High torque velomobile

[jawnn]

I have decided to to use a 1000w motor 1800 rpm 48 volt hopefully with open frame or a fan ....it could be 1200w but I have no idea what we will find.....just thought that the really big motor is just a waste .....and then if the motor I get doesn't climb good enough, i can just reduce the gears more.

I am just burned out thinking about it and see that you can climb bigger hills with only 1 hp.....the gear reduction I will use is not more than 5.5" on the axle and as small as possible on the motor.... 2.5"? and it would be good to use a freewheel , but if it's hard to find....not.

so if you know of reason that I should not use a smaller motor, I need to hear it soon. also if you can mention a motor...well I have the local motor shop looking.

still dreaming.

 

[chuck]

Jawnn,

I am getting ready for work, not a lot of time to write, I will try to keep this brief.

I currently use a 1.6 hp motor at 450 lbs of weight on these hills.
When I used a 1 hp motor I weighed in at around 350 lbs.

The power I use comes from my batteries, agm odyssey batteries. With the either motor I am able to supply from the battery all of the amps (power) necessary to climb these hills. The controller is able to handle 300 amps for short periods.



You are estimating a weight of around 550 lbs.
Now, you want to find a less powerful motor. I have searched for this 1000 to 1200 watt motor for years, 48 volts and low rpm such as 1800 rpm. I have not found it.
The motor you original posted is about as ideal a motor for your application that you will find.

You must think of this as a system. The batteries, controller, motor, and gear reduction. All 4 of these need to work together efficiently. All 4 of these must be chosen carefully to work together. All 4 must meet the power requirements and fit in a fairly small package.

The motor you are describing now will require a change in design, a jackshaft will be required. Do you have enough room for this additional component? a jackshaft and additional pulleys and belt could easily on its own cost $200.

chuck

 

[TylerDurden]

Now, you want to find a less powerful motor. I have searched for this 1000 to 1200 watt motor for years, 48 volts and low rpm such as 1800 rpm. I have not found it.

Check this: http://www.thesuperkids.com/scs1izi1core.html

Here are the mechanicals: http://endless-sphere.com/forums/viewtopic.php?f=28&t=13622&start=0

The S1000 scooter ships as a 36V system. The s750 may be the same hardware run at 24V. This motor/wheel setup could be easily built into a trailer; or with some fabbing, the motor/gearing mounted on a frame to power a wheel. It does not freewheel, so that should be noted.

 

[jawnn]

I think my original question should have been: what is the smallewst motor I can use, and is there a slow rpm motor that will work?
So you think there is not a good 1800 rpm motor, at any hp? I saw one but it was 50lbs!....then it disapeared from the web.

I don't think they make that etek motor any more, but they are saying to get the newer version, but I just dont want to carry around too much weight. As is I will probly have to put the batterys in the trailer just to not stress out the two rear wheels.

I did build heavy duty wheels but the HD version of this trike has a limit of 400lbs and I am cronicly over weight, 300, so if I add more than 100lbs.....and I still may end up with too much weight.

also if the motor is a large diameter it will be much harder to move 12" from the axle.

some one is just going have to point out the motorfor me to use....like this one? http://www.robotmarketplace.com/products/ETK-ETEKBL.html

 

[chuck]

Jawnn,

That motor pmac motor is available from other places. It would work, the brushless controllers for it are pretty pricey, just so you know.

Very similar motor here, brushed.
http://www.thunderstruck-ev.com/index.php?dispatch=products.view&product_id=4

$400 motor
$200 alltrax controller
$100 drive reduction
$50 magura throttle
$100 wire, fuse, connectors
$200 for 2 diehard platinum chargers
$400 for 2 diehard odyssey batteries

This Is the motor that I will purchase for my next project. Thunderstruck ev will be able to tell you exactly what rpm to shoot for at 24 volts. Remember, a quality motor like this will last a very long time. Overall, I like the simplicity of brushed series wound motors. And the ruggedness of brushed controllers.

A pusher trailer?

A budget?

Your fabrication skills?

TD that would probably work, for Jawnns needs it would take two of those. I work with a lot of industrial drives. I currently have two baldor 90 volt dc 1/10 hp motors with gear reduction almost identical to that on my bench right now. To ask those gears to take a 1000 watt even intermitently, that is asking a lot. 500 + lbs up some pretty good slopes. I would imagine that is a 1000 watt peak, 2 to 3 hundred watts continous.

chuck

 

[REdiculous]

How bout a treadmill motor? 3HP (1.5HP cont) is pretty common and at 36v a lot will spin right around 1800rpm.

