A
Alaskavan
Guest
grndslm, many are. For example:
http://www.americanchaindrive.com/
http://www.americanchaindrive.com/
S
SirJakesus
Guest
I would figure most homebrew ones are chain driven. Internally geared hubs don't offer continuously variable gearing like this thing.
I saw somebody doing one on endless sphere a few hours after posting that.. d'oh!
I saw somebody doing one on endless sphere a few hours after posting that.. d'oh!
Z
Zomby Builder
Guest
e bike
Batteries are getting mo betta. I have also seen a killer right side drive emotor. Don't recall the thread but it's here someplace. A-Dog has the only pics that I have seen but it all works right sided with a freewheel. Not too $$ either. NV is a perfect match for that.
Batteries are getting mo betta. I have also seen a killer right side drive emotor. Don't recall the thread but it's here someplace. A-Dog has the only pics that I have seen but it all works right sided with a freewheel. Not too $$ either. NV is a perfect match for that.
D
duivendyk
Guest
If people had read my post,"power,torque and rpm",with application to Nuvinci,they might have gained an understanding about the capabilities & limitations of the Nuvinci hub.The math in it is really not all that hard.The hub is torque limited,and not power limited per se.This means that the power it can handle is proportional to input rpm.The formula is Power =0.193*Torque*rpm/1000 ,the max input torque is 95 ft.lbs, the power is in horsepower (HP),rpm is the input speed of the hub in rev/min ,the * denotes multiplication,.so we get : Power =0.0183*rpm.For instance at 200 rpm input,the hub can handle a max HP of .0183*200 or 3.66 HP. 200 rpm corresponds to about 15mph road speed (26" wheel), assuming that the hub control is set for a 1 to 1 transfer ratio.The overall range of the hub is 1.87 to 1/1.87
(0.535).So the road speed could be from 28 to 8 mph. (with a 26" wheel).Assuming that our 3.6 HP engine runs at 6000rpm,this implies a reduction of 6000/200 or 30.If you use a LARGER reduction you will apply excessive input torque to it.If you had a larger engine that is, one with higher output torque say a 5 HP one, the speed reduction would have to be less than 22
(30*3.6/5 ).These still are substantial reductions,difficult to come by without some kind of gearbox.You might wonder what a torque of 95 ft.lbs will do for you.The radius of a 26' wheel is about 1ft, so the radial force(push) is about 95 lbs.(for a 1 to 1 transfer ratio), and it can vary from 177 to 51 lbs.Let's assume that the bike + rider is 350 lbs,that means you can get up a max 30 degree slope.If you had more power you could not safely get up a steeper grade but you could get up it faster than 8mph (with a 5HP engine you could do 11 mph)
The upshot of all this is that with more engine power the reduction ratio from engine to hub has to be reduced,which is not a problem unless you are severely overweight and live in the mountains.The other point I want to make is that 95 ft.lbs is a max value,it is not clear if this is an absolute max (with no safety factor,or a permissible design limit for normal use).I would derate it by at least 40% say to 55 ft.lbs,to be on the safe side.The 0.0183 factor then becomes 0.011 and the max input power 2.2 HP instead of 3.6HP.(at 200 rpm), but you could still tackle a 16 degree incline.
To put it as simply as possible,small displacement IC engines have fairly flat torque characteristics, with peak torque in the 5000 to 6000 rpm range,and a speed range af 3000 to 8000 rpm.The torque output is roughly proportional to the power output.To prevent torque overload of the hub at max power, the gearing between engine and the hub has to be changed in inverse proportion to the max engine power capability (HP) in order to keep the input torque in the safe range.More power means more speed overall,I don't know if the Nuvinci has intrinsic rpm limitations,400 rpm input in high "gear" is 750 rpm wheel speed
(56 mph !).It was designed after all for "sedate" bicycling.
(0.535).So the road speed could be from 28 to 8 mph. (with a 26" wheel).Assuming that our 3.6 HP engine runs at 6000rpm,this implies a reduction of 6000/200 or 30.If you use a LARGER reduction you will apply excessive input torque to it.If you had a larger engine that is, one with higher output torque say a 5 HP one, the speed reduction would have to be less than 22
(30*3.6/5 ).These still are substantial reductions,difficult to come by without some kind of gearbox.You might wonder what a torque of 95 ft.lbs will do for you.The radius of a 26' wheel is about 1ft, so the radial force(push) is about 95 lbs.(for a 1 to 1 transfer ratio), and it can vary from 177 to 51 lbs.Let's assume that the bike + rider is 350 lbs,that means you can get up a max 30 degree slope.If you had more power you could not safely get up a steeper grade but you could get up it faster than 8mph (with a 5HP engine you could do 11 mph)
The upshot of all this is that with more engine power the reduction ratio from engine to hub has to be reduced,which is not a problem unless you are severely overweight and live in the mountains.The other point I want to make is that 95 ft.lbs is a max value,it is not clear if this is an absolute max (with no safety factor,or a permissible design limit for normal use).I would derate it by at least 40% say to 55 ft.lbs,to be on the safe side.The 0.0183 factor then becomes 0.011 and the max input power 2.2 HP instead of 3.6HP.(at 200 rpm), but you could still tackle a 16 degree incline.
To put it as simply as possible,small displacement IC engines have fairly flat torque characteristics, with peak torque in the 5000 to 6000 rpm range,and a speed range af 3000 to 8000 rpm.The torque output is roughly proportional to the power output.To prevent torque overload of the hub at max power, the gearing between engine and the hub has to be changed in inverse proportion to the max engine power capability (HP) in order to keep the input torque in the safe range.More power means more speed overall,I don't know if the Nuvinci has intrinsic rpm limitations,400 rpm input in high "gear" is 750 rpm wheel speed
(56 mph !).It was designed after all for "sedate" bicycling.
T
Torques
Guest
huh?
W
wanger
Guest
M
mickey
Guest
Will the HT run happily in reverse though? I still hope to try this.
W
wanger
Guest
by turning upside down arnt u reversing the direction <180> thus elimenating running moter backwards??? not sure just thinking and wouldent this make it more oil residue under piston therefore wrist bearing gets more lubrication
M
mickey
Guest
by turning upside down arnt u reversing the direction <180> thus elimenating running moter backwards??? not sure just thinking and wouldent this make it more oil residue under piston therefore wrist bearing gets more lubrication
Nope. Picture the rotation in your mind. Normal is counterclockwise when viewed from the sprocket side of the engine. The rotation on a bicycle crank is clockwise when viewed from the right.
We've discussed this type of arrangement here, but as far as I know, no one has tried it yet. The issue that will have to be addressed is spark advance, but I doubt that the HT has much.
EDIT: I'm actually keen to try this. I hope to get my spare engine back from my son soon and will mount it to an old frame for a bench test. Finding an affordable freewheel crank is hard. The cheapest I've found is about $200 for the assembly. Thats more than I paid for my bike!
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W
wanger
Guest
my wrong just mocked up and chain going anticlockwise when looking from derailer side bike
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