New cargobike build input before purchase: 52v Gmac 26" 8T or 10T (moved from E-vehicles)

[merdi55]

Hello! I'm just opening a thread for input from anyone with opinions before I make a purchase from Grin for my xtracycle. Do I need more battery? Is there a better motor option I should be considering? I guess I need to stick with the 10T vs 8t, in order to handle my biggest loads, outside of my primary commute (which I'll only be making between twice/week and once/2weeks).

Thanks for taking the time to look and help!

Located in Madison County Ky, USA.
Max deisred Mph: 35
Desired range/speed: 75miles/25MPH (when the wind isn't bad at least). (specifically this trip simulator: https://www.ebikes.ca/tools/trip-si...27982&md=38_31596+-84_80144&x=&y=&lx=&rx=&rw=) [And thanks to Justin and the folks at ebikes.ca for making things like this... wow.]

I'm looking at a rear Gmac 8T or 10T with 2 Reention DP9 52V 20Ah batteries and a Baserunner L10 controller, on a 26" wheel with disc brake.

I weigh 200lbs.
Putting motor on a Surly LHT with an xtracycle. My commutes on this route will not be especially loaded down, but there will be times I ride with extra weight, pushing 400 lbs total , in somewhat hillier terrain, but shorter distances, and no real mountains to speak of.

I can ride this route on the bike without motor in 7 hours, including resting and decent headwind. The handlebars are lowered, a bit, and I can keep a fairly tucked position for most of the ride.

As I play with the simulator, the biggest difference seems to come in the headwind # and resulting amphours used. The results I get from that show no substantive difference between an 8t and 10T winding, and looks like if I just lower the max speed I could keep over 20Mph average, even on the windiest days I imagine riding in, and keep the consumed amp-hours to around 36-38 (of the nominal 40Ah of two combined Reention DP9 52V 20Ah). I suppose I will be able to just adjust the PAS to lower assistance on headwindy days to achieve the same end.

So, I'm just open to thoughts on how realistic this looks?

Whether I in fact am obviously going to need more batteries to pull this off regularly? (I am buying the Satiator charger, so I could probably stop half way and squeeze in a bit of charging, but hopefully would only be necessary on the windiest days.)

Whether anyone (with experience) thinks there's some other motor that will serve me much better that I should consider?

Any advantage to the 8t for me? or 10t will be fast enough? I suppose I'm more concerned total engergy effiency more than max speed, but hey we all want to burn it up every once in a while. One thread I found made it sound like higher windings seemed to help that author squeeze out some extra miles that didn't show up in the simulator.

Are there any critical extra bits I should consider buying at the same time?

I'm trying not to scrimp as I'm car-free and just trying to get something to make my statewide excursions easier and faster.

I've got a new Continental Top Contact II tire and disc brake hardware on the way (upgrading to disc from rim at the same time).
In my ebikes.ca cart aside from the Gmac ready to roll kit:
L10 cable ext to get to the extended rear wheel
CA steerer bracket
Analog auxilary control knob
wire route kit
multimeter
USB->TTL PROGRAMMING CABLE
triple bobs for batteries
handle bobs for accessories on drop bars

in the GMAC kit:
GMAC READY-TO-ROLL KIT
Motor Winding Speed
1 x GMAC10T
Include Cassette?
1 x CS9Spd1132
Frame Clamp and Torque Arm
1 x Frame Clamp and Torque Arm
Include Spokes?
36 x Sapim Strong 13-14g Butted Spoke, Black
Include Rim?
1 x Rim26_DM18
Include Wheelbuild?
1 x WheelBuild
Battery Model
1 x B5220LiM-DT
Charger Model - choose the right voltage for your battery
1 x Satiator Upgrade
Baserunner Controller
1 x Baserunner_L10
V3 Cycle Analyst
1 x CA3-WP
CA3 Aux Adjust and Power Switch
1 x CA3_MFSwitch
Pedal Sensor Type
1 x ERider68_5B
Throttle Choice
1 x T-Lever
eBrake Cutoffs?
1 x TripWire_Pull
Include Disk Rotor?
1 x Disk_203

Thank you so much!
Ben

 

[Jenming]

The baserunner works really well with this motor.

