Amphibious Electric Boat Trailer

[eBoatTrailer]

I am currently beach launching a boat RINKER 192 (1.3T) using two 12V caravan (trailer) movers that engage to my trailer tyres. It's a 15 year old system which is waterproof, but it lacks power and torque. Simple 2 pole brush motors with single speed gearbox (brand Powrmover)
Looking at the many new in hub motors on the market I would like to add two additional Quadbike wheels / tyres with an in-hub motor in each (leaving the trailer axle untouched for towing). The idea is to replace my old system with this new generation of motor giving me more torque, power and variable speed.
Key points:
1) The wheels will be raised during road transport and lower to engage with the sand for launch.
2) Motors have to have low speed (slow, medium and fast walking pace) , high torque to move 2T at walking speed.
3) They have to be water proof to IP68 as the trailer drives for 50M under water to a depth of 0.5 meters (tidal beach)
4) Batteries LiPo 48V and power electronics placed in my current battery box concept.
MY PROBLEM - I cannot find any such motors, they all seem to be high speed for EV or eScooter. Any ideas which supplier might help me?

I've added a photo of my current set up and a sketch to give you a better understanding of my concept.

 

[eBoatTrailer]

Is the tow vehicle coupled to the trailer during beach launch? Images of the boat resting on the trailer?

No the trailer is driven by the two motors

 

[eBoatTrailer]

The boat is waiting for the trailer in approx 0.5M of water. The trailer simply drives under the boat due to the depth of water and we hook the bow with the ratchet strap and reverse the motors to drive the boat out of the sea back to the car. The only issue here is power and torque as the weight of the boat and the beach gradient approx 3 degrees make the drive slow to a stop. I need better motors and more power and torque.

 

[Papa]

Is this salt water?

 

[offGridDownUnder]

Can you drive the tires via a belt from a motor set well above the water?

My trike (see signature below) uses this to couple the motor set behind the seat to the rear wheel. Height above water is not a primary design feature, but it's true that my deraileur will not contact water/mud/dirt/plants as much due to this aspect.

Note that you must scroll down in the signature thread to see a picture with the later evolution with the Gates belt.

Gates produces "stainless" (quotes there is no such thing - in Aerospace we specified it as CRES - Corrosion REsistant Steel) sprockets in 22T, 24T, 26T, 28T that have mounting holes that mate directly to the 6 bolt ISO 44mm BCD brake rotor mounting on the left side of many bicycle motors, and many larger sprockets in 34T - 70T that match either the 4 bolt 104mm BCD or 5 bolt 130mm BCD mounting pattern of bicycle chainrings.

I use both of these in my design - I had 4 and 5 arm spiders laser-cut or water-cut from 5mm aluminium plate to match the brake rotor pattern on my hubs to the chainring mounting pattern. Presumably you would need to work out the match from your existing wheels to effect this, or you could add on separate wheels as you are considering and simply lift them clear for road transport.

A 22T - 70T match gives over a 3x reduction in speed from a motor, and I've noticed they also sell a 74T chainring sprocket for tandems that probably also fits, although I haven't looked too closely at that.

5083 Aluminium is used by boat builders - it seems the most corrosion resistant alloy. It does not require heat treatment post-welding. You can use that for your spiders and the framework. The small sprockets are CRES. The larger Gates sprockets are aluminium alloy and I don't know their composition or treatments, but they are specified for global cycle touring - and you can rinse them off after each episode.

I recommend water-cut. Laser cut builds up heat stress.

 

[Papa]

Can you drive the tires via a belt from a motor set well above the water?

My trike (see signature below) uses this to couple the motor set behind the seat to the rear wheel. Height above water is not a primary design feature, but it's true that my deraileur will not contact water/mud/dirt/plants as much due to this aspect.

Note that you must scroll down to see a picture with the later evolution with the Gates belt.

Gates produces "stainless" (quotes there is no such thing - in Aerospace we specified it as CRES - Corrosion REsistant Steel) sprockets in 22T, 24T, 26T, 28T that have mounting holes that mate directly to the 6 bolt ISO 44mm BCD brake rotor mounting on the left side of many bicycle motors, and many larger sprockets in 34T - 70T that match either the 4 bolt 104mm BCD or 5 bolt 130mm BCD mounting pattern of bicycle chainrings.

I use both of these in my design - I had 4 and 5 arm spiders laser-cut or water-cut from 5mm aluminium plate to match the brake rotor pattern on my hubs to the chainring mounting pattern. Presumably you would need to work out the match from your existing wheels to effect this, or you could add on separate wheels as you are considering and simply lift them clear for road transport.

