheels. I doubt wheel strength would be an issue in Martian G.

Also, because of the Martian G, you won't fall as hard.. hence, less likey to rip suit. But I am sure there is some sort of advanced rip-proof fabrics being developed by companies such as Dupont et al as we speak.

Single Speed bikes are incredible simple and would work well! Also. with Titanium , pivotless full suspension is capable..

http://www.petry.org/markp/bowti.htm]Ibis BowTi

Best Picture I could find... hasn't been made for a few years.. But Titanium on bikes is a beautiful thing!

quasar777 · 2004-10-14 09:32:03

hi Seth, i don`t like 2 wheeled bikes for this use because: not enough cargo capacity. we may find this is easier than we think so we may as well go for broke. 3 wheels are far more stable, not as far to fall. i think the only good thing left for upright bikes is the fact that one can put one`s weight on pedals, `not same in less g. also i don`t think this will be a cyclic drive, it will be treadle. cyclic involves far more mtion than any suit would allow. altho treadle drive is slightly more complicated. btw, i`m getting this from the artemis article. i`m not sure who all has read this, so please do so as it`s enlightening. many people don`t read entire posts, so that`s why i`m mentioning it. they`ve been working on this longer than we here have, so they a few more insights. another thing abt 3 whls is it`s easier to semi-enclose it. we would want this to be versatile & 2 wheelers have limited versatility. i don`t this should be an end product in itself.

quasar777 · 2004-10-14 09:38:44

i`m even thinkin we oughta configure an unmanned probe this way, munus seat, pedals, enclosure,etc.
I'm dubious about this. A recumbent tricycle still relies in large part upon it's rider for active balance, espeicaly upon rough terrian. A rover has no easy way to simulate this (I mean you could use gryscopes or what not, but that would be heavy). Without active balance, a low center of gravity and more points of stability are even more important, and most small rovers have more than enough power a 4 wheeled transport, I mean they are rolling around up there right now. Why mess with what works?

ok back to this, if the probe has outlived it`s usefulness, why couldn`t just the 2wheeled "axle" part of it be used? just split the probe in the middle, then you would have 2 axles.

Timeslicer · 2004-11-25 00:29:17

While the pumping action of a bike might be difficult for someone in a space suit, we could go back to the ancient form of bike - just a couple of wheels and a seat, no pedals. More like a scooter - give a push and let it roll.

Or maybe incorporate a more suitable (no pun intended) pumping mechanism - say a rocker, so the rider just shifts weight from front to back to pump it up and down - far smaller movement of each joint. Attach the rocker directly to the rear wheel axle for extreme simplicity, or through a bit of gearing if necessary for proper mechanical advantage and speed.

quasar777 · 2004-11-26 01:20:54

i like it. there have been many scooters powered this way. some are side-to-side, some front-to-back. kinda like treadle drive though using only one "treadle". now that i think about it, this is how skateboards are propelled uphill. a form of cross-country skiing horizontally is this way as well, it`s ski-skating. there`s a great tale of Nikola Tesla using a little black box using this method came close to bringing an unfinished building down in several minutes. he took the little box away & walked away writing notes. i heard of a boat that had 2 spinning, unbalanced weights on platters as it`s only propulsion.

one can feel this force by holding an electric drill loosely & turning it on very quickly. also if one has a dented pot or pan or if your eye on your stove is lightly askew, & you get the vessel shaking, as it heats the shaking will continue.

quasar777 · 2005-01-23 15:17:06

there should be a new xprize for this.

SpaceNut · 2005-01-24 05:38:59

Here is a thought, cross a run of the mill tread mill, a flywheel for energy storage and give it 4 wheels that each are steering capable. Now the astronaut can just walk his way there.

Commodore · 2005-01-24 21:57:35

Here is a thought, cross a run of the mill tread mill, a flywheel for energy storage and give it 4 wheels that each are steering capable. Now the astronaut can just walk his way there.

How bout a heavy duty Segway? Thats probably been mentioned already.

SpaceNut · 2005-01-24 23:06:09

yup Battery powered..
My thought was human powered.

