C Cab Hot Rod Power Advice

[Just_Ed]

Ed here.

I've been aware of this site for a number of years, and have looked in, now and then. But now I'm getting to the point in my build that I need, the kind of help this site seems to be able to provide.

I'm currently building a C Cab Hot Rod, and I'm seeking advice on what power will be needed to make it .... GO. It started as a pedal car project, (named StreetRunner) and has since morphed into what you see below. A renaming to ILLUSION may be more accurate.

Anyway
The following pics should give you an idea what I'm working on.
I'm at this stage as of this post. 1/16/2020




Basic information for your consideration.

The idea behind this build is to replicate the Hot Rod 'look' while not using a real engine/transmission etc.
For example the engine is not real. It is actually hollow. Its made from perforated sheet metal, PVC pipe, and yes those are 'empty' Budweiser cans for the carburetors.


Current thinking is 48 volt 1800 watt motor.
https://www.ebay.com/itm/48V-1800W-Electric-Brushless-Speed-Controller-Motor-Grip-fit-ATV-Go-Kart-Scooter/274048053097?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D20160908110712%26meid%3D29b7316fed1c419e9291474184d3ba8f%26pid%3D100677%26rk%3D3%26rkt%3D30%26sd%3D303293310776%26itm%3D274048053097%26pmt%3D1%26noa%3D0%26pg%3D2386202&_trksid=p2386202.c100677.m4598
or a geared motor as in the link.

https://www.ebay.com/i/162582832023?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=162582832023&targetid=858219882363&device=c&mktype=pla&googleloc=1013549&poi=&campaignid=6470552634&mkgroupid=90044703518&rlsatarget=pla-858219882363&abcId=1139336&merchantid=101988296&gclid=EAIaIQobChMIwuvLyOqI5wIVlP5kCh0-KAHWEAYYASABEgJ4pfD_BwE

Gearing/motor sized for a max speed of 25 mph.
Current vehicle weight is +/- 200 lbs
Anticipated gross weight +/- 500-600 lbs.
Rear tires 24 inch diameter
3/4" drive axle
Not much head room in the motor bay area, under the seat.

Maybe there are some here, that are aware of Brad Graham, and his https://atomiczombie.com/forum/ website. My build thread name is,
Ed's StreetRunner Quad Build. https://atomiczombie.com/forum/threads/eds-streetrunner-quad-build.11/. It can be viewed there.

I am working with the intention of driving it in this years local Christmas parade, as well as future events. So any interest in my project and any suggestion/opinions, as how to best power it, will be greatly appreciated.

More photos and info, provided as desired.

Thank you
Ed

 

[fechter]

Cool.

The geared motor will be much closer to what you need. It will likely take more than 1800w to go 25mph with that much weight.

A golf car rear end + motor would be closer to what you want. Sometimes you can find used ones pretty cheap.
Where to put the batteries will be a little harder. A bike sized battery won't be able to run a golf car motor but the 1800w geared motor should be OK.

How much range do you want?

 

[Just_Ed]

Hi and thanks fetcher

As I'm building this just for the pleasure of the creation, be able to show it, and take part in some local parades, a range of 20-30 miles or so, is probably more than I need, but gives a margin to work with. Most local parade routes are a couple of miles, and then back. Or pick up on my trailer.

I'm also keeping in mind the Calif, NEV laws/requirements. As I understand them, there isn't any wattage restrictions, and the remaining requirements are basically things like lights, brake/turn signals, DOT windshield glass, etc.etc. Plus there are some restrictions for use, but those are not a problem for me, with this build.

I have a local golf cart shop not too far from me, that may be of some use.

 

[amberwolf]

neat vehicle--especailly being scratchbuilt.

do you want it to actually accelerate like a hotrod?

or do mind long acceleration times from a stop (or going uphill, etc)?


fwiw, about 1000w would likely get it to 20mph; maybe less depending on exactly how aero it is.

that's about what it takes for my sb cruiser trike, which is around 500lbs wiht me on it, around 600 lbs with a big load of groceries or one of the smaller dogs in the back. i can maintain that speed even with 10mph+ headwinds, though it slows down quite a bit when those (rarely) go up to 20-30mph or more. i try to stay out of winds above that cuz i'm afraid they'll rip the canopy off.

the sb cruiser has a canopy and other features that probably make it similar in aero to yours as well.

i don't know what mine would take to get to 25mph, but typically it takes significantly more to go just 5mph faster as you get to higher speeds, especially with less-aero stuff like ours.

