Input for long range commuter build?

[4speed]

Having gathered information for some time I just recently found out about this forum that appears like THE ebike forum - especially for DIY which is not a big thing in my neck of the woods.
I am considering swapping diesel for pedals, for commuting 30 km one way. That will not happen without electricity since I am nowhere near fit and do not expect to be able to keep up a speed that covers the distance in reasonable time. Also I need to be able to actually work when I get there...

Distance is 30 km, essentially flat but headwind at times. I am around 200 lbs and need a minimum of baggage. Reasonable time for me is around 45 mins at the most, so ideally need to sustain at least 40 km/h (25 mph).
From the Trip Simulator at Grin webpage I realize that this will take a bit of battery. I can charge at work but that of course also means twice the cycle count. I am free to choose motor type, bike model etc and optimize for this specific application and this is where I would appreciate experienced input.

I lean towards a hybrid type bike or possibly mtb, with a half-forward riding position, 26-28". For simplicity I am happy with rim brakes.
As for motor - I believe that a direct drive hub motor would be nice for several reasons, but I really want to avoid a large hub that draws attention. Hence rear wheel would seem better = more discreet. Or a geared hub motor in front, IF they stand the wear in this application. Motor weight is not a big issue though.
Mid motor might also be an alternative but since I will be going long distance with continous fairly high power I suspect that chain/gear wear may become an issue.
I believe that 750 W or so would do the job but here again I am out in the deep end. Better to go for smaller motor at higher load or the opposite?

Maybe the biggest question for me is if battery requirement will be the killing factor, both money- and size-wise. Maybe it is too big a bite to chew...

Budget is of course an issue too. Aim is for drive kit in total (just kit, not bike) not to exceed EUR 1000 (roughly USD 1000), does that sound doable or must I step it up?

If/when this project comes to real life, I will of course share the proceedings.

 

[JES2020]

Sounds like you have done most of the homework.
$1000 is more than enough to get you a 750w motor (I'd vote for a geared rear hub), small size good power and it hides behind the bike gears. It is also very quiet.
I put a 750w IGH with a 48v 21 ah battery on a Trek and was able to get 60 to 80 miles on a charge without trying, 30 plus mph. All in cost excluding the bike was $700.
One other thing, the direct drive motor has a drag effect when not under power, you will not coast very far.

 

[4speed]

Sounds like you have done most of the homework.
$1000 is more than enough to get you a 750w motor (I'd vote for a geared rear hub), small size good power and it hides behind the bike gears. It is also very quiet.
I put a 750w IGH with a 48v 21 ah battery on a Trek and was able to get 60 to 80 miles on a charge without trying, 30 plus mph. All in cost excluding the bike was $700.
One other thing, the direct drive motor has a drag effect when not under power, you will not coast very far.

Thanks for the input, that sounds more reassuring than I had hoped for.
I find it difficult to get a feel for how much drag a gearless motor would make in real life but maybe a geared motor would be best after all, not least because of its size. I can live with a faint hiss sound if that would be the case, really mostly worried about two things - lifespan of the actual gear wheels and, correspondingly, the rpm of the whole thing. Is 25-30 mph pushing the design limits for these things? Suppose the nylon gear wheels can be replaced as long as the housing can be opened at all, and not riveted together.

As for the battery, I am considering riding with a generic shink tubed pack stuffed in a regular (rain proof) side bag. Partly for cost, partly for ease of supply, partly for... the stealth factor. Any thoughts on that? If the pack gets too hot I would pack it accordingly.

 

[JES2020]

lifespan of the actual gear wheels and, correspondingly, the rpm of the whole thing. Is 25-30 mph pushing the design limits for these things?

30 mph is a reasonable top speed for a IGH 750 w speed wound motor. Speed is a factor of voltage, these motors can be over-volted (within reason) and go even faster.
I have never seen an IGH that can not be opened, that said the nylon gears are very long lasting and can be replaced if needed. There is also a metal replacement gear but it is louder.

As for the battery, I am considering riding with a generic shink tubed pack stuffed in a regular (rain proof) side bag. Partly for cost, partly for ease of supply, partly for... the stealth factor. Any thoughts on that? If the pack gets too hot I would pack it accordingly.

Some people put their batteries in a back pack, so I don't think your idea would be a problem.

