Where to get a drive sprocket to fit an eTek/Mars

Electric Motors and Controllers

Re: Where to get a drive sprocket to fit an eTek/Mars

Postby Njay » Mon Jan 16, 2012 12:43 pm

Thanks for the answers, Steve, also on the other topic. I'll probably ask you a quote, on a drive sprocket. I'm trying hard to find off-the-self parts, for obvious reasons and also because I will want/need to try at least 3 gearing ratios without going empty pockets.

One thing "funny" I found is that there are off the-self-rear sprockets for the Aprilia (up to 51 teeth :D !) with 415 chain, marketed as "for racing"; now, I was looking at this 415 chain's specs and it seems so much weaker (less tensile strength, much lighter) than the original 520! Doesn't seem to make sense :? .
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby frodus » Mon Jan 16, 2012 2:52 pm

The motor is a pretty small motor, do you need 520 chain as opposed to 415/420? I'm pretty sure the etek has lower torque than the original engine. Not likely that you'll ever put that chain to its limits. Might be good to look into smaller chain. I know other people that have made the switch to smaller lighter chain.

I mean, you totally could get it running in it's stock form, which is what I did. It went OK, but acceleration was poop and the motor drew tons of amps because the gear ratio was too low. Maybe use the rear you have, add on a few 520 links, get a 520 front sprocket (use a 530 and machine it down, or order one from Jozzer), and get it running to see what you need.

How many volts are you using?
Going off of the data I can find, it's ~72RPM/Volt, so usuing 72V, it's ~5100RPM, unloaded. Your moto has a 24" diameter, and with a 4500RPM redline (it'l be lower than max RPM, likely somewhere around 4500RPM....)

I get about 65mph with a 5:1 ratio and 72V, just by gearing/voltage alone. It'l be a bit lower in reality, but it's far from 45mph.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby Njay » Mon Jan 16, 2012 3:12 pm

Since I want to go off-the-shelf as much as possible, that locks me in to a rear sprocket (and chain) of 520 or 415. I may starting doing just as you said, order some of those cheap 530 drive sprockets and machine them down to 520 (let's see how much machine work will cost me... but heck, I'll grind them down myself if I have to even if it takes me days, it's not a final part anyways). And then I'll test and decide what to what ratio

I'm using 48V, which is the recommended "nominal" maximum voltage for the eTek. I did calculations based on an eTek rpm of 3250 (which corresponds to a bit over 100A) and the wheel radius of my bike. I got to a reduction of about 4:1 to reach around 57.5 mph. I don't have the calcs here with me so I can't post the data. There are no eTek motor curves for over 3500 rpm nor for over 48V nominal, so I won't design for continuous use over those values.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby frodus » Mon Jan 16, 2012 3:28 pm

Yes, it's a 48V motor, but it is a range, 48-72V. Take a look at EVAlbum, most of the etek users on motorcycles use 72V. Same thing with Agni, although, they can go to 96V+

on a brushed motor, going 1.5-2x the base voltage is nothing big. Especially at low voltage like 72V.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby Njay » Mon Jan 16, 2012 10:56 pm

The motor's datasheet from B&S says 48V is the maximum voltage and also says in another section to not use battery pack voltages above 48V. I know parts have tolerances, but since I don't have experience with these and I can't afford to sacrifice 1 or 2 motors to know their limits, I'm going to stick to the nominal 48V. You'll also find that some 72V eTek systems on evalbum had motor problems. I do admit from the start to push it a little more, but no more than some 58V nominal (18 Li series cells). In my commute I'll be at least 20 minutes at max speed (ideally at 50+mph).

On the other hand, the datasheet says it's ok to stick 330A through it over 1 minute. Thermal management apart, I think that's a pretty bold statement about the motor's ability to handle current, so I prefer to have a good cooling system and rely on it's current handling capability to compensate for low reduction's low torque at starts. From my calculations, 250A with a 4:1 reduction are enough to have a torque similar to a vulgar 125cc bike in 1st gear, which is perfectly ok for me.

I can't however ignore your reports of too much heating with low gearing such as the 4:1 I'm planning to use. How heavy is "super light bike" for you? My initial estimate for final weight of the conversion is 350 lbs, but there are too many weight unknowns and I hope, also from what I seen from other conversions and commercial electric scooters, to have it a good bit below that.

I did some general comparisons with other electric bikes, both conversions and commercial Chinese scooters (I know a few owners of such scooters), and achieving ~55mph with a motor with similar power to the eTek is common. Therefore I believe it shouldn't be too hard to get there...
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby frodus » Tue Jan 17, 2012 11:42 am

light would be under 200lbs

I doubt you'll get over 50mph with 48V, even with the gearing you want. Start considering 60V, that will help.