A 22T - 70T match gives over a 3x reduction in speed from a motor, and I've noticed they also sell a 74T chainring sprocket for tandems that probably also fits, although I haven't looked to closely at that.

5083 Aluminium is used by boat builders - it seems the most corrosion resistant alloy. It does not require heat treatment post-welding. You can use that for your spiders and the framework. The small sprockets are CRES. The larger Gates sprockets are aluminium alloy and I don't know their composition or treatments, but they are specified for global cycle touring - and you can rinse them off after each episode.

Interesting idea, but I'm dubious bicycle components (hub, chains and/or belts) will tolerate the torque necessary to haul, what appears to be, well over 1000 lbs/453 kg. (boat, trailer and gradient).

 

[offGridDownUnder]

well over 1000 lbs/453 kg. (boat, trailer and gradient)

Yes.

Put it in the Grin Simulator. My own design spec is 160kg, no rider input, 12 degree slope, no motor overheat ever, 48V battery, Baserunner (for the ampere limit). I am designing for something that gets me home no matter the hills, wind, injuries, groceries.

NOTE: I find when I open URLs like this the Grin Simulator may arbitrarily change some parameters, and you won't get the correct results. Check for the mid-drive settings that the ratio is 1:1 (there is no internal reduction from the All-Axle as there is from most mid-drives). The type of bicycle may also be re-set (not so important for this low-speed case), and perhaps other settings. Double check that all settings are sane for your use case.

https://ebikes.ca/resources/web-too...b=650b&mid=true&tf=22&tr=70&autothrot_b=false

With two motors, that's 320kg already, and a 3 degree slope vs 12 degrees also gives a significant multiplication factor. Perhaps it comes within the requirements.

A GMAC or any other motor with a 6 bolt ISO brake rotor mount can be used for more power.

 

[Papa]

....high torque to move 2T at walking speed

After rereading, I'm guessing he means 2 tons.

Edit: RINKER 192 (1.3T) 2,790 pounds (boat only)

Rinker 192 Captiva: Nimble Number - boats.com

Rinker 192 Captiva: Expect crisp handling and you won't be disappointed.

www.boats.com

 

[offGridDownUnder]

guessing he means 2 tons.

Still interesting.

I plugged in 1000kg (per each of two motors), 26" tire, 3% grade.

46.8A at 12.9Km/hr, and it never overheats.

Greater than a 26" wheel with the 22T-70T combination, it will overheat, but using the 74T tandem sprocket the simulator doesn't report overheating up to a 28" wheel at 47.6A. The hubs will still be submerged with those diameters, but not the motors.

I can't resolve the accuracy of the simulator, but it seems plausible even with the higher weight using two motors. A danger is to go too slow - this results in inefficiency and overheating. That could be a problem. I'll want to think about "walking speed" - perhaps another motor? (I am modeling the Grin All-Axle v3.)

Or smaller wheels? 1/3 of a 27" wheel is a 9" wheel - 12" are not unknown and fat tires are available in those diameters. That 12Km/hr comes in at 5 or so.

It's also possible to permit overheating after 30 minutes to permit more possible combinations.

Here: A GMAC 10T, 22T-74T sprockets, 24V SLA battery, 12" tires, 3% grade never overheats at 3.6km/hr, which is within walking speed, and the power and amps are well below any limits.

 

[offGridDownUnder]

Here: A GMAC 10T, 22T-74T sprockets, 24V SLA battery, 12" tires, 3% grade never overheats at 3.6km/hr, which is within walking speed, and the power and amps are well below any limits.

Actually, according to the simulator, a Bafang G310 Std Wind will do the job with those wheel sizes and sprockets. Just plug that motor into the above session.

Grin specified motors (as the above) can be easily yoked together to work from a single throttle, and the Bafang G310 is fully characterized according to Grin. I might still prefer a stronger motor with fewer failing parts. There will be undulations of the beach floor so the slope can be locally much steeper, and gears strip.

Consider using two Grin 45 Max All-Axle single speed motors - no gears.

Also, DD motors provide inherent braking if it's needed, and at walking speeds they are reversible at the flip of a switch. Two more problems solved.

 

[offGridDownUnder]

I cannot find any such motors, they all seem to be high speed for EV or eScooter. Any ideas which supplier might help me?

Hi. Read through the thread above for thoughts about motors/sprockets to meet your needs.