I've got mine setup so 2400-3600rpm equals 16-32mph and it's not bad but I'll probably gear it for more torque anyway. I'm running mine at 90v but I guess people have done it at 36v? Just an idea.

 

[chuck]

Jawnn,

Are you still lost? A couple of options on motors have been given here. I am concerned about the longevity of the scooter motors and the treadmill motors for your application.

I went to cloud electric this morning and priced the mars 909 motor at $375.
Pricing the controller, wire, wire lugs, pre charge resistor, manual contactor, throttle, 225 amp bussman fuse.
The entire cost was just under $900 for all of the above shipped.

This package has durability. It will not overheat on your hills. It will handle your 30 mile trips without overheating. Most importantly, it will do it everyday for a very long time with out any failures.

For under 20 mph operation a two stage reduction should be considered. The mars 909 motor at 24 volts will spin to fast for a single stage of reduction. Unless a very large rear pulley or sprocket could be used.

Torque. I have not made any torque calculations for any of the force calculations because it is not the way to calculate power or energy requirements.
In fact, torque calculations are not required at all.


For example, you said that you did not trust v-belts on a different post. I do not care for one drive over another, roller chain, timing belt, v belt. I design for efficiency, durability, longevity, and noise. And price.

You posted that you want to use a five inch sprocket or pulley vs the twelve inch that I suggested.

I can design that in. It will require two stages of reduction, two to three times the cost. a more complex design, and very probably, as much or more volumetric space to accomplish. It will be no more efficient. Probably less efficient.

Why a 12 inch pulley and not a 5 inch pulley.
Tension calculations are not particular difficult at static conditions. They can be very confusing and somewhat difficult to calculate once everything is in motion. I use charts from power transmission catalogs from major manufactures to design reduction drives. Makes it pretty simple.

A mental exercise in tension calculations.

Take your 20 inch wheel and mount it on a workbench. Remove the tire.
Take sewing thread, wrap several turns of thread around the rim in one direction.
Take the same thread, but, a different piece, attach it to a one pound weight.
The thread with the weight needs to be attached to the rim with the weight hanging freely.
Grasp the thread that is wrapped around the rim, it will have about one pound of tension on it.

Using the same setup,except, wind the thread around the hub of the wheel and grasp it. The tension of the thread is now, about, 10 pounds.

Now lets see, 10 times the force on the second thread. This is torque, it is static. There is only force to measure. No work is being done, no power is being transmitted, because there is no movement. Fundamentally, this is a torque calculation.

If there was movement, it should be easy to see that the thread around the hub would need to be 10 times stronger than the thread around the rim. And this is true.

For a given rotational power to be applied at a given wheel rpm, the velocity of the string around the rim needs to be 10 times the velocity of the string that is wrapped around the hub.

Power is force times velocity. For a given power to be applied, the higher velocity thread (the thread around the rim) will need less strength.

Generally, for good design, observe the following.
Chain is efficient at low velocity with high tension. Roller chain can only be highly efficient at very low velocities.
V belts are efficient at medium velocities with medium tensions
Timing belts, or synchronous drives are efficient at high velocities with low tensions

Good power transmission design basics using chain or belt
Keep the reduction per drive to less than 3 to 1
Maintain the largest practical center distances per drive. The center distance should not be less than the diameter of the larger pulley or sprocket. The center distance of the drive should not be more than 3 times the diameter of the larger sprocket or pulley.



How does this apply to POWER. Power being equal to force x velocity
The tension of the belt is the force in the power equation.
The velocity of the belt is the velocity in the power equation.

How does this apply to your 5 inch pulley. You will require a very large v belt, or chain to drive this smaller drive. It will not be as efficient. It will require a two stage reduction to be implemented.

Time to post and then I will discuss this some more mental exercises on motor size, weight and motor velocity for a given power output

chuck

 

[chuck]

Jawnn,

When I decided to build my first e bike I had no idea of where to get a motor or a controller. There were several e bike forums but they just did'nt talk about what I was interested in. Then I searched thru some electrathon racing websites, discovered the scott motors and the eteks that were just starting to be used.

Here is an excellent website with an excellent drive reduction using a 1 hp motor. I loosely designed my first build around Eric Peltzer's design. It worked great. Except, I used too large of a controller with this 1 hp scott motor. Tore up those timing belts. Tooo much torque because the Alltrax npx controller will supply to many amps for this setup. It worked great on the first bike if I stayed out of the throttle, second bike weighed quite a bit more, even larger batteries. I could not use the Eric Peltzer drive on the second bike.

