Bike motor

MisterBill2

Joined Jan 23, 2018
7,034
Consider how slowly the motor would be turning. only ten times as fast as your pedaling speed. Now conside how fast DC motors usually turn. Mostly over 1500RPM. So you would be running the motor in a stalled mode, unless it was made for that sort of application. Do some research of DC motors in a catalog and see about the normal operating speeds to deliver the rated power.
To do it that way you could use a DC motor with a gearbox built in. Thhose are quite common and that could provide the speed that you needed, in the range of 100 to 250 rpm. That would come close to your pedaling speed range.
If you put a larger sprocket on the opposite side of the rear hub and a small sprocket on the motor that might work fairly well. You may even find a surplus gear motor at a decent price.
You never mentioned what sort of bike. Ten speed, 15 or 18 speed, or single speed with a coaster brake.. I have seen an electric add-on for a three wheel bike that was awesome.
 

Thread Starter

beatsal

Joined Jan 21, 2018
169
Consider how slowly the motor would be turning. only ten times as fast as your pedaling speed. Now conside how fast DC motors usually turn. Mostly over 1500RPM. So you would be running the motor in a stalled mode, unless it was made for that sort of application. Do some research of DC motors in a catalog and see about the normal operating speeds to deliver the rated power.
To do it that way you could use a DC motor with a gearbox built in. Thhose are quite common and that could provide the speed that you needed, in the range of 100 to 250 rpm. That would come close to your pedaling speed range.
If you put a larger sprocket on the opposite side of the rear hub and a small sprocket on the motor that might work fairly well. You may even find a surplus gear motor at a decent price.
You never mentioned what sort of bike. Ten speed, 15 or 18 speed, or single speed with a coaster brake.. I have seen an electric add-on for a three wheel bike that was awesome.
Yes, I do have a 12 VDC geared motor, not sure of the gear ratio. Trying to visualize what you meant by "If you put a larger sprocket on the opposite side of the rear hub and a small sprocket on the motor that might work fairly well. " A sketch would help.
Thanks
 

MisterBill2

Joined Jan 23, 2018
7,034
Yes, I do have a 12 VDC geared motor, not sure of the gear ratio. Trying to visualize what you meant by "If you put a larger sprocket on the opposite side of the rear hub and a small sprocket on the motor that might work fairly well. " A sketch would help.
Thanks
What I mean byt "opposite side" is the side of the rear hub that does not have the free-wheel assembly. On bikes with disk brakes it is the side with the disk. A disk brake hub would be perfect if you could get one at a reasonable price, which I have not seen. You would need to enlarge the hole in the large sprocket quite a bit, and drill holes for the attachment bolts, but it would be a very sanitary way to go. If you put a belt-pulley on then you could easily disengage the motor when not using it.
 

Janis59

Joined Aug 21, 2017
1,227
I am using 350W 42V. Complications - if crising speed is 25 kmph, then driving up the bridge is 14 and if wind against then only 7 kmph. So the power is hardly too small. Voltage - as lover Amperage as better battery gives out the force
 

MisterBill2

Joined Jan 23, 2018
7,034
Where do you get that number? I ask since that would be hard *cadence*(pedalling RPM) for even a very fit biker to do. The most common cadence goal for people riding for exercise is only 60RPM.
That RPM number was for the small sprocket driving on the back side of the normal drive chain . The pedaling speed would be a lot less. read what the TS SAID IN POST #19 to understand what I was suggesting. if the gear-motor sprocket has one fifth as many teeth then the pedaling rate would be 20 to 50, a reasonable rate.
Gear ratios can be very handy.
 

shortbus

Joined Sep 30, 2009
7,945

Audioguru again

Joined Oct 21, 2019
1,921
Instead of adding an electric motor to my bike, I lost weight and now use my 75 years old muscles.
I already had a heart attack 11 years ago but luckily I survived and got fixed. Two blocked arteries were opened with stents and I changed my diet and take pills to eliminate cholesterol.

Exercising with my bike is preventing another heart attack, not causing one. Being sedentary with an electric bike is the same as sitting in a wheelchair ready to die, isn't it?
 

MisterBill2

Joined Jan 23, 2018
7,034
My suggestion is to have a low enough low gear and know when and how to use it. I often see folks riding by at a calm pace but their feet are flying on the pedals because they are in way to low a gear,. There is a time and a place for using hose bottom gears but it is seldom, and not on level paved roads.
 