I have an 8t with a 52v battery. 35mph is my max on flat ground and needs a pretty deep tuck and only comes in the upper half of the battery charge. So if max 35 mph is important you'll need the 8t.

Pulling 36 amp hours out of a 40 amp hour battery may be optimistic. You'll lose 10% from colder weather or just a year of battery aging. 38 doesn't seem realistic to me.

Also watch the heat. If you look at your simulation the motor is almost hot enough to boil water but the shell is sitting at 25c. Basically really bad heat transfer. If that's your worst case then it seems ok. But for long life and good reliability you may not want to go hotter.

If you're doing that route now with no assist, than 200 watt human power may be realistic. But it's not for me start dropping that or up the battery amp max to the baserunner defaults then heat and amp hours are an issue.

 

[ions82]

I'd go with a 10T. If you're ever moving 400 pounds (of you and cargo,) you'll want gear advantage. Wind resistance at 35 mph will be considerable. Using a motor that will only occasionally see 35 mph but suffer all other times doesn't seem like it would meet your needs.

For a battery, I'd consider a pair of Dire Wolfs from Luna. If you're willing to pedal along at 20-25 mph, they should carry you through 75 miles. I've been really happy with everything I've gotten from Luna (both products and support.)

 

[dogman dan]

10t for sure. its not that slow a motor.

Easy on loading to 400 pounds, 300 max is better, when its uphill, into 25 mph wind. But on a nice day on the flatter hills, you can do 400 pounds loads.

My advice though, would be a larger dd hub motor, then you can still ride at low watts all you need, but can rip out 2000w, for that time its loaded up, and cold, and windy, and uphill.

My longtails have no problems with anything at all, running a big fat old crystalyte hub motor, loaded down with everything that can fit.

 

[merdi55]

Thanks! I did some more reading and looking...

Seems like 10T, yes. I think I'm pretty set on the GMAC motor.
Hubsinks?
The trip simulator shows a great disparity between shell temp and internal, so I wonder if the hubsinks would be helpful... ??

Looked at a couple other cargobike builds...
Seems like I could go with these 72v 25ah bricks from Calibikes for just a couple hundred more $. And Phaserunner controller. I've got lot's of options to mount the awkward batteries and larger controller.
Seems like I want to be overboard on battery, and seems like folks say higher voltage, lower amps is easier on the system.

Then I should have plenty of juice to be gentle on the batteries. I intend to ride the motor pretty gently as well, at least for that long commute. I imagine I'd throttle the speed to something I can keep up with pedaling (looks like right around 30-32mph for my chainring-cog-wheel), throttling the amps and PAS to a reasonable level, together that should keep the heat doing alright I imagine. ???

And the 72v system will let me sprint around a bit faster when I'm on more local trips. I don't really need to hit any certain speeds, ever, it would just be nice to do that big commute faster, but most important to me is just not being quite so beat. I can do 45 miles now, on the cargobike with no motor, taking no real breaks, and feeling pretty great at the end. It's the last 25-30 miles that somewhat does me in.

Again, any input is welcome, but I'm feeling pretty good about my plan!
Thank you to all!
And gratitude for this forum.

 

[dogman dan]

WHAT YOU NEED TO DO, IS BUILD YOUR BIKE SO YOU DON'T OVERLOAD IT. OR OVERVOLT IT. 72v gonna kill your geared motor.

Heat sinks won't help if you ride it overloaded much, if any. Ferrofluid will improve the heat transfer to the outer shell, at which point your hub is connected to 36 long skinny heat sinks, the spokes. If you screwed up, then hose it down. At one point, I carried a squirt bottle to spray my motor every 5 miles. I was running REALLY the wrong motor at the time, a primitive brushed motor designed for use with a lead battery with 5 mile range.

