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

[Njay]

Hellos,

Do you know of places where I can get a motorcycle type 10-12 teeth pinion gear (drive sprocket) to fit an eTek? Something like this one in DrwAngel's motor:



I'm not familiar with chain sizes, but it should take a chain which is "520 Pitch", it's for an europpean bike (Aprilia RS125). The shaft is 5/8' inch diameter with a 0.25 inch width key. Any links are appreciated

Thanks!

[Farfle]

might try Mcmastercarr, http://www.mcmaster.com/#roller-chain-sprockets/=foxh1k

[Thud]

1 stop sprocket service at Surpluss center:
#40 sprockets:
https://www.surpluscenter.com/sort.asp? ... yword=PH40

#50:
https://www.surpluscenter.com/sort.asp? ... yword=PH50

way cheaper than mcmaster(slower shipping but still good)

[Njay]

Thanks guys! So far the surpluscenter was the closest... excellent prices... unfortunately, the shaft's keyway is 1/4 and they don't have 7/8 bores with 1/4 width keyways , only on the next bore diameter size (15/16).

[Thud]

fileing a key to fit the odd keyway to fit is quick & easy.
(we advance the timing on lawnmower engines by offsetting the key a bit.)

[Njay]

fileing a key to fit the odd keyway to fit is quick & easy.
(we advance the timing on lawnmower engines by offsetting the key a bit.)

Humm... I'm a bad machinist, but I guess that won't be that hard!

[dynamo dave]

I bought mine from BARSTOW INDUSTRIAL a hardware store here in Barstow, California. I don't remember having to do any work on it to fit it up.I also bought an 'A"plate sprocket that also was for a #40 chain that I had to change the 3/4 inch hole to about 2inch which I did by drilling a bunch of 1/16 holes in a carefully measured circle knocking out the middle and then getting busy with dremel tool. Nice job at the racing in Apple Valley.

[dynamo dave]

Here is another way to go.ON line is a source called electricmotorsport.com . They list the front sprocket you are looking for and they make custom rear sprockets that have the bolt pattern for whatever motorcycle you say. Plus you can order it for a #40 chain so you can make an all industrial size drive train not a mix match between motorcycle sprocket and industrial sprocket.

[frodus]

Thanks guys! So far the surpluscenter was the closest... excellent prices... unfortunately, the shaft's keyway is 1/4 and they don't have 7/8 bores with 1/4 width keyways , only on the next bore diameter size (15/16).

It's not 1/4"

It's 3/16 keyway on the Etek's (and for all 7/8" shafts I've seen).

the sprockets on surpluscenter are 3/16"
https://www.surpluscenter.com/Drawing/DR1-2124-12-D.pdf

It'l work. Don't get a 10 with 520/530 chain, it'l wear the chain quicker and maybe bind. Get 11 or 12.

Also, #50 is 530 chain. 520 chain is not as wide, so you'd have to machine the sprocket down to get it to fit 520 chain. Best option: Get a 530 rear sprocket for your bike, use 530 chain and use #50 front sprockets.

[Njay]

Thanks for another source Dave.

There are a number of suppliers here in europe for rear (wheel) sprockets specifically for my bike, so I'm planning on using those instead of trying to order custom. 11 tooths drive sprocket is my initial guess, but since it's a guess I'd like to try a 10 and a 12 to see what's best. Custom machining here is basically out of the question, even simple jobs are just too expensive.

Well, 1/4 is what the tech drawings show, I haven't do any measurements but now I will. And it seems I'll have to measure the chain too to be sure about what I have. But I've been looking and yes it loos like the #50 really is 530, and my bike takes a 520 :/. Thanks for the hints frodus.

[frodus]

There are a number of suppliers here in europe for rear (wheel) sprockets specifically for my bike, so I'm planning on using those instead of trying to order custom. 11 tooths drive sprocket is my initial guess, but since it's a guess I'd like to try a 10 and a 12 to see what's best. Custom machining here is basically out of the question, even simple jobs are just too expensive.

Well, 1/4 is what the tech drawings show, I haven't do any measurements but now I will. And it seems I'll have to measure the chain too to be sure about what I have. But I've been looking and yes it loos like the #50 really is 530, and my bike takes a 520 :/. Thanks for the hints frodus.