J.J. Moesker · 2005-01-28 06:17:03

In the Netherlands some young kids on the farm get around on so called 'mammout skelters'. These are four wheel pedal driven 'kart' type vehicles (I have no idea how these thing would be called in the US), and go trough almost all types of terrain. Very robust equipment.

One could imagine some sort of human powered quad or trike (static stable config) inspired on these types of vehicles. A recumbent position would be preferable, in such than you can provide counter pressure against the pedals. There are many advantages compared with an electrical powered vehicle:

* Very low mass, 10 to 15 Kg range if designed by aerospace engineers using Martian design loads. Maybe even less.
* Very simple technology, thus cheap to develop and easy to repair/ fix in the 'field'. Almost all repairs on a bike can be done with just a couple of different tools.
* No direct need for onboard electronics or any other complex system that can fail. Thus a fully passive means of transportation.
* The thing is always 'ready to go'.
* Store it in parts and assemble it easily on the surface.
* No need for batteries that require thermal protection.

There are however some engineering problems. The most important will be caused by the near vacuum pressure enviourment. On of the problems in designing space mechanisms is the out gassing of volatiles. A roller bearing, for example, can not be lubricated with grease or oil, since this will outgas. A lot of work has already been performed in this field. Similar problems will also have to be dealt with eclectic powered vehicle. Yet these types of issues will need to be addressed. Furthermore the most obvious show stopper would be the pressure suit.

If the pressure suit problem can be solved, human powered transportation would be quite useful for short-range (5km radius) transportation/ exploration. Suit design must go trough some radical changes to make physical work during EVA really doable.

It would be a nice student project. At moment here at Delft two groups are working on a human powered airplane and a H.P. submarine, both for student contests.

Below are some picture of these "mammout skelters", just for inspiration.

quasar777 · 2005-01-31 13:39:38

ya, the Dutch specifically & Europe are mostr advanced in human-powered vehicles. google: escargot canal cruiser. google: kinetic sculpture race arcata. the submarine race has been approx 20 yrs now. intl hpv race a lil longer since `75. i think, 78 mph has been broken. i think they`re goin for 100 for awhile now, it`s called DeciMach Challenge. it`s a kinda x-prize. i`ve been trying to find a picture of a modular suit which i think would fit this situation well. i think a suit torso should be rugged enough to constant remain outside a rover, habitat, or combination thereof. this has been mentioned on several other threads here. this would be also easier to keep clean as well as making more room in the larger artifact.

Austin Stanley · 2005-02-04 02:56:42

I think Mark Friedenbach had a great point, Exhaustion is a very major danger. Rember that the the astronauts are probably going to be on a 100% oxygen atmosphere during EVAs at a lower air-pressure then is typical her on Earth. They and very dependant upon the suit to remove CO2, provide oxygen, and remove excess heat. Even though mars is very cold, it's thin atmosphere is probably a very good insulator. There have been several near disasters during EVA for just this reason.

I would also point out that even with the lessend gravity a body in motion still has inertia, which is likely to be even greater on Mars, due to the additional mass of the spacesuit. In the event of an accident, even if the suit does not rip, their is still the dager of broken bones, and other damage to possible delicate spacesuit equipment, like the LSS and comunication systems.

idiom · 2005-02-04 13:18:00

It seems that the usefulness of a bike is directly dependent on the design of a suit. A sufficiently mobile suit would allow an explorer to strap the bike to ones back and scale a cliff and ride off at the top.

However for people stuck in tuna cans, just the ability to tear around the base in circles leaping off piles of construction debris would be an amazing amount of fun.

quasar777 · 2005-02-06 14:59:37

I finally learned how to cut & paste. in my earlier posts i mentioned this article & i was afraid it wasn`t read by all here. At the lunar outpost, there will be a need for different sorts of vehicles, and undoubtedly large hauling vehicles, whenever they are required, will need a good power source. They will likely be some high-output fuel cells, solar arrays or some similar technology.

But the type of vehicle needed for a small relatively self sufficient group should have a number of characteristics that few of the designs in the literature ever consider.

The motive source should be 100% field repairable preferably with only a few tools and simple spare parts.