i'd guess around 2000w ish, so 1800w might make it under pretty good conditions, but just a little slope or a little headwind could take a good chunk of speed off the top there.

similarly, accelerating from a stop will take you a while with only taht much power, dependign on your gearing and wheel size and actual torque you get out of it all.

with around twice the 1800w you're considering, in two hubmotored (mxus 450x) 22"ish wheels, i get 4-5seconds from 0-20mph under typical no-wind flat-road conditions with no load but me. at a guess, it would be another second or so to get to 25mph, maybe two, haven't tested that. using just one motor for half the power it takes maybe 15 seconds to get to 20mph, sometimes more.


because it determines a great deal about the battery you're going to need (which is going to be the biggest expense and the largest physical item to find a place for), the real question is, how much range do you need (30 miles?), at what speed (25mph?), under what conditions (assuming flat terrain for these guesstimates)?

guesstimate is it'll take 60-80wh/mile or more, maybe up to 100 depending on windiness and terrain. so for "worst case" 30miles x 100wh/mile = 3000wh needed. meaning, a 3kwh battery pack. if it's 48v (13s), that's about 63ah.

i have an aging 52v (14s) 40ah pack that gets me around 30ish miles at max of 20mph, average around 16-18mph. it weighs almost 40lbs iirc, and is the size of a small stack of hardback books.

 

[Just_Ed]

Hi amberwolf

Thanks so much for your input.
That's the sort of info/help I'm looking for.
The more examples/opinions I get the more I learn.

Sorta the educate me/advise me.

do you want it to actually accelerate like a hotrod?

or do mind long acceleration times from a stop (or going uphill, etc)?

No. Acceleration is not of real importance. However, the NEV requirement (Calif), states the vehicle must be able to attain at least 20 mph, within one mile, but not exceed 25 mph.
______________________________________________________________________

https://www.ebay.com/i/162582832023?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=162582832023&targetid=541453966012&device=c&mktype=pla&googleloc=1013549&poi=&campaignid=6470552634&mkgroupid=81274458647&rlsatarget=pla-541453966012&abcId=1139336&merchantid=101988296&gclid=EAIaIQobChMItd_vyqb-5gIVoxx9Ch3yOg1XEAkYAyABEgJ0SPD_BwE

Using the above motor for example, and using the below calculator, entering these parameters,
https://electricscooterparts.com/motorwheelgearratio.html

500 rpm (shaft speed)
11 tooth (motor sprocket)
16 tooth (axle sprocket)
24 inch (tire height)

I came up with 24.7 mph tops.

About battery choice

Lithium I guess, is the way to go, BUT, for my once or twice a year, I'm thinking something less expensive, but capable of getting me out there and back, on the day I use it.
There's not much room for a battery underneath the seat. I had originally designed the motor hollow, with the idea, that is where the battery would go.

In any case placement of the battery, is minor to getting one that will meet the bare minimum requirement of, lets say 15 miles.

Again thanks for your help
Ed

 

[amberwolf]

No. Acceleration is not of real importance. However, the NEV requirement (Calif), states the vehicle must be able to attain at least 20 mph, within one mile, but not exceed 25 mph.

then somewhere near a couple thousand watts or so would probably do what you're after. possibly less, depending on aerodynamics, speed, wind resistance, rolling resistance, etc. assuming you want 25mph max speed or so.

if you only need 20mph, 1000w will probably do it.

if it were a more aerodynamic shape, you could do it with less--a typical bicycle can probably do around 28mph with only 750w, and an aeroshelled recumbent could potentially do it with half that.

but with teh canopy "scoop" like my sb cruiser trike has, and the boxy rear shape (even with a windshield, especially a flat-on-to-the-wind one) that's a lot of drag; it's why my trike takes around 1000w to maintain 20mph, where around half that would be needed for a regular bike to do that.

i have more power available because i need the accleratino to be quick in traffic, but you would not need the extra--just enough to deal with the wnd resitance at speed you go, and any hills you must maintain that speed on.