I was already buying belts, sheaves etc from Bearing, Belt and Chain, see Eric Peltzer's website. Now, that supply for low cost parts is gone. Purvis bearing here in Dallas bought them. Expect to pay 3 times what Eric Peltzer qoutes for that drive system.

http://www.peltzer.net/ebike/

This scott motor would work for your needs, geared correctly. But, this scott 1 hp motor costs more than the 4 hp mars motor. 7 lbs difference in weight. The mars motor has quite a bit less rpm too. This makes gear reduction quite a bit easier. WITH NO LOSS IN EFFICIENCY.

How motors work. General principles that govern size.

Let us chose a perfect motor of 2 hp and 3000 rpm
A higher voltage motor will be smaller, a lower voltage motor will be larger at 2 hp 3000 rpm continous industrial rating

Let us chose a perfect motor of 2 hp and 1800 rpm
This motor will be larger than the 3000 rpm motor with a continuous industrial rating

Let us chose a 3 phase motor of 2 hp
This motor will be smaller than all of the above motors, it can be argued that it will be more efficient, it can be argued that it is not more efficient also. The controller for what we are designing here will need to be very robust. We have a large mass and some pretty good slopes, which will require a pretty powerful 3 phase controller. This controller is available, it is not cheap.

Let us chose a very high rpm motor of 2 hp, say 7000 rpm
It will be very small, active cooling will need to be implemented because of its low thermal mass. It will need quite a bit of reduction, probable that its inherent efficiency will be wiped out by the large reduction required.

http://endless-sphere.com/forums/viewtopic.php?f=2&t=10143&start=30

I wrote on page 3 the calculations due to a 10 lb weight on an electric vehicle on a 1 mile 5% slope uphill and downhill for a total of two miles.

10 lbs of weight results in a net of 7/10,000 loss of energy on a normal ride like yours,, .0007 penalty, getting a haircut will probably be more efficient than worrying about 10 lbs of weight.

Cloud electric has scooter motors, 700 watts etc, will they work? I would not waste my time on them, designed for kids on sidewalks. Their industrial rating would probably be around 10 minutes at the rated wattages. The smaller Kelley controllers may work for these small motors, with severe current limiting implemented.

chuck

 

[chuck]

found a motor, permanent magnet, continuous duty, 36 volt

http://www.surpluscenter.com/item.asp?item=5-1711&catname=electric

chuck

 

[chuck]

Jawnn,

The rated voltage of this motor is 28 amps at 36 volts. Power is volts x amps = 28 x 36= 1008 watts
The rated power of this motor is 746 watts, 1 hp = 746 watts.

The efficiency is power in / power out = to about 75%

Not real good, but it is cheap. Another way to look at this is you save money on drive reduction.
Take these savings and increase the size of the battery pack by 10%

For a 15 mph vehicle with a 20" drive wheel, the wheel rpm is as follows

To find velocity in feet per minute
15 mph x 5280 ft/mi x 1 hr/60 min = 1320 ft/min

To find the circumference of your wheel in feet, C = 2pi x radius or pi x diameter

20 in x 1 ft/12 in x pi = 5.24 ft

To find the wheel rpm divide the velocity in fpm by the circumference in feet
1320/5.24 = 252 rpm

To find the reduction ratio of the drive, divide the motor rpm by the wheel rpm
200 rpm/252 rpm = .7933

Lets find some chain sprockets that will equal .7933
45 tooth x .7933 = 35.6
44 tooth x .7933 = 34.9

The motor sprocket needs to be a 44 tooth,
The axle sprocket needs to be a 35 tooth

From my Morse chain book,
# 35 chain will be marginally adequate, it will handle about 1.5 hp with no service factor figured in, ie, shock loading
# 41 chain will not work
# 40 chain will handle 3.5 hp at this rpm

To find the hp required to climb that 16% grade velocity needs to be converted to ft/sec = 1320/60 = 22 ft/sec

Force of rolling, about 5 lbs

Force of wind resistance = 1/2 x coefficeint of drag x frontal area x density of air x velocity^2
Force of wind resistance = .5 x .9 x 4 x .0023 x 22^2 = 2 lbs

Force of weight is .16 x 600 lbs = 96 lbs

Add the 3 forces
5 + 2 + 96 = 103 lbs

To find the power multiply the force in pounds by the velocity
103 lbs x 22 ft/sec = 2266 ftlbs/sec

To find the hp, 1 hp = 550 ftlbs/sec
22/550 = about 4 hp

To find the watts, 746 watts = 1 hp
4 x 746 = about 3000 watts

The motor voltage is 36 volts
The amps required, hopefully short term
3000/36 = 83 amps

The motor efficiency is 75%
83 amps/.75 = 111 amps

We need to find a battery pack that can supply 111 amps for a short period

chuck

 

[chuck]

Jawnn,

Is this the motor that I would use. No
I would first contact the manufacturer, Imperial Electric, and ask them if a sprocket can be mounted on this motors shaft for your application.
Also, the whine of the gears on the motor may be objectionable. If so, shielding the motor would help.
Imperial owns Scott motors, this is probably a floor scrubber motor made by Scott.



