3D printed in-frame Motor

[Föppel]

This one here was also a bit of a pain to design...

it is the adapter for the freewheel on the side of the 1. reduction (Belt-Side)

"in the old days" i ordered and built 5 LR small block kit (-Bikes) for me and friends, and had some spare parts extra that i wanted to use...
But these were made from aluminum and after some time with 2000-3000 watt, they showed some play, resulting in wobbling Belt-Pulleys... so this one is made from D2 tool-steel, that should work.

I also tried to design it in a way so that it has a maximum possible contact area with the axis. It will be held in place by a 4mm key and 2 C-clips ( i think that is what they are called). Not 100% sure if these clips will hold it in place... Another thing that remains to be seen. I had all the metal parts made by PCBWay.com and they came out great.
To be transparent here, PCBWay is a sponsor of my YouTube channel, just to say...

In the background you can also see a blurry 3D-printed prototype of this part

 

[DanGT86]

Trial and error. That's what I was afraid you were going to say. I always ask and it seems most people who have had success with DIY pulleys had to fight it like that.

I was reading up on the various belt profiles and found some things that didn't play well with my perfectionist and anxious nature. I believe the amount of built in clearance actually changes based on the tooth count so technically its not as easy as just measuring the tooth and wrapping that negative shape around a pulley. I say technically because realistically people like you are out there successfully riding while I am obsessing about tolerances.

I am a bit of a specialist when it comes to letting the perfect be the enemy of the good. Results in more thinking than doing.

 

[DanGT86]

This one here was also a bit of a pain to design...

That's a nice looking part. The D2 will absolutely be better than aluminum long term. The aluminum slowly deforms. As for the retention on the shaft I have yet to find anything that works as well as 2 set screws 90 deg apart. One over the keyway to push down on the key and one 90 from that on the shaft.

Seems like even with a very tight tolerance fit between the shaft and bore, there will still be slight movement that wants to hammer against the key and deform the part. Most slip on fits retained by C-clips are hardened steel and splines.

That's not to say it wont work at the levels of torque you are messing with. Again, trying it beats thinking about it forever.

 

[Föppel]

Trial and error. That's what I was afraid you were going to say. I always ask and it seems most people who have had success with DIY pulleys had to fight it like that.

Thank you for writing that It took me about four full days to get it "right", and I despaired twice a day while working on it... I thought I was doing something wrong, and I didn't like the fact that I had to make adjustments to the measurement data "by hand", which didn't make sense to me in theory and only seemed to make kind of sense from a visual comparison perspective.

I think your theory makes sense, that tolerances could change depending on the size/number of teeth. That would also explain the various adjustments I had to make. Of course, manufacturing also plays a role. My 3D printer is pretty accurate, but it can't produce the part with 100% accuracy... I guess i also had to compensate for that to some extent in the CAD drawing.

"...That's not to say it wont work at the levels of torque you are messing with."
oh i hope so... and dont even know yet what power i will apply. Hoping for 2000w, but also like the idea of using 20 or 40V Powertool-batterys mounted on top of the motor assembly, that way, it would be light and very easy and fast to install/remove the whole thing... but i guess then it would be limited to something about 500w

 

[Nix Liou]

Interesting, have you had any issues with the plastic pulley breaking under peak power? I suppose the large contact area makes up for it being plastic.

You probably don't need to print the pulley entirely out of solid ASA though, it seems that in 3d printing most of the strength comes from the skin, ie wall count, and infill mostly helps to prevent buckling and keep it rigid. I know at least for 3d printed gears making sure the teeth and a bit of where they connect is solid is generally all that is needed.

I have had reasonable success with printing large fairly solid ASA with my P1S, by the high tech solution of wrapping the printer in towels and blankets and letting it sit for 30 minutes with 100C bed temp before printing... and letting it cool down fairly slowly too.

 

[Föppel]

Interesting, have you had any issues with the plastic pulley breaking under peak power? I suppose the large contact area makes up for it being plastic.

Hi Nix, yes the Pulley should be ok, like you mentioned i also guess that it is because the large contact area.
Right, i dont know if it was necessary to print it solid, maybe 5 or even 4 or 3 walls would be enough, but when slicing the model, i could not see that much infill anyway, so i made it solid, just to be sure

by the high tech solution of wrapping the printer in towels

Nice! i heard of this special technique hey when it works, it works!
i did the same in regard of letting it cool down very slowly, i run he print over night, and opened the printer next morning.

 

[Föppel]

i did not write about the bike much, so here is the reason why i wanted it to be a Kona Cowan (again)...

This one i built around... 2015 or so?
at some point i changed the wheels to 24" and it felt amazing. Not sure if it is the geometry (i guess) but i also really like the "kind of BMX"-look of it.

i frame-mounted a LR small block kit but had several problems with it, regarding things that bent and also the chain (not installed on this foto) that runs to the BB was way to long for my likings.

The Bike (frame) itself was/is solid, i rebuilt it several times with BMC and Bafang motors, and it was the perfect size for my Girlfriend, she loved it, but do to reasons, we had to sell it at some point.

Now 10 Years later, i wanted to build the exact same Bike but better for her again, and here we are.

 

[Föppel]

As for the controller, I wanted to try out an ESC and decided on the FS75100 from VESC. It's rated at 100 A... I think that's phase amps and the battery output is around 30 A (?).