______________________________________________________________________
Using the above motor for example, and using the below calculator, entering these parameters,
https://electricscooterparts.com/motorwheelgearratio.html

500 rpm (shaft speed)
11 tooth (motor sprocket)
16 tooth (axle sprocket)
24 inch (tire height)

I came up with 24.7 mph tops.

just keep in mind that 24.7mph will probably take more than the 1000w that motor is rated for. if so it's going to get hotter than expected, and you may have to put a fan on it.

also consider that some motors have a shaft speed rated as unloaded, meaning not hooked up to anything, for any particular voltage. the loaded shaft speed may be 80-90% of that. lets say your is on the low side, say 80%, which means you may only get 80% of that 24.7mph output, or around 20mph. so you might have to use a taller gear ont he axle by that amount to get the speed you want.

another issue is that the 500rpm is not constant across the whole battery discharge range--the voltage drops as it discharges, which slows down the motor. so assuming that 500rpm is at exactly 48v (probably isn't; you'd ahve to find that out probably by experimentation), then as the pack runs out down to 42v-ish, you'd get proportionaly less rpm. if i did the math right, thats around 87% of the 48v rpm. so by the time the battery is about empty, the max speed you can get is only that 87% of whatever the max speed is with the 48v speed, meaning if you only got 20mph at 48v, you'd only get around 17mph at that point.

you'll also get proportionally hgiher speed above the 48v, up to around the 52v or so it'd beat full charge.


just some more stuff to be aware of.

Lithium I guess, is the way to go, BUT, for my once or twice a year, I'm thinking something less expensive, but capable of getting me out there and back, on the day I use it.

lead-acid would work, but unless you keep it maintained and charged all the time, it'll possibly be dead and need replacing every time yo go to use it.

also, lead acid at the hihg current rates used drivng motors will only deliver around half the ah rating on the label, when new, under typical "shirtsleeve" temperatures. colder or hotter or at higher or lower current rates, or if t's older, will affect how much it actually delivers. so if for a particular range you needed say, 50ah using a lithium battery, you'd need up to around 100ah of lead-acd to do the same thing. lead is also a lot heavier and physically larger for the same capacity in lithium, so it would not take up just twice as much space and weight, it would be more (probably much more) than that.

depending on how often you have to replace them, and how much more la then li you would have to use, li may be much less expensive than la.

li can just sit there at half charge for a long long time (years?) as long as nothing is connected to the cells, like a bms (you would unplug it from the cells when storing the pack / hotrod for long periods).

there are also varying types and quality levels of lithium batteries, some of which can produce high curretns with small or less cells, and some of which need more or bigger cells to do that.

In any case placement of the battery, is minor to getting one that will meet the bare minimum requirement of, lets say 15 miles.

at what speed, on what terrain, with what kinds of starts and stops, etc? they all make a difference to the amount of battery needed.

assuming that's all at 25mph, and that you end up needing 100wh/mile, then you need about 1500wh of battery, whcih is around 31ah at 48v, for lithium. probably around 60ah+ for lead-acid.

if you need less wh/mile, it'll take less battery.

part of that depends on the actual aerodynamics of the hotrod, the speed you go and the wind if any. you can do a coastdown test to determine baseic aero numbers, if you have a way to get it up to the speed you'd cruise at (towing behind a car and releasing, etc). without having to make a windtunnel to do the tests.

part of that depends on the weight vs any hills or slopes, and vs stops and starts.


if it helps, you can go to the http://ebikes.ca/simulator , read the entire page so you know what everthing is and how it works, and how to use it, then play with different systems (especialy using the system a/ b compare mode) to get a handle on how each part affects the toher, for both how much power you will actually need out of the motor to move you, and how much capacity the battery will need to get you as far as you want to go.

it's designed around hubmotrs on bicycles, but you can use teh "custom" settings in each dropdown to simulate other stuff including something like the geared brushed motor you've linked to (you may have to guesstimate some properties of motor, battery, and controller, as well as aerodynamics).

 

[Just_Ed]

WOW ! That's a lot of information.

I'm super pleased. AND you explained in a manner that was/is understandable to a newbie to this sort of thing.

I'll be reading over your reply again, so to get more.
That may generate more questions....maybe

Thank you for taking the time, to explain.
P.S.
We have relatives living in Surprise

 

[amberwolf]

next time you come see them (if you ever do) you should pass thru phoenix and come say hi (though i expect you couldn't bring your project). meet the dogs, see the trike (or whatever i've built by then) in person.


till then you can see it over in the thread linked in my signature; it's evolved a lot in the almost four years since it was started, so most recent pics are near the end of the thread, maybe page before last, or the one before that. don't think there's any pics on the last page.

 

[Just_Ed]

Today I contacted the seller of this;
https://www.ebay.com/itm/48V-1800W-Electric-Brushless-Speed-Controller-Motor-Grip-fit-ATV-Go-Kart-Scooter/274048053097?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D20160908110712%26meid%3D29b7316fed1c419e9291474184d3ba8f%26pid%3D100677%26rk%3D3%26rkt%3D30%26sd%3D303293310776%26itm%3D274048053097%26pmt%3D1%26noa%3D0%26pg%3D2386202&_trksid=p2386202.c100677.m4598

Got their reply stating this motor would not be large enough for my application.
However, I didn't inform them that I would be making a jackshaft, that would change the gearing. I'm going to send them an update to the jack shaft sprocket choices, and see what their reply will be.

