Grin technology motor choicesstem

[taiwwa]

Hi,

I’ve been interested in Grin’s tech lately. They appear to be genuine enthusiasts without any annoying MBA’s mucking things up.

I have a number of applications that I think I could make use of Grin for. But to start off, the last ebike system that I used was Bionx. I thought that Bionx was kind of annoying to use on a regular steel bicycle because the weight on the rear wheel, the motor drag, and the overall weight of the system. The extra weight. Actually made it tiresome to ride even with assist because it would make the ride more uncomfortable with bumps on the road but also I would have to exert my hip muscles more to keep the bike balanced and this was more tiresome on long rides.

I thought that the Bionx system worked well in a recumbent that I installed it in. This is because the weight of the Bionx is well suited for a recumbent. It does not have to worry about balance with a three wheel setup. And the weight helps with rear wheel traction which is a problem for recumbents.

The most interesting motors to me from Grin are the all axle one that they build themselves, and the GMAC and also the SX1.

I compared the all axle to the GMAC in their simulator. The GMAC did perform better but I am worried some about the long term maintenance of the locked freewheel. The All Axle has less torque but not that much less torque and it appears to me that it would be lighter than the GMAC and also is less complex with fewer parts to need maintaining. The GMAC output 80nm of torque from a stop and the all axle output 65nm of torque.

I might also consider a gravel bike build or perhaps something more like a mountain bike with suspension. My area is very hilly and so regen is needed for the hills, as well as hill climb.

So, any feedback?

 

[amberwolf]

Some assorted thoughts and questions below:

I have a number of applications that I think I could make use of Grin for. But to start off, the last ebike system that I used was Bionx. I thought that Bionx was kind of annoying to use on a regular steel bicycle because the weight on the rear wheel, the motor drag, and the overall weight of the system. The extra weight. Actually made it tiresome to ride even with assist because it would make the ride more uncomfortable with bumps on the road but also I would have to exert my hip muscles more to keep the bike balanced and this was more tiresome on long rides.

The balancing usually depends more on where you put the battery than where the motor is, but the weight of the motor in the wheel certain affects handling and other ride characteristics (such as suspension behavior, etc). (same problem with cargo bikes; where and how the cargo is loaded, and what it is, whcih is one reason I built CrazyBike2 as a LWB 'bent instead of a regular bike like the DayGlo Avenger and other bikes I'd used for cargo before that).

This is because the weight of the Bionx is well suited for a recumbent. It does not have to worry about balance with a three wheel setup.

'Bents are available in more than three wheels, or less than three.

And the weight helps with rear wheel traction which is a problem for recumbents.

That depends on the 'bent design. CrazyBike2 had no problems with weight on the rear to give traction (just on the front). Ones with rider more forward could have too little weight on the rear. For trikes ('bent or not), tadpole trikes might have less rear weight than front, while delta trikes usually have more in the rear (like my SB Cruiser).

I compared the all axle to the GMAC in their simulator. The GMAC did perform better but I am worried some about the long term maintenance of the locked freewheel.

Since there isn't a freewheel, there isn't any maintenance to do on it. The gears might require maintenance, depending on your usage and whether you use a control method that at least slightly softens power application (easier on the gears), vs just slamming the power onto the motor regardless of what it was just doing or not doing (harder on the gears).

If you setup the controller to always lightly apply power to take up any gear lash before fully applying power, it will help with some of the modes of damage that can happen.

I have a (used) GMAC to install on the SB Cruiser heavy cargo trike, but haven't yet had time to alter the frame to be able to install and test it, so I will get to pre-install inspection pics and then at some point (say, a year in) I'll open it up to get comparison pics for wear evaluation, and post those...but that will be at least a year from now (and more likely a year and a half, since it will not be real soon that I will have time to do the frame modifications).

