My project, progress and problems


#21

I’ve got a bearing at the top, half way down, and bottom my drive shaft. I’ve had very little vibration from my drive shaft during a short tests with it in.


#22

Hi Daniel, what’s your drive shaft made of. I used 12mm stainless but can’t find a straight piece. I have roller bearings top and bottom with a brass bush mid mast, so much the same as yours. I’ve only tested with a cordless drill and vibrations were worse at low rpm. I’m thinking next time I might try a smaller diameter rod that’s more flexible but in a ridged tube that’s lined with a ptfe tube so it’s supported all the way and lighter.


#23

I’m using a 6mm mild steel rod welded directly to the input shaft on my gear box. I was getting too much vibration from a coupler and wanted the total size under .5".

My mast is a .5" x 1.5" welded steel core with a 3d printed fairing around it. The drive shaft runs through the 3d printed part. The top and mid bearings are in 1" aluminum square tube segments so they are against aluminum not plastic.


#24

I’ve tested so far with a 6s battery but once my second battery arrives and I can do a full power 12s thrust test I’ll do a proper build post.


#25

very nice idea! love this concept, please keep us updated!!


#26

Hi Daniel, any progress on yours? I’m stalled waiting for a speed controller. I’m curious to know how the 6mm drive shaft holds up under load.


#27

Did a short full power test. My shaft held up fine but some other parts not so much, I’m using a chain reduction at the board end so my total reduction is around 5:1. Apparently my chain got a bit hot because it started smoking some of the links seized solid. I’m going to make up a new chain and make a housing around it that can hold some grease in. The other option is to make up a longer chain so it has time to cool between sprockets. My other issue was my motor was twisting in its mount so I need a better way of mounting the motor.

Got 15kg of thrust out of it so far. Aiming for over 20kg but I feel like it was a decent start.


#28

This is still basic my setup

I’ve made a lot of changes but the same concept.


#29

Good to hear about the shaft, I haven’t had mine running in the hull yet but I think vibrations will make it loud. Surprised to hear about the chain, if it’s getting that hot it must be running well beyond its capacity, be careful, imagine the damage it would do if it broke. I don’t know much about chains but I think whilst grease will prolong the life of the chain but it will eventually just create a whole lot of smoke as most of it will flick off due to the high rpm. An oil bath might be better so the oil is always in contact with the chain and able to circulate so it can be cooled, but a challenge to contain the oil. I’m fortunate enough to have accidentally purchased a giant overkill low KV motor so I can go 1:1 direct drive so I only have the lower gearbox to worry about. My coupling is metal to metal so that will get hot and probably fail at some point, failure leads to innovation though right.


#30

Just looked it up (I know… It’s the sort of thing I should have done first). Tensile strength of #35 roller chain is 800 kg. The chain breaking is pretty low on my list of fears. Now a sprocket coming loose and the chain launching is a little scarier, but it going to be encased in plastic and plywood so should be pretty contained if it decides to grenade.