Here is the latest numbers, put into the calculator. https://electricscooterparts.com/motorwheelgearratio.html

Using a jackshaft to get the gearing to keep it under 25mph.

4300-4500 rpm (motor shaft speed)
9t (Motor sprocket )
32t (Jack shaft input sprocket)
12t (Jack shaft output sprocket)
45 (Axle sprocket)

Result: ( 24.18 mph)(13.33:1)

The numbers seem to work, ( in the calculations ), but not sure about the motor to make it work. A 4500 rpm, 1800 watt motor may have the numbers, but is it strong enough to handle the 'load'.

I'm going to visit a couple of golf cart shops near me, tomorrow. Maybe they will have some idea's that will work, and not cost me too much.

Still looking for more input here. Especially from those that have practicable experience, with installed working motors.

I'm going to have to make a determination soon, as some of the next work, is predicated on the installation of the power, and battery choice.

Ed
I

 

[fechter]

Got their reply stating this motor would not be large enough for my application.
However, I didn't inform them that I would be making a jackshaft, that would change the gearing. I'm going to send them an update to the jack shaft sprocket choices, and see what their reply will be.

I tend to agree. 1800w is not going to be enough. It might work for a short distance but the motor will overheat. You need to consider hills too.

Other than golf cars, you can sometimes find older NEVs for next to nothing with dead batteries. Check your local Craigslist.

 

[amberwolf]

hils and wind are your killers. evena slight sloope will require a lot more power because of thew eight. even a little headwind will require a lot more ower because of the lack of aero.

since you still haven't givendetails of that kidn of stuff, can't relaly help you any more than that on thsat part.

for alternate motor sources, if you have the space for it, motorcycle-style scooter hubmotors, intended for up to a few thousand watts, would also work, mounted in the frame and used to drive a chain to the axle. even higher-power ebike hubmtors would do it too. lots of these kinds of things end up scrap too, on cl and the like, and even used here on the forum in the for sale sections.

there's at least one section of the nonhubmotor sticky index thrad that has links to posts and threads aout doing midmount hubmotors like that.

because they'rae already meant to spin at wheel speeds you don't meed mch gearing change, if any.

but theyll be heavier and larger than a higher rpm motor for the same power, gneraly.

 

[Just_Ed]

fetcher, amberwolf

Thanks for your input. It has helped. Some of the other inputs, though well meaning and appreciated, are filled with theory, formulas, etc., which takes a degree in physics to understand. You have presented the information that is relatively comprehensible. I thank you for that.

I have more to explore.

I might add, that normally any wind we have here, wouldn't be an issue.
Hills and inclines, of 2-5 percent might be a factor.

I have been scouring the internet, including Craigslist, for used/salvage golf cars. I have found a handful, but I'm just not knowledgeable yet, to know whether I'm buying junk, or if I can actually use what I'm buying. I have to weigh the cost of buying a complete car, against just buying the components needed. As I'm interested in just the running gear, steering, electrical and maybe the brake system, the rest is just junk that I would have to dispose of. Which is OK, as long as I benefit from the usable parts.

One last thing.

I guess I'm a little confused about the use of jack shaft's. I am of the understanding that they make using a small motor easier, as well as setting the gear ratio, to achieve either more torque, or higher speed.

I was sure that with the addition of the jack shaft, using the sprocket sizes previously mentioned, that the 1800 watt motor would work. Could it be that, although the motor has a 1800 watt capacity, it just isn't 'physically' large enough?
What am I not comprehending here?

Again thanks for your help.

For now I'm going to the library for 'Battery' and 'Motor' technology.

Regards
Ed

 

[fechter]

I have a bicycle with a gross weight of about 250lb and has a 2000w motor and it can barely go over 25mph. With "car" tires and a lot more weight, I think the power requirements are going to be higher, which means heavier batteries, motor, etc.

Also, if you look at the performance of a typical golf car, top speed, weight etc. and look at how big the motor on one of those is you will get an idea.

With enough gear reduction, the 1800w motor will make it go, but I don't think 25mph is going to be realistic.

 

[Just_Ed]

Thanks fetcher

Point taken.

I'm going over to the cart shop, which as it turns out, is just around the corner about a 1/2 mile from my house. Must be an omen....right?