Without doing all of the calculations you will need for a 30 mile trip with a healthy reserve about a 1300 watt hour pack

1300 watt hour/36 volts = 36 amp hour pack that will supply short term currents at the 3c rate

I am not in your shoes, here is one suggestion

http://www.electricmotorsport.com/store/ems_ev_parts_batteries_thunder_sky.php

The 36 volt system will need about 12 cells at $60 each, about $720
1 kg = 2.2 lbs,, at 1.5 kg per cell, this pack will weigh 40 lbs
If you get 2000 cycles out of them you will get a very conservative 60,000 miles before replacement
Others here can advise you on how to charge these and to keep them balanced etc.

I use Sears diehard platinum batteries and chargers, 3 batteries and chargers will set you back about $900 with tax. 3 year warranty
The batteries weigh 50 lbs each, 150 lbs total
Take care of them, they will provide 400 cycles, or about 12,000 miles. I expect to get quite a bit more cycles out of mine since I never discharge them more than 50%.

With the help of this forum I would think that the thundersky batteries will be about the ideal solution.

chuck

 

[chuck]

Jawn,
http://elitepowersolutions.com/products/product_info.php?cPath=26_32&products_id=105&osCsid=a8bcef8873621b73740d10cbcfc99405
Thunder sky batteries, complete package $871.70
1.54 kwh
15 amp charger
Battery balancer (eps)
42 lbs
1 year warranty

Before you decide, ask questions on this system to forum members here, I don't know if this is a good deal, or anything about the company

chuck

Edit, forgot to add the website

How the eps balancers work, this is not a battery management system, there is no low voltage shutdown, cell monitoring, or overcurrent protection
http://elitepowersolutions.com/docs/EPS_Balancers.pdf

 

[jawnn]

I was looking at the rear of the trike and decided that the big Etek motor will fit on a flat plate.

Then I realized that the 2 or 4g wire may not be flexible enough to carry in a trailer, may need to use Lithium batteries (or 12ah LAG for the shorter 10 mile round trip only).
And may need to move the under-seat steering bars to “over seat” to fit the batteries under the seat.

And with so much torque coming from the axle threw the spokes, I think I should solder the spokes where they cross.

5.5” pulley is max that will fit on the axle, so if I don’t need to reduce the gears much I could use a 3 or 4” on the motor?
I was reminded how unstable this trike is when I was going down a hill fast and twitched the front wheel bit. I keep thinking there must be a way to limit the speed like with a programmable controller, but probably not and the extra price will be too much, I am already going to have to raise more money (http://funnyfarmart.com). Wish I could just build a bigger trike.

 

[chuck]

Jawnn,

Use 2 gauge welding cable. Very flexible. Put the batteries in the trailer. With a motor, you will not have to pedal with a motor this size. I wish we could come up with a freewheel system.

Did you look at the Eric Peltzer Website I posted above? That is about what is needed for a drive reduction. Could something like this be adapted?, drive the wheel instead of the axle?

With a size limit of a 5.5 inch sprocket on the axle, a 2 stage reduction is absolutely mandatory.

Keep your spirits up

chuck

 

[jawnn]

I really like the peltzer set up and think I can build one like it. The only access to the drive train is the inside of the axle.
ths is a photo of the same trike with gasoline engine: http://www.staton-inc.com/photo_gallery_large.asp?PhotoID=277

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

Is the Gt2 belt the same as the BX belts?

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

With a size limit of a 5.5 inch sprocket on the axle, a 2 stage reduction is absolutely mandatory.

what ratio do you think should be used? actualy I can probably do this one at the max speed of 20 mph? not that I under stand just why...

 

[jawnn]

Perhaps I could motorize my bicycle much easier if I could use 500watt motor. Has any one done this?: A sheave made from a 24” wheel rim (almost 20”) bolted on the spokes of a 26” wheel maybe 13 to 1 ratio?

May need to gear it down twice but is it even possible to move 350lbs plus the motor and batteries up a 10% grade? At about 5 mph?

I could walk up the big hills. But I don’t think that bikes are practical to motorize for real utility use.

How can the Cyclone and Eco-speed motors work? No one could tell me yet they keep selling them. I know this is simple math right.

