Optimal Gear Setup for Acceleration - BBSHD 230lbs All In

MacGuyver_Season1

MacGuyver_Season1

100 mW
Joined
Feb 5, 2017
Messages
37
Location
GA, USA
Hello All, great information on here! Have an old Style A BBSHD from Luna w/ a 52v battery and 850c display, on a (2014-15ish?) Trek X-Caliber 29er w/Luna 42t chainring and 11-34 9 spd cassette. During COVID I set it up on a Wahoo trainer {did not use motor} and lost 40lbs (well, after I gained 50lbs). Sorry, I know, get to the point…

Anyway, took bike off trainer last weekend (still works great!) and thinking about using it to commute. Live and work in inner-city urban area, so biggest concern is being able to accelerate, to say, 35mph from a stop light. So I don’t get run over by a car :). Was able to hit top speed of 41mph (gps verified on iphone and Dragy) but very long stretch on back neighborhood roads (umm, in another country of course). I know first answer will be to get a smaller chainring, but issue there will be shifting during acceleration which generally is not what these bikes were made for. Have been looking at calculators online, etc. Welcome any thoughts, open to getting more gear if needed. Basically would like to be quicker/safer than a 49cc moped.
 
I don't have the math, but you can calculate how long (time or distance) it will take to accelerate your mass (bike and you, etc) to a given speed with a certain amount of power, or torque, given the specific gearing you want to stay in without shifting, given your specific terrain, wind, and road conditions. Then if you have a goal on that acceleration time, you can use that as a ratio to figure out how much power or torque to add to the system, once you know how much you've already got. (the simulator at ebikes.ca has a middrive option with various standard gear sizes already in it, you just have to setup the BBS motor/controller system with "custom" fields as it's not listed yet).

If your trainer has a watt or torque (Nm, ft-lbs) readout, you can set the bike up on that and see what you get in various gear combinations, then you'll have numbers on what it can do now.

WIth that, you can see if just shifting gears at the appropriate times will get you what you want (probably) or if you will have to add more power or torque by changing your gearing or adding a second motor, controller, and battery***, or replacing what you have with something bigger. If you don't want to shift gears the way these systems are designed to do to appropriatley use the power they have, then the latter two are your main options****.

Note that changing your gearing for better torque will decrease your top speed, unless you are just changing the lower gears (small ring in front, big in back) and not the higher ones (big ring in front, small in back).


***your existing battery probably wouldn't handle a second motor, at least not without enough voltage sag to lose you power you need to accelerate quickly, so you would likely need a second battery to run it. Similarly, if you replace with a bigger system, the existing battery probably would sag there as well. Depends on the specifics of the battery, and how much it sags under load now.

****another option is to increase the power of the system you have now, by replacing the existing controller/display with something more powerful, but this risks overheating the motor or damaging the clutches/gears in it, depending on how high you have to go for what you want. There are a number of threads on doing this to various versions of the BBSxx drives, most commonly using the ebikes.ca Phaserunner on the BBSHD.


FWIW, a 49cc moped is probably around the same power you already have...but you have gears to shift that power thru to vary the ratio of speed to torque, where the moped doesn't, so if you are willing to use them and to setup the ratios with the right sprockets and chainrings for the max torque you need at low gear and the max speed you need at high gear, you can probably beat what the moped could do easily enough.

Also note that many localities have speed and/or power limits for bicycles, and some of them enforce them more heavily than others, so you might want to look into this to see if it could be an issue for you.
 
Thanks for the info! I set up the bike on my trainer and tested it out in each gear. Will not be doing that anytime soon as both the motor and trainer were getting hot within 10 minutes. Here is what I got from gears 1-9 (34-11t). I really don’t think the trainer is made for this kind of analysis, but I guess somewhat informative. Max of 1300 watts (observed by trainer; after transmission), max speed of 37.1mph. The trainer is supposed to simulate a load on the bike with my weight and rear wheel size (though it is the basic setting that doesn’t let you factor in bike weight). I also have a Zwift account but don’t want to skew my stats and “cheaters” will get hated on and kicked off with unrealistic power figures like this. I guess this gives me a ballpark baseline at least. IMG_1018.jpeg
 
