First build, random questions about hub motors and overall build

This past week, I was hoping to get an old EVG 24v, but the seller sold it before I was able to get it.

So, I'm back to square 1, looking for a cheap old-style moped for a conversion. I've seen multiple folks comment on their build requiring custom forks, so I figured I'd be safer to ask in advance - what mopeds (1970's-80's style jama, puch, etc.) are the /easiest/ to convert? I'm thinking a hub motor (saves space, less complicated?).

The older style moped is my focus because:
* Larger and wider tires than an trail bike
* General design will make it easier to haul my chainsaw and other small tools around the property
* Some also have the easier step-through design, less likely to throw my back out

After conversion, I won't need the foot pedals, and I won't be on public streets, just our property

I'd rather spend some time up front and get a conversion-friendly moped (hub motor), rather than getting any moped and later finding out that conversion is beyond my capabilities.

Or, if there are not a few specific "easy" models, what should I be looking out for (or to avoid), e.g. certain types of forks, etc?

Thank you!!

What kind of riding? Enduro racing or offroad strolling? I’d assume all old mopeds would need a lot of attention on brakes and suspension since 30-40 years take it’s toll on stuff.

I’d buy a derbi senda or rieju from year >2000 to be on the more modern side of things. That’s european choices, don’t know what is available in US? It’d be a nice ride mated with a QS 205 hub motor kit if you’re just into riding, not racing.

The TYPE of moped bound to be easiest has a complete frame independent of the engine. You see them with the engine providing structure as either the swingarm or as a stressed member in the frame, which means either you build a replacement to the presence or you let it be in the way adding weight.

If you could find one with the pedals and crank not built into the engine that will mean you get to keep the pedals without building a solution. Can't name any bikes like that.

I think the line is 30 mph+ and no peddles and most bike hubmotors will fit 135mm rear fork and have one or more speeds. As the motor gets wide 150mm - 200mm you know this is no bike motor so now you need moped or motorcycle frame with no peddles.
the basics are mostly the same and it all get bigger and heaver and more expensive.

Hi all-

Still completely new to this, trying to find the best options for my needs. I was looking at fat tire bikes, but am now leaning back toward a moped conversion. I can get a used moped in my area for anywhere from $150-250 as my starting point. I think the mopeds I'm looking at generally have 20" tires

For the conversion,
* I need something technically simple (a kit, no welding). I am a fairly handy person, but am looking to make this relatively plug-and-play
* My assumption is that I'd remove the gas motor, pedals, and chain and this is just an e-moped, throttle on the handlebar for speed
* 'm thinking rear hub, and would only add a low power front hub if I found that I was having traction problems getting up hills (spinouts on wet leaves, etc)

I don't need a lot of mileage from a charge (5 miles would be overkill), nor do I need speed (15mph would be plenty) but I do need to go up and down hills, up to about 30 degrees, with a 200lb rider and gear (chainsaw and/or other tools). This is for use outdoors/offroad to get around for property maintenance.

I find low maintenance to be appealing (gearless hub?) although in my case I'm not sure if I should look at geared because of the intermittent torque that will be needed, I don't fully understand the pros/cons for my use case.

I'd welcome thoughts/suggestions (and links to example conversion kits, if that is allowed here)

Thank you!

For the steep hills on your property, you need a mid drive. Fat tire may not be needed, that just depends on how deep the mud is, or snow. But most of the season you'd ride anyway, a regular mid drive mtb should suit your needs well.

Hub motor will just overheat on the steep, unless its really high powered, motorcycle like power. That can be done also, on a regular high end mtb frame.

But still, you need a mid drive.

Hi, I am not sure what you are looking to do? Are you looking to modify a moped so it is street legal? Every state/country/area has different laws regarding legality of conversions/etc. I would think a moped could be converted to an e-moped. I would think the best (easiest) way would be to mount an electric motor in place of the gas motor and use a chain to drive the rear wheel. You would probably need to fabricate some sort of mount for the motor. You would also need a device to cut the battery voltage down to run your lights, etc. This way you would be able to utilize everything else on the moped like brakes, etc. Otherwise you would need to replace the rear wheel hub with a motorized one and have it laced into the wheel, and you might have to reinforce the dropouts or something as well and also come up with another braking solution. Batteries would not be much of an issue for only 5 miles, that would be a rather small battery but with cells with high amp output.