 

[chuck]

Jawnn,

Would a 2 hp 3 phase motor weigh less? Yes, a little at the 24 to 36 volt range we are talking about. 22 lbs listed here, about $75 more.
http://www.electricmotorsport.com/store/ems_ev_parts_motors_pmac.php

The problem is you will be pushing large amps to climb this hill, so a standard 3 phase hubmotor type controller would need serious modification at these voltages and current. The 3 phase controller that would work without modification is here. $525 for the controller,limited to 36 volts. This 36 volts increases the motor speed, which means even more gear reduction.
http://www.electricmotorsport.com/store/ems_ev_parts_controllers_millipak.php

To go 3 phase will almost double your cost on the motor and controller at these voltages, and increase the cost of the drive train reduction. With no noticeable increase in efficiency over the mars 909 motor and alltrax npx 4834 brushed series wound motor.

The belt that Eric Peltzer uses is made by gates and is generically speaking, a timing belt. Not a v-belt. Nice drive, for your set up I would estimate about $350 dollars for a set up similar to that with the motors I have suggested using the pg2 belt primary drive and a secondary chain drive. The gates drives can be designed into a smaller package than a v belt drive. Properly designed this drive would be about as efficient as one could get.
Remember, we have about 2 1/2 times the weight to push up your hill. Eric Peltzer weighs 160 lbs and His bike weighs 85 lbs. AAnndd, your hills are larger.

I do not have much experience with the cyclone set up. Post some links. The cyclone sounds like a great drive for your trike. If motor heating can be controlled on your hills. I hope you understand that this could be a fantastic boost up those hills.

The drive I have designed, along with the lithium batteries, would push you up those hills at 15 mph and cruise at 15 mph, for an easy 30 miles. Heavy trailer included. Your input would be limited to steering and stopping. No pedalling required at all.

I too, wonder if your trike is an ideal platform for an etek type motor. I would, remember I am a welder fabricator, cut the back half of your trike off and redesign the whole rear end. Easy for me.

For a bike, forget the Peltzer set up, go hub motor, get Dogman here on this forum to help you. Make sure the bike you chose has disk brakes that you can upgrade. I feel front suspension is mandatory. Even at 15 mph.

This is an old picture of my bike with the 1 hp motor, it has gone through several upgrades so that it now handles and drives as well as a motorcycle at 30 mph. It has very good acceleration and very good hill climbing ability, good range, maybe even 30 miles if I was very easy on the throttle. But, I drive it just like a small motorcycle and it performs very well for me.



View attachment 1



I have changed from a pg2 gates drive to the monster drive pictured, then to a much smaller 3vx v-belt drive.

Look closely, no pedals at all.

Keep thinking about it Jawnn, there is a satisfactory system that will work on that trike, or bike for your needs. Luck,

chuck

 

[chuck]

Jawnn,

I did not see this,

what ratio do you think should be used? actualy I can probably do this one at the max speed of 20 mph? not that I under stand just why...

Ooooh, yea,

OK, A permanent magnet motor has a speed that it is efficient at. The rpm at the motor shaft must be maintained. The motors we have discussed are efficient at a motor speed of about 1600 at 24 volts. If I put a load on the motor such that the motor could only spin at 800 rpm at 15 mph, the motor would rapidly overheat, it is out of its efficiency range. This heat will demagnetize the magnets in the motor and will melt the enamel coating on the armature winding. Quickly ruining the motor. Most of the energy from the battery will be wasted as heat, not motion.

The motors we are discussing for your electric vehicle application are series wound motors. At 48 volts they should be run at about 3200 rpm and will output 6 hp continously. at 36 volts they will run efficiently at about 2400 rpm and will output 4 hp continuously. At 24 volts, 1600 rpm about 3 hp. At 12 volts, 800 rpm and about 1.5 hp.

So we figure out the hp required at the top speed of the vehicle and use a reduction between the motor and the wheel. In your case, I chose 20 mph as the vehicle speed and geared that wheel speed so that the motor will spin at 1600 rpm which puts the motor is in its efficient speed at 24 volts. If I had chosen 15 mph then to keep the motor happy we would have had to gear down even more, which adds expense and... the more we gear down the less efficient the drive.

Now, the controller varies the voltage going to the motor and hence, the speed of the motor.

The controller varies the voltage that the motor sees. At half throttle the controller turns your 24 volt battieries into 12 volts at the motor. The motor now is efficient at 800 rpm. The controller is not quite as efficient at this reduced speed, but, the load on the motor is less, because we are traveling slower. We can go farther at the lower speed, the motor is happy, it is at 12 volts spinning happily along, you are happy at 10 mph, the controller is happy because it is not pushing out too much energy for the 10 mph load.