In any case, it looks nice and is small enough for my intended use.
i hooked it up to the motor and to my Laptop by USB, run the calibration, and everything seems to work.
I tested it with a 52V Battery from EM3EV. But I'm not sure yet what kind of battery I'll ultimately use. Maybe I'll even try power tool batteries, as they are small and light... 2x 20 volt packs in series... Not sure if that would be enough power for me...
any suggestions?

 

[Nix Liou]

As for the controller, I wanted to try out an ESC and decided on the FS75100 from VESC. It's rated at 100 A... I think that's phase amps and the battery output is around 30 A (?).

In any case, it looks nice and is small enough for my intended use.
i hooked it up to the motor and to my Laptop by USB, run the calibration, and everything seems to work.
I tested it with a 52V Battery from EM3EV. But I'm not sure yet what kind of battery I'll ultimately use. Maybe I'll even try power tool batteries, as they are small and light... 2x 20 volt packs in series... Not sure if that would be enough power for me...
any suggestions?

I don't recommend using power tool batteries. They are usually pretty shit, as they only need to survive short bursts usually. Often they rely on charge balancing only, or sometimes no balancing at all (milwaukee).

Most controllers are rated for phase amps (2.5x or 3x) of the battery amps, so that is probably correct, but you can usually find some reported number for it in a datasheet somewhere. Looks about right for the size though.

Luckily 30A is not that much power relatively, so you can find a few options at least. What's the target voltage here? It would be based on motor kv, the reduction stages, and the target speed. Or however much speed you think the power output of the motor could handle.

If you want something sleek and made to fit the bike, you may want to look into custom builds for the triangle. It's hard to tell the exact dimensions but I think if you don't need a ton of capacity, a suitable pack could be designed to fit in the remaining space around the motor. It might be pretty close though. A 48v 5Ah pack using tabless power cells like the RS50 or EVE 50PL would have just 13 cells, and be somewhat similar to using 2 power tool batteries, but could have actual discharge protection from a BMS.

Of course, 30A from a 5Ah battery will give you around 10 minutes of full throttle power, which may be limiting. A pack like the slim pack offered by affordable ebikes would probably fit well on the under side of the downtube for example, without getting in the way of the front tire, especially with smaller tires on it. That may be the simplest option.

 

[DanGT86]

Looking forward to seeing how this outrunner in a box design works out for you with heat management. I always wonder if the efficiency of a small high RPM motor is lost when the weight of the enclosure is added up. Doesn't take much additional weight to equal something like the lightning-rods LMX style inrunner.

 

[A-DamW]

Cool, did you already built something with the 6368 Motors? i chose this kind of Motor as there are so many of these available from different manufacturers. Even saw some more expensive ones from Flipsky (?) with lower KVs that would maybe even be a better fit.

I have not done anything with them yet, I got them used in new condition for dirt cheap, and how many motors are enough?

N+1 of course!

 

[Föppel]

If you want something sleek and made to fit the bike, you may want to look into custom builds for the triangle. It's hard to tell the exact dimensions but I think if you don't need a ton of capacity, a suitable pack could be designed to fit in the remaining space around the motor. It might be pretty close though. A 48v 5Ah pack using tabless power cells like the RS50 or EVE 50PL would have just 13 cells, and be somewhat similar to using 2 power tool batteries, but could have actual discharge protection from a BMS.

Of course, 30A from a 5Ah battery will give you around 10 minutes of full throttle power, which may be limiting. A pack like the slim pack offered by affordable ebikes would probably fit well on the under side of the downtube for example, without getting in the way of the front tire, especially with smaller tires on it. That may be the simplest option.

Hi Nix, and thanks for your thoughts and Ideas. Much appreciated!
Yes you are right, the Powertool batteries would have been a bad idea. Sleek, but to much of a compromise in regard of power.

I ordered a BMS for 10-14S and plan to re-use some of my Samsung 30Q to make a 10-14S 1P pack. I want it on top of the Motor assembly, together with the Flipsky controller. So that everything can be removed and mounted with only the 4 "Butten-Bolts" (?).

if money would not be a problem, i would go with some high discharge 21700 5Ah. That would be optimal, but i will use what i have for now. For longer rides i can hook up a bigger pack when it is needed, but i want something as small and light as possible for this this to begin with.

 

[Föppel]

As you can see, i already hove some holes at the top of the Motor assembly. They are meant to hold the Controller and Battery... in some way that i have to figure out

 

[Föppel]

so here we go, starting with the battery for this Bike, or should i say for this Motor-Kit… because as i wrote before, i want both, the bike going 1500 - or even 2000 Watt, and the battery beeing as small and lightweight as possible. Here are the components i bought to make a small battery (probably 10s1p) that should fit on the motor kit in the bikes frame.

BMS with bluetooth for 10-14s battery

quite small, and 40A discharge will be way to much for 1p, but that should work.

then i also wanted to have the charger as small and light as possible, so i found this cheap one here:

… that one comes with a 5.2mm charging plug

so i bought some of these female 5.2mm plugs to solder one to the BMS and integrate the plug on the side of the battery.

i started drawing some battery Ideas in CAD, but had not much time to really work on it, e.g. printing some prototypes.
In the upcoming weeks i will work on that and post some pictures of the progress.

It is clear that the motor will not run on more than... lets say 250 watt or so with this kind of battery, but that is okay for its intended use (of this battery, not on the motor kit itself). For the testing with higher power, i will probably just make a XT60 connector on the Controller to hook up a 14S5p battery that will go in my backpack for the fun rides

the reduction of the motor is more set to a 10s pack than to 14s, but i think (hope) that in the highest gear it should be fine

Thanks for the good tips and thoughts Nix