8Fun CST 250w and 350w, what is the difference?

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8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 05 2013 7:48am

Hi, I have been looking at the CST motor from greenbikekit.com because it is the only motor I have found that accepts a normal cassette.
I can choose between 250w and 350w but I don't understand what the difference is when it is a bare motor without controller. I asked Anna Lee and she answered "There is no other difference expect the power and torque.". If I use a controller set to 15amps and 48volts will there be any difference between them? If they are, as I expect, the same motor with different labels then I'll buy the 250w version because of the label. If not I would like to know what the difference is.

As said I am not going to use the supplied controller, but a 3rd party programmable one, probably a 6Fet Infineon.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by Sunder » Jan 06 2013 7:06am

The Greenbikekit website appears to be down at the moment, but from the way that they're posting it on other sites, it sounds like it's the same motor, but one is marked to 250w as a marketing gimmick to satisfy regulations in areas with a 250w limit.

From the size/weight of it, I suspect it will cope with well more than either 250 or 350 anyway.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 06 2013 8:38am

Thanks for confirming my suspicion. It should be good for 500 watts then according to the manufactures web page.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by motomech » Jan 06 2013 9:57am

It's just a BMP 350 with a different cover.
Be for warned however, there have been reports here of breakage of the Cassette mount where it joins the vertical plan of the cover.
This, of course, happens to many hub motors, but early reports would indicate an fairly high rate of failures with the CST version.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 06 2013 10:25am

motomech wrote:It's just a BMP 350 with a different cover.
Be for warned however, there have been reports here of breakage of the Cassette mount where it joins the vertical plan of the cover.
This, of course, happens to many hub motors, but early reports would indicate an fairly high rate of failures with the CST version.
That is worrying. I need to think long and hard on how important the CST is for me and if I should go for a MAC motor instead.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by d8veh » Jan 07 2013 12:39pm

As far as I know, there's no difference between 250w and 350w apart from the marking, but why not get the 500w and stick a 250w label on like we have? The 500w one is quite a bit more powerful than the 350w one. I have both, so I can compare.

I'm not sure that Motomech's right about the CST breaking. I've got a feeling he's thinking of the BPM2, which looks similar. I've never heard of a CST braking yet. Perhaps he'll confirm this.

I'm not sure that they're any better. http://endless-sphere.com/forums/viewto ... el#p629854

You can now get a replacement side-plate for BPM and BPM2 with free-wheel attachment for $4 from greenbikekit.
http://www.greenbikekit.com/index.php/a ... overs.html
It's a shame they don't do the one for the CST because that would make a very cheap upgrade for a BPM1 to CST

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 07 2013 1:51pm

d8veh wrote:As far as I know, there's no difference between 250w and 350w apart from the marking, but why not get the 500w and stick a 250w label on like we have? The 500w one is quite a bit more powerful than the 350w one. I have both, so I can compare.

I'm not sure that Motomech's right about the CST breaking. I've got a feeling he's thinking of the BPM2, which looks similar. I've never heard of a CST braking yet. Perhaps he'll confirm this.

I'm not sure that they're any better. http://endless-sphere.com/forums/viewto ... el#p629854

You can now get a replacement side-plate for BPM and BPM2 with free-wheel attachment for $4 from greenbikekit.
http://www.greenbikekit.com/index.php/a ... overs.html
It's a shame they don't do the one for the CST because that would make a very cheap upgrade for a BPM1 to CST
Thanks, I've heard about the BPM2 covers failing too and I was afraid it applied to the CST too after Motomech warned me. I hope he was mistaken. If the BPM covers fits the CST then buying one of them together with the motor will be a good insurance.

Buying the 500w version is a good idea, but I can't find it anywhere. I know greenbikekits.com listed it earlier, but not anymore.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by N!co » Jan 07 2013 1:56pm

Crystalyte has a motor that accepts a cassette too, the G-series.

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 07 2013 2:33pm

Thanks N!co, I didn't know about that one. With all the hills around here I think I'll go for a geared hub though.I have a small DD already (the SmartPie) and that one stalls on every hill.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by Herrsprocket » Jan 08 2013 4:16pm

Howdy. From the correspondence I have had with Bafang in the past, I believe that the only real difference between the 250 W and 350 W CST is simply the variance of power that is being put through it. You may notice on the Bafang website, that the CST is rated from 250 W to 500 W. The smaller powered 250 W and 350 W CST are manufactured with the 135mm nut to nut dropout width, whereas the 500 W version is manufactured for a 150 mm dropout width. From my conversations with them, it would seem that the magnets internally are a bit dimensionally different from the BPM motors. That is why they are having difficulty in making the larger more powerful 500 W version in a 135mm dropout.