You have some pretty hefty hills where you are at. You want this vehicle to push some pretty large loads. For the money, the alltrax controller, the mars 909 motor, those lithium batteries, less than 2000 dollars and you have an absolutely bullet proof, medium speed, multispeed, hill climbing monster. And, it will be a very long lived system, good for well over 60,000 miles.

I have not been able to find any motor other than the mars 909 motor that will do the job you asked for it to do for less money. If you could find a 2 hp motor, permanent magnet, less than 22 lbs, with a 1600 rpm rating at 24 volts, it would also work fine. For the money, the 909 is a steal.

Beef up that trike a little, the steering problems will need to be addressed and fixed. Brakes and wheels will need to be studied. It will ultimately be your decision if the trike can handle this system. The system can, I assure you, handle the load very efficiently.

chuck

 

[chuck]

Jawnn,

To optimize the drive train and the reduction ratio I first have to know the specifications of the motor.
The battery pack voltage.
The exact circumference of the tire measured with a string wrapped around it.

I would like to have the following to calculate the actual load on level ground.
The rolling resistance of the vehicle. Measured with a spring scale. Pull the loaded vehicle and trailer on level ground with the spring scale. The rolling resistance will be calculated from the weight of the vehicle during this test and from the reading on the scale.
The weight of the vehicle, the trailer, your weight, and the weight of the motor, drivetrain and batteries .
The frontal area. To measure the frontal area I need a picture of you on the trike with a 3 foot yardstick across your chest. The camera about 10 foot directly in front of you at the height of the yardstick.

Then, I calculate the 3 forces

The force of rolling,
The force of wind resistance,
The force of the hills

With the above known, then we can finalize the actual drive train reduction specifications.

With the information you have given me so far I have estimated possible drive train solutions.The drive reduction must be exact for efficiency. A one tooth difference on a sprocket results in large changes in speed reduction on the drive. If I calculate that you must use a 12 inch pulley and you use a 5.5 inch pulley the drive will fail, the motor will burn up, and you will have wasted your time and money. If I calculate a 54 tooth sprocket and you use a 50 tooth sprocket, the motor will run harder, efficiency will plummet, and you will not be able to climb those hills and travel the distance I calculate.

Once determined, no part of the drive train can be changed, if I suggest #40 chain, no other chain can be used, same with the belts. Any substitutions will result in inefficiencies and possible drive train failure.

If I design a drive and it won't fit, then a complete drive redesign will be required until one can be found that will work.

chuck

 

[jawnn]

It may not be brain surgery but it does seem like rocket science to me.

If 2.6” is that smallest pulley I can use on the motor and 10” the biggest I can squeeze next to the motor, 5.95 to one reduction is going to be it.

That’s going to be about 35 mph at 20 amps (using the old Etek motor’s graphic chart)
Powered by 48 volts is 20in/lbs (but is it the same at 24 volts? I have to take the last few posts home to read them more carefully)

I would need a 20” pulley with the 2.6” on the first stage redux just to get the speed down to 21mph…well I think you were just saying it would be less, I hate having to use the library computers and getting here by pedal power on bad knees…well any how I know a man that uses the old Etek with a rim sheave of about 16”? (Off a 20 wheel) with no other reduction and he is pushing about 500lbs (total combined) with the tandom trike.

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

I do not want to use a chain on the secondary redux , they wear out too easy. I think the BX belts you were mentioning will do, but how wide? Are the power grip GT belts better for speed?

I really don’t think I could use the cyclone motor unless I avoided the steepest hills ( a good idea) and pedaled up the 10% hills……but I still would not trust them after so many people telling me to use the big Etek. http://www.cyclone-usa.com/ they maybe ok for a bicycle.

 

[chuck]

Jawnn,

You are making calculations using a torque constant based on current,,,,, this constant is referenced to voltage, that you will need to convert to power, using radians. Then you will need to convert the inch pounds to foot pounds. Then you can convert this to power. Then convert this to horsepower

Electric motors have many ,torque values, take up torque, stall torque, torque at current saturation, no load torque. There are also mechanical torques that need to be calculated to properly size the shaft.

Series wound dc motors have many benefits useful to electric vehicles, short time currents many times the continuous rating, short term power output many times the continuous power rating.

Jawnn, read the following very carefully...

We already know the power of the motor .

It is printed on the label attached to the motor.

In other words you are trying to use a static motor parameter that is , by far, the most difficult, by a large magnitude, method to solve a hill climbing problem. At one time I was a mathematician, 30 years ago, and I would not have solved this problem then, nor will I now, using the torque constant of a motor.

So, we do not need to use torque in our calculations.
The three resistive forces of air drag, rolling resistance and hill climbing resistance are very easy to calculate.
We multiply the three forces by velocity to get power. In our case power in ftlbs/sec, convert this to horsepower, and compare that to the continuous hp rating of the motor. 8th grade math.