The issue I see is the moped is going to be very heavy for what it does and it is not very well suited for holding batteries, etc. (unless you are going to cut into the gas tank perhaps) so unless you are trying to build a high speed street legal moped it might be better to build a cargo bicycle, again depending on local laws. A cargo bicycle would be much lighter and you could add a small hub drive motor or a mid drive motor to replace the cranks (tsdz2, bafang bbs02/bbshd/lingbei, etc). A small 52v 5ah battery would be more than enough for 5 miles at 15-20mph (depending on how much of that is uphill). If you can find a bicycle that suits your needs and has a 68-73mm wide bottom bracket at the cranks then there is a good chance you could build an ebike with a mid drive. The cheapest of the mid drives plus a small battery would probably cost about $450, as would a decent hub kit like the mac 12t. The bbshd and small battery would be more like $850+ but that is capable of putting out twice the power of the other motors.

If the hill you need to climb is really 30 degrees (that is very, very, very steep - 6 ft rise only 10 ft away!) then you are going to need a powerful motor or a very low gear ratio. My guess is 1st gear would probably need to max out at under 3mph to be able to climb that hill with a sub 1000w motor. Even if using a wide ratio 8spd cassette means your top speed would max out at about 10mph in 8th gear. I would check that hill you need to climb before building anything. I am in Italy and even I have yet to come across a hill that steep. I climbed a goat trail up a mountain once which was probably 25 degrees in places and I had a hard time keeping the front wheel on the ground while trying to climb it. I made it up but I worked my @ss off!

Personally I like the idea of converting a moped or small motorcycle into an electric driven vehicle, but only if the right donor vehicle came around and only if I could get it to be street legal (registered, insured, etc). Until then I will be sticking to my ebike

I finally managed to get a cheap donor moped; it is this type but the engine was blown and partly disassembled, which is why I got it super cheap I'm not trying to save the pedals, my desire is to run this on throttle (e)power only.


* I'm relatively handy, but not a mechanic (and zero welding experience) so I'm primarily interested in hub motor(s) instead of trying to install a mid-mount
* I don't have a battery pack in mind yet (but assume li-ion), figuring I can cut open & convert the gas tank and/or put batteries under the seat, or worst case, figure out a way to mount a battery pack where the engine was, but that is last resort as I want to maximize ground clearance.
* I don't need long range or high top speed, but I do need sustained torque for hills at lower speeds (geared motor?). Actual range of 1-2 miles and top speed of 10-15mph is plenty. Does not have to be street legal.
* for more torque on hills, I'm thinking of going 2WD to minimize stress on the forks and torquearms (so the front motor needs to have a freewheel to keep down parasitic power draw per the 2WD FAQ?)
* For what its worth, the donor moped has disc brake in front, drum in rear. I'm assuming the least complex solution will be to keep the same arrangement(?)
* the donor moped has solid wheels (no bike spokes) and I'm tempted to look for the same in a hub motor, to support the overall moped weight, and the motor torque (but I have no idea if that is actually necessary/helpful)
* although i'm happy to buy from a USA vendor if the price is competitive, at the moment I'm also looking at my favorite chinese importer for options
* since this is a moped and heavier than a bike, I'm now starting to look at stronger hub motors I think were designed for motorcycles? Part of my logic is (I think) the original 49cc motor was probably around 3hp, so to get similar power (again, I don't care about distance or top speed, but I do need to climb hills) I think that means I need at least 3K total e-power? Please correct me if I'm misunderstanding the power conversion.

I'm not entire sure which hub motor measurements are critical, as vendors don't list everything I would have thought important. The original back wheel is 17", with a M62 3-17 tire

As I look at options, few of them specify if they are direct drive vs geared. None of them clearly indicate if the (front) motor can freewheel. Now that I've moved to looking at higher wattage, I'm also not finding any that are drum brakes, and I don't understand the implication of regenerative braking (does that replace both drum and disc, so I wouldn't need either?).