The All Axle has less torque but not that much less torque and it appears to me that it would be lighter than the GMAC and also is less complex with fewer parts to need maintaining. The GMAC output 80nm of torque from a stop and the all axle output 65nm of torque.

Any DD hub will generally be less complex than any geared hub, and only has the axle bearings to maintain or replace as wear parts. The rest is "solid state" and unless overheated or corroded doesn't typically need maintenance.

A geared hub usually has those axle bearings plus three planetary gears (some have six in two stages of three) with their own bearings. Some cheap ones may use bushings that wear faster; if the planets are plastic (most common) then the sun and ring gears don't need maintenance normally; if the planets are metal it may wear the sun and ring faster and require those to be replaced with the planets...the sun is usually part of the axle, so may require motor replacement if you can't machine a new one as parts may not be available. The ring is sometimes part of the hub shell... Then there are the clutch / freewheel parts if it has one (most do).

For the same torque, a geared hub will often be smaller and weigh less...but they shed heat less well as there are multiple layers of materials and air to get thru before the heat can escape the motor. The DD hub only has one air gap to get across to reach the covers and escape, and there are certain methods (statorade, etc) that can help more directly shed some heat in a DD that aren't easy or possible in a geared hub.

I might also consider a gravel bike build or perhaps something more like a mountain bike with suspension. My area is very hilly and so regen is needed for the hills, as well as hill climb.

The base bike you use should be something that is suited to the specific job you need the bike to do for you, and that you are comfortable riding for the duration required. (If it doesn't fit you, and isn't comfy, it won't be any better as an ebike).

What do you need the regen to do for you? (how you setup the system and what parts to choose will partly depend on that)

Keep in mind that it will generate heat just as using it for a motor does (sometimes more, depending on the specific braking method used by the controller), so if you climb the hill with the motor heating it up, and brake on the way down, it will never get to "rest and cool off" as long as you are going up and down.

I don't know how regen will help you with the hill climb itself, though--it would make it harder to pedal and wouldn't be assisting you while regenning.

 

[taiwwa]

Some assorted thoughts and questions below:


The balancing usually depends more on where you put the battery than where the motor is, but the weight of the motor in the wheel certain affects handling and other ride characteristics (such as suspension behavior, etc). (same problem with cargo bikes; where and how the cargo is loaded, and what it is, whcih is one reason I built CrazyBike2 as a LWB 'bent instead of a regular bike like the DayGlo Avenger and other bikes I'd used for cargo before that).


'Bents are available in more than three wheels, or less than three.


That depends on the 'bent design. CrazyBike2 had no problems with weight on the rear to give traction (just on the front). Ones with rider more forward could have too little weight on the rear. For trikes ('bent or not), tadpole trikes might have less rear weight than front, while delta trikes usually have more in the rear (like my SB Cruiser).




Since there isn't a freewheel, there isn't any maintenance to do on it. The gears might require maintenance, depending on your usage and whether you use a control method that at least slightly softens power application (easier on the gears), vs just slamming the power onto the motor regardless of what it was just doing or not doing (harder on the gears).

If you setup the controller to always lightly apply power to take up any gear lash before fully applying power, it will help with some of the modes of damage that can happen.

I have a (used) GMAC to install on the SB Cruiser heavy cargo trike, but haven't yet had time to alter the frame to be able to install and test it, so I will get to pre-install inspection pics and then at some point (say, a year in) I'll open it up to get comparison pics for wear evaluation, and post those...but that will be at least a year from now (and more likely a year and a half, since it will not be real soon that I will have time to do the frame modifications).




Any DD hub will generally be less complex than any geared hub, and only has the axle bearings to maintain or replace as wear parts. The rest is "solid state" and unless overheated or corroded doesn't typically need maintenance.