The maximum power needed is useful, it is used to size the battery pack. The battery pack is not rated in torque, it is rated in Watts (power) and Watthours (energy). .

It is very important to determine the maximum power that the electric vehicle will need.
THIS IS VERY IMPORTANT, THE BATTERY SUPPLIES THE POWER, NOT THE MOTOR.
Then we find a battery, the ultimate source of the vehicles power, that can supply this maximum power.
Then we find a motor, which converts electrical power into mechanical power, that can handle this maximum power.

We have found 2 motors,
the mars 708 with an approximate 1600 rpm, 3 hp continuous rating at 24 volts , $434.....weight 30 lbs, diameter 8 inches
the mars 909 with an approximate 2130 rpm, 2.7 hp continuous rating at 24 volts, $375...weight 24 lbs, diameter 6 inches

The reduction required for 20 mph for the 708 is 1600/336 = 4.76 at a wheel rpm of 336, a one stage reduction is barely possible, you say it is not possible.
The reduction required for 20 mph for the 909 is 2130/336 = 6.34 at a wheel rpm of 336, a two stage reduction is mandatory,

I rule out the 30 lb 8 inch diameter 708 due to size and weight.
I do not rule out the 909 because it is more likely to fit.

A chain on a two stage reduction, designed properly, will last, 10 to 20 thousand miles with low maintenance, and will be fairly silent.

Most of the time, you will not need the 2.7 hp of the 909 motor. A very nice feature of series wound motors is that they will adjust themselves to the load. It will only draw from the battery the power that is needed to push the load that is applied to it. Making it efficient at whatever load you apply to it.

chuck

Jawnn, I will be out of town this week, if I have time I will check in and work on the caluclations from scratch, using the 909 motor,
I will more accurately determine the three forces now that I know the application better
Re size the battery pack based on maximum power
Find a power transmission solution with part numbers that you will be able to bring to a bearing, belt and chain supplier to cost for you.

 

[jawnn]

ok this is deffinatly rocket science.



This is how I got there... for the 1600 rpm motor.

[20”d tire x 3.14 x 1600 / 12” x 60min. / 5280 = 95.15mph]

95.15 / 20 = 4.7575 then 1600 / 4.7575 = 336.31 wheel RPM

so the ratio should be 4.7575 to 1 so it looks like the first stage reduction should be 2.6 to 7” and the second the same 2.6 to 5.5”



I use BMX 100psi tires to keep them on the rims at high lateral stress. If the whole power system needs to be calculated so any closer than that I should just build a heavy duty trike with the two wheels in front so it won’t twitch. Mine is just not built for speed.

They tell me that air drag is next to nil at less than 20mph even for human power only.

 

[chuck]

Jawnn,

Your math is correct, but 1600 is the rpm of the 708 motor. Grammatically, your math is hard to follow.

We need a 6.34 reduction for the 909 motor. It spins faster.

For a 2 stage reduction the first stage times the second stage needs to equal 6.34

The size of the motor driven pulley is determined by the peak power and the rpm of the motor. Manufacturer's publish the rpm and power data in charts so that we can determine what combination of belts, pulleys, chains, sprockets are needed for the application.

A 2.6" drive pulley or sprocket is quite small and hurts efficiency and the longevity of all but the lightest duty chains and belts. We try to use a 3 to 3 1/2" inch motor pulley's as minimums to keep the size of the belt as small as possible.

The larger the motor pulley, the more efficient and longer lasting the drive will be. And the belt will be smaller.
There are many sizes of v-belts
A and B belts are considered light duty belts, generally for grinders, home workshop, light duty lawn tractors, small compressors, large fans etc.
3v and 5v belts are considered industrial quality belts, are generally more efficient when larger loads, shock loads, accelerative loads are encountered.
Throw in automotive belts, even more sizes are encountered but sheaves are hard to come by,

The X, such as BX or 3vx or AX denotes a better quality belt, better belting, notched, increased load capability and will run cooler, last longer, more efficient.

To calculate a 2 stage drive, we have to play around a little to get a possible solution.
For your drive, we have a limit, the final pulley or sprocket must be smaller than 5 inches in diameter, I know you said 5.5 inches, 5 inches will give us a mere 1/4 inch clearance.

Ideal situation, take the square root of the reduction ratio, 6.34, this gives us the reduction ratio of each drive.
The square root of 6.34,,ie. (6.34)^1/2 = to about 2.52 reduction ratio for each drive.

The motor rpm / the reduction ratio = 2130/2.52 = the jackshaft rpm or about 845 rpm.