At this point, I'm mostly trying to avoid making a costly mistake by ordering something that won't fit, or won't work for my needs. I welcome the insight of the group on any/all of this.

Thank you!

I suggest the Leaf Bike 1500W direct drive hub motor In the rear, if 135mm hub spacing can be made to work in your swingarm. They’ll wind it for whatever speed/wheel diameter you need (by request). It’s inexpensive, not too heavy, and unusually efficient over a wide speed range. If you get a suitably slow winding, the torque with a 35A or 40A controller should be ample, and heat buildup minimal. My 29er MTB with an inappropriately fast wound Leaf hub is able to break 30 mph with a heavy load, but doesn’t get hot when climbing at much lower speed.

It will be more expensive and complicated to get similar performance at low speed if you use dual motors, or a bigger heavier motor that’s intended for substantially higher speed.

The lower your target speed, the less power it will take to achieve the hill-climbing torque you require. Watt for watt, electric motors do the job of stinking gas motors that have much higher hp/kW ratings. My guess is that 1500W nominal or 2000W from the battery should be more than adequate for what you describe.

Your target range is so short, I wonder what you have in mind for this bike?

Thank you for the reply! I'll look at the motor you recommend, and measure the spacing on the moped more precisely - eyeballing it with a ruler, the rear looks like maybe 175mm and the front is maybe 120? I think the back is so large because of that drum brake.

My 'use case' is checking the fenceline of a 20 acre farm (about .75 miles of fence/ battery range, plus enough spare juice that I can go back to the house for supplies 1-2x if needed), in a moderately hilly environment. The moped will carry me (200lbs) and a few small tools (chainsaw if needed, or a t-post, fence puller and hand-winch, etc.).

The first/main rise from the house is several hundred feet, best guess is 10-15% slope, but after that it is more level (smaller slopes).

One additional advantage I was hoping to get from the 2WD was extra traction on the hill (especially after rain / wet leaves) but I'm absolutely ok starting with one hub motor and only adding a second if necessary (and I'll research controllers and battery configurations to support two from the get-go, I'd rather pay for a little more now and have the option to expand, instead of potentially having to change everything out later if I do add a second motor)

Thanks!!

I don’t think you’ll be able to use very much power in front when the trail is steepest and you need it most. In that case, weight shifts to the rear wheel and there won’t be much traction available in front.

Yours is a good application for radio control model batteries. Those are capable of delivering huge currents in proportion to their energy capacity, so you can get lots of power without having to buy a lot more range than you need. You will need a secure (fireproof) place to charge them, though. Though they are mostly reliable, they carry a higher risk of spontaneous fire than other common battery types.

Surely you will need good torque arms and a motor-battery combination that tops out at pretty low RPM, for what you’re doing. Hundreds of feet of vertical relief in 20 acres of farm is not like the farms I’m familiar with. Seems like you’d have to glue the soil onto the ground.

There is a 16 inches magic pie hub setup in todays posts. Might be too fast winding though. I have old 9 continent , slow wind in 20 inch wheel. It only does 16mph at 48 v. Sounds like what you need.

the other threads on this project were moved into this one, so the info in them will help people help you, especially since you tend not to answer when they are trying to help, and instead start a new thread later on.

if you keep all your project questions/posts in this thread, and be sure to answer questions those helping you are asking, it will help us help you.

..and get a mid drive
30 degree slow riding is not where hub motors shine

QS 3000w mid drive kit would fit this project, paired with a large reduction like 10t:100t you'd get a monstrous 560Nm at the rear wheel

> QS 3000w mid drive kit

link?

https://www.google.com/search?q=qs+3000w+mid+drive+kit&oq=qs+3000w+mid+drive+kit&aqs=chrome..69i57.15119j0j7&sourceid=chrome&ie=UTF-8

that wasn't too hard, right? :wink: