My Own Trainer Project
- Thread starter Alex Simmons
- Start date
Well I'm now investigating the use of hysteresis brakes and power controls, which would enable quite fine and regulated torque control. They would simply be an extension to the axle and would remove all lateral forces. Control down to 5W increments could well be possible. Torque from these brakes is independent of the rotational speed of the brake and the power control auto adjusts for changes due to heating.
Will let you know how that goes. They are probably quite expensive though.
The pic I posted is not my trainer but a mate's. It was the inspiration for what I'm looking at though. I'll try to get a pic of the prototype unit this will be based on.
I am assuming the flywheel will be rotating at something like 200-800rpm depending on gearing. The flywheel and hub weighs in at 44kg by the way
One thing is for sure - I'm not a mechanical / electrical / engineer anything
This is fun though.
Will let you know how that goes. They are probably quite expensive though.
The pic I posted is not my trainer but a mate's. It was the inspiration for what I'm looking at though. I'll try to get a pic of the prototype unit this will be based on.
I am assuming the flywheel will be rotating at something like 200-800rpm depending on gearing. The flywheel and hub weighs in at 44kg by the way
One thing is for sure - I'm not a mechanical / electrical / engineer anything
This is fun though.
BTW - the intended location for my trainer is in a new attic room I've had built into my home. Will be quite fun to get it up there though!
It would probably be easier to take the roof off and hire a crane for the afternoon. Anyway, it looks like an AWESOME setup.Alex Simmons said:
Tyson
Holy ****!! I only just had a whole new roof put on - I'm not pulling it off againSillyoldtwit said:It would probably be easier to take the roof off and hire a crane for the afternoon. Anyway, it looks like an AWESOME setup.
That looks similar to something my old coach used to have but in reverse:
http://www.abcc.co.uk/Articles/int_train1.html
He went on to integrate it into a box section "frame" where the bars and seat were free from the contraints of a standard bike frame. You could put the saddle anywhere between an effective seat angle of 40 and 100 degrees if you'd so wish. Due to the massively over engineered design, flex wasn't apparent either - you could probably stick Michael Hubner or Curt Harnett on that and it'd stay solid. LOL
http://www.abcc.co.uk/Articles/int_train1.html
He went on to integrate it into a box section "frame" where the bars and seat were free from the contraints of a standard bike frame. You could put the saddle anywhere between an effective seat angle of 40 and 100 degrees if you'd so wish. Due to the massively over engineered design, flex wasn't apparent either - you could probably stick Michael Hubner or Curt Harnett on that and it'd stay solid. LOL
Update:
1. I have just picked up a 2nd hand SRM Pro / PCV to put on the trainer.
2. No response from hysterisis brake rep here in Oz. The US guy was quick but local guy has not exactly been forthcoming. Need to follow up again.... I may just go back to the idea of some strong magnet proximity. It's cheap to try. Magnets like those found on the home trainer in earlier post are ~$4 -$5 each.
3. Some pics of the prototype. Mine is yet to be built. I won't be cutting out sections on the flywheel like this one - rather I'll reduce the diameter an inch or so.
1. I have just picked up a 2nd hand SRM Pro / PCV to put on the trainer.
2. No response from hysterisis brake rep here in Oz. The US guy was quick but local guy has not exactly been forthcoming. Need to follow up again.... I may just go back to the idea of some strong magnet proximity. It's cheap to try. Magnets like those found on the home trainer in earlier post are ~$4 -$5 each.
3. Some pics of the prototype. Mine is yet to be built. I won't be cutting out sections on the flywheel like this one - rather I'll reduce the diameter an inch or so.
Have you considered putting an SRM on a good spinning bike?
For example, this one has a 46 lb geared flywheel and seems like it could emulate the fit of a road bike. Many spin bikes have English threaded BBs so you can install your choice of BBs.
The new Lemond indoor bikes have powermeters and aren't terribly expensive either.
For example, this one has a 46 lb geared flywheel and seems like it could emulate the fit of a road bike. Many spin bikes have English threaded BBs so you can install your choice of BBs.
The new Lemond indoor bikes have powermeters and aren't terribly expensive either.
Oh yes - the chain!! Funny - it looks worse in the photos than in real life - but it's a shocker!!. I've considered some form of chainguard to keep the sweat away.Steve_B said:OK, also - keep your chain lubricated and don't use an ergomo.
My model will have the adjustment bolts in better places etc. We could use round tubing as well.
I've ordered two large (46x30x10 mm) powerful rare earth magnets for the grand total of A$16 and we are going to rig up a device on the prototype to see what effect they have.
I've bought an SRM for the trainer.
The chains will suit the chainrings/cogs chosen. They'll cope. It's not like I'll be putting out any more power or torque than I normally do on the road.mikesbytes said:
I spoke with the guy from the hysteresis brake company today - most helpful - so he is following through with engineering in the US on the model that would best suit. It's probably a ~ A$1,500 solution though. Still, I'm investigating anyway.
In the meantime, we'll play with the eddy current effect of the rare earth magnets.
Just another quick update.
The uber strong rare earth magnets arrived for the eddy current resistance experiment.
I got two of them. They are not big - 40x30x10 mm rectangular prisms but boy do they stick!! @ A$8 it was an experiment that wouldn't break the bank.