 

[4speed]

Happy to hear.
One thing that feels a bit insecure is that actual performance specs for motors often seem(?) to derive from empirical trial-and-error user experiences rather than from manufacturer's documentation. Meaning that if I aim for, say, a +50% performance (power, temp, voltage, rpm, whatever) headroom in the choice of motor to promote life span, as opposed to pushing things right to the limit, I can not be as certain of that margin as I would in other engineering designs.

Oh well. I keep scanning regional ads for the right bicycle, that will have to take its time, and from that decide about specific motor model.

 

[indianajo]

After taking 5.7 hours to make my 27 miles commute into a 25 mph headwind, I added electricity to the cargo bike left. $2000 with accessories delivered. Great bike; I have ~8000 miles on it. Conversion was $870 with $630 of that a 17.5 AH 48 v battery.
I've only seen one set of replacement gears available, for a motor I didn't own. The vendor didn't have the motor the gears fit in stock either. I wore out the gears in a $221 hub motor in ~4500 miles. I rode a motor to destination & back to maintenance base with worn out gears without drag. I had the spare power wheel in the garage, and the only reason it took 2 afternoons to replace was that the controller was different and I had to make a new mount for it. I've since bought a couple of rental takeoff motors in wheels with brake disk for $78 + freight +tax. Without wheel they are $23 each: I bought 2 more of those. Don't forget to install a torque arm. I had to remake the clamp & arm when I changed brand of motor.
I mount my battery in an enclosure made of aluminum angle and poly foam batts. With 18 machine screws with elastic stop nuts, it takes some time to disassemble. More time than 2 wannabe thieves at the grocery store were willing to spend. Both times 2 nuts were loosened but not until they came off. One other barrier, takes a screwdriver with 8" shaft to reach the screw heads inside the enclosure. My cargo bike has bosses in the frame to hang the battery off the front without steering it. I find that more balanced than a 9 lb battery on the rear along with the 8 lb motor.
I ride motor on the front. Don't use front power on slick ice, wet steel plate, wet or muddy rock, or wet wood bridge deck. Don't climb mountains off road with a front motor. I started with a DD motor on the back but my bike came with 8 speed 32-11 cluster. I never was able to find a 32-12 7 speed freewheel in stock on the N.A. continent, and I needed both ends for my riding. DD dragged unpowered like being in 2 higher sprockets than I actually was. Since I ride unpowered about 80% of the time I found this annoying. With your desired speed DD motor might be desirable, aside from them being huge burglar magnets. I use a 1/2" SS sling to lock while shopping or meeting or working. In high theft zones I use an additional 3/8" SS sling through the power wheel. I lock to power poles gas meters & live electrical conduits, not to those cheap bolt down tubes cities install. The sling rolls up in the pannier bag shown, and weighs half of what a chain of the same thickness and alloy weighs.
If you live in southern Italy Sicily or Malta you may be okay with rim brakes. I had rim brakes when I hit the car that ran the 4 way stop sign, after I had stopped. Rim brakes lose 2/3 the stopping power after running through a puddle. All it did was bend the front wheel.
My 1300 w ebikeling motor was capable of about 25 mph with 48 v drive. I cross 66 hills with that one in 27 miles, no overheating problems. When it wore out I changed to a Mac12t wound for torque, which accelerates faster across 6 lane highways to finish before the light turns red. Pulls faster up 15% hills with 60 lb groceries, too. Mac12t would go about 23 mph with 48 v. I only go that fast on perfect pavement. With no suspension on a cargo bike it is pretty rough at 23 mph or faster, even with 2.1" tires. I only ride fast if I have an appointment I am trying to make or storm I'm trying to beat to destination. Usually 9 mph powered or not.

 

[tomjasz]

I live in a small city. No challenging hills. My last build is a Cutler MAC 10T rear Gear Drive with a variable voltage Grin controller. It's a one-speed. 42T x 16T. Pictured incomplete. This was a "scratch" build. Marin let loose with a bunch of warranty stock bare frames some years back. Now has panniers, rack pack, horn, lighting, and Grin CA3. The lessons were invaluable and cemeted my ability to make most repairs as needed.

 

[4speed]

Thanks for that input! Because of the parts issue mentioned, and compatibility with controllers etc, I hope to be able to decide on as common motor as possible.
@indianajo , I will not need to stop-and-go at all between home and work, and no need to keep the battery on the bike when I leave it. As for brakes, I really think I can do with rim brakes. Traffic is really sparse and most of the distance is countryside. Good input on the motors. Road is essentially flat and my aim is to be able to sustain around 28 mph.
@tomjasz , did you build that wheel yourself, replacing the hub? Difficult to get it right?