Unfortunately, it wouldn't be possible to affix a CST cover to an existing BPM motor. That would be cool wouldn't it? But as you can see from the pictures from the website, the attaching screws and methods for affixing the cover to the internal guts of the motor are different than the BPM models. http://www.szbaf.com/product.asp?id=2

Tom

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by motomech » Jan 08 2013 9:20pm

Yes, I was confusing the CST with the BMP II.
Hopefully the CST won't have breakage problems.
Motomech

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 09 2013 6:38am

Herrsprocket wrote:Howdy. From the correspondence I have had with Bafang in the past, I believe that the only real difference between the 250 W and 350 W CST is simply the variance of power that is being put through it. You may notice on the Bafang website, that the CST is rated from 250 W to 500 W. The smaller powered 250 W and 350 W CST are manufactured with the 135mm nut to nut dropout width, whereas the 500 W version is manufactured for a 150 mm dropout width. From my conversations with them, it would seem that the magnets internally are a bit dimensionally different from the BPM motors. That is why they are having difficulty in making the larger more powerful 500 W version in a 135mm dropout.

Unfortunately, it wouldn't be possible to affix a CST cover to an existing BPM motor. That would be cool wouldn't it? But as you can see from the pictures from the website, the attaching screws and methods for affixing the cover to the internal guts of the motor are different than the BPM models. http://www.szbaf.com/product.asp?id=2

Tom
I have been looking more into the differences between the 250/300w and the 500. I have found two places that sell the 500w CST: http://www.batterybikekit.com and bmsbattery.com
Non of them shows any difference between 500w and 350w (except price on batterybikekit). For me it looks like the 135/155mm dropout has to do with whether you use 9s or more speed cassette. If the dropout width actually differs between the 250 and the 500w version then many buyers at those places might get burned and it might also explain why greenbikekit.com don't have the 500w version. I did send a mail to bf@szbaf.com asking about it. Maybe they will answer.

Looking at the drawings and comparing the pictures of BPM and CST I can't see anything that indicates that the covers wont interchange. But looking at the drawings and comparing I suspect that a BPM with a CST cover will be too wide to fit a 135mm dropout.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by Herrsprocket » Jan 10 2013 5:28am

Going back through some of my old emails with the Bafang rep (of which he was extraordinarily helpful), I was looking to find some of the differences in the motors (BPM and the CST), which are the same questions as the ones being posed here. If you look closely at the drawings for the two motors, the bolt hole diameters are slightly different on the two hubs. The freewheel cover of the BPM is 168mm, while the bolt diameter of the CST is 162.5 mm. Also you will notice that there are 6 screws that are nearby and circumscribe the cassette mounting body. Those screws afix a specifically designed ratcheting mechanism that meshes with this new freehub body. The cassette mechanism and this newly designed ratcheting system are integral to each other.

From further conversations regarding the dropout widths, the 500 watt version was definitely going to be designed with a 155mm dropout (as according to communications this past spring). The 250 watt version can accommodate an 8 - 9 speed cassette as it is. Looking again at the drawings for comparison, you will see that there is a difference in the flange to flange distance between the two motors. This is where there is a physical difference in the size of the magnetic components. For the CST to have the power of the BPM, they tell me they would have to increase the internal components (and internal compartment size ) by several mm's, to match the size of the BPM's. Ergo, a lot more real estate on the outside too.

I admit, I have not communicated with the Bafang rep for about 6 months now, so things have possibly have changed. However, by looking at the website information that is currently being displayed, it would appear that the CST is fairly much the way it was half a year ago. 250 watts with an 8 - 9 speed cassette, and what was projected to be a 500 watt version with a 155mm dropout. Still, a decent motor at 250 watts, if that suits ya.

Tom

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 10 2013 7:58am

Thank you Tom. You may have saved me from all the hassle I would have got if I bought a 500w version. According to BMSBattery the 500w CST fits a 135mm dropout, but I have learned long ago that BMSBattery has no quality control on their specifications. I'll probably buy the 350w motor kit from greenbikekit and get a label from 1060graphics. That way I get a 350w controller I can use as backup.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by Herrsprocket » Jan 10 2013 6:50pm

If you did get something back from Bafang that confirms one way or the other regarding the 500 watt dropout width, please post the info for all to see. :) I am very interested in Bafang's progress on the CST and it would be fascinating to know if they have somehow circumvented the difficulties of putting the larger "guts" into the hub, while still keeping the dropout width to 135mm.

Tom

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by d8veh » Jan 11 2013 11:45am

I've fitted two 500w CSTmotors and they dropped straight in to the bikes, which had 135mm drop-outs. One of then was an upgrade from a 350w CST: I hooked out the 350w wheel and dropped in the 500w one. I would therefore say that the 500w CST is made for 135mm drop-outs not 150mm.

