MAC 8t versus 9C2806

[MonkeyWrench]

So, I'm considering what motor to use for my second bike build (first was stolen last Friday )

Comparing the MAC 500/1000w (8 turn) from em3ev http://em3ev.com/store/index.php?route=product/product&path=40&product_id=52

to the 9C 500w clone (970 RPM @ 36v) also from em3ev: http://em3ev.com/store/index.php?route=product/product&path=40&product_id=111

I'm coming from the yescom GM 901 motor, which rocked & seemed very capable of handling much more wattage than the 12s/44.4v Lipo and 30A controller was dishing out. Road speed on the flat with the GM 901 running 12s was ~30 mph hot off charge. However, it was a lot of motor to haul around if I don't need that much thermal mass. My goal for the new build is to top out at 35+ mph running 18s.

For purposes of using the ebikes.ca simulator Am I correct in assuming the MAC 8 turn ~= BMCV2Speed and the 9C,370RPM ~= 9C2806 ? I was mostly trying to match up the kV ratings.

The ebike.ca simulator indicates that (if I am correct in my assumptions above) both motors will get me there speed-wise. BUT the MAC has much more impressive thrust while accelerating. Here is the screen output comparing the two:


Now, I realize the geared MAC has less heat capacity than a direct drive, even the comparatively wimpy 9C clone. I am tempted by the oil bath approach for both cooling and corrosion resistance (planning on commuting in the winter- in Seattle).

I'd appreciate it if someone more familiar with the motor choices could confirm my assumptions on the simulator settings.

Thanks!

~Matthew

EDIT: ok, found one of neptronix's youtube vids that confirms the MAC 8t is equivalent to the BMC-V2speed http://www.youtube.com/watch?v=UD_K_TRGcs4 Yeah, 45 MPH is a bit much!!

 

[DAND214]

I really like my Macs but I think 18s LiPo is too much. I went rom 15s to 12s and still see over 30mph.

If you are going to push the 8t Mac for 8 miles is stretching it. Better with the 1206 which is also a push for the speed you want, with any wind or hills.

Maybe a 10t but then again 18s is too much for the geared motors IMO.

Dan

 

[spinningmagnets]

Here's a link to a MAC teardown with lots of pics of the internals. http://endless-sphere.com/forums/viewtopic.php?f=16&t=51310

At 18S, I would recommend a slow wind of the large diameter direct drive motor in a 26-inch wheel. Or, for even better hill climbing, a fast wind in a DD hub in a 20-inch wheel.

 

[MonkeyWrench]

Thanks gents- I'm trying to get the best acceleration possible while keeping the 35(ish) mph top end available. I do a lot of stop & go on my commute, but there are a few sections where true 35 mph will keep me in full control of the lane (versus doing 30 mph alongside).

Dan, which MAC wind do you have? I'm stuck with 6s intervals as I have the 6s Turnigy packs. Are you thinking shredded gears at 18s, or heat dissipation issues? What do you mean by the 1206?

Spinning, thanks for the link on the teardown. I know buying another yescom kit would fit the bill speed-wise and more than handle the 2.7 kW from the 18s setup, but I'd like to give cell-man/em3ev the business as I am leaning towards one of his 12 fet Infineons. The GM 901 that comes with the yescom has a relatively high kV, just want to make sure whatever I get next is a hot wind like that...

I see the simulator is saying 32.2 mph on the 9C 2808 motor (next highest wind available on em3ev) on fresh pack voltage. That isn't hitting the top end I'd really like... Are you thinking that the 9C 6 turn motor will be melting down pushing that much wattage peak?

 

[MonkeyWrench]

Ok, Spinning- I see why you guys go for the overvolted DD hubs on the small rims. Here is simulator screen shot for the 9C 6t on a 20 inch rim vs the MAC 8t on a 26 inch rim:


Note how the thrust is almost dead on identical from 0-25 MPH. Plus you get a decent efficiency bump for the DD "geared" through the smaller rim size.

Much to ponder!

 

[DAND214]

Dan, which MAC wind do you have? I'm stuck with 6s intervals as I have the 6s Turnigy packs. Are you thinking shredded gears at 18s, or heat dissipation issues? What do you mean by the 1206?

I have 3 8t all on 12s now. Was running 15s and didn't see a whole lot differance in performance on the routes I ride.

I had 6s mainly but split some to make 3s to get 15s. I could and still can run 18 to 24s but see no gain in my situation. I do know, the faster you go the more load is placed on the motor and controller.

I built my controllers from kits from Keywin 2 winters ago, 3 6fet and 3 12 fet all with 100v caps and fets. All beind EB3xx models.

As for 1206, it's just another way of saying 2806 being a 6 turn. I still have one of the earlier ones for EBIKEKIT.COM.
Still runs great with good performance in a 26" wheel. Not as aggressave as the Macs on the low end but great once rolling.

As Spinningmagnets said fast wind D in a small wheel or slow wind 26" high voltage. that is what you are asking for, not a geared hub running HV since it probaly won't last as long.

Dan

 

[MonkeyWrench]

Thanks Dan, makes sense now.

I'm sure either way will feel like an upgrade going from 12s to 18s. Interesting to hear that you gravitated back to the 12s. Really, I can't complain about my current "laptimes" on the commute, but... I race sportbikes locally and I like the zooom.

 

[DAND214]

I know what you mean of the Zoom. Raced enduro kart for years. So speed is not my enemy, I love it as much as another.

I just don't see 35 to 40mph is for me in my situation. No real place to use it without getting busted.

My favorite pleaser ride is about 15 miles RT. It's a little lake in town that i ride to daily. Last Friday I was informed the the park district will be enforcing a 8 mph ride speed. This is all due to ayoung kid ridding faster that the normaal fflow passed a guy and ran over a little old lady, she died. So now they are going to screw up a butiful plac to a priso zone. So at that point I could go to 6s and still be speeding.

 

[agniusm]

i hope i am not out of place here. I was thinking about using MAC 6T 500/1000W from cellman in 17" moped rim which works out at 21" with tire i suppose in 16S system with 12FET controller. Would that work on cargo bike:

?

 

[spinningmagnets]

According to em3ev.com website, 6T is 400-RPM @ 36V. Your 16S LiFePO4 would be around 50V?. 6T loaded kV is 11.1-RPM/volt (X 50V) = 555-RPMs?

30-MPH in a 20-inch wheel is 504-RPM, so 555-RPM in a 20-inch wheel would be 10% faster? =33-MPH? then, a 21-inch tire would be 'approximately' 5% faster? = 34-MPH?

8T compared to faster 6T is approximately 20% slower (320-RPM / 400-RPM @ 36V), so at 50V and 21-inch tire, perhaps 27-MPH?

The 7T might be halfway between the two at around 30/31-MPH? for heavy cargo, I would recommend the 8T @ 27-MPH