Turbo trainers are more suitable for aerobic work than anaerobic, just use the highest gear you can spin smoothly and work on technique - it sounds like you're pedalling in squares rather than circles if you;re breaking traction. I occasionally use free rollers when I don't feel like going out but feel I should get some bike time - they use only the rolling resistance of tyres on rollers but I can work up a good sweat in the right gear. As for flywheels - there's not much point adding mass near the centre - wrapping some lead sheet (or old lead pipe beaten flat) around the outside of the existing flywheel will have more effect for less farting around - just attach it with a large jubilee clip. You'll probably need to balance it by trimming a bit off here and there.
Yes. Once an normal flywheel is up to speed, little matters. But the flywhe el on a bike trainer is a proxy for forward momentum on a real road.
And the feed of power from pedals is not 'linear'. pedals provide almost si nusoidal power (low-high-low on each downstroke). It is the 'high' bit (whe n pedal cranks are approaching horizontal, pedal similar height both sides of the bike) when LOTS of torque is being added, and the flywheeel does no t (CAN not) 'feel' like the actual resistance of linear pedal to angular ge ars/wheel to linear inertia.
It is peculiar, hard to explain. I was not expecting it to be quite so obvi ous. But if you get to try a bike trainer, set it on high resistance, but i n a low gear, and you will quickly see what I mean.
My issue is that even at the highest gear, it is still very noticeable. Off putting and not 'natural'
diameter) with this material. I need a ~1cm diameter hole in the centre for access to a nut: Imagine a shallow wide bowl, with an attachment in the b ottom. (See further down if you really want to know why).
e thread on the existing spindle (hence the fillable cylinder with the nut access). A machined piece (with suitable centre holes cut) would suit very well, but is beyond my means.
but empty. I need to fill it with something heavy.
n wet, but I suspect less than 1.0 (water) when dry.
and not that dense.
ay suit, but I cannot fine useful indications of density when dry. Anyone a ny experience?
eded - as long as it done not 'slosh around' or easily leak, it should be O K)
scenario is not pleasant. (see below)
with embedded ball bearings?). But stability and failure scenarios are an issue.
ally big, thick washer) which could be securely fixed inside my 'bowl' woul d be great. I have considered dumbbell type weights, but none I can find su it the size limits I have. And actually, something TOO heavy is likely to s trip of the short thread/nut I have available on the existing end of the ax is in the device.)
o back wheel of my bike) for excerise etc. during winter. It has an integra l flywheel around 10cm diameter, listed at 1.25 Kg.
on pedals), there is so little angular inertia that I 'fall' rather that a dd power. Not explaining very well, but more simply: I want to add extra we ight/angular inertia to my existing flywheel.
nces are not good: e.g. ball bearing scattering at high speed (have you see n Swordfish? (don't bother if you have not...)).
portion of sand I can add to remain stable at high rotations?
I suspect no-one's ever tested sand/epoxy mixes for spin stability. But you can buy ready sand epoxy mixes sold as repair mortars. Balance requires an even spread somehow. And I might leave a series of little gaps round the o uter edge for later placement of balance weights, in case necessary. Polyst yrene could make the gaps.
Yes. An extra cylinder attached on the same axle, but further out
yes the 'baking dish' approach is what I am using. A 'cylinder/bowl' similar size and shape to the existing flywheeel, but empty, and facing out away from it. So I am extend along the line of the axle.
Think of articulated lorries with an extra tyre at the end of the axle..
Do you think adding weight will increase the effort required very much?
I have a cross-trainer that works on the same mechanism, and most of the effort is required to overcome the magnetic/eddy current braking, the level of exercise is controlled by moving the magnet closer to the spinning wheel, when the magnet is away there's not much force required merely to spin the flywheel.
I have the mathematics knowledge, but not the practical.
I do find it hard to just 'cycle' as if I am on a flat plane, though I appreciate the trainer is probably best for this.
What I am try to do is adjust the base characteristics of it so that it feels a little more like a real bike. It is very obvious that increasing the gear while decreasing the magnetic resistance DOES help, but I am reaching the limit.
I am hoping (with what I have read) that a larger angular inertia will make the feel more like being on a real bike with my linear inertia (mass).
m diameter) with this material. I need a ~1cm diameter hole in the centre f or access to a nut: Imagine a shallow wide bowl, with an attachment in the bottom. (See further down if you really want to know why).
ble thread on the existing spindle (hence the fillable cylinder with the nu t access). A machined piece (with suitable centre holes cut) would suit ver y well, but is beyond my means.