A geared hub usually has those axle bearings plus three planetary gears (some have six in two stages of three) with their own bearings. Some cheap ones may use bushings that wear faster; if the planets are plastic (most common) then the sun and ring gears don't need maintenance normally; if the planets are metal it may wear the sun and ring faster and require those to be replaced with the planets...the sun is usually part of the axle, so may require motor replacement if you can't machine a new one as parts may not be available. The ring is sometimes part of the hub shell... Then there are the clutch / freewheel parts if it has one (most do).

For the same torque, a geared hub will often be smaller and weigh less...but they shed heat less well as there are multiple layers of materials and air to get thru before the heat can escape the motor. The DD hub only has one air gap to get across to reach the covers and escape, and there are certain methods (statorade, etc) that can help more directly shed some heat in a DD that aren't easy or possible in a geared hub.



The base bike you use should be something that is suited to the specific job you need the bike to do for you, and that you are comfortable riding for the duration required. (If it doesn't fit you, and isn't comfy, it won't be any better as an ebike).

What do you need the regen to do for you? (how you setup the system and what parts to choose will partly depend on that)

Keep in mind that it will generate heat just as using it for a motor does (sometimes more, depending on the specific braking method used by the controller), so if you climb the hill with the motor heating it up, and brake on the way down, it will never get to "rest and cool off" as long as you are going up and down.

I don't know how regen will help you with the hill climb itself, though--it would make it harder to pedal and wouldn't be assisting you while regenning.

I would use the gravel bike for an around town application. Panniers and rack.

I did look it up though and it looks like the hubs that I mentioned are about as heavy as the Bionx. I understand that they are also more powerful and more capable motors but still they will have the same balance issues as the Bionx. The Bionx was also on a road bike with 700c wheels so the side of the wheel likely contributed to the problem. A lighter weight hub would make sense or a mid drive but it appears that these hubs are not best suited for gravel/road, and that for those bikes a mid probably is best. It’s a shame because melting brakes are a problem for gravel and road and a lighter weight hub that could regen would be fantastic, but most motors look like they’re too big and heavy.

 

[amberwolf]

I don't really understand the "balance" issues you're referring to; I've always ridden bicycles (car-free life) of various types and sizes since I was a kid a few decades ago for just riding and for cargo (with and without trailers, racks, panniers, etc) in city traffic (and various bike paths) and started electrifying my bikes almost a decade and a half ago (and started building my very custom bikes somewhere around then), and have used some hefty hubmotors heavier than those you've listed, without any trouble balancing anything.

When i put cargo or batteries or whatnot on racks, or generally above the middle of the wheels, *then* I have had some balancing issues, and other handling problems....

If you can better describe the problem, perhaps we can find a solution for it.


I do agree that hubmotors can be heavy, sometimes VERY heavy, and they weaken the wheel for a few reasons. Depending on the power requirements, some of the middrives may weigh as much as smaller geared hubmotors...but they may pack more power into that small space, and be able to use your bikes' gearing for slower but steadier hillclimbs (just like when pedalling). But the middrives do wear the drivetrain notably faster than most humans do, requiring fairly regular front chainwheel, chain, and rear sprocket / cluster replacements. (and sometimes internal motor parts like gearing or one-way clutches).



Also, how hard are you pushing your brakes, and what kind(s) of brakes? We might be able to find a solution for that, too, depending on the specifics.

(besides regen, which may help but will heat the motor and controller in the process as they generate heat in the conversion process just as brakes do)

Mind you I'm not braking down hills, as the only serious hill I ever deal with (rarely) is on North Mountain, with 40MPH+ traffic passing me, and it's not so steep that air resistance doesn't keep me slowed down below 30MPH on the old CrazyBike2 (probably the most aero I ever had), and about 20MPH on SB Cruiser, but I've used rim brakes (variety of brands and types and pads, even including doubling up linear-pulls on the front wheel with one set in front of and one set behind the fork) and more recently disc (Avid BB7 MTN, 200mm), even on my SB Cruiser heavy cargo trike that the single front brake has to repeatedly stop the 400-600lbs+ in traffic from 20MPH, and I haven't melted any of them. (had plenty of insufficient braking problems with crappy brakes, but not melting).

