I’ve never worked it out, but it is definitely a notable weight increase than just the cells. It should be relatively easy to make a reasonably accurate formula in my battery quoting spreadsheet though.
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Just pulling a number out of my ass, I’d ballpark ~20% or so. Could be lower or higher depending on the construction materials and methods used, but that would be my wild-ass guess.
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Is there any reason to use a pulley key if the pulley also uses set screws? The ones I have now have two holes for set screws and I already bought more so that way both the holes would be in use (only came with one set screw per pulley). Do I need to also figure out what size key to use and install them or can I go without them?
Currently, the pulleys will not budge at all with both set screws installed. Hell, even with one set screw I couldn’t get them to move at all. I just added more to be safe.
Also I have to use a clamp in order to fully push the pulley onto the motor shaft and need to pry it off using the back of a hammer since it is on there so tight even without the set screws. Not sure if that matters or not when determining whether to use a key.
Photos for reference if needed:
second new years eve in a row spent working on a board instead of going to loud and packed places
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the key is what’s transferring the torque from motor shaft to pulley, then to ur wheel, a set screw isn’t gonna hold that force for long befor backing out or just getting disintegrated
u need a way to lock the pulley to the motor shaft securely that can withstand the force u putting through it, a set screw CAN work, but for how long
why can’t u just use a motor key?
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Because I don’t have any and have no clue what size I’d need. Hence me asking if I need to try to figure out the size so I can (buy and) install them. Although if there is any sort of standard size knowing that would be helpful as a starting point
Also do I just shove it into the hole after the pulley is on, or do I need that hole to line up to the little grove in the motor shaft?
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motor key is usually 3mm x 3mm, and length depends on how long the groove is on ur motor. usually i would try to get a close enough length one to fit the slot, but u technically don’t have to.
yes, that’s how the motor and pulley are mechnically lock along single axle, i would also suggest u dab a little green loctite on the groove before hammering the key in, so it won’t rattle or somehow destroy itself during operation
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I think that matches the size of the little grove in the pulley. At the very least I do know that it is a pretty normal sized pulley. Same size as the ones on my other belt setup (which came with the pulleys basically permanently attached already)
Is there a best place to buy them? A google search did show up with keys available at hardware stores but they’re all in trash american units. Also they will 100% be at least triple the normal cost if not more.
Also how tf would you even remove the pulley after putting the key in? they’re already pretty hard to get off the shaft without one so I don’t see how you’d do it after wedging a key in the shaft grove 
If there’s a local outlet that sells metric keys here in the US I’ll eat my battery pack. I was able to order an assortment set online though.
Install the key with retaining compound in the motor axle keyway, then squeeze the key in with a mallet or pliers. The set screws should just keep it from sliding off the shaft.
Remove the pulley by heating it with a lighter or torch, and using a pry bar between the motor face and the pulley.
idk for u, probably someone around u has a few spare if u ask nicely 
u slide the pulley along the motor shaft to remove it?
the key sits into the motor shaft, so it will fit nicely between the groove and pulley slot gap, that’s how it was design for
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That is the same number I pulled out of my ass, but it could just be similar biases. Next time I open up a board I’ll weigh the pack and check how it compares to the cells, cheers
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Yeah fair question, but once you see one installed it gets a bit clearer. The key fits snugly but with almost zero force into the keyway in the axle, and a bit less precisely into the pulley. There’s basically no extra friction along the blue axis, it’s not really tightly rubbing against the inside of the pulley
It has very little play in the green rotation axis though. As frame said, the axle pushes on the key and the key pushes on the pulley. For the pulley to slip past, it would have to shear the hardened steel. In the case where it’s just set screws, you don’t have to shear anything you just have to overcome the friction between the stainless steel and the axle, that’s much easier to do and will grind it away quite easily. I’ve managed to smush through m6 set screws, never mind the little m2 or 1.5 or whatever these are
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u explained better than i did, that’s what i meant. im dum with words sometimes
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I am pretty sure they are M5 set screws as that was written on the bag at Lowe’s but also I can’t be bothered to get up to double check via the bag of the two spares I bought.
My biggest issue is that the motor shaft does not have that grove reach the end of the shaft. There is like a mm or so at the end which is why it looks round at the end and you can’t see the little indent. Probably would be better to take a photo of the shaft but the pulleys are hard for me to get off.
