Direct driving with a mid-drive kit????

Hugh-Jassman · Jul 29, 2015

Ok, I have been racking my mind for a way to avoid using the bikes gears from a mid-mounted motor. Because I think it may produce too much chain wear from driving up our 8% grade with about 350-400lbs too often; and the gear changing problems.

This would last longer if I were to run a heavier BMX chain to the right sized sprocket cog, (or a Gates belt pulley) to climb our steep hills without bogging down. Leaving room for a 6 or 7 speed cassette; I do not know what size to put on the drive wheel, but would not be very large if the motor's second stage reduction output is only around 100rpm.

Will the motor bog down when climbing a 3-5% grade? Seems like the only drawback would be that the powered cruising speed would be so slow that I would want to use my legs. It seems like a fair trade off. What other problems could there be?

This will also make the bike more legal. It looks to me that if a mid-drive can drive your bicycle faster than 20 mph even with your cadence at 80 RPM, it can't be considered legal. Not that the cops care, but the lawyer of the drunk driver that runs into you could screw you to the wall.

opperpanter · Jul 29, 2015

What are you proposing? replacing the rear cassette by a single gear?

GreyVlad · Jul 30, 2015

Hugh-Jassman said:
Ok, I have been racking my mind for a way to avoid using the bikes gears from a mid-mounted motor. Because I think it may produce too much chain wear from driving up our 8% grade with about 350-400lbs too often; and the gear changing problems.

This would last longer if I were to run a heavier BMX chain to the right sized sprocket cog, (or a Gates belt pulley) to climb our steep hills without bogging down. Leaving room for a 6 or 7 speed cassette; I do not know what size to put on the drive wheel, but would not be very large if the motor's second stage reduction output is only around 100rpm.

Will the motor bog down when climbing a 3-5% grade? Seems like the only drawback would be that the powered cruising speed would be so slow that I would want to use my legs. It seems like a fair trade off. What other problems could there be?

IMHO no problems, except for some complexity of a second (left hand) driving chain setup. Perhaps, a suitable hub motor in a rear wheel would be just a more simple project in your case.

Hugh-Jassman · Jul 30, 2015

for some reason I do not like hub motors.....I have seen photos of drive with two chain on the casset side.

I really liked the nuvinci with two chain driving it, but too expensive etc.

can anoy one tell me what the rpm put-put of the Lightening Rods 1500watt kit at 1500 watts is?? I am looking for a power graph for it now.

That's about all I would need for 400lbs on an 8 % grade at 20mph. maybe ai should gear for 18mph.

GreyVlad · Jul 31, 2015

Sorry for my misunderstanding of your first post, Hugh-Jassman.
(I should like to see the practical power chart of the motor too, but don't know who will measure that parameters)
If we input your parameters (400 lbs, 18 mph, 8% grade) to EBike Powercalc Rev6 then after some calculations we can see that theoretically the motor should be suitable for that conditions at 22.2 Amp, 61 volts, 4082 rpm if wheel diameter is 0.49 m and total reduction ratio is 13:1 from the motor to a rear wheel rpm.

But I disregarded that efficiency of the motor is less than 100%.

Hugh-Jassman · Aug 1, 2015

thanks...that should help....I really need to figure out how to operate those calculators.

I tryed several times to open an account at the EBike Powercalc Rev6.....but their computer would not let me in.

are there any calculators that are easy to use, that I can get into?

this one is only for hub motors http://www.ebikes.ca/tools/simulator.html

maybe this will work, but ai will have to do teh gear reduction my self...?
http://www.electric-bicycle-guide.com/electric-bicycle-calculators.html

this one comes close but not perfect....well with out all the details it will never get very close.
http://www.electric-bicycle-guide.com/electric-bicycle-calculators.html

Hugh-Jassman · Aug 1, 2015

why is it that I cannot find any photos of a two stage reduction to the drive wheel????ok I found two but not very clear, but ai need more.

Is it that every one wants to build their bike into an illegal motrocycle?

GreyVlad · Aug 3, 2015

Hugh-Jassman said:
thanks...that should help....I really need to figure out how to operate those calculators.

I tryed several times to open an account at the EBike Powercalc Rev6.....but their computer would not let me in.

are there any calculators that are easy to use, that I can get into?