Thread Starter

beatsal

Joined Jan 21, 2018
169
If you go by that then your 100 to 250RPM would be way too slow. "Typical MTB cranks with three chainrins of 44, 32 and 22 teeth" - https://bike.bikegremlin.com/104/bicycle-gear-ratios-speeds-gear-inches/

At 60 rpm the chain is moving at
44 x 60 = 2640 and 22 X60 = 1320 links per minute to the rear sprocket no matter it's tooth count.
I am thinking of mounting the geared motor as shown in attached sketch. I had asked this before but w.o. sketch. Any comments/suggestions?
 

Attachments

MisterBill2

Joined Jan 23, 2018
7,034
OK, if the gear motor has a ten tooth sprocket, then
At 60 rpm the chain is moving at
44 x 60 = 2640 and 22 X60 = 1320 links per minute to the rear sprocket no matter it's tooth count. then at ten teeth per revolution=10 links per revolution we get 132 rev per minute.
Pedaling my bike at 60 crank revs per minute is moving fairly fast, since I tend to cruise in top gear. I know that Lance Armstrong can keep that up for hours at a time, "I ain't him."
 

shortbus

Joined Sep 30, 2009
7,945
I am thinking of mounting the geared motor as shown in attached sketch. I had asked this before but w.o. sketch. Any comments/suggestions?
What type bike? That may work with a single speed type bike, but don't think it will with a multi speed, if you change gears. As the chain is shifted it also goes at an angle between the front and rear sprockets, so you would need to accommodate for that. And doing it like you propose would mean you would always need to keep pedaling at what ever speed the motor is moving. Unless you come up with a modification to the pedal/sprocket using what is called a one way bearing or sprag clutch. https://www.bocabearings.com/products/bearing-and-ball-types/one-way-clutch-bearings?ProductType=0

I still stand by my earlier post about the old Whizzer type of motorized bike. It is also how the very earliest motorcycles were made. Doing it that way is less work and unless you can machine your own parts will be cheaper. Here is a forum pretty much dedicated to what your trying to do, read a lot and get some more ideas before spending you money, unless your rich.:) https://motorbicycling.com/threads/rear-belt-drive.32125/page-5
 

Thread Starter

beatsal

Joined Jan 21, 2018
169
What type bike? That may work with a single speed type bike, but don't think it will with a multi speed, if you change gears. As the chain is shifted it also goes at an angle between the front and rear sprockets, so you would need to accommodate for that. And doing it like you propose would mean you would always need to keep pedaling at what ever speed the motor is moving. Unless you come up with a modification to the pedal/sprocket using what is called a one way bearing or sprag clutch. https://www.bocabearings.com/products/bearing-and-ball-types/one-way-clutch-bearings?ProductType=0

I still stand by my earlier post about the old Whizzer type of motorized bike. It is also how the very earliest motorcycles were made. Doing it that way is less work and unless you can machine your own parts will be cheaper. Here is a forum pretty much dedicated to what your trying to do, read a lot and get some more ideas before spending you money, unless your rich.:) https://motorbicycling.com/threads/rear-belt-drive.32125/page-5
Thanks. What is the post # for Whizzer type; could not find much in the link
 

shortbus

Joined Sep 30, 2009
7,945
Thanks. What is the post # for Whizzer type; could not find much in the link
Post #15 the one with the alternator motor Youtube. Under it is a link to what a Whizzer was. For electric you would just substitute an electric motor for a gas engine. The rear wheel pulleys where available new on Ebay, haven't looked lately though. If they are still on Ebay I'll post a link.
 

Thread Starter

beatsal

Joined Jan 21, 2018
169
The connection of the engine to the bike, looks like a pulley arrangement? Not very clear. Also, the motor U-tube, the alternator shows 3 stator terminals so how does it connect to DC as a motor?
 