Spare parts should be such that they can be manufactured locally from small amounts of raw materials.

The vehicle should have a fail safe criteria that it can bring the driver home under almost any circumstance in which the driver is still capable of driving.

It must use indigenous energy supplies.
If you look at this problem with the eyes of an engineer you immediately come to the conclusion that a human powered vehicle is just the ticket.

Research backs this up. In a Scientific American issue on Human Powered Vehicles a number of years ago, an article on bicycles had an extra data point for the performance of a vehicle on the moon. A racing biker, with no air resistance and 1/6 g could break 1000km/h in sprints. A normal, healthy person could cruise at over 100km/h all day, and could easily pull a trailer load at the equivalent of typical earth bound auto driving speeds.

The form of the vehicle is the recumbent bicycle like that used by Stephen K. Roberts (Computing Across America). And in fact, he would probably be the best person to speak to on the design of a lunar rover. He crossed the USA from end to end several times on his recumbent, traveling up and down through the Rockies, keeping up reasonable highway speeds, and all the while pulling a trailer that included solar power gathering and a satellite uplink so he could type on the keyboard in front of him (while peddling) and submit articles to magazines that funded his journeys. He also had navigation and maps built into his console processor. There is little that a lunar rover built for days of unsupported prospecting would need that he didn't do 5-6 years ago.

Now that is not to say there aren't issues unique to the moon. There is the issue of traction and off road travel which will drive the gearing ratios, axle loading, weight and balance, and wheel design. Braking will have to be dynamic, feeding the energy back into a dynamo. Normal friction brakes are a bad idea for two reasons, (1) the abrasiveness of the regolith; and (2) brake cooling is purely by radiation to the background and conduction through the frame. Radiators are a problem as has been suggested before; and since I expect the frame to be composites, conduction is not very good either.

Gears and chains and deraileurs will have to be very robust and spares will be required. A design that can be field-welded would be a good idea. Better to trade off a bit of elegance and performance for field maintainability. These parts can be built very ruggedly (we're not talking about racing bikes here) and would need to be able to withstand the rigors of large temperature swings and abrasive particles. One could seal them, but then it is more difficult to field-strip. And not to mention which, without herculean efforts the lunar grit will get in anyway. Desert Storm is a case in point.

Another area of concern is space suit cooling. The loads will not be excessive under normal cruising since the peddling is only enough to replace frictional losses.

Use of a small motor like that in a minibike could solve a number of problems (if they don't add too much complexity on their own). The motor could be the means by which braking returns energy to storage. Energy can be recovered on downhill stretches and used to ease uphill travel. It also can reduce the heat-loading on the space suit during acceleration from a standing start, or indeed any acceleration under load.

The motor would of course need to be built such that it can be disconnected from the system entirely if it fails. The overall system would have to be able to get the lunatic back home reqardless. So think of it only as a luxury item on the bike.

The suit would be a live-in suit, so that puts some extra design load on it. You might have to do better than a diaper if you're going to be out for a week, but this is a problem that needs to be solved anyway. The Star Wars rovers that some NASA scenarios show us are not going to be feasible on any realistic budget, and in any case you'd only be able to afford one of them for the cost of giving every lunatic their own personal lunabike.

While walking home recently one night I remembered some thoughts I had on lunar rovers a number of years back. There will be a need for different sorts of vehicles, and undoubtedly large hauling vehicles, whenever they are required, will need a good power source. Whether that be fuel cell, battery, solar power, beamed power or some mix I won't go into here. But the type of vehicle needed for a small, relatively self-sufficient group should have a number of characteristics that few of the designs in the literature ever consider.

The motive source should be 100% field repairable preferably with only a few tools and simple spare parts.

Spare parts should be such that they can be manufactured locally from small amounts of raw materials.

The vehicle should have a fail safe criteria that it can bring the driver home under almost any circumstances in which the driver is still capable of driving.

It must use indigenous energy supplies.

Now if you look at these requirements through the old-fashioned NASA eyes, you will come up with a billion dollar project. If you look at it with the eyes of an engineer, you immediately come to the conclusion that a human powered vehicle is just the ticket.