To be fair, I’m also very tired and get less smart the more tired I get. 
I still doubt my ability to get them off after putting the key in but I think it will be way more obvious once I have the keys to try it on Tuesday night. just bought a variety pack off amazon as the only other sources I could find shipped out of China which is just asking for it to take a month or two to arrive. Plus I think $13 for 140 keys is a better deal than $0.90 for one key even if I have no idea if I’ll ever need the fatter keys in the set
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Yup so the mm or so at the end is part of the design. At the start it looks like this, and you drop/seat the key in the purple axis, then it can’t move anywhere except the way it came in and it looks like pic 2.
After that you slide the pulley on as normal, and it shouldn’t add much if any friction. Now the key can’t go anywhere, the pulley turns with the axle with very little play, and the only way anything can move is the pulley along the blue axis of the axle. There’s very little force in that direction, and that’s what the set screws are for. They stop the pulley sliding off the axle. Obviously that doesn’t seem likely in your case if you have to force them on and off, but they can’t migrate over time or do anything weird under vibration
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OOHHH I thought you would put the pulley on and then hammer the key into the little hole on it. Which is why I was confused as to how you’d get it out again 
I figured you could just keep hitting it with a pick and hammer to push it far enough in for it to drop into that groove.
Also I’m glad I bought the key set with the curved ends now since that is what the motor shaft has and with your diagrams it makes it clear I need to match that. they cost less but also I could cut the end off if I needed it to be flat
To be fair, I am not known for my upper arm/ shoulder strength. It is possible that someone else would have no problems getting them on. Although the amount of force needed while using the back of a hammer for leverage does tell me that they’d be hard to remove for anyone.
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Yeah no worries, the wonky drawings are usually required because it isn’t intuitive. TBF the curved profile and exact length aren’t essential, if they’re the right width then there’s no play in the rotational axis and you’re good. If they’re too short they could theoretically slide along the blue axis but the pulleys usually have two set screws so it’s unlikely they’d move and there is still an outer limit on how far it can slide because it’s captive. If they’re not tall or long enough you might not have enough meat transferring the torque and maybe a higher chance you’d smush them over but 3x3xL mm is standard so you’re probably grand either way unless L is way off
Also lol at the upper arm strength, it’s been a while since I put one of those on but I also remember a hammer and some swearing now that I think about it
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The kit I bought has the 3mm x 3mm as the smallest option available, so if they have too much give I could just grind down the next biggest size to fit it more snug. Or I could just add a thin layer of epoxy to the 3mm ones since that works well. I did the same to the bottom of the motor mount clamp to remove the slight wobble and it worked super well. I may need to eventually redo it in a few months or years if it wears down too fast though.
This pulley did come used and a bit beat up so I think the tolerances on it are super tight I did take pliers to it to unbend some of the sides so the 15mm belt would fit on it again since with the bends it didn’t sit flush on the pulley teeth.
Plus now I have another reason to give myself until Tues or Wed before testing stuff out. The new belts were supposed to come in on Tuesday which I planned for but then USPS decided to deliver them today out of no where. 
Even though I still have some epoxy work to be done
How it looked when the belts arrived:
I need to add in holes for the phase wires and sensor wires and fit in the water proof wire pass through things still on top of needing to carve away extra material on the under side so I don’t have to fit them through an inch of fiber glass and epoxy and like 2mm of abs
I just bought a foot of 3x3mm key stock and cut pieces as needed. A hacksaw or a pair of mini bolt cutters makes quick work of it, and a quick cleanup with a file is all that’s needed to make them fit.
You can fine-tune the fit with a file or sandpaper too - sometimes the key stock is just a bit oversize for a given keyway and doesn’t want to slide in nicely. A few strokes with a file will fix that.
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I did see some long stock of the 3mm stuff on Amazon, but, it is currently way more expensive than the variety set was. Plus I can probably use the other key ways for something in the future? or it will just go into my hoard of various parts
Also if you don’t have one already, a dremel with some metal cutting disks would make quick work of cutting the key stock to size. 10/10 everyone should buy a Dremel brand rotary tool
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Is this a special kind of thing or can one just use some square steel rod?
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