 

[taiwwa]

I don't really understand the "balance" issues you're referring to; I've always ridden bicycles (car-free life) of various types and sizes since I was a kid a few decades ago for just riding and for cargo (with and without trailers, racks, panniers, etc) in city traffic (and various bike paths) and started electrifying my bikes almost a decade and a half ago (and started building my very custom bikes somewhere around then), and have used some hefty hubmotors heavier than those you've listed, without any trouble balancing anything.

When i put cargo or batteries or whatnot on racks, or generally above the middle of the wheels, *then* I have had some balancing issues, and other handling problems....

If you can better describe the problem, perhaps we can find a solution for it.


I do agree that hubmotors can be heavy, sometimes VERY heavy, and they weaken the wheel for a few reasons. Depending on the power requirements, some of the middrives may weigh as much as smaller geared hubmotors...but they may pack more power into that small space, and be able to use your bikes' gearing for slower but steadier hillclimbs (just like when pedalling). But the middrives do wear the drivetrain notably faster than most humans do, requiring fairly regular front chainwheel, chain, and rear sprocket / cluster replacements. (and sometimes internal motor parts like gearing or one-way clutches).



Also, how hard are you pushing your brakes, and what kind(s) of brakes? We might be able to find a solution for that, too, depending on the specifics.

(besides regen, which may help but will heat the motor and controller in the process as they generate heat in the conversion process just as brakes do)

Mind you I'm not braking down hills, as the only serious hill I ever deal with (rarely) is on North Mountain, with 40MPH+ traffic passing me, and it's not so steep that air resistance doesn't keep me slowed down below 30MPH on the old CrazyBike2 (probably the most aero I ever had), and about 20MPH on SB Cruiser, but I've used rim brakes (variety of brands and types and pads, even including doubling up linear-pulls on the front wheel with one set in front of and one set behind the fork) and more recently disc (Avid BB7 MTN, 200mm), even on my SB Cruiser heavy cargo trike that the single front brake has to repeatedly stop the 400-600lbs+ in traffic from 20MPH, and I haven't melted any of them. (had plenty of insufficient braking problems with crappy brakes, but not melting).

A hub motor on a 700c wheel will have a higher center of gravity because of the height of the wheel itself. I’ve ridden one and the weight and thudding feeling of the hub motor on the 700c wheel isn’t great. Hub motors make sense for smaller wheels. Likely 26 inches and under. Likely not even 26 inches are that great.

If we could somehow have lighter weight hub motors that could regen that would be great. I think a dual hub awd could be smaller in that way and as well there ought to be a way to shed heat maybe to the frame itself or have some sort of external radiator for heat allowing for smaller motors.

Like, a direct drive hub that was somehow 3lbs and have two of them. That could work out for a 700c gravel bike.

 

[E-HP]

If we could somehow have lighter weight hub motors that could regen that would be great. I think a dual hub awd could be smaller in that way and as well there ought to be a way to shed heat maybe to the frame itself or have some sort of external radiator for heat allowing for smaller motors.

Like, a direct drive hub that was somehow 3lbs and have two of them. That could work out for a 700c gravel bike.

Well it seems that the future hasn't arrived yet, so you may want to check back in a decade or two if you're aiming toward a DIY ebike. Nobody besides maybe Grin is investing in R&D for DIY ebikes. Virtually all of the parts, even for factory bikes, are just stamped out in
China, and people buy them. Parts for factory bikes may differ, per the buyer's specs, since they are paying for them, but for DIY, you get what you get. So your dream of little light motors with regen is a ways off.

It looks like there are several ebike shops in your vicinity. You could test ride several ebikes to see whether your "balance" issue is present in all of them or better for some, and see which models work better for you, to take note of the weight and weight distribution of the components to design your DIY. Or, there may be a factory ebike that meets all of your needs, then problem solved.