Anyway, I will be going over later this morning, and see what help/suggestions they might have.

Ed

 

[amberwolf]

I guess I'm a little confused about the use of jack shaft's. I am of the understanding that they make using a small motor easier, as well as setting the gear ratio, to achieve either more torque, or higher speed.

what a jackshaft itself does is just transmit power from one part of drivetrain to another.

if you're using a jackshaft for a gearing change, like in your case, then they convert torque to speed, or speed to torque.

it only changes the rpm of a fast motor down into torque to mvoe something heavy slowly, or the torque of a slow motor into speed to move a ligther things fast. or some compromise between.

it doesn't change the amount of power (which would be torque x speed in this case), so if a certain amount of power is needed to move something at the speed you want under the conditions you have, but the motor doesn't have enough, it doesn't create more. it actually wastes some small percentage; typical bicycle chain is about 2% loss per chain/reduction stage, so you lose about 4% of your power just in the two chains from the motor to the axle. so, assuming you actually got 1800w output from the motor's output gear* then you lose 72w in the reduction, and only get 1728w.

regarding efficiency of the motor, the 1800w is usually the input from the controller/battery, the motor's efficiency if brushed is probably in the 70s or 80s, so let's just say it's 80% at the speed you'll run it at. that means that the 1800w it takes from the controller/battery is down to only 1440w. minus the 72w or so lost in the reductions, now you only have 1368w at the axle. how much of that goes to the ground depends on the rolling resistance of the tires, for one more step of effiicency losses.


i wish it wasnt' all this complicated...if you just throw enough power at a system it'll do what you want; that's kinda how i did it with my trike, but it also added a lot of weight i don't need. if I really wanted to make my trike perform better, i'd have to figure things out the complicated way, and use just enough of a motor to handle my few seconds of peak power needs at startup, and still give enough at crusiing speed without overheating the mtoor.


so as i said before, the actual amount of power needed for a certain speed depends on a few things:

-- the aerodynamics of the object being moved, for wind resistance at various speeds, which goes up rapidly, especially with something that has a large cross-section and especially if it's flat-fronted, even more if it has "scoops" that act as drag brakes, like the "canopy" of my trike or your hotrod.

-- the rolling resistance of the wheels the object is on, along with the surface it's rolling on. skinny bicycle tires at high pressure have lower rr than big wide car tires, for instance. just varying the pressure can greatly change the rr of a particular tire, too.

-- the weight of the object being moved, vs the rolling resistance and any upward slope.

so...the heavier t is, the more power to get it moving in the first place, especially if the wheels have high rolling resistance, and even more if it's on an upward slope. really the weigth is only going to matter much for accleration from a stop, to get to the speed you need before the motor overheats, and to maintain speed on hills without overheating.

the worse teh aero, the more power it wlll take for any given speed, evne if theres no headiwnds.


so if you really want to know what power it will take, you can do a simple coast-down test from speeds like you're after, as i suggested before, and this will give you numbers you can use to determien power-at-speed based on aero. at the speeds you're after, the aero will dominate the power usage, though rr & weigth makes some difference.

for a bit more accurate data, you can look up the rr for your tires; it's quite possbile the manufacturers have this information listed. if not, it's likely that osmeone has a page with data on similar tires that's close enough. some of the power calculators also use rr, as well as the cda numbers.

I was sure that with the addition of the jack shaft, using the sprocket sizes previously mentioned, that the 1800 watt motor would work. Could it be that, although the motor has a 1800 watt capacity, it just isn't 'physically' large enough?

first, you don't actually need a jackshaft unless you're doing a double reduction or you can't align the chain output from the motor with the chain input of the axle. if you have a single sprocket for each end of a single chain, and they are aligned for a good chainline, ther'es no need for a jackshaft.

if you have four sprockets total, and two chains, to run in series to get a specific ratio from one end to the toher you can't get in just two sprockets, then you need a jackshaft. or if the chains can't be lined up becuase of structural restrictions in the drivetrain.



second, what the watt rating of a motor usually means is how many continous watts of power it can handle (within it's other limitations such as voltage (usually volts per rpm or kv, sometimes just given as a single overall voltage), based on it's efficiency under those limitations / conditions, becuse of the amount of heat it can get rid of. some motors (like rc airplane motors) are very small for their power ratings, because they are meant to be in intense airflow that would get rid of that heat.

so if you have a motor that otherwise couldn't handle a certain amount of power, you can use various cooling methods to extract the extra heat, and for as long as those are effective at keeping the coils and magnets cool enough, then the motor can handle as much power as it's mechanical strength will allow. so..if it has a geabox, or a driveshaft, etc., the strenght of that would then be the limiting factor.