, but empty. I need to fill it with something heavy.
hen wet, but I suspect less than 1.0 (water) when dry.
ve and not that dense.
may suit, but I cannot fine useful indications of density when dry. Anyone any experience?
needed - as long as it done not 'slosh around' or easily leak, it should be OK)
e scenario is not pleasant. (see below)
y, with embedded ball bearings?). But stability and failure scenarios are a n issue.
really big, thick washer) which could be securely fixed inside my 'bowl' wo uld be great. I have considered dumbbell type weights, but none I can find suit the size limits I have. And actually, something TOO heavy is likely to strip of the short thread/nut I have available on the existing end of the axis in the device.)
to back wheel of my bike) for excerise etc. during winter. It has an integ ral flywheel around 10cm diameter, listed at 1.25 Kg.
nd on pedals), there is so little angular inertia that I 'fall' rather that add power. Not explaining very well, but more simply: I want to add extra weight/angular inertia to my existing flywheel.
uences are not good: e.g. ball bearing scattering at high speed (have you s een Swordfish? (don't bother if you have not...)).
roportion of sand I can add to remain stable at high rotations?
ou can buy ready sand epoxy mixes sold as repair mortars. Balance requires an even spread somehow. And I might leave a series of little gaps round the outer edge for later placement of balance weights, in case necessary. Poly styrene could make the gaps.
That sounds good. I have the advantage of a 'former' which is neatly circul ar already.
And as I have said, there is already a fair degree of instability in the wh ole 'bicycle with heavy cyclist whose tyre is pressed against roller to dri ve a magnetically braked flywheel axle' system , that the imbalance may be (relatively) undiscernible.
I am not trying to increase the effort, I am trying to damp down the variat ion in input from pedals. On a flat plane, with cleats, one can pedal apply ing a fairly continuous torque at all positions of you legs/feet. But when accelerating, downstrokes are much more variable. The most torque is presen t when cranks are horizontal, the least (at the end of each leg's downstrok e) when the cranks are vertical (one up, one down). It is the variability h ere I am trying to dampen.
The resistance in a trainer represents the air resistance/friction/incline on a real road. The flywheel represents momentum: Momentum cannot change in stantaneously (you cannot go from stationary to 20 mph in an instant). Neit her can a flywheel.
If you are on a bike attached to a frame with nothing restraining the rear wheel, and stand on the pedal, you 'drop' fast, and the wheel accelerate fa st. The only thing stopping your leg dropping as if it were not on a pedal is the angular inertia of the tyre. If you were on a road, it would ALSO be constrain by the requirement for you and the bike to gain linear momentum forward.
This latter forward momentum change is what thee flywheel on a trainer is t here for, but it relates heavily to the torque (and mass) of the cyclist up on it.
That sounds like a physics lecture, and for that I apologise. I am still tr ying to work my head around the practical application of what (I think) I u nderstand the theory to be.
Understood. I have several cycles, a MTB tandem and big magnetic exercise bike. ;-)
Understood, but I'm not sure how much rotational mass you would need to add to change that? The flywheel on our exercise bike is both large (~400 mm diameter) and very very heavy, yet I can still spin it up easily when the load is turned off. With the load wound up I can stand up and it's like cycling though treacle.
I believe I do.
I do understand that to get the right real-world feel you may need something more sophisticated than your existing trainer?
Understood.
When cycling on the flat at a moderate speed, most people will feel the advantage of the mass of the cycle carrying them over TDC of the pedal action. As any incline increases (or forward wind resistance) the inertial doesn't carry you as well / far during the TDC so you get a more erratic / pulsy forward movement.
For a trainer this means matching the load to the flywheel / pseudo inertia combo, possibly not that easy on a clip-on trainer compared with a dedicated machine?
diameter) with this material. I need a ~1cm diameter hole in the centre fo r access to a nut: Imagine a shallow wide bowl, with an attachment in the bottom. (See further down if you really want to know why).
le thread on the existing spindle (hence the fillable cylinder with the nut access). A machined piece (with suitable centre holes cut) would suit very well, but is beyond my means.
but empty. I need to fill it with something heavy.
en wet, but I suspect less than 1.0 (water) when dry.
e and not that dense.
may suit, but I cannot fine useful indications of density when dry. Anyone any experience?
eeded - as long as it done not 'slosh around' or easily leak, it should be OK)
scenario is not pleasant. (see below)
, with embedded ball bearings?). But stability and failure scenarios are an issue.
eally big, thick washer) which could be securely fixed inside my 'bowl' wou ld be great. I have considered dumbbell type weights, but none I can find s uit the size limits I have. And actually, something TOO heavy is likely to strip of the short thread/nut I have available on the existing end of the a xis in the device.)
to back wheel of my bike) for excerise etc. during winter. It has an integr al flywheel around 10cm diameter, listed at 1.25 Kg.
d on pedals), there is so little angular inertia that I 'fall' rather that add power. Not explaining very well, but more simply: I want to add extra w eight/angular inertia to my existing flywheel.
ences are not good: e.g. ball bearing scattering at high speed (have you se en Swordfish? (don't bother if you have not...)).
proportion of sand I can add to remain stable at high rotations?
you can buy ready sand epoxy mixes sold as repair mortars. Balance require s an even spread somehow. And I might leave a series of little gaps round t he outer edge for later placement of balance weights, in case necessary. Po lystyrene could make the gaps.
