Drunkskunk
100 GW
This is one of those non relivant, theoretical questions. Whats more efficent for an electric motor to push over your average city street: No suspension, or Full suspension?
Full suspension VS no suspension
- Thread starter Drunkskunk
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Ypedal
100 TW
For your question, No-suspension.. ( less weight to push )
For rider = full suspension !
For rider = full suspension !
vanilla ice
1 MW
Not just weight tho. The rear suspension causes some squat under accel right? Which means xx% of your power is being used to heat up the rear shock.
Ypedal
100 TW
Considering the weight we strap on to these things, the benefits of suspension outweigh the technical challenges of battery mounting and wire routing..
My full suspension bike is by far.. FAR.. more comfortable to ride any distance..
And really.. comfort on a bicycle is what Ebikes are all about !
My full suspension bike is by far.. FAR.. more comfortable to ride any distance..
And really.. comfort on a bicycle is what Ebikes are all about !
Gregory
100 kW
I have a theory that Full Suspension bikes encourage the rider to hit bigger bumps than a hard tail because the rider doesn't feel them as much. But the bike is still subject to the whole thump, increasing mechanical failure like pinch flats, stress fractures.
Where as a hard tail rider takes time to better match speed to road condition and avoid hitting rocks/potholes/kerbs, and I would think this translates to less stress on the bike.
But I can see why we compromise for comfort too.
Where as a hard tail rider takes time to better match speed to road condition and avoid hitting rocks/potholes/kerbs, and I would think this translates to less stress on the bike.
But I can see why we compromise for comfort too.
I've actually quit riding my non suspension e-bike because my back can't take it anymore. The roads just aren't good enough and too much construction. I've had it. Its over. I'm done. Looking at new frames now. I think it might be cheaper to get the full suspension frame and fork and then transfer everything from my existing bike rather then dump $1000+ and get a bike that already has the fork steer tube cut off which results in a non comfortable mountain bike style handle bar position. I want the front end to be jacked up to the sky. Get at least 100mm fork and 130 degree stem and a crap load of spacers. Probably won't even cut the steer tube.
Ypedal
100 TW
http://www.youtube.com/watch?v=IsrpzLA3ODg
Doing this on a non-suspended bike would be a tad rough..
Doing this on a non-suspended bike would be a tad rough..
BiGH
100 kW
i've got a front suspension lockout on the front of my bike and i ahve eto say i prefer to leave the lockout off - so i get front suspension. I've ridden rear suspension bikes too - i'd love it if i could find a really strong framed downhill bike that i could dual motorise.... (with 150mm dropouts)
one can dream.
one can dream.
Mark_A_W
100 kW
Me likee Miss Dually
A dually is a good match for a motor, as pedal bob becomes less of an issue, as does the extra weight (although my stock dually is lighter than my hardtail...that's just down to cost).
Suspension on the motor wheel helps protect the rim. But with a 4kg front wheel, my bomber forks don't do much for "little" bumps, only for drops like gutters.
A dually is a good match for a motor, as pedal bob becomes less of an issue, as does the extra weight (although my stock dually is lighter than my hardtail...that's just down to cost).
Suspension on the motor wheel helps protect the rim. But with a 4kg front wheel, my bomber forks don't do much for "little" bumps, only for drops like gutters.
disndat
100 W
Hey guys I have been wondering about this stuff myself.I now use a Kona Hoss frame(really beefy) and I have seat post suspension and marzoochi forks.For riding on the trails I have no problems with comfort,but I want to make an off road monster low top speed but heavy torque to climb dirt trails and hills.I never use just the motor(I dont mind pedaling)but the guys at the LBS say I would have better contol and handling if I stayed with a hard tail.Plus I'm told they are virtually maintenance free.What do you guys think?The motor will be an 5304 on a 20" rim with 10 gauge spokes.
TylerDurden
100 GW
Comfort is one thing, distributing the energy from impact over time is another. Those shock-forces can crack welds, cave wheels and fatigue metals.
Without suspension, wheels take a royal bashing. The weight of bike, rider, powertrain, batteries and any cargo all focus on those little hubs and spokes.
When dropping off curbs or riding over rocks, I'll take a thump over a bang any day.