Here I'm adding a thought - with your existing system, can you remove just the motor, make a custom attachment to the shaft coming from the remaining drive, and run a belt up to the motors you might chose (as discussed above)? I can't tell from your picture about the options to mount such and I can't know the insides of the existing drive system.

OTOH, ff there are enough other drawbacks to your current system, that might provide the impetus to favor replacing the system and permit making any solution that satisfies.

 

[eBoatTrailer]

Is this salt water?

Yes salt water, the good old Bristol channel

 

[eBoatTrailer]

Me?... I would trash-can the original trailer axle, then mount a used Dana 25 (or equivalent) 4x4 pickup front axle in its place... lock (weld) the spindles and install lock-out hubs for freewheel transport. Run a small tube drive shaft forward to, and between the hitch A-frames. Couple the driveshaft to a single chain reduction (W/#40 chain) and use a single (relatively inexpensive) 3-5kW BLDC motor mounted up.. and above the expected water line. Piece a cake... and likely a hell-of-alot cheaper.

Hi Papa, sound idea! funny, but yesterday we had a similar idea about putting the motor in a divers helmet box (like my battery box which has kept them dry for 15 years) above the two drive wheels and connecting the ATV on a single axle with chain drive. I'll look into the drive shaft, might be lighter and cheaper as you say. Thx.

 

[eBoatTrailer]

Hi. Read through the thread above for thoughts about motors/sprockets to meet your needs.

Here I'm adding a thought - with your existing system, can you remove just the motor, make a custom attachment to the shaft coming from the remaining drive, and run a belt up to the motors you might chose (as discussed above)? I can't tell from your picture about the options to mount such and I can't know the insides of the existing drive system.

OTOH, ff there are enough other drawbacks to your current system, that might provide the impetus to favor replacing the system and permit making any solution that satisfies.

The current system needs replacing. It has done it's job, but I have had to maintain and nurse it through the seasons over the years. Looking for a simple robust system going forward. The roller on the tyre is a good concept as you have a simple road / launch separation. There are millions of these things driving caravans so they cannot be all bad.

 

[eBoatTrailer]

After rereading, I'm guessing he means 2 tons.

Edit: RINKER 192 (1.3T) 2,790 pounds (boat only)

Rinker 192 Captiva: Nimble Number - boats.com

Rinker 192 Captiva: Expect crisp handling and you won't be disappointed.

www.boats.com

Yes as the total rig boat, trailer, launch system, petrol, passengers - I'm heading for the 2 tons mark.

 

[eBoatTrailer]

Me?... I would trash-can the original trailer axle, then mount a used Dana 25 (or equivalent) 4x4 pickup front axle in its place... lock (weld) the spindles and install lock-out hubs for freewheel transport. Run a small tube drive shaft forward to, and between the hitch A-frames. Couple the driveshaft to a single chain reduction (W/#40 chain) and use a single (relatively inexpensive) 3-5kW BLDC motor mounted up.. and above the expected water line. Piece a cake... and likely a hell-of-alot cheaper.

 

[eBoatTrailer]

As a follow up to your idea, I've made a sketch of a two wheel system on an angled gear box with vertical shaft. The system idea is to transport it horizontally during road transport and drop down on the beach using a simple 90 degree bracket / pin system, lock in position and activate the motors to drive the trailer. As you mentioned simple motor selection (even using a reversable winch motor), Need to find a gearbox that is IP68 to keep the salt water out. The batteries would remain in the boxes as today (divers helmet concept which has served me well for many years). Any hints? Need to figure out gear ratios to maximise the torque at low speed. I'd be happy with a walking top speed

 

[eBoatTrailer]

See my post two wheel vertical drive as a possible solution.

 

[Papa]

Of the top of my pea brain (and too much java this morn',...)

Rear wheel drive vehicles (RWD) W/independent rear suspension (IRS). isolated differential carrier with one input and two outputs. Think older Corvettes, and I think i've seen smaller, similar (gocart, DIY, etc) carriers on ebay. Problem here, however, is the differential's ratio probably won't be low enough so you'd probably need to couple the motor first to a reduction (gearbox or chain) prior to the carrier.

 

[A-DamW]

See my post two wheel vertical drive as a possible solution.

Dual shaft worm gears are very common on irrigation pivots
Go find a farmer with irrigation pivots, ask to pick through his boneyard of parts.
They also tend to be fairly well sealed, designed for a lifetime of constant water exposure.
Here is one with a 58:1 ratio