Polyester resin is new to me. But sounds pretty perfect (available, practic al, cheap) along with lead weights/flashing on within the outer rim.
sinusoidal power (low-high-low on each downstroke).
l similar height both sides of the bike) when LOTS of torque is being added , and the flywheeel does not (CAN not) 'feel' like the actual resistance o f linear pedal to angular gears/wheel to linear inertia.
bvious. But if you get to try a bike trainer, set it on high resistance, bu t in a low gear, and you will quickly see what I mean.
Off putting and not 'natural'
Yes.
Looks like you have a very clear understanding and experience of this stuff . So it may be a pipe dream
In my head, I 'feel' that I can aim to proxy both the resistance (air etc.) of a bike ride (through the magnetic brake) but also the effects of linear momentum (via angular momentum of flywheel).
From what you say, it appears unlikely. Though do you think/believe that a larger flywheel would suit a a larger person?
I think I need to sit down and do the mathematics.
Well, I've been cycling for over 50 years and experimented with a couple of dedicated cycle trainers etc so I know 'a bit' (but just a bit). ;-)
Only in as much of the limits you may have with the kit you have there.
Understood.
Well, possibly but that doesn't mean you shouldn't explore the options yourself. ;-)
I'd say 'a more powerful / experienced cyclist'. ;-)
At the end of the day, some things just need to be tried and so *if* you can get to where you think you want to be without 1) damaging anything 2) wasting too much time or 3) wasting too much money (based on your own levels of interest etc) then it might be worth a go.
So, I'd start with whatever would give you the biggest effect for the lest effort / risk, so if it's practical sticking ally wheel balance weights (your local tyre fitters might give you a couple of strips if you go in and ask nicely) round the outside and backed up with some wire and tape etc? If the inside of the flywheel is useable then that would be easier of course.
You are very welcome ... I'd be interested in the outcome of anything you do try. ;-)
With a ~10cm diameter flywheel you have about a 31.4 cm circumference and each 7gm weight is ~16mm wide you should be able to get 20 weights = about 140gms right around the outside (= best effect). That's only an increase in total mass of about 1/9th but it might be noticeable if it's all concentrated around the outside (assuming my maths is ok)?
Now that I know what its for I do think an opportunity exists here for a rechargeable battery device so you can use your efforts to do more than heat up a friction pad. Brian
In this case it's not a friction pad but a magnetic 'load' Brian but I've always thought that all this energy is being wasted in gyms around the world.
The problem is being creating a suitable load that will accept all the power whilst not being overcharged but still being of use.
So, use an MPPT type charge controller to charge a battery and then use that battery to run the lights?
diameter) with this material. I need a ~1cm diameter hole in the centre fo r access to a nut: Imagine a shallow wide bowl, with an attachment in the bottom. (See further down if you really want to know why).
le thread on the existing spindle (hence the fillable cylinder with the nut access). A machined piece (with suitable centre holes cut) would suit very well, but is beyond my means.
but empty. I need to fill it with something heavy.
en wet, but I suspect less than 1.0 (water) when dry.
e and not that dense.
may suit, but I cannot fine useful indications of density when dry. Anyone any experience?
eeded - as long as it done not 'slosh around' or easily leak, it should be OK)
scenario is not pleasant. (see below)
, with embedded ball bearings?). But stability and failure scenarios are an issue.
eally big, thick washer) which could be securely fixed inside my 'bowl' wou ld be great. I have considered dumbbell type weights, but none I can find s uit the size limits I have. And actually, something TOO heavy is likely to strip of the short thread/nut I have available on the existing end of the a xis in the device.)
to back wheel of my bike) for excerise etc. during winter. It has an integr al flywheel around 10cm diameter, listed at 1.25 Kg.
d on pedals), there is so little angular inertia that I 'fall' rather that add power. Not explaining very well, but more simply: I want to add extra w eight/angular inertia to my existing flywheel.
ences are not good: e.g. ball bearing scattering at high speed (have you se en Swordfish? (don't bother if you have not...)).
proportion of sand I can add to remain stable at high rotations?
you can buy ready sand epoxy mixes sold as repair mortars. Balance require s an even spread somehow. And I might leave a series of little gaps round t he outer edge for later placement of balance weights, in case necessary. Po lystyrene could make the gaps.
Not impossibly expensive at all, but certainly a bit of car body filler & s and could be cheaper. I doubt anyone knows what ratio to use though.
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