Without suspension, wheels take a royal bashing. The weight of bike, rider, powertrain, batteries and any cargo all focus on those little hubs and spokes.
When dropping off curbs or riding over rocks, I'll take a thump over a bang any day.
Jeremy Harris
100 MW
I agree with all the other comments, sometimes comfort, reliability and reduced maintenance/repair costs are more important than outright efficiency.
However, the original question asked about efficiency. I interpret this as being "would an electric bike with suspension use more or less energy to travel over a given course than an electric bike without suspension, assuming that the weight and aerodynamic drag were the same for both bikes".
At the moment, the answer has to be that the suspended bike would use more energy, as the suspension systems that are available all absorb energy and convert it to heat.
If we had suspension systems that were able to absorb the energy of going over bumps, then put 100% of it back into propelling the bike, then we'd get the best of both worlds, comfort and the same efficiency as a rigid frame.
One thing worth looking at is the range of suspension movement. For a road bike this doesn't need to be very great, even just 1/2" of travel will soak up a very great deal of road harshness. Generally, the smaller the suspension travel the less energy it absorbs. I'm only going to use a very modest travel, rising rate, system for my project, just enough to smooth out the worst that British roads have to offer..............
Jeremy
However, the original question asked about efficiency. I interpret this as being "would an electric bike with suspension use more or less energy to travel over a given course than an electric bike without suspension, assuming that the weight and aerodynamic drag were the same for both bikes".
At the moment, the answer has to be that the suspended bike would use more energy, as the suspension systems that are available all absorb energy and convert it to heat.
If we had suspension systems that were able to absorb the energy of going over bumps, then put 100% of it back into propelling the bike, then we'd get the best of both worlds, comfort and the same efficiency as a rigid frame.
One thing worth looking at is the range of suspension movement. For a road bike this doesn't need to be very great, even just 1/2" of travel will soak up a very great deal of road harshness. Generally, the smaller the suspension travel the less energy it absorbs. I'm only going to use a very modest travel, rising rate, system for my project, just enough to smooth out the worst that British roads have to offer..............
Jeremy
sulphuric99
10 mW
With a full suspension bike, the wheels should spend more time gripping the ground and less time bumping all over the place. So maybe the overall efficiency at the same speed could be higher depending on how rough the terrain is.
I've put several hundred miles on my two ebikes - one a downhill with full suspension, and the other a hardtail. Both are heavy steel bikes. For me, I greatly prefer the full suspension bike. On the hardtail, a "large" (5-6 inch) drop off a curb feels tramautic, particularly to the ~30 pounds of batteries on the back rack. By comparison, the suspension bike doesn't even blink. Also, I'm much more willing to take the occasional offroad shortcut with suspension.
The extra weight of full suspension is probably no big deal in most setups considering the weight of the motor and batteries.
I've put several hundred miles on my two ebikes - one a downhill with full suspension, and the other a hardtail. Both are heavy steel bikes. For me, I greatly prefer the full suspension bike. On the hardtail, a "large" (5-6 inch) drop off a curb feels tramautic, particularly to the ~30 pounds of batteries on the back rack. By comparison, the suspension bike doesn't even blink. Also, I'm much more willing to take the occasional offroad shortcut with suspension.
The extra weight of full suspension is probably no big deal in most setups considering the weight of the motor and batteries.
safe
1 GW
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Back in 1978 I remember going to the library (well before the internet) and finding a book that was about bicycle theory. They went through all the basics of aerodynamics and the like and they also came up with a few interesting results:
The diameter of the tire has more to do with rolling resistance than tire width. In other words, "bigger tires roll easier" and as long as you keep the weight down on the tire and keep high inflation pressures there is little in the way of losses due to tire width.
Suspension allows the center of mass of the bike and rider to maintain a straight path rather than having to ride up and down little mountains. (bumps) Since the bike no longer has to lift the bike up and over all these little "mini-mountains" it has less work to do and therefore it's more efficient.
Aerodynamically you lose more to the wind than all other losses above about 20 mph. This one everyone knows, but the two above are less known.
...the book had a lot of other things in it, but is was 29 years ago so my memory is fading.
