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Old 19-10-2014, 23:04   #1
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Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

Hello Sailing Friends,

I have to maintain cardio fitness, I mean I have a slightly defective heart valve, in my 60's that is no threat as long as I maintain cardio fitness.. Anyway, for twenty years I have thought that a 10-20 speed stainless bike to charge batteries would be cool. Now that I have a cat with huge amounts of room with the Helia 44, is it a possibility.. ? Like maybe with a DC permanent magnet motor, or better yet with an alternator with a regulator bypass to a variable potentiometer that you could dial up the charge on... ?? Before I re-invent the wheel here, I am just wondering if any of you have seen such a production model?

It is not so much about power.. Yes, I have solar, plus portable solar, and a 9.5 kva Cummins Onan. And yes I am up with wind generators, I have had them before.. A bit noisy at times.. This is for when at anchor... I will have no power problems for maybe 30 days in summer when it is so hot I will run the genset a few hours at night to get to sleep in a hot spell.. (I cannot sleep if over 30 C or so..) Maybe about 30 days in winter it will be nice to run the genset a few hours a night for heat as my multiple Cruiseaire units are salt water condensed reverse cycle. The rest of the year though, I will be trying to run as much on solar as possible and this could be a little boost. I mean my workout on it for 45 min- hour, my Wife, maybe my Daughter or guests?? That plus the solar might supplement the power for my three refrigeration systems.. This would be cardio exercise with a purpose... ??

So, really not for the power, more for the cardio-vascular work when cruising, with a purpose... But 10-20 amps or more might make it worthwhile...

Look Friends, if you can show me it is just crazy, fine. I do not remember my engineering math enough to calculate the horsepower for say 10-20 amps at 14 volts, gear drive down with say maybe a 20 speed bike drive or if it is even possible. Something tells me it would be too much torque, but then I was thinking get it going on a low gear and then step it up changing gears???? ...

Tell me I am nuts and I can forget about it forever... That or tell me if you have seen one OK? Anyone can have this idea if it works and could go into production.. I will be job one.. heh he..

Helia 44
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Old 19-10-2014, 23:19   #2
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

So are you looking for something like this, except only 12V and no 120V tap?

Buy Now Pedal Power Bicycle Generator Alternative Green Human Power Energy

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Old 19-10-2014, 23:19   #3
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

> But 10-20 amps or more might make it worthwhile...

Stationary bike generation has been discussed a few times. In the last thread that I recall ( Anyone Tried Making your own Watermaker?) I gave the numbers:

"A top pro cyclist can sustain around 300 watts (5 or 6 times as much in a short burst). Figure your average sailing cruiser would be lucky to do 1/3 of that for any reasonable length of time. So about 8 amps @12v"
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Old 19-10-2014, 23:21   #4
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

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Interesting - the ad gives the same figures that I did, "up to 300 Watts" and "usually put out about 100 Watts of power".
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Old 19-10-2014, 23:47   #5
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

You will spend more on food to replace the calories you use to pedal the bike than you will spend to fuel the genny to make the same amount of power you generated. You would be best off just buying a cheap or used exercise bike and just give it away when it corrodes.
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Old 19-10-2014, 23:53   #6
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

Hmmm...

Very good StuM.. That is pretty close.. They say the average person can do 100-120 watts.. ? That is not great at sort of 8-10 amps. I went to Google, and found it Currently unavailable.
We don't know when or if this item will be back in stock.


Oh well, maybe another good idea I can bury and not to think of again... Stu, your estimate of 8 amps was very good, and it makes it not worth the effort or space... Unless someone comes up with a 10-20 speed gear drive version or something... 8 amps is not efficient enough. Right now I am testing a 240 watt flat flexible panel sika-flexed (Matrix polyurethane adhesive) on to a white fiberglass canopy like a boat deck.. It is putting out 11 amps..

Unless someone knows of a better exercise bike/charger I may have to get my cardio somehow else. Too bulky for only 8 amps reward.. I was hoping for the 10-20 amps to make the space use worthwhile... OH well

Another good idea...
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Old 20-10-2014, 00:00   #7
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

Gearing will make no difference, it just means that your 100 watts moves more weight more slowly or less weight faster. Total available power is still going to be what your muscles can generate - around 100 watts.
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Old 20-10-2014, 00:12   #8
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

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Gearing will make no difference, it just means that your 100 watts moves more weight more slowly or less weight faster. Total available power is still going to be what your muscles can generate - around 100 watts.

True enough.
But I've often wondered if a great heavy flywheel would solve the problem. The gears could let you get the wheel up to speed, then engage the generator, and a 'maintenance' pace could keep the wheel spinning at the higher revs.
Presumably a clever poindexter has tried such a thing and found it to be unworkable, but you never know...
In cars a heavy flywheel helps fuel economy for highway driving thanks to that momentum, but worsens fuel economy in stop-start driving. Perhaps this principle could work here.


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Old 20-10-2014, 00:46   #9
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

TANSTAAFL
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Old 20-10-2014, 01:19   #10
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

Power out is derived from power in, minus losses to friction, heat, etc.

No amount of clever gears or flywheels or perpetual motion devices will get past the reality that a human being can only put out so much.

I used to build ergo-metric devices for a university and I was quite dismayed when I found out how little power we put out, even the top level athletes who came to see us for assistance.

Quite frankly, I am sceptical about maintaining 100 watts, I am a commuter cyclist who frequently rides 20km to work, and I would not back myself to maintain 100 watts for more than half an hour.

Matt

P.S. Gears are the last thing you would want. If you went down this path you would calculate the optimum drive ratio for your generator that involved you pedalling at around 90 rpm (optimum power output for most cyclists is around 90 rpm.). Gears are just drag, weight and maintenance.
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Old 20-10-2014, 07:06   #11
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

Due respect to your Uni days Matt, power out does indeed equal power in minus losses.
But momentum is velocity x mass; the greater the mass the less power is required to maintain the velocity. Which would you prefer, being hit in the head by a ping pong ball or a golf ball, assuming identical velocity?
Putting momentum in the same sentence as perpetual motion is adding hyperbole into an otherwise rational engineering discussion.


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Old 20-10-2014, 08:46   #12
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

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But momentum is velocity x mass; the greater the mass the less power is required to maintain the velocity.
Nope. Using that logic, a heavier car will get better gas mileage.

There is no free lunch. F=ma

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Old 20-10-2014, 09:02   #13
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

All i can think of are the old hand powered 12V generators.

https://www.readymaderesources.com/c.../prod_325.html



Of course they can be powered by foot as well.
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Old 20-10-2014, 10:42   #14
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

I think you guys are barking up the wrong tree here. Mankind's evolutionary advantage is that he thinks, not that he is strong. I get enough exercise sailing. If I gain weight while sailing, I start taking the graveyard shift. (nobody around and lots of work to do while on passage)
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Old 20-10-2014, 14:29   #15
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Re: Anyone seen a stainless exercise bike that would charge batteries at 10-20 amps?

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Due respect to your Uni days Matt, power out does indeed equal power in minus losses.
But momentum is velocity x mass; the greater the mass the less power is required to maintain the velocity. Which would you prefer, being hit in the head by a ping pong ball or a golf ball, assuming identical velocity?
Putting momentum in the same sentence as perpetual motion is adding hyperbole into an otherwise rational engineering discussion.


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Yes, but to get the momentum you have to put power in. So you still don't solve anything with the heavy flywheel.

Sorry if the perpetual motion remark confused things, I was being light hearted.

Matt
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