 

[m@Robertson]

Sustaining 28 mph as an average is going to happen only if you put some effort into pedaling. Your terrain and route sounds like best-case for making that happen. I weigh 250 lbs though, and to comfortably hold 28 mph on flat land I needed 2 motors, although I also got the benefit of really peppy performance. But in my area we get regular afternoon headwinds that are always steady and can be in the 15 mph range. For those, I need that second motor to maintain speed. If you have steady headwinds (or even adverse crosswinds) and a single 750w geared hub motor (as in geared hubs have more torque than direct drive) you can forget about that average speed. There is no help for this given your budget. Just be aware of this.

As for battery, bigger is always better. 31ah in my case, and a custom build. Without question your budget doesn't allow for this. You will need a charging station at your work. Even if that station is under your desk and out of sight. And since you are riding daily, and charging twice daily (you will need to charge back up again at home) that just points again to the need for a bigger pack so you can charge to 80% to preserve pack life, and not be royally screwed if for some reason you goof and forget to charge. Relying on an ebike for transportation means you have to have some fudge built in for when things do not go according to plan. Its not like you can sleep over at the office if you forget to plug in the charger one day.

 

[m@Robertson]

One thing that feels a bit insecure is that actual performance specs for motors often seem(?) to derive from empirical trial-and-error user experiences rather than from manufacturer's documentation. Meaning that if I aim for, say, a +50% performance (power, temp, voltage, rpm, whatever) headroom in the choice of motor to promote life span, as opposed to pushing things right to the limit, I can not be as certain of that margin as I would in other engineering designs.

This is smart thinking, but frankly your budget doesn't allow it (it being a 50% power fudge factor). $1000 is enough to fund a large battery from a reliable manufacturer (I do not count junk factories like UPP as acceptable battery vendors). Being in Europe, you are in a tough spot as reliable battery vendors are very thin on the ground there. EM3EV is probably the best that will ship to the EU from their home base in China.

You are correct that you cannot rely on manufacturer representations or specs. With some experience in the market you'll be better able to spot the baloney. One thing to know is that a motor's wattage rating is only indicative of how much sustained punishment it can take - assuming the manufacturer (or the vendor selling to you) is not making up stuff out of whole cloth.

Top speed/motor rpms is/are determined by battery voltage. That is the equivalent in automotive terms to horsepower. Acceleration (or the ability to sustain motor rpms in a headwind) is determined by controller amps. Again in automotive terms this is translated to torque. Direct drive hub motors have the least torque. Geared hubs have more. Mid drives have the most. For flat land commuting at speed I originally chose geared hubs, and would continue to say they are the best option for that terrain, along with a high amp controller. Geared hubs also freewheel forward unpowered with no added drag, so coasting is an option.

When buying your gear, pay close attention to controller amps. Not just the peak rating, but the continuous rating, which is what will matter keeping you rolling down a road. I personally try and stick with Bafang geared hubs mated to KT controllers/displays, although the only hubs I am using now are for front wheels as part of a 2wd mid-drive+hub commuter and cargo setup.

 

[4speed]

@ m@Robertson, I much appreciate the input and realize that my demands may overshoot my budget. There may be some adjusting on both. I do intend to put in leg power but I need to keep those expectations realistic especially in the beginning. At the same time I need for this to work so well that I actually do it and keep it up, considering the investment - as I have little use for an ebike outside of the commuting. Everywhere else I want to go is either short enough to pedal without boost, or too far for electricity.
That said, headwind is not always strong here, or present at all, and sometimes there is even tailwind. And I expect to be able to put in more pedal power as my shape improves.

As I mentioned I am not really looking for a fancy hard shell click-on-frame battery but rather happy with a reasonably well shrink tubed pack. Is there money to save in DIY:ing such a pack or is it a bad idea? Downside of course is no guarantee, on the other hand of how much actual value is the guarantee from a (typically Chinese) vendor the other side of the world, with freight cost and time and potential customs/taxes hassle?

As motors suffer from several limitations I find it hard to make an informed choice. Generally in gears high torque at low rpm causes one type of wear, low torque at high rpm causes another - and both torque and rpm are limiting variables on their own. Ideally one would like to know what the design limits of a certain motor are, but that obviously is not going to happen. Same with temperature tolerance; there seems to be no way to know how close you are to frying a motor until you actually did.

Thanks for the advice about controllers and current!

 

[tomjasz]

As I mentioned I am not really looking for a fancy hard shell click-on-frame battery but rather happy with a reasonably well shrink tubed pack. Is there money to save in DIY:ing such a pack or is it a bad idea?