The diameter of the tire has more to do with rolling resistance than tire width. In other words, "bigger tires roll easier" and as long as you keep the weight down on the tire and keep high inflation pressures there is little in the way of losses due to tire width. Suspension allows the center of mass of the bike and rider to maintain a straight path rather than having to ride up and down little mountains. (bumps) Since the bike no longer has to lift the bike up and over all these little "mini-mountains" it has less work to do and therefore it's more efficient. Aerodynamically you lose more to the wind than all other losses above about 20 mph. This one everyone knows, but the two above are less known....the book had a lot of other things in it, but is was 29 years ago so my memory is fading.
safe
1 GW
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The Last Word on Rear Suspension
I can remember that for years and years people just couldn't figure out a way to get the rear suspension to not bob up and down as a result of pedaling. The reason is that when you pedal on a normal swingarm the pulling of the chain makes the rear shock compress. In response designers would move the swingarm pivot point up a little and then it would work better, but once you went past the center of the pivot it would revert back to the same problem. (or it would do the reverse and introduce lockout)
Finally people realized:
"What if you had an infinitely variable rear pivot point location?"
...and that's what they've arrived at. It's called "Virtual Pivot Point" and Santa Cruz bicycles is very protective of their patent. (and has forced other manufacturers to trash their designs because they infringed on theirs) There are a few variations out there that get past the patent but implement the same basic concept.
So the path of the rear wheel now looks like this:
I can remember that for years and years people just couldn't figure out a way to get the rear suspension to not bob up and down as a result of pedaling. The reason is that when you pedal on a normal swingarm the pulling of the chain makes the rear shock compress. In response designers would move the swingarm pivot point up a little and then it would work better, but once you went past the center of the pivot it would revert back to the same problem. (or it would do the reverse and introduce lockout)
Finally people realized:"What if you had an infinitely variable rear pivot point location?"
...and that's what they've arrived at. It's called "Virtual Pivot Point" and Santa Cruz bicycles is very protective of their patent. (and has forced other manufacturers to trash their designs because they infringed on theirs) There are a few variations out there that get past the patent but implement the same basic concept.
So the path of the rear wheel now looks like this:
safe said:
(snarf) not hardly!
there's numerous <A HREF="http://www.dreambike.com/suspension.htm">dissenting views</A> about the effectiveness of a VPP or if it's simply hype.
I've read in other places as well that the wheel path is an 'S' & not vertical.
I know nothing of suspension systems.
As such I resort to first principles to answer the question of which is more efficient.
To cut to the chase, my reasoning is that in terms of absolute efficiency,
*NO* suspension is always more efficient than full suspension.Consequently to date I've refused to own anything more than a hardtail, though that may change now that suspensions have vastly improved.
The drawback of added weight aside, as I see it any suspension system requires energy input to operate.
Any energy that goes into the suspension is energy that isn't making it to the ground for propulsion.
Even though some of the suspension's energy is recovered, any system has losses associated with it
You can see that energy out to the ground will always be less than the energy in, be it from an electric, gas or human motor.
But, like I said, that's only in theoretical terms, in real life the efficiency depends on the situation.
The prime function of any suspension system is for control, in those instances where you have an abundance of energy to spare but because of terrain or whatever it's not making it to the ground to move forward faster.
In that case it's a net gain to lose some of the available energy to the shock & take the efficiency hit since you're not benefitting from the excess energy anyway.
The problem is that with a human motor there's generally not a whole lot of extra energy to spare to make this tradeoff worthwhile.
The only(?) time there is a surplus of energy is when going downhill where the potential energy from altitude is added to the riders input
So for DH riding, FS recoups some this added energy & translates it into faster forward motion while maintaining control.
On flat smooth terrain over a long haul, the spring sucks energy out of the rider, is much more tiring & is why I had no interest in FS.
However with the assault on BOB in the newer suspensions, with things like 'brass mass' (which is cutesy marketing hype & big bucks for something a basic as a check valve) I expect their efficiency to be much better & I'm tempted to try FS once again.
Now in the case with an added motor/battery energy delivery system, you have excess energy input available to you all the time, so FS makes more sense.
Even so, with motor only you would (theoretically) squeeze out more range with no rear suspension to bleed off some of your battery's supply, but I would think the difference to be minor.