Or consider talking to John Fiorenza at Motenergy. He designed the original B&S.... he's a great guy and very helpful. Don't take our word for it, take his.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby Njay » Tue Jan 17, 2012 10:17 pm

frodus wrote:light would be under 200lbs

fffiuuu, looks like I'm screwed. My estimate (that is, with data I could gather not from my own measurements) of the bike's weight without the ICE is some 210lbs, which in fact I think it's too much for that bike. I have a big and heavy bat pack for her, a TS 3KWh 16s1p 60Ah with total weight of 88 lbs.

frodus wrote:I doubt you'll get over 50mph with 48V, even with the gearing you want. Start considering 60V, that will help.

50mph is fine for the legalization, then 2 more cells to 58V nominal.... may do the trick... This sure is going to be fun :mrgreen: .

frodus wrote:Or consider talking to John Fiorenza at Motenergy. He designed the original B&S.... he's a great guy and very helpful. Don't take our word for it, take his.

I guess I can try, I hope I don't annoy him.

I need to investigate more and do more "real world" measurements to see better where I'm going. Thank you for your help frodus. I think I've been on your blog before. Good to know you went LLC :).
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby frodus » Tue Jan 17, 2012 11:39 pm

Just start slow. Maybe just do as you're thinking, just use the stock sprocket for now, get a 520 front machined somewhere, and use some cheap chain. Get it running and then see if you need to go higher or lower on the ratio. Much cheaper.

From everything I've heard, John is very helpful with all of his customers. Even back when I was considering Mars(Motenergy now), he was great.

And if you have questions, ask me (as well as Steve and a handful of other guys). It's easier to work things out now... and save yourself from disappointment later.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby Njay » Sun Jan 22, 2012 7:51 pm

Thanks a lot for the eye opening. I've been playing with a Physics spreadsheet I once got from a guy who made a conversion and in fact the "torque issue" is there. I didn't notice it before because I got concentrated on the required power only and overlooked the torque needs. Anyways, I won't change anything for now, I'll just get a drive sprocket and do some tests with what I have now, see exactly what will be the final weight of the bike, and then we'll see what needs to change.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby kirks » Wed Jan 25, 2012 9:15 pm

Hi folks,

We stock motor sprockets that fit the Etek's (wheel sprockets too), but mostly in the #35 size. However, if you have a specific size & tooth count in mind, let me know and I'll check availability with our suppliers. I've ran B&S Etek's since 2003. Some MARS motors too. Hit over 80mph with our Etek in a very efficient streamliner. I wouldn't expect it to sustain that without overheat, in my vehicle. That configuration was about 36V nominal and used #35 chain. That's probably not what you want to hear (#35), but the bigger chain is probably overkill assuming you're running one motor at any voltage and amperage (continuously) which the won't fry the motor. However, the bigger chains will stretch less and last longer as a benefit. Adding another Etek might give you the grunt you're looking for ;-) We occasionally get some in, and are posting six for sale in the next few hours.

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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby silverrich1 » Sun Mar 25, 2012 12:53 pm

you'll burn his motor giving him advice about pancake motors. no pancake motors do not survive over-volting well, perm pmg132 are the worst for high voltage melt-down, the old original etek pictured is terrible at over-volting, max 60v and that's pushing it. ideally he wants a D series lynch motor, D132 for more than 88v etc... it'll do it.
72T sprocket / #40 chain / #40 7/8" 3/16 14T for the original etek = 0-70mph with great torque.

Best thing to do is to stick to 60volts. period.

frodus wrote:Yes, it's a 48V motor, but it is a range, 48-72V. Take a look at EVAlbum, most of the etek users on motorcycles use 72V. Same thing with Agni, although, they can go to 96V+

on a brushed motor, going 1.5-2x the base voltage is nothing big. Especially at low voltage like 72V.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby frodus » Sun Mar 25, 2012 2:12 pm

That's a MAYBE.... Overvolting this motor to 72V isn't what really hurts it, The issue is people overamp this motor at the higher voltage and overpower it. They put too many amps into it and it gives them issues.

There are tons of people using 72V on the mars and Etek motor on evalbum without any issues.
http://evalbum.com/mtrbr/MARS

Hell, Mars 0709 is a 72V motor on their datasheet for it. I've seen curves for other Mars motors and it's the same thing, they have 72V curves. It's not about the overvolting, it's overloading the motor and not putting in place correct current limits on the motor controller.

I've not seen any examples of a 48V pancake motor "melting down" at 72V with correct current limits in place..... maybe you would be kind enough to provide some examples? I'm being serious, if there are example I think the myself and the OP would like to know. Maybe there's some quality issues with new ones?
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby Jozzer » Tue Mar 27, 2012 4:12 am

The problem with overvolting these motors is the max RPM that they fall apart at. As I understand it, the Etek can do this at 4krpm or less (especially if it's been heated till the solder softens!), which would be not much over 48v...