then keep in mind that any motor has an efficiency curve, meaning that at any particular motor speed you get only so much power out of it, for the amount of heat it makes in the motor.


so what it comes down to is that first you have to know how much power it will really take to do what you want. (if your hotrod has similar power requirements to my sb cruiser trike of similar shape and weight, then on the flats 1800w would certainly get you 20mph and might get you 25mph...but a little hill could drag you way slower than that)...but we don't really know your power requirements yet; we're guessing.


then you need a motor that gives you the power you want at the motor speed you want, at the system voltage you have.


i think i laready said this, but if you go to http://ebikes.ca/simulator and read the entire page so you know how it works and how to use it, then play with different systems to get an idea of how each part of a system affects the others. if you can get the aero numbers for your hotrod, it'll also help you figure out approximately how much power it will take for a certain speed on a certain slope (which may vary with different motors, because of their efficiencies, and depending on the gearing).

 

[Just_Ed]

Thanks amberwolf for the very lengthy and understandable explanation.

You must be, or have been a teacher/instructor of some sort.
I was an instructor for about 9 years, and I always tried my best to explain the subject matter in ways that ALL my students could understand. What's simple and comprehend-able to one, can be a challenge for another.

About this project

I will admit I didn't really think this part of the build was going to create this amount of decision making to figure out.
However I am adding new brain cells, because of it. So I guess I'm benefiting from the experience, which is good.

Golf Cart Shop Input

The golf cart shop owner, came to my house to see what I was working on. As I anticipated,( which I hoped wouldn't happen ) he gave advice that if taken, would alter the complete rear axle and frame. Which was to replace it with a complete golf cart axle and drive motor. Although that may be doable, it would add, we guessed at 100-150 lbs to the vehicle weight. That would mean my 200 lb car, would jump to 300-350 lbs, just as you see it now. AND we haven't moved yet !

AND that doesn't account for the minimum of four cart batteries, he thought it would take. Which could mean somewhere between 160- 280 lbs. Now we're up to 460 - 630 lbs.....yup we still haven't moved.

I haven't ruled this option out yet. Just getting it in my mind how to proceed, if I were to change directions a bit.
His cost for the used differential with brakes, with a tested motor is $300.00. I also found two golf carts on Craigslist, for $600.00. There are a lot of benefits for this purchase, in the way of additional parts, either for this project or the next one. Waiting on a reply from the seller.

It's looking like the lithium battery cost, isn't so bad, considering the trade off's.

I went to http://ebikes.ca/simulator and found there was a lot of information needed, that I just didn't have any idea where to get. I will look at it again today, and try my best to come up with the required info that's needed.

I think I'm going to look into geared motors with controllers again. The one example I gave earlier, may be a good place to start. Add to that a proper size lithium battery.

Thanks again for your valued lesson.

 

[fechter]

Is the "stock" hot rod something with pedals you can actually pedal around? What does it have for a rear axle?

 

[Just_Ed]

Is the "stock" hot rod something with pedals you can actually pedal around? What does it have for a rear axle?

Actually this whole project started as pedal car project. Having previously built a PVC pedal car, which turned out to be too heavy for one person to pedal, and the likelihood of no one else to help pedal it, that project was abandoned.

Enter this StreetRunner project which also started as a 'tandem' pedal car idea, but I saw early on my chance to build a dream vehicle, (23 T Bucket) style vehicle, but all electric. So the pedal version morphed into what you see now.

Rear Axle

The rear axle is 3/4 " cold rolled steel, with pillow blocks. The picture shows it still in one long piece. The intent is to cut it, where and when the drive components are decided and installed.



My experience following various builds on https://atomiczombie.com/forum/ is 3/4" is plenty for this type build. Having said that, I would go up to 1 " if needed, since the overall weight is less of a concern now.....within reason.

New thinking

Lets say for discussion sake, that I was to use the https://www.ebay.com/itm/48V-1800W-Electric-Brushless-Controller-motor-grip-fit-ATV-Go-Kart-Cart-Scooter/133268521826?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3Dd5fc713161f3497b9c5426a6b8794f7b%26pid%3D100005%26rk%3D8%26rkt%3D12%26mehot%3Dco%26sd%3D274048053097%26itm%3D133268521826%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851
but with a lithium battery, AND the motor isn't strong enough

I could be stuck with a motor that isn't needed or possibly burnt out. Now for a ....what if.

