The Electric Boat Thread

[Jeremy Harris]

Time for a long-overdue update. Apart from playing about with ways to get a more efficient drive unit, I've also ordered a custom built hull. I've just got the first pictures from the builder and have to say that it's looking pretty good. Here's a sneak preview of the super lightweight (4mm marine ply) hull, minus the deck and transom:





The motor drive has evolved so that I no longer need the noisy and expensive right angle drive reduction gearbox. Instead I'm using a belt reduction drive coupled to a double universal joint. This is extremely smooth and absorbs less power than the gearbox, plus it's a lot cheaper. Here's a photo of a prototype 100 degree angled drive using this method:



I made a composite housing by laying up some epoxy/glass over that alloy mandrel in the photo, then I split the moulding in two with a Dremel to get a housing that locates the two bearing housings. The output shaft housing includes a seal and the input shaft will be bonded into the drive leg. When finished, the whole sealed lower leg will be filled with light oil. I've opted to use a slightly bigger angle for the final version, of 120 degrees, because it fits the transom profile of the boat better when lifted up (the motor shaft fits through a centreboard-like case in the stern compartment of the boat, so will be invisible normally from outside the boat).

The next job is to make a fairing to go around the leg, so that it's nice a low drag. Total power losses at maximum speed on the prototype motor, controller, belt drive, bearings, seals and universal joint are 12 watts. At cruise power the losses should be around 8 watts. This means I'm probably on track for my target of no more than 100 watts to cruise at 4 mph, making solar power augmented cruising viable.

Jeremy

[liveforphysics]

Very cool Jeremy! I always enjoy seeing your great projects.

That center section of the driveline will have continous rotational speed changes twice every rotation based on the amount of angularity at each joint. Running the second joint 180 out of phase counters the shaft deltaV for the remainder of the shaft/prop, but the section between the two will be a continous source of some of that 12w inefficiency, and getting as light as possible on that mid-shaft section reduces this loss. At your low speed range though, it may be trivial.

[Jeremy Harris]

You're right, Luke, the short centre section between the two UJs does have a fair variation in rotational velocity with each rev. You can just feel this as a sort of very slight pulsing if you hold the casing whilst it's spinning. I haven't measured the UJ losses alone, but the lower unit losses, which includes the bearings and the shaft seal are 5 watts at maximum rpm and around 3 watts at cruise rpm. Most of the loss comes from the shaft seal, which I know soaks up around 2 to 3 watts at full speed. From this I would guess that the UJ and bearings absorb around 2 to 3 watts, which is tiny enough not to worry about.

Jeremy

[BMI]

For all those who are in Australia and interested in electric boating I hope you can make it to the Sanctuary Cove International Boat Show which is on next week from 20th May until the 23rd May. This is one of the largest boat shows in the world.

I will be at the Torqeedo motor stand and will have various LiFeTech batteries on display including our 48V 45Ah battery which will be supplied to Sanctuary Cove for their electric patrol boats which should be starting construction soon. I will be demonstrating the battery/computer interface for monitoring/diagnostics so feel free to drop by and say hi.
Hope to see you there!

http://www.sanctuarycoveboatshow.com.au ... 0-show.php

[John in CR]

Very cool Jeremy! I always enjoy seeing your great projects.

That center section of the driveline will have continous rotational speed changes twice every rotation based on the amount of angularity at each joint. Running the second joint 180 out of phase counters the shaft deltaV for the remainder of the shaft/prop, but the section between the two will be a continous source of some of that 12w inefficiency, and getting as light as possible on that mid-shaft section reduces this loss. At your low speed range though, it may be trivial.

So a double U-joint results in constant velocity of the output shaft? I've gotta do a shaft drive now. I don't think I showed you the big brushed motor I have. It's too long to reasonably mount with the drive shaft parallel to the wheel axle, so that's been on hold pending a good right angle gearbox solution.

[Jeremy Harris]

So a double U-joint results in constant velocity of the output shaft? I've gotta do a shaft drive now. I don't think I showed you the big brushed motor I have. It's too long to reasonably mount with the drive shaft parallel to the wheel axle, so that's been on hold pending a good right angle gearbox solution.

That's right, John, using a double joint like this does give you a CV joint. The joints are pretty nicely made, too and run very smoothly. The one I'm using was made by a company called Lenze (http://www.techdrives.co.uk/html/universal_joints.html) and cost around £30 (~$45). My power and torque requirements are modest, so the joint I'm using is only 22mm in diameter, but they make much bigger ones, capable of handling pretty high torque levels and higher rotational speeds.

Jeremy

[FeralDog]

Jeremy : great job.
Your engineering concept of that "double u-joint" encased in the composite housing is interesting.
Just my opinion, from practical decades of u-jointed power-shaft boat usage: It may have some "wear" problems if that is the end to be submerged.