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 11 2013 12:01pm

d8veh wrote:I've fitted two 500w CSTmotors and they dropped straight in to the bikes, which had 135mm drop-outs. One of then was an upgrade from a 350w CST: I hooked out the 350w wheel and dropped in the 500w one. I would therefore say that the 500w CST is made for 135mm drop-outs not 150mm.
Interesting. Was there a lot of difference? Weight, power or top speed?
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by d8veh » Jan 12 2013 2:36pm

lollandster wrote:
d8veh wrote:I've fitted two 500w CSTmotors and they dropped straight in to the bikes, which had 135mm drop-outs. One of then was an upgrade from a 350w CST: I hooked out the 350w wheel and dropped in the 500w one. I would therefore say that the 500w CST is made for 135mm drop-outs not 150mm.
Interesting. Was there a lot of difference? Weight, power or top speed?
I had the 500w BPM at 30 amps in my other bike, so that was the bench-mark. I started with the 350w CST at 22 amps, where it was a lot less than the BPM. I then tried the same 30 amp controller as my BPM, which made it marginally better, but nowhere near the bpm. Finally I upgraded to the 500w CST and 30 amps. Now it's the same as the BPM. I didn't weigh each, but I believe that the 350 is a few grams lighter, but otherwise, they're identical.

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by Herrsprocket » Jan 12 2013 7:14pm

Wow Dave, that is certainly news to me. My last contacts with Bafang only six months ago, gave me the definite impression that the 500 W CST was a dimensionally different beast. Every communication I had with them indicated to me that a 500 W version is only available with a 155 mm drop out and was going to remain that way for quite some time. The rep I was talking to was giving me direct input from their engineers in which they stated that a 500 W cassette style hub had to be of a larger dropout dimension. He had mentioned, that if they were going to keep the 135 mm dropout with, they could do so but only with a thread on type cover, which of course is much more like a BPM motor. So if they have figured out a way to circumvent the internal power increases while keeping the same 135 dropout width with a cassette hub, that is fantastic news!

Just for grins Dave, since you have both a 350 W version and a 500 W version, does it appear that there is more distance from flange to flange, or possibly the hub diameter itself is larger? I know you said that the 350 W and the 500 W model seem to have a slight weight difference, so I'm just curious as to dimensional differences. If they are slightly different in flange to flange or dimensional differences, then that would mean spoking them up would be slightly different. But not too much of a difference if they are only a millimeter or two in difference.

Which controllers were you using at both the 22 amps and at 30 A? Were these controllers supplied by BMS? Or are these Lyen type programmable controllers? The controllers that come typically from BMS have all been terminated to fit the Bafang motors, which some people feel that the wiring is a little small in diameter. Did you do any upgrades if you used the supplied BMS controllers?

Thanks again for your wonderful input. That is indeed good news.

Tom

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jan 13 2013 4:10am

I just got an interesting mail from greenbikekit.com:
Ms Anna Lee wrote:We don't source 500W CST motor since 8fun told us that the 500W version is not that stable. Auctally 350W CST motor can reach 400W as they told.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by d8veh » Jan 15 2013 11:51am

Interesting comments!
Unfortunately I've just sold the 350w one, so I can't measure it. I haven't actually measured the 500w CST, but all I can say is that I didn't have any problems slotting them in to the two bikes I built with them. I would say that even with 9 speed cassettes, they dropped in easier than a 500w BPM, but not much difference.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by Racer_X » Jan 15 2013 4:31pm

I have been following this thread with interest. I like the new bafang hub motors phenomena, but what concerns me a bit is that the hub motor axles are 12mm instead of 14mm like other hub motors. Do you feel safe that it will not spin even with the right torque arms? I know on my 9c even at a modest 48v 30amps it wants to open my chrome moly heavy duty forks. I am on my thirds pair since 2009. same motor by the way.
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Re: 8Fun CST 250w and 350w, what is the difference?

Post by Herrsprocket » Jan 15 2013 5:45pm

Hello Dave.
Nice picture of you on a cool day in the UK. Looks to me like there is a bit of flooding going on behind you in that picture as the water levels are creeping into the pastureland. Can't be that cold though. What! No gloves? :-)

I agree that it is unfortunate that we can't measure a possible difference between the 350 W version and this new 500 W version. However, it was fortunate that you were able to sell it though! Good for you! That would've been interesting just to see if there was any physical differences "between" the same 135mm nut to nut dropout measurement. Ah well, it all sounds very intriguing and I look forward to investigating these motors anewed.

But tell me Dave, what type of controllers were you using? And did you have to do any modification to them?

Cheers,
Tom

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by d8veh » Jan 16 2013 11:50am

Actually, that's my friend Steve. Your right about the floods. It was even worse the week before, and the road was flooded too, so we got wet feet. Gloves are on the wall out of view. You're very observant! I only look at the bikes.
We use bog-standard KU123 controllers on the middle setting of the three-speed switch. We get about 22mph and really good climbing power.We see up to 32 amps on our wattmeters. The 350w CST felt a lot less powerful.

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Re: 8Fun CST 250w and 350w, what is the difference?

Post by lollandster » Jul 14 2013 11:46am

Sorry to wake up this thread again, but I have a follow up question.
I have just bought a new bike (Giant talon 29er) with a 10 gear Dyna sys rear gearing. Will that fit on the CST?
From the specs I could find on the Internet the 10 speed cassette is 1.8mm wider than the 8 speed cassette and this extra width is done with overhang on the left side (to still allow for 135mm dropout) meaning that the big cog will be closer to the motor. Is there enough space between the big cog and the motor when a 8 speed is installed to allow for 1.8mm less space there?
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