In #40 chain, a 15 tooth jackshaft sprocket will handle 4 hp at 845 rpm.

For the reduction to equal 2.52,, the rear sprocket will need to be 2.52 x 15 teeth = 38 tooth sprocket.
And a 38 tooth sprocket #40 has a diameter of 6.33 inches. Will not fit.

Running this much power through a 15 tooth motor sprocket is'nt to ideal either.
Generally, the driven sprocket on any size chain should be larger than 20 teeth. For long life.

But, anyhow,
The only #40 sprocket that will fit is a 32 tooth sprocket with an outside diameter of 5.38 inches. The 31 tooth #40 sprocket has an outside diameter of 5.22 inches.

Let's compromise, a 31 tooth wheel sprocket and a 18 tooth jackshaft sprocket for a ratio of 31/18 = 1.722


Looking up in my Morse chain manual, a

 

[chuck]

whoops,

continue

6.34/1.722 = the new motor to jackshaft ratio = 3.68 ratio

motor rpm of 2130/3.68 = the jackshaft rpm of 578 rpm

Back to the Morse chain manual, 18 tooth #40 sprocket at 578 rpm will handle about 3.5 hp.

Not good, But the only option. It will work though, since the chain will not be continously driven at this rate.

Now that the rear drive is solved, we need to find a belt drive that will work.

Lets start with what I consider the smallest acceptable v-belt drive sheave, at 3" the jackshaft sheave will need to be about 11 inches. If you have the room for it, a BX belt will work, rated at 4.1 hp with a 3 inch drive pulley.
The only jackshaft sheave available cheaply is that 17 dollar sheave from tractor supply at 12".
Do you have room? A 3.2 inch diameter sheave is available for the motor.

So, the drive ratio is, (31/18) X (12/3.2) = 6.45, a little too much, really,
With permanent magnet motors, over revving the motor because the load is too light kills efficiency.
It is better to use a little less reduction than too much reduction.

If it will fit use a 32 inch wheel sprocket and a 3.4 inch motor sheave. (32/18) X (12/3.4) = 6.27, this will be an overall little better fit.

I am tired,
If this will fit, jackshaft, 12 inch sheave, this would be a cheap drive, under a 100 dollars, well, we need a jackshaft and jackshaft bearings, lets call it $150.

Otherwise, to eliminate the 12 inch jackshaft sheave, an 8mm pitch timing belt would be the only option. These pulleys get pricey, real quick, probably 250.00 conservatively, just for the pulleys and lock bushings,(the collar that clamps these pulleys to the shafts, many sizes and types, will discuss as part numbers only if needed)
To keep the size small, a timing belt can just keep getting wider to handle the power. A 2 inch wide belt handles twice the power as a one inch belt. Efficiency suffers with the wider belts.
Timing belts also require absolutely perfect alignment for longevity. It takes a well designed platform for a wider belt. Another limitation is the length of the shaft of the motor, this limits us to probably a 1.5" belt, the overall drive size saved will not be significant maybe a 2 or 3 inch diameter savings without looking it up.

Look at one of my earlier pictures, I have a 3vx(v-belt) drive next to a timing belt drive(3/8 pitch L 1 inch wide), Both have about a 2.5 reduction, the 3vx drive (v-belt) handles about 4.5 hp at 2800 rpm, the timing belt about 4 hp. The v-belt is also more efficient at this rpm. The picture shows that both type drives are about the same size and center distance, in this case the v-belt is the better drive. If size was important, (center distance) then a wider timing belt woud be incorportated, allowing the use of smaller pulleys, which combined, decreases the efficiency of the drive. If more hp was required, 2 3vx belts would be used.

So, sometimes, its all a toss up, not rocket science, use what will work, try to keep the costs down.

chuck

 

[jawnn]

For the 2130-rpm motor I will need an 11” pulley with the 2.6” on the motor. If 3.5" is the smallest usable then the whole thing may need a three stage reduction, unless your saying that the chain will make it all fit better, well I need to mesure the area behind the seat better.

5.5" will give 1/4" clearance

No idea where to get a 31 sprocket gear to fit on the shaft that is about 1.5ft long. maybe longer. Is the chain you wont to use is stronger than bicycle chain?

The makers of this trike have a bicycle free wheel adaptor....but not very heavy duty.


OOOOPs! just wasted $36 on a new axle made of mild steel, may twist apart?
May need a machine shop to make one out of chromium-molybdenum with a .25” key way and ends drilled and taped.

Maybe I should just build a bigger heavy-duty trike that can use a motorcycle drive wheel. Or build a wheel with 48 12g spokes. And use hydraulics disc brakes on the front wheels.