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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby frodus » Tue Mar 27, 2012 10:25 am

If that is the case, and they fall apart at higher RPM's, then I guess someone should say something to Motenergy and Perm so they can change their datasheets and inform their vendors they they won't run at 72V. Maybe the original B&S was 48, but Mars was in the subject line and it sounds like he hasn't chosen a motor yet.

72V curves:
0709 curve at 72V From Mars/Motenergy:
http://www.evdrives.com/images/Motors/M ... _72vdc.pdf

PMG132 72V curve on PMG's website:
http://www.perm-motor.de/en/download/do ... nical-data

Webpages and datasheets stating 72V
Motenergy:
http://motenergy.com/mebrtoen.html
http://motenergy.com/me1003.html
http://motenergy.com/me0709.html

Perm:
http://www.perm-motor.de/en/products/dc-motors
http://www.perm-motor.de/en/download/do ... nical-data

Distributor websites stating 72V with datasheets and curves:
Motenergy:
http://www.cloudelectric.com/product_p/mo-me1003.htm
http://www.thunderstruck-ev.com/motenergy-me1003.html
http://www.evdrives.com/mars_motor_me1003.html
http://www.electricmotorsport.com/store ... me1003.php
http://www.cloudelectric.com/product_p/mo-me1008.htm
http://www.cloudelectric.com/product_p/mo-me0709.htm
http://www.thunderstruck-ev.com/motenergy-me0709.html
http://www.evdrives.com/mars_motor_me0709_etek-rt.html
http://www.electricmotorsport.com/store ... me0709.php

Perm:
http://www.cloudelectric.com/product_p/mo-pmg-132.htm
http://www.thunderstruck-ev.com/perm-pmg-132.html
http://www.electricmotorsport.com/store ... pmg132.php


So wouldn't you think it'd be a huge liability for Mars and Perm to advertise 72V but when run by individuals at 72V they fly apart/burn up/melt down?

I've seen and riden Perm motors running at 72V on a dirtbike with A123 and an Alltrax without any issues. Several conversions with an Etek 0709 and 1003 at 72V without issues. Those were the ones I was referring to. I should have been more specific.... Mars/Motenergy sells 72V rated pancake motors.

Long and short of it, run the motor at manufacturer recommended specs.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby Njay » Tue Mar 27, 2012 6:29 pm

I think there's a slight confusing here, frodus; we're talking about the eTek only when we speak of 48V limit. Mars has other models that it specs to more than 48V. The Mars equivalent of the eTek (eTek => B&S) is the Mars708, which is also spec'ed at 48V max, although spec'ed at 5krpm max. I think I saw the limit of the eTek to be 4krpm, but I don't remember where and it was not in the datasheet. The datasheet shows only tests up to some ~3550rpm, so it makes sense that the limit is 4krpm.
I do agree with you that voltage is not that important given that current/temperature is under the limits, but there's still the max rpm limit to consider.
Furthermore, the eTek is already tough on the controllers due to its low inductance. Raising the voltage also raises the current raise speed. Many details to consider.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby frodus » Tue Mar 27, 2012 7:22 pm

Exactly.... Mars/Motenergy markets their 0708 and 0709 as Etek motors..... I had no clue which you're referring to. If you're truly speaking of the original B&S Etek, then yes, 48V is probably about it for that motor. I've not seen a curve for 72V on that (nor at 48V for that matter).

If you need 72V, the Perm and 0709 from Motenergy are rated for 72V operation, and as you mentioned, that's dependant on temperature and current as well. The even better solution is an Agni 95R Reinforced motor, they're made for higher RPM... and overvolting :)
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby Njay » Tue Mar 27, 2012 7:52 pm

frodus wrote:Exactly.... Mars/Motenergy markets their 0708 and 0709 as Etek motors.....

A common confusion, but actually not true :). It is the retailers who name them "Eteks"; Motenergy never used those terms and actually discourages their use as far as I now ("Etek" is a trademark from B&S).

There's only one Etek, the original B&S Etek. The Moternegy are MExxxx. ME0708 has performance equivalent to the Etek (but 42% more weight!). You can find some Etek curves on-line (not generated by B&S but by some other companies, I think), but here's one (with some presentation changes I made for inclusion in an article):

Image

I'm going to squeeze this old Etek, then we'll see. If it blows, the other only motors worth considering are the Agnis yes, or the LEMCOs (roughly same tech), but I'll have to save a ton of $$ for that.


update: changed "eTek" to "Etek"
Last edited by Njay on Wed Mar 28, 2012 12:33 am, edited 1 time in total.
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Re: Where to get a drive sprocket to fit an eTek/Mars

Postby frodus » Tue Mar 27, 2012 10:24 pm

touche,

it's EMS and a few others that call it etek.
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