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You can see how it matches up with the Grin simulator, or tweaked the simulator to your specific situation (riding position, etc.). If the point is not to shift, then you probably only need to test certain gears that can achieve the target speed.
I use 30 for a target speed. That usually lets me get about a 1/2 block ahead of any cars at the light, so I can be in a better position to navigate past the parked cars on my right. In your case, you could shift at that point.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...
ebikes.ca ebikes.ca
 
You might try using only two or three gears (I have 11-17-28, spaced 8-speed, on my BBS02-equipped off road hardtail), like 11-17, pedal like crazy and use the throttle off the line with the "17", then shift to the "11". Disclaimer: this may be stupid, and I've never tried it, but for flat terrain, if something like this doesn't work, you're probably going to need a bigger motor. Other option: add a front hub system (FME, using a 1500w rear DD and front 350w PAS, each with independent controller and battery, provided really fast off the line power and I could keep up with urban traffic easily).
 
E-HP said:
You can see how it matches up with the Grin simulator, or tweaked the simulator to your specific situation (riding position, etc.). If the point is not to shift, then you probably only need to test certain gears that can achieve the target speed.
I use 30 for a target speed. That usually lets me get about a 1/2 block ahead of any cars at the light, so I can be in a better position to navigate past the parked cars on my right. In your case, you could shift at that point.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...
ebikes.ca ebikes.ca
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Any clue what values to put in for the custom BBSHD on the grin calculator? Looked at that and was completely confused.
 
2old said:
You might try using only two or three gears (I have 11-17-28, spaced 8-speed, on my BBS02-equipped off road hardtail), like 11-17, pedal like crazy and use the throttle off the line with the "17", then shift to the "11". Disclaimer: this may be stupid, and I've never tried it, but for flat terrain, if something like this doesn't work, you're probably going to need a bigger motor. Other option: add a front hub system (FME, using a 1500w rear DD and front 350w PAS, each with independent controller and battery, provided really fast off the line power and I could keep up with urban traffic easily).
Click to expand...
Thought about that. Maybe rearrange the cassette and only use 2-3 gears? For adding a second motor to the front, concern there has always been bending/breaking the front suspension fork that came standard on my bike. Have heard bad stories, but maybe ok if you keep power well below real wheel?
 
MacGuyver_Season1 said:
Any clue what values to put in for the custom BBSHD on the grin calculator? Looked at that and was completely confused.
Click to expand...
I don't know what your particular version is. I just put in values based on stuff I found on Luna's website and adjusted the voltage to fully charged. It still didn't get to 41 mph in any gear, so something must be different with your setup.
 
MacGuyver_Season1 said:
Thought about that. Maybe rearrange the cassette and only use 2-3 gears? For adding a second motor to the front, concern there has always been bending/breaking the front suspension fork that came standard on my bike. Have heard bad stories, but maybe ok if you keep power well below real wheel?
Click to expand...
I forgot about the suspension fork which could be a problem (mine was rigid), but look at Grin's all axle motor as that could provide a real boost. The other advantage(s) of only a couple of gears is they are spaced at the end of the cassette and (for BBS02's) provide a straight(er) chainline (mine is straight with the "17", so perfect) therefore less wear to the drivetrain and you can space 8-speed for maybe a stronger (wider) chain and less expensive components (maybe a short cage rear derailleur for more ground clearance).
 
2old said:
I forgot about the suspension fork which could be a problem (mine was rigid), but look at Grin's all axle motor as that could provide a real boost. The other advantage(s) of only a couple of gears is they are spaced at the end of the cassette and (for BBS02's) provide a straight(er) chainline (mine is straight with the "17", so perfect) therefore less wear to the drivetrain and you can space 8-speed for maybe a stronger (wider) chain and less expensive components (maybe a short cage rear derailleur for more ground clearance).
Click to expand...
This All-Axle Hub Motor - Grin Products - Product Info to put on the rear? I suppose it would boost low-end torque/acceleration as the mid-drive is winding up?
 
E-HP said:
I don't know what your particular version is. I just put in values based on stuff I found on Luna's website and adjusted the voltage to fully charged. It still didn't get to 41 mph in any gear, so something must be different with your setup.
Click to expand...
It has the “Hot rod” programming, but not the “Ludicrous“ V1 or V2. Basically stock with all of the settings optimized by Luna at the time in 2016. The 52v battery will also go to 58v or so fully charged (I know I shouldn’t do that for life of battery). I don’t know (too old can’t remember) what the max BMS amp is from the battery. I thought it was 50A but I believe Panasonic GAs so should be lower from what I can research. Either way, controller maxes out at 30A unless you do some sort of modification or get an aftermarket beefed up controller. But thank you for checking, for sure!
 