DO NOT USE A 10. It's too small on 520/530 chain. This is from experience of me, and others here, elmoto, etc. Use a larger front sprocket. The bend radius is way too small for the chain and it could bind, and it will definitely wear quicker.

Can you upload/link what tech drawing you have? If you're ordering (or ordered) a newer Etek (which is a mars motor), it's 3/16.

And remember, Just because your bike is a 520 doesn't matter. You're replacing the front and rear sprockets, so why do you HAVE to use 520? Since you're getting a sprocket made, get one 530 and you'll be done with it. Having them substitute a 530 for the rear isn't a huge deal, they do it all the time. You won't find a 520 front sprocket for a 7/8" shaft without paying for something custom. They just don't make them.

[Njay]

Ok, I measured the thing and the keyway width really is 3/16 and not 1/4" as on the drawing I have, that's good news. The motor is a B&S eTek not a Mars. The bad news is that the chain of the bike really is 520. My intention is not to go to a custom rear sprocket; they are already sold for my bike without the need to do anything custom, but they are for the bike's chain size which is 520 and I can get from 39 to 43 teeth. I'm going to search if there are any made rear sprockets for my bike with 530.

Ok, I got it, no 10 teeth drive sprocket. Thanks!

[frodus]

You will want something higher than a 4:1 on a B&S etek. I don't know of anyone that goes with lower than 5:1 on that motor. I wouldn't go that low because it'l pull a ton of current and cause overheating. If it's a super light bike with low range, it might be ok. But if it's a decent range bike, the weight and that gear ratio is a little on the low side. You should have something in the 55-66 tooth range, 43 is way too low, IMHO.

And it doesn't matter what the chain is, you'll be throwing the original chain out and getting your own. The original will be too short. The motor will be in front of the pivot, further forward than the original front sprocket, so the new placement will require a longer chain.

Where are you getting your sprockets?


Where are you located?

[Njay]

You will want something higher than a 4:1 on a B&S etek. I don't know of anyone that goes with lower than 5:1 on that motor. I wouldn't go that low because it'l pull a ton of current and cause overheating. If it's a super light bike with low range, it might be ok. But if it's a decent range bike, the weight and that gear ratio is a little on the low side. You should have something in the 55-66 tooth range, 43 is way too low, IMHO.

What's a super light bike for you? I have a 125cc (the '99 model of this bike here: http://en.wikipedia.org/wiki/Aprilia_RS125). I've found up to 45 teeth ready-made rear sprockets actually (and not 43), and was planning to use 43.
I can image it with a 45 teeth rear sprocket (11 front) which would go for a theoretical 55mph top speed, but higher ratio than that would be too slow... would prefer to invest on motor cooling, or will have to re-think the motor to use. 55 teeth is an exact 5:1 ratio but top speed would be a staggering low 45mph. Almost unusable and unsafe for highway here.

And it doesn't matter what the chain is, you'll be throwing the original chain out and getting your own. The original will be too short. The motor will be in front of the pivot, further forward than the original front sprocket, so the new placement will require a longer chain.

It does matter, because the rear sprocket ready-made I found so far is for a 520 chain. Or I find a ready-made (or cheap) rear sprocket for my bike and a 530 chain.

Where are you getting your sprockets?
Where are you located?

There's this brand "PBR" that makes tons of transmission kits for bikes, I think they're from Italy. I'm from Portugal.

[Jozzer]

We can make them up here at Jozztek, I can get any size blank and machine it to match your wheel/shaft.

I've found anything less than 13 tooth on the front will wear very fast and be super noisy (as well as giving a "notchy" feel). 428 chain is big enough for this much power, which helps keep the sprocket size down. With a 13-60 you can just about keep a clean chain run on the Aprilia..

Drop me a line if you want a quote, steve at jozztek.com.

[Njay]

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 !) 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 .

[frodus]

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.

[Njay]

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.

[frodus]

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.

[Njay]

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...

[frodus]

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.

[Njay]

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.

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 .

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 .

[frodus]

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.

[Njay]

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.

[kirks]

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.

-Kirk
http://www.destinyparts.com