Research backs this up. In a Scientific American issue on Human Powered Vehicles a number of years ago, an article on bicycles had an extra data point for the performance of a vehicle on the moon. A racing biker, with no air resistance and 1/6 g could break 1000km/h in sprints. A normal, healthy person could cruise at over 100km/h all day, and could easily pull a trailer load at the equivalent of typical Earth-bound auto driving speeds.

The form of the vehicle is the recumbent bicycle like that used by Stephen K. Roberts (Computing Across America). And in fact, he would probably be the best person to speak to on the design of a lunar rover. He crossed the USA from end to end several times on his recumbent, traveling up and down through the Rockies, keeping up reasonable highway speeds - and all the while with a trailer that included solar power gathering and a satellite uplink so he could type on the keyboard in front of him (while peddling) and submit articles to magazines that funded his journeys. He also had navigation and maps built into his console processor. I don't think there is anything that a lunar rover built for days of unsupported prospecting would need that he didn't do 5-6 years ago.

Now, that is not to say there aren't issues unique to the moon. There is the issue of traction and off-road travel, which will drive the gearing ratios, axle loading, weight and balance, and wheel design.

Braking will have to be dynamic, feeding the energy back into a dynamo. Normal friction brakes are a bad idea for two reasons - 1) The abrasiveness of the regolith. 2) Brake cooling is purely by radiation to the background and conduction through the frame. Radiators are a problem as has been suggested before; and since I expect the frame to be composites, conduction is not very good either.

Gears and chains and deraileurs will have to be very robust and spares will be required. A design that can be field welded would be a good idea. Better to trade off a bit of elegance and performance for field maintainability. These parts can be built very ruggedly (I'm not talking about racing bikes here!!) and would need to be able to withstand the rigours of large temperature swings and abrasive particles. One could seal them, but then it is more difficult to field strip. And not to mention which, without herculean efforts the lunar grit will get in anyway. If anyone out there was in Desert Storm...

Another area of concern is space suit cooling. The loads will not be excessive under normal cruising since the peddling is only enough to replace frictional losses.

Use of a small motor like that in a minibike could solve a number of problems (if they don't add too much complexity on their own). The motor could be the means by which braking returns energy to storage. Energy can be recovered on downhill stretches and used to ease uphill travel. It also can reduce the heat loading on the space suit during acceleration from a standing start, or indeed any acceleration under load. The motor would, of course, need to be built such that it can be disconnected from the system entirely if it fails. The overall system would have to be able to get the lunan back home regardless. So think of it only as a luxury item on the bike.

The suit would be a live-in suit, so that puts some extra design load on it. You might have to do better than a diaper if you're going to be out for a week.... But this is a problem that needs to be solved anyway. The Stars Wars rovers that some NASA scenarios show us are not going to be feasible on any realistic budget, and in any case you'd only be able to afford one of them for the same price as giving every lunan their own personal lunabike.

It seems wholly superior to any rover concept I've yet to see. Just about anyone out there could have run circles around the Lunar Rover and been out 20 km and back before it was barely out of sight of the LEM...

Ah, you say, bikes are good on highways, but off-road you're going to want a trike! The lunar surface has huge areas that are much like beaches and dunes. Covered with hardpacked fine regolith that follows the contours of the land in a very smooth and gentlly rolling fashion. This is not to say that crater rims and such are quite the same - but large tracts of the moon should be easily negotiable.

As to bike vs. trike, there is no inference above, of a two wheel design - in fact I believe the recumbents are usually trikes. At least the Robertson one that I saw in 1989 was... DA

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Out-vac trike-suits are a challenge
by Peter Kokh Sounds delightfully low-tech, doesn't it? Tired and stressed out after a long day's work in your lunar office, mine, or factory? Just don your out-vac trike suit and head for the airlock and get some heal-all unwinding exercise! Reminds me of an Arthur C. Clarke story where the hero does a kangaroo-lope to safety 600 km across Mare Imbrium in just a spacesuit.