Thread Starter

beatsal

Joined Jan 21, 2018
169
The connection of the engine to the bike, looks like a pulley arrangement? Not very clear. Also, the motor U-tube, the alternator shows 3 stator terminals so how does it connect to DC as a motor?
Is it possible to buy this as a kit; my mech. skills are not good!
 

shortbus

Joined Sep 30, 2009
7,945
The connection of the engine to the bike, looks like a pulley arrangement? Not very clear. Also, the motor U-tube, the alternator shows 3 stator terminals so how does it connect to DC as a motor?
The alt/motor becomes a BLDC motor and uses a ESC just like a hub motor. And yes the Whizzer is belt drive, old system but works. Here are some links that could work for you -
The rear wheel sheave/pulley - https://www.ebay.com/itm/Rear-wheel-sheave-fits-Cruzzer-whizzer-motorbikes-and-motorized-bicycles/224163485426?hash=item34312f56f2:g:ZGQAAOSwrklVFznC

Here is another type that is a replacement for a chian drive for a gas motor. It mounts on the opposite side of the rear wheel, the side without the pdal chain. No reason it couldn't be used with an electric motor. - https://www.ebay.com/itm/Drive-Pulley-Rear-Wheel-Pulley-T-Belt-Kit-For-2-Stroke-66cc-Motorized-Bike/143711199384?hash=item2175dae098:g:3nAAAOSwxYNfTGFz



Is it possible to buy this as a kit; my mech. skills are not good!
Didn't you say you wanted to do this yourself? Since there is no kit to do what you want any thing other than a hub motor rear wheel is going to need mechanical skills. One other thing is when you add more power to a bicycle or anything that moves, you need to upgrade the brakes too. Not just from the extra speed available but the added weight.

If you want something to help the bike on hills why not a gasoline motor? There are many "kits" to do that and they are not too expensive. Plus gasoline is cheaper than batteries any day. https://www.ebay.com/itm/Full-Set-24-26-80cc-2-Stroke-Bike-Gas-Motor-Engine-Kit-Cycle-Motorized-Bicycle/142903619427?_trkparms=aid=1110006&algo=HOMESPLICE.SIM&ao=1&asc=227685&meid=3c1fd3b5e6bd4ccfadc267e5e153eaa6&pid=100005&rk=6&rkt=12&mehot=co&sd=133221911808&itm=142903619427&pmt=1&noa=0&pg=2047675&algv=SimplAMLv5PairwiseWebWithDarwoV3BBEV2b&brand=Unbranded/Generic&_trksid=p2047675.c100005.m1851
 

Thread Starter

beatsal

Joined Jan 21, 2018
169
The alt/motor becomes a BLDC motor and uses a ESC just like a hub motor. And yes the Whizzer is belt drive, old system but works. Here are some links that could work for you -
The rear wheel sheave/pulley - https://www.ebay.com/itm/Rear-wheel-sheave-fits-Cruzzer-whizzer-motorbikes-and-motorized-bicycles/224163485426?hash=item34312f56f2:g:ZGQAAOSwrklVFznC

Here is another type that is a replacement for a chian drive for a gas motor. It mounts on the opposite side of the rear wheel, the side without the pdal chain. No reason it couldn't be used with an electric motor. - https://www.ebay.com/itm/Drive-Pulley-Rear-Wheel-Pulley-T-Belt-Kit-For-2-Stroke-66cc-Motorized-Bike/143711199384?hash=item2175dae098:g:3nAAAOSwxYNfTGFz





Didn't you say you wanted to do this yourself? Since there is no kit to do what you want any thing other than a hub motor rear wheel is going to need mechanical skills. One other thing is when you add more power to a bicycle or anything that moves, you need to upgrade the brakes too. Not just from the extra speed available but the added weight.

If you want something to help the bike on hills why not a gasoline motor? There are many "kits" to do that and they are not too expensive. Plus gasoline is cheaper than batteries any day. https://www.ebay.com/itm/Full-Set-24-26-80cc-2-Stroke-Bike-Gas-Motor-Engine-Kit-Cycle-Motorized-Bicycle/142903619427?_trkparms=aid=1110006&algo=HOMESPLICE.SIM&ao=1&asc=227685&meid=3c1fd3b5e6bd4ccfadc267e5e153eaa6&pid=100005&rk=6&rkt=12&mehot=co&sd=133221911808&itm=142903619427&pmt=1&noa=0&pg=2047675&algv=SimplAMLv5PairwiseWebWithDarwoV3BBEV2b&brand=Unbranded/Generic&_trksid=p2047675.c100005.m1851
I first thought of a gas engine but it increases the weight more than a motor? Hence, dropped it.
 
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