Traditionally, propulsion units that use a U-joint to shift direction get a bit of "wobble" on the joint. Your light oil filling of the inner housing can leak out pretty quick.
This was the case of "J" tubed cable-shafted electric boat motors from before WW1. The heat and cooling causes expansion & contraction, and if the lower seal is left in the water, well the seal often leaked.
May I suggest you use screw-on caps with "O" ring seals at each end of your housing (use of Oilite bronze bearings in the center of the caps)? Put zerk fitting on the housing casing , then use marine grease instead of oil. The pressure/viscosity of the grease keeps the U-joint better lubed, and wont weep/leak out so easily.

Oh, I am curious. Since you may extend the angle to 120 degrees, why not stick the whole shaft/joint into a bent piece of pipe with appropriate inner diameter?

[Jeremy Harris]

Thanks for those tips, I'd love to know more about the old J tubed electric drives, I'm thinking that these may have looked a bit like a bent tube strimmer drive (weed whacker in US-speak), would that be right?

I did try to get away with feeding the shafts and UJ down inside a tube, but couldn't find a way to do it. Whatever way I tried I needed to get the lower end of the UJ out the end to connect the prop drive shaft, and the geometry just didn't seem to work to allow this to happen.

I'm running at low power (around 100 watts), so I'm hoping that wear won't be a big issue. The boat won't be kept in the water, either, it's not much bigger or heavier than a canoe, so the plan is to keep it at home and trailer it to the rivers and canals nearby.

The output shaft is supported by two ball races, with a seal on the outer end. Similarly, the long input shaft is supported by a single ball race at the lower end and a pair of races at the upper end (to take the side load from the driven pulley). The UJ is therefore pretty well supported, as the UJ outer ends are butting up against the inner races of the bearings on each shaft.

The other factor that makes me hopeful that this will last, is the relatively low operating rpm. Maximum prop rpm is just over 700 rpm, cruise will be around 500 to 600 rpm.

I'm off now to Google up on J tube drives!

Jeremy

[FeralDog]

Jeremy: The drive J tube is similar to weed wackers.
It worked , it still does.
The earliest I have seen for either a "J tube" or straight shaft using an inner cable (flexible shaft)to prop was a W. S. Salisbury electric motor from 1892.

The reason for a cable (or coiled wire) drive was to keep the power-head above the water, give good steering geometry, and make manufacturing simple.
The cable was great if kept lubed, took some good shock absorption from prop strikes, and worked better if the "bend" in the housing wasn't too tight.
The cable fell out of favor somewhat in USA 1940's when oil seals got better so that the whole electric power-head was submerged for better motor cooling and steering control on some boats(submerged power heads were used since 1899 in USA).
I think the practical difference between a J Tube cable to prop, and a U-joint (or bevel gear) is really just your motor (power-head balance), steering geometry, and RPM's.
In short, a cable in tube "J drive" might work for you too.

(In general , we don't use many submerged ball , or roller bearing support parts versus a simple plain bearing. Around water, the plain bearing is much more forgiving.)

[Jeremy Harris]

The interesting thing about this J drive is that I did toy with the idea of doing something similar. I bought a flexible shaft, intended for use with a drill. The thing that stopped me going any further with it was that this particular flexible shaft wouldn't take a reverse drive, plus it was marginal at handling the torque from my big propeller.

One of my first drives used a plain bearing on the output shaft, but the frictional losses were very high. Similarly, the gearbox came filled with grease, but I found that the grease alone absorbed about 5 watts, way too much for what I'm looking at. For every watt absorbed in the drive train, I need to generate about 1.5 watts from the solar panels. My total power target is 100 watts maximum for cruise power, I'm actually hoping that I can get away with less power.

Most of the ideas I'm using have come from the leading human powered boat developers, people like Rick Willoughby. They also have a limited power budget, pretty similar to my target, so their techniques tend to work OK for my application. The pedal boat version of the hull I'm using uses ball bearings throughout and the drive train has been very reliable after three or four years use.

Jeremy

[Jeremy Harris]

An update on this rather long drawn out project. I made a 9 hours round trip today, to the far West of Wales, to collect the hull for my project boat. Here are a few photos (although please bear in mind that the hull is only painted in primer and the woodwork hasn't been oiled yet).







The next step is to fit the propulsion system, give the boat a coat of paint, then go and do some trials on the water to see if the performance matches expectations.

Jeremy

[regmeister]

deleted

[MrKang]

What a beauty Jeremy! a friend of us took us with his little boat (normal gasoline powered) for a trip. For me it was the first time.
It looked so peacefull and quit on those little water creeks/canals. And when i saw your snapshots ....wow...must be very relaxing.

Are you going to use some solar storage in the future?

[liveforphysics]

Beautiful boat my friend!

[John in CR]

Beautiful lines Jeremy. What's she weigh as-is?

[Jeremy Harris]

Many thanks for all the kind words. I don't know the weight for sure, but I can easily lift one end up with one hand. I lifted the whole hull, single handed, from the trailer on to a couple of saw horses yesterday and it was no effort. My guess is that the hull as it stands probably weighs about as much as a big canoe.