The question arises: without an open air heat sink, where does all the body heat generated by such exertion go? An out-vac triking suit needs not only to be self-contained (in RV-camper-trailer talk that means "with toilet"), but able to handle/shed internally-generated heat, and perspiration as well. That also means being able to keep the wearer from getting a chill soaked in his/her own sweat once the exertion is over. Perhaps the suit's insulation material could be an eutectic salt in a quilt of pocket cells, melting to absorb internally-generated heat, solidifying to release it - automatically, on demand. PK
The question arises: without an open air heat sink, where does all the body heat generated by such exertion go? An out-vac triking suit needs not only to be self-contained (in RV-camper-trailer talk that means "with toilet"), but able to handle/shed internally-generated heat, and perspiration as well. That also means being able to keep the wearer from getting a chill soaked in his/her own sweat once the exertion is over. Perhaps the suit's insulation material could be an eutectic salt in a quilt of pocket cells, melting to absorb internally-generated heat, solidifying to release it - automatically, on demand. PK

by Phil Chapman
[* Buppet: etym. from Body Puppet, on the analogy of Muppet from Mitten Puppet.
Note: "buppet" is the editor's word, not the writer's]
Having tried both [an EVA suit and a diver's dry suit], let me tell you that a pressurized conventional spacesuit is much more restricting than a drysuit.

Spacesuit design has been hampered by thinking of it only as a garment. It is also a small space vehicle. A conventional suit is no place to be for more than a few hours. For longer durations, you need to be able to pull your arms in so that you can scratch, or eat, or sleep, or void. This suggests that the lunabike should be integrated with the suit -- in other words, the suit would be a light-weight pressurized canister with wheels (4, for stability), with a shirt-sleeve internal environment for pedaling and living. The canister would be equipped with pressurized gloves, waldoes or other attached tools for manipulating the external environment.

It might be necessary to carry a conventional suit, donnable inside the canister, so that you could get out and get under if something broke, or go climb that cliff over there (where, as Arthur Clarke has told us, The Sentinel is waiting), or, in extremis, walk home. For routine use, (such as getting from one pressurized dome to another) the mobile canister alone might be sufficient. The real safety reason for carrying a conventional suit is to avoid potentially fatal single-point failure modes, an objective that might be met by careful design of the canister/bike alone. PC

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No, what we need is a Volkscycle!
Response from Dale Amon to Chapman's suggestion

[What I have in mind is an outvac cycle that fits every lunan's budget. So] the bike must be mostly buildable from local materials with simple tools and basic stock materials; all systems required for it to function as transport must be field repairable. Simplicity. Something a back yard mechanic can build and repair - exclusive of the electronics, of course - but there should be no electronics that are absolutely required for the bike to operate. Electronics must be something that is bolted on and if necessary unbolted and tossed into a crater to lighten the load.

The minute part of the design requires a special tool or material, my design criteria demands that that element be discarded from consideration. Simple. Indigenous. Independent.

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Human-Powered Moon Trike
Call for a Technology Demo for ISDC '98 - Milwaukee
One of the more ambitious goals outlined in the plan for ISDC '98 - Milwaukee is to present a number of low budget ($100-$5,000) technology demonstrations of tidbits of technology that will be needed, or useful on the space frontier, and which should not take that much money to demonstrate.

A human-powered Moon Trike is such a possibility. Because gravity is only 1/6th Earth-normal, but momentum remains full Earth-normal, to prevent tipping, the vehicle should have a very wide track, wheels that lean into turns, and a low center of gravity.

Rxke · 2005-08-16 15:18:44

Not a bike, if powered...

A tweel ope ATV thingy looks interesting:

http://hoop.exblog.jp/1693089

Kevin Renner · 2005-09-14 15:13:43

As stated the big killer for such devices as bicycles on mars are the P-suit type used. A suit that relies on retaining pressure like the ones currently favored by NASA makes the use of a manually powered bike impossible IMO. Using a P-suit that actively supports the body (lets face it we might as well call it a SkinTight) will allow the use of bikes in a Martian enviroment but I do see some problems. One is the inertia problem when braking and suspension control. The suspension problem can most likely be over come with adequate dampening. Braking might be a bigger problem. The image of some one flying over the handlebars is not funny. The other is the physical exhaustion problem but at lower speeds (10-15 KPH it might not be too bad, 20KPH is easily sustainable for some one in adequate shape on Earth) The sinking into the dust problem. That is something that we will not realy know for sure until some one actaully goes there. Plus it is likely to be varied over the Martian surface. There are comercially available electric powered bicycles sold today and they might be a viable option. Another option might be tandems

