Saltwater crawler.

[•Axle]

I realise that electronics, bearings, certain metals and any kind of water are not the best of friends, but I have had an idea in my head for a very long time as I like amphibious vehicles.

My question to you is what would it take to have a hassle free crawler that could take a carefree dip at my local beach?

I’m thinking;

• Full ceramic bearings, including brushless motor bearings. Should I worry about impacts if the RC is going slowly?

• Titanium screws all round.

• Sealing up the chassis with silicone, all holes including around the motor?

• Marine grease where drive shaft cups come out.

• Some sort of weight attached to the very bottom keeping the vehicle upright in water.

• Are ESCs fully submersible?

• What do people do about batteries?

The rig will obviously not be maintenance free, but there must be a lot of things that can be done to reduce the impact of saltwater.

Cheers,

Al   

 

[MadInventor]

Just to answer the question about batteries, when I was driving my king tiger through deep water that came up to the top of the hull, I used a NimH battery, the old type that had end caps and was held together with heat shrink. As the heat shrink was waterproof, I simply used a blob of silicone to seal up the hole where the wires came out. This was however fresh water (well, not salty, I wouldn't have anted to drink it).

The Mtronics waterproof ESCs I used got fully submerged and it didn't seem to hurt them. 

Instead of the expense of ceramic bearings, I would use bronze bushings on the axles. If you're running a crawler then the axles are not going to see a lot of rpm, and it may still be possible to wash fine grit into ceramic bearings.

I'd also think about sealing the axle seams where they join together with silicone, this will help to keep water out of the internals, as well as putting thick grease behind the bushes for the input / output shafts to prevent water getting in.

 

What sort of chassis are you thinking of using ? Most crawlers are ladderframes, so do you have bathtub chassis in mind. If using a ladderframe, I'd be tempted to try and fit more of the electronics inside a waterproof box. 

The motor is going to be your biggest issue, and even with brushless motors the end bell is usually an aluminium alloy, which the saltwater will love.

Are you planning to fully submerge the vehicle / drive it out of it's depth ? Rather than trying to waterproof everything it might possible to re-design it to have things like the motor high up in model to reduce the chance of it getting wet. Going back to the king tiger, I never bothered waterproofing the receiver, I just stuck to the top of the inside of the turret to prevent it being submerged.

 

[•Axle]

Thanks for you insight into crawling, very useful.

I’m unsure of a chassis as of yet, I could make a non conventional crawler / trail runner out of stuff I already I have, I’m not really wanting to drive controlled over large rocks.

It’s got to be able to take a few unplanned large waves, so probably yes be capable of fully going underwater.

Going to do my homework of ladderframe chassis and motors then, thanks!

 

[Lee76]

This might be one of those times you actually replace all the ball bearings with the original supplied Nylon plain bearings!  Cheaper than all ceramic  Is it possible to get the chassis or electronics vacuum sealed? Just need to take care of the few things that have to pass through it then. I wonder what RC boat designs do for sealing in the sensitive parts? Just a PTFE lip seal in the output shaft probably and a sealed box for the electronics? Might be worth a look. Keen to see how this develops though. Might be nice to run in and out of the sea.

[•Axle]

Has anyone ever come across something like this but for a motor? It attaches to the end of a Dremel and allows you to use a thinner grip. I was thinking about something like this to remount the motor to a more desirable location on a chassis.

[•Axle]

I do like the idea of shifting everything that can be into click lid tupperware box and mounting that on top of the chassis, enough air could provide buoyancy as well.

[Lee76]

I’ve seen flexible drive shafts for power drills, though I imagine they are fairly lossy for power and heavy too, Something to experiment with perhaps. If you’re doing something that extreme what about using the parts from a 4WD, remount the motor and use it as a 2WD, the transmission/prop shaft can have lip seals on it somewhere it passes through from the upper to lower deck.

[•Axle]

Fantastic idea, thank you! This is it, I know what I would like to do but not mechanically minded enough to get there without making a Homer-mobile.

[Lee76]

11 minutes ago, •Axle said:

Fantastic idea, thank you! This is it, I know what I would like to do but not mechanically minded enough to get there without making a Homer-mobile.

I’d like to see someone make the homer mobile... make that your next goal. I’m now going to google and see if someone has...