I found this calculator http://endless-sphere.com/forums/viewtopic.php?t=538 very useful. It is clear and 'open source' and so it is 'expandable' for your own needs.
Miles, thank you very much!
I only inserted ATAN() at G17 cell: =9.8*Mass*(G10/3.6)*SIN(ATAN(Grade/100))
Of course, we have 'to play with' various gear ratios and it is interesting.

Hugh-Jassman · Aug 3, 2015

thanks .... am going to need some caffine now.....

Hugh-Jassman · Aug 5, 2015

What would be the lost energy percentage for each belt driven, gear reduction? And do chains loose more energy?

And what other losses are there? Like the motor it's self can't be 100% efficient....?

Some one should do a graph of that motor from the LightningRods kit,

GreyVlad said:
Sorry for my misunderstanding of your first post, Hugh-Jassman.
(I should like to see the practical power chart of the motor too, but don't know who will measure that parameters)
If we input your parameters (400 lbs, 18 mph, 8% grade) to EBike Powercalc Rev6 then after some calculations we can see that theoretically the motor should be suitable for that conditions at 22.2 Amp, 61 volts, 4082 rpm if wheel diameter is 0.49 m and total reduction ratio is 13:1 from the motor to a rear wheel rpm.

But I disregarded that efficiency of the motor is less than 100%.

Lurkin · Aug 5, 2015

Let me get this straight - you want to lose the main functionality of a mid drive to do exactly what that functionality is for - climbing ability without compromise to ordinary travel.....
Have you stopped and thought about what this is going to be like to ride on the flat and downhill?... Gears will also allow you to use less power (and thus less weight/ expense) to achieve the same climb.

You need to work out the gearing to get the gearing ratios between the motor you want to use and the gradient/speed you want to climb at. Actually, working this out will also assist with how much power you need, and therefore what mid drive motor to buy....

GreyVlad · Aug 6, 2015

Hugh-Jassman said:
What would be the lost energy percentage for each belt driven, gear reduction? And do chains loose more energy?

And what other losses are there? Like the motor it's self can't be 100% efficient....?

Some one should do a graph of that motor from the LightningRods kit,

Total transmission losses from a mid-motor shaft to a rear tire are not less than 5%.

It is possible to model the LightningRod motor performance graph after reading the first two pages of the great post by safe
http://endless-sphere.com/forums/viewtopic.php?f=2&t=1062 and following his 'Motor University Lessons...zip'.
Only need to know the motor resistance and no-load current.
The Excel diagram may look like that attached. (It is not the diagram of the motor of the LightningRod's kit)

ScooterMan101 · Aug 19, 2015

First of all , what mid - drive motor do you have ?
also
Why are you making this so complicated ?
Example:
You have gears now Right ?
So
Put your chain around on of those gears, Leave the Rear Derailleur on for now to act as a chain tensioner .
Now Drive on that Front Chainring , Rear Cog, combo on your route.
then change to a different rear cog. same route.
then to a different rear cog. same route.
and on until you do all combinations .
Now you have , right in front of your eyes, the front chainring size, and rear single cog size !
Have we come to rely so much on computers that you can forget how to do real world testing ?

>

Hugh-Jassman said:
Ok, I have been racking my mind for a way to avoid using the bikes gears from a mid-mounted motor. Because I think it may produce too much chain wear from driving up our 8% grade with about 350-400lbs too often; and the gear changing problems.

This would last longer if I were to run a heavier BMX chain to the right sized sprocket cog, (or a Gates belt pulley) to climb our steep hills without bogging down. Leaving room for a 6 or 7 speed cassette; I do not know what size to put on the drive wheel, but would not be very large if the motor's second stage reduction output is only around 100rpm.

Will the motor bog down when climbing a 3-5% grade? Seems like the only drawback would be that the powered cruising speed would be so slow that I would want to use my legs. It seems like a fair trade off. What other problems could there be?

This will also make the bike more legal. It looks to me that if a mid-drive can drive your bicycle faster than 20 mph even with your cadence at 80 RPM, it can't be considered legal. Not that the cops care, but the lawyer of the drunk driver that runs into you could screw you to the wall.

Direct driving with a mid-drive kit????

Hugh-Jassman

1 kW

opperpanter

100 W

GreyVlad

100 mW

Hugh-Jassman

1 kW

GreyVlad

100 mW

Hugh-Jassman

1 kW

Hugh-Jassman

1 kW

GreyVlad

100 mW

Hugh-Jassman

1 kW

Hugh-Jassman

1 kW

Lurkin

100 kW

GreyVlad

100 mW

ScooterMan101

1 MW

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