I have to tap them with a rubber mallet to remove them from anything they are so damn strong. Impossible by hand to remove them from magnetically attracted materials. No pacemakers or hearing aids near these suckers!
Anyway, we rigged up a bodgy device which enabled me with a wooden lever to move the magnets in and away from the flywheel on the prototype trainer. No more than basically close or not close - no fine tuning possible.
It definitely caused quite a deal of resistance - John said it felt like going from 1st gear (in the 7-speed the hub gear) to to 4th gear. And all I did was bring them in a bit closer. I could sense some mechanical pulsing through the wooden level but John couldn't detect any through the cranks. Given the flywheel is "spoked" (refer earlier pictures) I suspect the effect will be better on a solid flywheel. I calculated how much to reduce the radius of the 44kg flywheel by, so mine will be a solid disk unlike John's prototype.
So John is taking the magnets to our machining friend to come up with an easy way to have the magnets held close to the flywheel and moved up/down and/or in/out. I figured installing some kind of small screw lift device that could lift the magnets up and down with reasonable precision would be ideal.
The uber strong rare earth magnets arrived for the eddy current resistance experiment.
I got two of them. They are not big - 40x30x10 mm rectangular prisms but boy do they stick!! @ A$8 it was an experiment that wouldn't break the bank.
I have to tap them with a rubber mallet to remove them from anything they are so damn strong. Impossible by hand to remove them from magnetically attracted materials. No pacemakers or hearing aids near these suckers!
Anyway, we rigged up a bodgy device which enabled me with a wooden lever to move the magnets in and away from the flywheel on the prototype trainer. No more than basically close or not close - no fine tuning possible.
It definitely caused quite a deal of resistance - John said it felt like going from 1st gear (in the 7-speed the hub gear) to to 4th gear. And all I did was bring them in a bit closer. I could sense some mechanical pulsing through the wooden level but John couldn't detect any through the cranks. Given the flywheel is "spoked" (refer earlier pictures) I suspect the effect will be better on a solid flywheel. I calculated how much to reduce the radius of the 44kg flywheel by, so mine will be a solid disk unlike John's prototype.
So John is taking the magnets to our machining friend to come up with an easy way to have the magnets held close to the flywheel and moved up/down and/or in/out. I figured installing some kind of small screw lift device that could lift the magnets up and down with reasonable precision would be ideal.
Nice thinking, and that's the sort of action I meant, although only one jaw moves in a vice, so for perpendicular control that wouldn't work for a magnet rither side of the flywheel.Steve_B said:
I was thinking of the magnets moving parallel to the plane of the flywheel, more than perpendicular. My gut tells me that the resistance will vary depending on the radial position of the magnets relative to the flywheel axle. I figure that moving the magnets a mm parallel to the flywheel axle will be a much finer change in resitance than a mm perpendicular. But I could be oh so wrong!
But being able to easily control both directions would be nice.
I think that you're right about that.Alex Simmons said:
These are the basic assumptions that I'm working with on my project (although in this instance, "working with" means "thinking about after I've had a few beers")...
* Resistance increases with strength of the magnetic field.
* Resistance increases with speed of the conductor through the magnetic field
* Resistance decreases with the SQUARE of the distance between the magnet and the moving conductor.
This implies that if you increase the perpendicular distance by a mm, say 10 to 11 mm, then you'll decrease the resistance by about 21%. (1.0^2 compared to 1.1^2) But if you decrease the radial distance by a mm, say 200 to 199 then the speed of the conductor will only decrease by about 1% . (200^2 compared to 199^2)
I've got ten of the strong magnets to experiment with on my 300PT, and my current 'best idea' is to use two or four or six or eight of them at a time at a pre-set position to set the rough range of resistance, and use the last pair moving radially to fine tune it.
-- Bryan
Disected my RavX trainer a while back. It uses eddy current braking too. The way they did the cable actuation is kinda neat. The Braking occurs in a flat aluminum ring with 6 magnets on the inside diameter, and 6 on the outside. The inside 6 are stationary while the outside 6 rotate concentric with the spinning aluminum ring. When all 12 magnets are aligned as close as possible (There's a gap to allow the ring to spin between them) the resistance is highest. When the 6 outer magnets are rotated away (staggered) from the inner 6 the resistance is lowest.Alex Simmons said:
So on your flywheel, I'm thinking one magnent could be stationary, while the other one simply moves in-plane (not sure if the xy axis would matter) with the disk.
If it helps I can draw a diagram...
Dave
Yes pleasevladav said:
It need to be a simple mechanism, easy to craft up from something and keeping the cost down.
Ugggh, me likey simple.Alex Simmons said:Yes please
It need to be a simple mechanism, easy to craft up from something and keeping the cost down.
http://render-2.snapfish.com/render2/is=Yup6aQQ%7C%3Dup6RKKt%3Axxr%3D0-qpDPfRt7Pf7mrPfrj7t%3DzrRfDUX%3AeQaQxg%3Dr%3F87KR6xqpxQQQGxlPJxne0xQQQGlPJne00aaqpfVtB%3F*KUp7BHSHqqy7XH6gX0QPJn%7CRup6l0n%7C/of=50,554,443
AutoCAD it ain't.
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