MacGuyver_Season1 said:
Thanks for the info! I set up the bike on my trainer and tested it out in each gear. Will not be doing that anytime soon as both the motor and trainer were getting hot within 10 minutes. Here is what I got from gears 1-9 (34-11t). I really don’t think the trainer is made for this kind of analysis, but I guess somewhat informative. Max of 1300 watts (observed by trainer; after transmission), max speed of 37.1mph. The trainer is supposed to simulate a load on the bike with my weight and rear wheel size (though it is the basic setting that doesn’t let you factor in bike weight). I also have a Zwift account but don’t want to skew my stats and “cheaters” will get hated on and kicked off with unrealistic power figures like this. I guess this gives me a ballpark baseline at least. View attachment 339802
Click to expand...
Looking at this more, seems very odd that top 4 gears would peak at 1300 watts. Again, not what the trainer was designed for I guess.
 
MacGuyver_Season1 said:
It has the “Hot rod” programming, but not the “Ludicrous“ V1 or V2. Basically stock with all of the settings optimized by Luna at the time in 2016. The 52v battery will also go to 58v or so fully charged (I know I shouldn’t do that for life of battery). I don’t know (too old can’t remember) what the max BMS amp is from the battery. I thought it was 50A but I believe Panasonic GAs so should be lower from what I can research. Either way, controller maxes out at 30A unless you do some sort of modification or get an aftermarket beefed up controller. But thank you for checking, for sure!
Click to expand...

I’m going to give this a shot. We shall see!

How To, 50A BBSHD Controller Mod
 
2old said:
The front; the motor was designed to work with suspension forks since it has an internal torque arm. Ask them about it as they're very transparent and helpful.
Click to expand...
Interesting, good info on that site. Going to try the 50amp mod in post above first. Who knows, may burn through controller or something else.
 
I'm a big boy too looking for occasional mega acceleration power

BBSHD seems like the only good diy motor and figure I might as well get max performance out of this boat anchor

HD 52v 30amp vs 72v 50a etc for 90 percent casual 1000w use, does this motor get unhappy just doing quick 2.5-5kw turbo boosts to clear obstacles or quick acceleration?

I demoed the HD and found 750-1000w was comfortable on flats and 1500-1700w adequate uphill as is (240lb self). But looking at products like chimera eBMX I could see where the increased boost could really help or even keep me safer in traffic. (Can the throttle be programmed to deliver varied power depending on how hard it's pulled? I wouldn't want to be popping huge wheelies when I just need 1700w, this would be for like uphill acceleration)

Also I'm such an electronics noob, if I am "set up" for the more amps and volts, will a 72v last longer than 52v running mostly at the same power level if you consider watt hours, say both have a 20ah battery. That would be awesome too, running a 15/20ah battery with more overall range.

I think with a good hybrid, gravel, or rigid fork MTB bike with lightweight components, this could be a good lightweight build overall. Figure I might get the extra power out of the motor as it's there, the internal permanent magnet rotor is appealing, and the idea of actually getting more range out of 72v would be good. (Can you do like 72v 30amp? Can you go to 90v or beyond with the BBSHD ran low for more range? I'm really uneducated on electronics and ebikes, I'm just seeing more/less numbers=good/bad) . Dropping battery weight would be really significant and make me less nervous about mounting so much weight on the bottom bracket and downtube.

I am
 
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docw009 said:
Looking at the big picture, how did Macguyver do in the real world with wind resistance? I don't often read about BBSHD's cruising at 33 mph on a bike with flat bars , but I guess people do it.
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25mph is pretty ideal, but getting that extra kick for acceleration would be great, or using a 90-100v controller to get more range instead of power would be ideal, and being able to run a 10/14ah battery if it Will actually work to save weight. Id love a build around 17lb base weight in road or 20-24 base weight rigid fork MTB/ flat bar gravel. Trying to scoop up some used Ti road or MTB build with lightweight groupset and hubs and carbon rims
 
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