What If

What if, I were to use...2 motors at 1800 watts each. Connect the two motors electrically, using one controller for the pair. The cost of a second motor would be +/- $130, which is less than the cost of the 4 batteries in the other purchase option.
In my mind, what it would mean, is it would require a jackshaft connecting the two motors, ( rotation changed on one motor) then down to a single/double sprocket/s. Using a non-geared motor, I will need to use a jackshaft anyway, to get the motor shaft output rpm, down from 4500 rpm, to around 500-600 rpm.

Will there be any advantage/disadvantage. Increased/decreased voltage, ah, etc.
Additional batteries ?
Is there less stress on each motor ?
I have enough room to make it work.....I think.

Not sure about the feasibility for this simplistic, method.

 

[amberwolf]

You must be, or have been a teacher/instructor of some sort.

no, i'm just good at working out steps to learn things or figure them out, and so i can use the same to show others.

Which was to replace it with a complete golf cart axle and drive motor. Although that may be doable, it would add, we guessed at 100-150 lbs to the vehicle weight. That would mean my 200 lb car, would jump to 300-350 lbs, just as you see it now. AND we haven't moved yet !

well, the advantage is that the gc drivetrain (gcd) is complete, and is a "bolt on" solution, assuming the motor is part of a "transaxle" setup (even htough it requires altering the frame). and the existing axle/differential/etc is built to work "all day" every day with lots of stops and starts, etc., and (presumably) also has disc or drum brakes built into the wheels, which I don't know if you've got yet.

but...since you're talking about something to be used a couple times a year, at most, i don't know if you really need the whole thing for the reliability aspect. just might be nice for the ease of not having to build a connection method between motor and axle, and maybe the brakes would be nice. myself, i wouldn't want to add that much weight, unless it was something i intended to use all teh time, and needed the reliability.

AND that doesn't account for the minimum of four cart batteries, he thought it would take. Which could mean somewhere between 160- 280 lbs. Now we're up to 460 - 630 lbs.....yup we still haven't moved.

If you're using lead acid, then yeah, it's gonna be super-heavy. la is generally *at least* four times as heavy as comparable lithium options....

 

[Just_Ed]

While surfing the net for the feasibility of dual dc motor applications,
and the effect such a set up has on the motors, I ran across this article.

https://engineering.stackexchange.com/questions/2777/effective-ways-to-drive-a-single-shaft-with-multiple-motors

P.S. I'm still looking for how the motors are affected.

 

[amberwolf]

What if, I were to use...2 motors at 1800 watts each. Connect the two motors electrically, using one controller for the pair. The cost of a second motor would be +/- $130, which is less than the cost of the 4 batteries in the other purchase option.
In my mind, what it would mean, is it would require a jackshaft connecting the two motors, ( rotation changed on one motor) then down to a single/double sprocket/s. Using a non-geared motor, I will need to use a jackshaft anyway, to get the motor shaft output rpm, down from 4500 rpm, to around 500-600 rpm.

assuming that 3600w is sufficient for your needs (which we still don't actually know, though it probably is for 25mph on the flats, and likely for small inclines) it should work just fine, keepng in mind that the motors never share load perfectly (one always ends up with a little more than the other). this also assumes that the motors can physically handle the torque needed, which is likely.

buuuut...normally you have to have a separate controller for each motor, because of the way brushless motors work. (unlike brushed motors)

unless you setup a collar that locks the two motor shafts together, and when assembling this collar on the shafts, you wire the motors up so that each phase wire is paralelled together with it's equivalent on both motors (for instance, it might be green - green, blue - yellow,, yellow - blue, with that pair swapped because of the "flipped" motor), and then pass a sufficient current thru any two of those phase wire connectors to lock both rotors to the same position, then tighten the collar down on both shafts. then disconnect the current. now the rotors are aligned and a signle controller should be able to run both.

if the mtoros have hall sensors, you will only use the set from one motor. (the other can be a spare set in case the first has problems). because one motor is reversed you'll need to figure out it's hall sensor combination differently from the other one, if you have to use it's hall sensors.