But again, if you plan on packing on the weight and riding up hills, then you need either a big motor, or a second motor to help on the hills.. Or best of all for any longtail, a mid drive.df

If you want to run 72v,, Your ONLY choice is a larger hub motor.

Don't listen to us either.. I know you wont.

 

[merdi55]

Dogman, sounds like you've had some rough experiences on here trying to help people ("Don't listen to us either.. I know you wont."). Obviously you've got a lot of experience building up e-cargobikes. I appreciate your feedback and I have put in much work with your response in mind.

I looked again at mid-drives... but I don't see any of your longtails with mid-drives, I only looked at your sig links? Maybe you wanted the 72v? Thus went with a bigger hub motor as you suggested I do. I'm partly inclined towards a hub motor because I need a new rear wheel right now anyhow... which maybe isn't the best reason to buy a specific type of motor. But, for a variety of reasons I think I need to go with a rear hub motor.

I've found more options for batteries. So I think I can easily just buy enough Ah's at 52v to make my primary journey.

As for overloading and overheating a GMAC 10t. I have played with the trip simulator quite a bit, now. Unless there is something else I should know, it would seem that even under worst-case scenarios (ambient temps, headwinds, and a heavy load), some combination of throttling the speed, amps, and proportional assistance, I should be able to make all my planned rides without pushing the temp limits. I won't be asking this setup to do anything but help me with rides I already do with no assistance. I don't mind asking for less help, and/or going slower due to weather, load, and terrain. Under good conditions, it looks to me like I should be overbuilt for my desires, which is the goal.

For instance, here's the simulator for about the hilliest ride that would be in my repetoire, with 24 KPH headwinds, 330lb total load, and 34C ambient temps limited to 25KPH. Shows me barely exceeding what Grin claims is the max constant operating temp for the GMAC of 110C. https://www.ebikes.ca/tools/trip-si...&md=37_48551+-83_91162&x=&y=&lx=405&rx=0&rw=0

From my limited understanding, IRL I should be able to use whatever limiters I want as I approach these hills instead of limiting the speed for the entire route (my only simulator option), and still maintain higher speeds for much of the ride, while helping control temperature.

I don't need to ever see 35MPH max. 30 would be fine. I won't be disappointed by rides averaging 20 or even 15 mph when the conditions are bad, as I normally would either not make those rides, or would have to accept 10MPH, or slower. It's not really that hilly around here, or at least I always have options to minimize the hills (one of the worst hills around, and included in that sim above is avg 6.5% grade). Mostly I'm riding the easy rollers of Bluegrass Ky. The occasional hillier rides with a bit of extra gear, will be much shorter, and, like I said, are still rides I accomplish without assistance.

This makes me think surely even on the hills, I can ask this GMAC to make up for it's own added weight, and give me some decent help beyond that (like 600-800W total) without over heating. But if that seems wrong, I would like to know!

Oh, and yes, I figured the hubsinks would not help in this scenario, and the ferrofluid is unsuitable for geared motors like the GMAC, I believe.

Thanks Dogman Dan and all for reading and feedback.

 

[merdi55]

Hahaha.

Yeah, Dogman, I just saw your location, so I did a random google map ride from downtown Las Cruses east on route 70. You have a hair more vertical climb in that 28 mile ride than on my 70 mile ride, which includes riding "all the way" down and back up the Ky river gorge, a "big climb" which accounts for over 1/3 of the vertical climb for the entire ride. Elevation changes are mostly pretty chill around here. I try to tell everyone I know that doesn't ride, that we live in a cycling wonderland here in central Ky, and that they should bike, you know, at least every once in a while. To little avail.

 

[john61ct]

I'm currently figuring that multiple motors is the way to satisfy my heavy-cargo / steep mountain roads need for highest possible torque especially at lower rpm.

The mid-drive with gearing looks the way to go for one of them, then a DD on front, ability to use either or both for a given stretch, plus redundancy for getting back to base alone in the desert.

But I'm looking at at least 400# ideally 500, and some tall mountains to get over. . .