A case is $40 retail. Not a big driver of pricing. One of my 3 new batteries is a 21700 shrink wrap pack. Because I specified the build components and used a seller that warranties ALL packs there wasn’t much savings. By the time I added a high quality rack pack or triangle bags there is no savings. My nylon padded case was $20 more than a Shark case.

I do think shrink wrapped batteries are useful and can be virtually water proof.

 

[tomjasz]

Same with temperature tolerance; there seems to be no way to know how close you are to frying a motor until you actually did.

Just not true at all. Actually the entire paragraph is simply not true.
see ebikes.ca motor simulator. You’re just not reading from the source.
a charge simulator as well... sadly only Satiator data.

 

[4speed]

Just not true at all. Actually the entire paragraph is simply not true.
see ebikes.ca motor simulator. You’re just not reading from the source.
a charge simulator as well... sadly only Satiator data.

I was unclear; I did not mean to say that boundaries are unknown but rather that the knowledge of the limits would in this case come from Grin empirically probing them rather than from manufacturer's specs.

 

[mclewis1]

I was unclear; I did not mean to say that boundaries are unknown but rather that the knowledge of the limits would in this case come from Grin empirically probing them rather than from manufacturer's specs.

Agreed, but the Grin numbers appear to be well proven (both from bench testing and customer experiences) and apply to the common materials (gears, adhesives, etc.) used in popular hub motors ... and so seem to be very reasonable guidelines to follow regardless of the source of the motor.

From the setting used in Grin's popular control system (the Cycle Analyst) it appears that concern over internal temperatures of geared hub motors starts at about 90°C and should not be allowed to exceed 130°, with permanent damage occurring above 150°C. Direct drive motors seem to have a wider amount of variability due to size, materials, and the presence of a cooling aid (Statorade or similar).

 

[harryS]

In flat country, 24 miles (30K) is feasible, but if you want to go a sustained 28 mph, you need a lot of battery. Think 30 wh/mile. Think that a 48W20AH is 900WH, actually more but you can't access all of it.

I would go with a +1000W direct drive motor. Buy the sturdiest rear rack you can find and hang two solid panniers off of it. It's going to carry an 8-10lb rectangular battery on either side. Rig them in parallel (safe if one follows basic rules). Don't worry about pedal drag, this is not a bike you will ride for fun. You're not going to be able to match the cadence at 28 mph. Actually, a two motor system with double batteries would be better for mission critical riding.

By the way. I just converted the rear brakes on a cheap cruiser bike to disk, cheap zoom hydraulic disks with hydraulic hose. What a difference, even at 14 mph.

 

[harryS]

Is the stealth factor because powerful ebikes are illegal in your area? Being stealthy won't matter if you crash, are deemed liable, and your secrets are scattered all over the highway.

Personally,I think a more reasonable scenario is to double the commute time. Go half as fast. Be twice as safe.

 

[m@Robertson]

Personally,I think a more reasonable scenario is to double the commute time. Go half as fast. Be twice as safe.

I have to say as a daily commuter and utility rider, living most of the time where land is cheap so people build out and not up (distances are long to get from one place to another, typically) going half as fast is not an option. Time is money to put it to a cliche. This is not recreational riding this is a job getting done. Halve your productivity on anything and see how thats received. I know I am not describing a perfect comparison to what you are advocating, nonetheless if I had to slow my 28-30 mph commuter to 14 I'd be doing a lot more driving. And since I took the time to build the bike with strong parts and brakes with that increased speed in mind, and I stick to roads not paths, I'll also say the increased safety argument doesn't apply anywhere near a 2:1 ratio, either.

A note on the comments about the Grin motor simulator: They are spot on. If you want to know a given config's performance, thats the gold standard for finding it out.

 

[4speed]

Is the stealth factor because powerful ebikes are illegal in your area? Being stealthy won't matter if you crash, are deemed liable, and your secrets are scattered all over the highway.

Personally,I think a more reasonable scenario is to double the commute time. Go half as fast. Be twice as safe.

I understand your point. But doubling the 40-45 minutes for the 30 km one way commute means way too much time on the road than I am willing to spend. If I can't go at least 25 mph it is simply not going to happen.

Commuting by car is not free of risk either, and certainly not by motorcycle. And neither gives me any exercise.

 

[4speed]

The victim has been chosen. A bit of TLC on the brakes and a new chain, then on to electrification.