JonClarke · 2005-09-17 22:29:46

The social, economic, and military impact of bicycles has been grossly understudied but has arguably been as profound as that of the motor vehicle. Bikes have corssed deserts, jungles, mountains, and deserts on earth and performed with extraordinary reliability. I think they have great applicability on Mars and the Moon.

The biggest issue will, I think be cultural. A society that uses a car to drive round the block will not tend to think of human powered vehicles as a viable option. A culture that thinks nothing of walking 5 km or cycling 20 may well look favourably on the bike.

Jon

quasar777 · 2005-11-22 14:52:43

excellent post, jon. i think one of the reasons HPV`s are more popular elsewhere than the US is fuel cost. that & there are quite a few areas of the world other than the US where horses &/or buggies are still used. quite a few homeless on the US west coast, live virtually on pedal powered vehicles. American yuppies are extremely far behind the times as far as some things go.

quasar777 · 2006-06-29 17:58:48

sorry folks i just had to dredge this one up.

F1-X!? · 2006-07-08 09:35:10

Didn't see it here, nor on any other site (didn't look too hard, though)
Considering bikes are *the* single most effective non-motorised way of getting somewhere, wouldn't it be worthwhile to think about them?
Ok, it's a funny idea, guys 'n gals in suits on a bike, but those things are fairly cheap, simple to repair etc...
you could make three-wheelers with an extra cart, if you wish, and they'd double as excercise equipment, too.
imagine a base with semi-well cleaned 'roads', wouldn't it be simpler to take a quick jump on a bike to the nearest reactor, powerplant, whatever, it being half a mile away...if you take a buggy, you have to check the engine and stuff, plus they weigh a *lot* (transport to Mars) compared too a sturdy bike.
you could ship dozens, insttead of one, two personal mini-rovers...
has there been experiments, and if not, why not? People afraid of being laughed at? The current suits much too stiff to do that?

It's a great idea...except any manual expenditure of energy requires oxygen. On Mars the bike would need to have a reserve supply - which would increase the weight of the bike...resulting in great energy expenditure...so a solar-electric /boosted powered bike would be probably better: especially if loads have to be carried. But it will be lighter and simpler than a four-wheeled vehicle, that's for sure 8)

Rxke · 2006-07-08 11:08:14

manual expenditure of energy requires oxygen.

Hm. Good point... People riding bikes can easily consume 20-fold as much oxy than people resting...

Austin Stanley · 2006-07-08 22:26:25

Hm. Good point... People riding bikes can easily consume 20-fold as much oxy than people resting...

Which is a BIG problem for people designing those spacesuits. Space suits (regardless of type) are likely use a pure O2 life support atmosphere, at realitivly low pressures, like Apollo did. This will likely be combined with some sort of re-breather system that will absorb the CO2 out of the air-supply. If the consumtion of oxygen raises drasticly, so will the production of CO2, possibly beyond the suits ability to supply and purify, which would be a very bad thing.

Another issue is how the extral thermal energy will be dissipated. Working hard means the body heats up and must cool itself via persperation. In a normal presurised suit there are limits to the rate in which this heat can be dissipated. In a tension suit, I'm not sure how the heat will be dissipated at all. The mechanical pressure the suit puts on the skin doesn't leave alot of room for the bodies sweat to be wicked away or idealy evaporated.

quasar777 · 2006-07-21 12:48:17

i think the original authors of the moonbike did indeed leave a bit to be desired in these departments. i`m not sure everyone has read all the references to this. one of the ways this is "beaten" is by a linear dirve rather than cyclic. cyclic pedaling has a greater range of motion than linear.

quasar777 · 2006-08-02 15:08:23

the legs (below the knees, anyway) don`t need to move up & down in linear pedaling(actually it`s called treadling) therefore less sweating, chafing, etc..

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