On generally even city pavement where I do most of my riding, a hardtail with suspension seatpost is what I have now following this line of logic because I have a small 8Ah battery pack.
When I do get an FS this will probably be the first comparison I'll test out to nail down exactly how much range a suspsension costs, if any.
EMF
100 kW
I suppose that a full suspension bike is less efficient in power transmission than a ridgid frame model. How much this affects the ride time, I don't know if it is significant or not. But, on my next project, I'm gonna be looking for a full suspension frame, just to try one out with electric. My present bike has no suspension at all, I also keep the tires pumped up to the max for efficiency reasons and due to this, I can feel every crack in the pavement.
In my town, most of the roads are just not in that great of condition, plus they have dips for drainage etc. I find this extremely annoying as I ride.
I would trade off the transmission loss if I could smooth out the road with a nice suspension system...one that reallly works.
In my town, most of the roads are just not in that great of condition, plus they have dips for drainage etc. I find this extremely annoying as I ride.
I would trade off the transmission loss if I could smooth out the road with a nice suspension system...one that reallly works.
Ypedal
100 TW
Quality Suspension ( I emphasize quality.. as cheap suspension is nothing more than a spring on a rod.. ) and 60 psi tires are the ticket for Ebikes !
I can, and do hit 1" deep potholes at 40 km/h without loosing my fillings ! lmao.. or getting pinch flats. :wink:
I honestly don't think the little bit of energy lost in the suspension is that considerable.
How many of you out there can stand on the pedals and crank hard *( with yout butt off the seat ) on your ebikes ? i suspect not many.
Generally, you power on.. and pedal at your hearts contempt while sitting down, this does not cause much Bobbing of the bike and the suspension losses don't really come into play..
Safe's 1978 book is obsolete ! ( I was born in 78 !!! )
I can, and do hit 1" deep potholes at 40 km/h without loosing my fillings ! lmao.. or getting pinch flats. :wink:
I honestly don't think the little bit of energy lost in the suspension is that considerable.
How many of you out there can stand on the pedals and crank hard *( with yout butt off the seat ) on your ebikes ? i suspect not many.
Generally, you power on.. and pedal at your hearts contempt while sitting down, this does not cause much Bobbing of the bike and the suspension losses don't really come into play..
Safe's 1978 book is obsolete ! ( I was born in 78 !!!
)
Geez Ypedal, sir, you are like almost 130 years old!! I'd wager your even older than safe (no offence)!. How you do that?
I think that some nice use of spring steel, can make a sweet suspension frame design- you can tailor it to the weight and shock effect you want.
Negligible loss with rear suspension imho. A smoothing out of unnecessary spinal cord vibration is always good, especially for older skeletal systems.
I think that some nice use of spring steel, can make a sweet suspension frame design- you can tailor it to the weight and shock effect you want.
Negligible loss with rear suspension imho. A smoothing out of unnecessary spinal cord vibration is always good, especially for older skeletal systems.
Jeremy Harris
100 MW
The suspension power loss isn't from the drive, in the main (so called "bobbing loss") it's from the deflection of the suspension itself and the energy that it absorbs from bumps.
The really easy way to show this is to ride an air shock bike hard over some bumps then feel the heat in the shock. That heat has come from somewhere. The only source is rider/motor effort.
As a wheel hits a bump it deflects upwards, but the vector is angled rearwards, due to wheel rotation and forward motion.
On a suspension bike this compresses the spring/damper, on the non-suspended bike it just lifts the bike and rider.
When the wheel has passed the bump, the unsuspended bike very quickly pushes back down, as there is no damper, which, again because of wheel rotation and the angle of the bump, gets converted partially into forward drive as the wheel rolls off the other side of the bump. In effect, the bike weight is slightly increased as it bounces back down on the slight slope of the bump down face.
On a suspended bike, the damper will slow the return stroke quite a bit, so the energy return is a great deal less.
The most energy efficient bikes are those that have very rigid wheels and frames, although they are also extremely uncomfortable on rough surfaces.
Jeremy
The really easy way to show this is to ride an air shock bike hard over some bumps then feel the heat in the shock. That heat has come from somewhere. The only source is rider/motor effort.
As a wheel hits a bump it deflects upwards, but the vector is angled rearwards, due to wheel rotation and forward motion.