However...the controller that ocmes with the single motor in that link cant even provide the original single one the full 1800w (it's only 48v 32a, around 1500w max). so you'd need a controller capable of twice the current of a single motor (which would be 48v 40a for about 1900w; there isn't really a 39a controller for the 1800w, but the motor says it's acutally rated for up to 2000w in the specs on that link. as long as that's true, and not just marketing blather, which is unfortunately common enough).

so you'd need a 48v 40a sensored brushless controller. (if you use sensorless you may have trouble getting started from a stop if the motor is in just the wrong position, with common cheap controllers like these).

presumably teh collar would be built with a sprocket or sprocket holder in it's center, so both motor shafts drive it via the collar.

i don't know what torque the chains proviced with the system are designed to handle. if you're not sure, you can run both chains in parallel, using two sprockets on the collar, two chains from that to two input sprockets on yoru axle or jackshaft, and so on.

there will be lower torque at the higher rpm, so if you do need more than one chain to handle the final torque you could still use just one from the collar to the jackshaft, then two from jackshaft to axle.

i don't know how to determine teh torques you'll see, or what the spec for the chain is. some of those chains are really tough...i just don't know how tough. i know bicycle chain won't handle that kind of power very long without wearing quickly; never used kart chain so no experience on that.



the motors will work better as a pair than as a single motor, as long as they are correctly synchronized. (if they are not, the currents from the controller to each motor won't arrive at the right time for each one relative to the magnets on rotor, and they'll run rough or heat up a lot from wasted energy, and won't provide as much output power).

because there's twice the thermal mass, there's half the heating for the same power level, etc.

lots of threads on es about 2wd or awd or dual wheel drive systems, which are effectively the same as what you want to do, though typically we end up using a single hubmotor in each of two wheels, like i do on my sb cruiser trike and my crazybike2.


you can simulate two motors at once (as 2wd) in that simulator, to see what would happen.

you do not have to have any special information to use the simulator to learn how systems work. just use existing stuff in the list and work with it per the instructions, to learn the relationships.


if you want to simulate your specific setup, then you do need the aero numbers, which you can get from a coastdown, and if you want to simulate a specific motor you would need the motor's critical parameters it asks for, but you can try out pretty much any motor, with a controller that can provide it the right amount of current to get the power you think you'll need (start at 1800-2000w, which is around 40A at 48v and go up as necessary), with a wheel size similar to yours, and the right gross weight, and the right voltage battery (just pick the biggest one of the right voltage). then you get to start seeing some generalized numbers for what it takes to move your hotrod at the speeds you want.

the aero number is really the only thing you *have* to have to do that.

 

[Just_Ed]

well, the advantage is that the gc drivetrain (gcd) is complete, and is a "bolt on" solution, assuming the motor is part of a "transaxle" setup (even htough it requires altering the frame). and the existing axle/differential/etc is built to work "all day" every day with lots of stops and starts, etc., and (presumably) also has disc or drum brakes built into the wheels, which I don't know if you've got yet.

True it is/was complete. It came with drum brakes. But it's not so much a 'bolt-on' affair. As you mentioned it would take a redesign and fabrication of leaf spring connections, shackles, etc. Much less work making a jackshaft as needed.

but...since you're talking about something to be used a couple times a year, at most, i don't know if you really need the whole thing for the reliability aspect. just might be nice for the ease of not having to build a connection method between motor and axle, and maybe the brakes would be nice. myself, i wouldn't want to add that much weight, unless it was something i intended to use all teh time, and needed the reliability.

I will agree here, at least for the time being. The added weight is really a deal breaker. Not to mention this is a solo man project. So trying manhandle 100-150 lbs of steel around isn't appealing. Especially if I can put two motors to work, thus reducing the load on just one, while maybe getting the additional power needed to meet my basic speed requirement, of 20-25 mph, and gaining some running longevity as well. Still looking for more info/stats on how this type of set up works.

Just saw your last post. Must go read it.

 

[SlowCo]

..........

Cool project!

NTDWM but this might be of interest?:

https://endless-sphere.com/forums/viewtopic.php?f=31&t=104152

 

[Just_Ed]

..........

Cool project!

NTDWM but this might be of interest?:

https://endless-sphere.com/forums/viewtopic.php?f=31&t=104152

Thanks SlowCo

Not sure why you think..NTDWM?

Appreciate the suggestion. Now I have another source to consider.

 

[fechter]

Using two of the 1800w motor is not a bad idea. If you can figure out a way to independently gear each rear wheel, the dual motor setup can work like a differential to allow easier turning. With brushed motors, you can easily use two with a single controller.

With a jack shaft or large ratio single reduction, you should be able to gear down enough to make the motors happy. You could even possibly have more than one gear using a derailleur or internally geared hub. I've seen some pedicabs that are close to your project so you may want to look at various pedicab designs. Most have a differential but with dual motors you could avoid the need for one.

If you can accept relatively short range, you can keep the battery size fairly small. I would be looking at used Nissan Leaf batteries for something like that. If you find the range is too short later, you can always add more batteries.