Here are a couple of the latest pictures of the drive unit. First, the power head, with the TowerPro outrunner, belt reduction drive and modified 6 FET controller:



The 1" stainless tube that contains the drive shaft goes through an O ring seal inside the machined alloy block to the right of the photo and the diecast alloy box that the whole unit is in is sealed to IP66, so I'm confident that it'll cope with working in a damp environment. This unit is actually fitted inside a watertight compartment in the stern of the boat, so it should stay pretty dry, but I've learned over the years that water gets pretty much everywhere on board a boat!

The underwater drive part, using the double universal joint system, looks like this:



The 1" stainless tube fits inside a bearing tube that is sealed but which allows the unit to be rotated to steer the boat. The prop that is going on this is the stainless steel folding one that I've shown earlier in this thread.

The UJ has the advantage of absorbing very little power. My total losses (electrical and mechanical) at full throttle, running in air with no prop fitted to the shaft, are just 12 watts. The controller accounts for about 1 watt, the motor losses are about 5 watts, the belt drive absorbs about 3 watts so I'm losing about 3 watts in the bearings, universal joint and prop shaft seal. I know that the seal is absorbing around 2 watts, so that means that the bearings and universal joint are only soaking up around 1 watt - pretty good when compared to a right angle gearbox and it runs silently.

Jeremy

[northernmike]

Hyvaa plywood, Jeremy

Suomalainen plywood!

That is one beautiful boat. Thanks for keeping us in the loop.

[Malcolm]

Those are impressively low power loss figures Jeremy. The fish won't even hear you coming

I had a dream last night that I'd finished rebuilding my motorbike and taken it out for its first test drive. I was over the moon with it because it was totally silent...

[northernmike]

Anything to report? I do love this thread..

[Jeremy Harris]

Anything to report? I do love this thread..

Thanks! Sorry for the delay in updating, I'm on holiday in France at the moment, going around French Chateaux with 'She Who Must Be Obeyed'. Off to see the house where Leonardo de Vinci spent his last years today and visit his tomb at the nearby Amboise Chateau chapel. Should be interesting, as they have re-created many of his inventions in the grounds of the house.

I have another week off when I get back next week, to spend working on the boat, so there should be a progress report in a weeks time. The flexible solar panels arrived from China just before I left, so I may even have the solar charging system built into a canopy by the end of the week.

Jeremy

[Jay64]

Jeremy, are you going to seal in the flexible solar panels at all? I was looking into some for a idea I had, but wanted to see if they would still work if they somehow were sealed like with a resin or something. I'm sure that would diminish the effectivness, I just don't know if it would make it completely not work.

[Jeremy Harris]

Jay,

The panels I've bought are already sealed, they seem to have been made by laminating the cells inside a couple of layers of thick clear plastic, maybe 1/16" thick. The back of the panel is a thin sheet of aluminium, bonded to the clear plastic. I was going to make my own panels from raw cells, but got impatient and so just bought some ready made ones.

The ones I got were from here: http://www.sunflexsolar.com/

Jeremy

[Fizban]

I remember a family friend building an approx 2m long hydroplane in the 70s powered by a 2stroke lawnmower motor using a flexible shaft from a whipper snipper, weed whacker to drive the prop. The boat performed well he claimed it used to get to 50kmh easily but the flexible shaft would work harden after a while and shatter. He eventually gave up used a v-drive but was disappointed with the power loss and reduced performance. Here is something worth checking I think.
http://www.soloray.com.au/
The flagship and explorer models with the solar panels mounted as sunshades are a good idea to me.
http://www.duckflatwoodenboats.com/mainpages/mundoo.php
Scroll down to the electric model, would these be usable in the canals in the U.K. ?
They may be a little wide but they might be willing to make adjustments to the plans for a narrower beam if you ask nicely, I have read articles where they have major adjustments to accommodate a customers needs.
Oh and I nearly forgot here is a place to find some great displacement hull designs that may be suitable for electric power, the xlnc model sticks out to me.
http://www.atkinboatplans.com/
I hope these interest you and others here.

[GaryB]

my e-yac does the job.

[lifepo4ever]

I came across this: http://www.autocanoe.com/. Looks like a fun candidate for both road and water use, plus it includes paddles...

Hmmmm... I'd be cautious about anything touted using an oxymoron like "Happy Wife"...<hehe>

In that pic:

The attachment Autocanoe.jpg is no longer available

How exactly would you (well, female brought along for purpose) actually paddle the thing? Wouldn't the wheel cowlings be in the way? Could oars w/locks be employed instead? Dunno. Also, in the same "happy" pic, there seems to be quite a bit of turbulence/water being lifted/left behind by the paddles/wheels?

My suspicion is that the Autocanoe serves better on the hard than afloat!

And, according to the Internet Archive Wayback Machine:
http://web.archive.org/web/20031217064815/http://www.autocanoe.com/

The part about "Coming soon Electric powered Autocanoe!" has been posted on their site since December 2003 approx.? Hmmmmmmm.....

No pics on the site yet (after 5-6yrs) of smiling happy clients who have built the plans?

Never mind a movie of how it performs on land, I want to see/know how it performs on water!
...and if they are still married.
Tks
Lock

with this boat you get more then a happy wife you get 10 !! for sure