On a suspension bike this compresses the spring/damper, on the non-suspended bike it just lifts the bike and rider.
When the wheel has passed the bump, the unsuspended bike very quickly pushes back down, as there is no damper, which, again because of wheel rotation and the angle of the bump, gets converted partially into forward drive as the wheel rolls off the other side of the bump. In effect, the bike weight is slightly increased as it bounces back down on the slight slope of the bump down face.
On a suspended bike, the damper will slow the return stroke quite a bit, so the energy return is a great deal less.
The most energy efficient bikes are those that have very rigid wheels and frames, although they are also extremely uncomfortable on rough surfaces.
Jeremy
jerryt
100 W
I have ridden a non-suspension ebike maybe 2 hours per day for only about a month on city streets so I don't have a lot of experience. Its pretty rough on my old back especially when I can't see the bumps which makes me want suspension. For me, the asphalt is worse than concrete because the black color camoflages where a tree root has raised the street.
I believe 2 things happen: First the wheels leave the ground termporarily (expending energy lost). Second the bike tends to weave probably due to my surprise at being jolted and the bikes top heavy nature. I tend to let off the throttle as I try to regain control and lose more energy.
I believe suspension will keep the wheel on the ground plus the obvious comfort.
I believe 2 things happen: First the wheels leave the ground termporarily (expending energy lost). Second the bike tends to weave probably due to my surprise at being jolted and the bikes top heavy nature. I tend to let off the throttle as I try to regain control and lose more energy.
I believe suspension will keep the wheel on the ground plus the obvious comfort.
Well my backs feeling better since I quit riding. I use to have a Schwinn mesa gsx hardtail with front rock shox but sold it when my knee kept getting inflammed from constant pedalling. It was a pretty good bike at $500 back then but I remember the posture was no good being all bent over from the large frame and long top tube. Lot of pressure on the arms. I've taken up walking right now and the knee can go for about 2 miles before starting to flame up. Took a couple pills, its ready to go again.
The worst bumps for a non suspension bike are the ones where they dig a trench for road work and then they do a horrible patch job resulting in a mini speed bump. Or just poor road paving. Its like moguls out here! The road crews should loose there jobs for such poor quality. Walking around with there big beer bellys and scratching there ass. And you know what else they do? They will just re-pave the middle section of the road and not the bike lane/shoulder part letting it deteriorate into a bikers worst nightmare.
The worst bumps for a non suspension bike are the ones where they dig a trench for road work and then they do a horrible patch job resulting in a mini speed bump. Or just poor road paving. Its like moguls out here! The road crews should loose there jobs for such poor quality. Walking around with there big beer bellys and scratching there ass. And you know what else they do? They will just re-pave the middle section of the road and not the bike lane/shoulder part letting it deteriorate into a bikers worst nightmare.
Jeremy Harris
100 MW
For energy to be "lost" (in reality just converted to another form, most likely heat) work needs to be done. The bike just jumping up a bit in the air won't do much work against the air around it, so little energy will be lost.
If you think of suspension units like bike tyre pumps (which they are very similar to in many ways) then it's clear that when they move they convert some of the energy put into the piston rod into heat.
A rigid frame bike also does this to some extent, as the frame deflects under load it also warms up a bit. The major difference is one of scale, a rigid frame does not deflect anywhere near as much as a suspension unit, so absorbs less of the riders energy.
I'd be the first to say that some form of suspension is very nice to have, but the trade off we accept for comfort and reliability is a small overall efficiency loss.
Jeremy
jerryt
100 W
I'm trying to say that when the power propelled wheel is spinning and not touching the ground it therefore is not using its energy to propel the bike.
Sorry if I was unclear.
jerryt
100 W
Hey D-Man I can identify with what you're saying
I'm riding mine almost like a motorcycle and just pedal on start-up. I've got such a large seat and its set down too far to make pedaling comfortable.
Walkings good and I'm glad its working out for you.
I've had to adjust and readjust my ride to get comfortable and get the pressure off my hands, arms and back.
I'm riding mine almost like a motorcycle and just pedal on start-up. I've got such a large seat and its set down too far to make pedaling comfortable.
Walkings good and I'm glad its working out for you.
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