Efficient electric boat

Discussion in 'Boat Design' started by Jeremy Harris, Jun 22, 2009.

  1. portacruise
    Joined: Jun 2009
    Posts: 1,475
    Likes: 178, Points: 63, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Jeremy, here's something I have used to quiet noisy gears somewhat in the past. Cheap and easy enough to try anyway. It will depend on the ratio that cut of the gears that are meshed, and usually works on helical gears a little better. Will not get rid of all the noise, however. Try a lube called triflon in USA. It is pretty amazing stuff, especially on worn out bushing type bearings. It is made of teflon particles in a hydrocarbon base. The grease triflon is usually better than the spray lube. It will take a few hours of operation and venting for the stuff to evaporate and leave behind a teflon plating on the metal parts. Maybe it will quiet some of the metal to metal grinding with the coating it forms. Does not add additional friction in the cases I have measured. This is amazing stuff when used on motor bushings that have locked up due to wear. I have extended the useful life of cheap bushing motors by a factor of 1000 or more in some cases. It is better if you can clean the old grease or lube off first before using a couple of separate applications.

    Hope this helps.

    Porta
    Hope this helps

    Hope this helps.


     
  2. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 60, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    Thanks for that tip, I'll certainly give it a try. If it works then it will save a lot of hard work!

    For interest, here's a photo of the nearly-finished gearbox drive leg:

    [​IMG]

    The leg fairing isn't fitted in this photo, but is intended to be fixed to a hinged section in the bottom of the hull. The bottom part of the leg rotates to provide steering. The motor is contained within the sealed ABS box at the top of the leg and the cable conduit is fitted through a sealed gland, making the whole unit waterproof. I debated whether or not the prop protection skeg was needed, but eventually decided it was, if only to provide some rudder effect.

    Jeremy
     
  3. Guest625101138

    Guest625101138 Previous Member

    Will be a shame if the noise is annoying after all the effort to put it together. You will at least have to try it on the boat.

    Rick
     
  4. portacruise
    Joined: Jun 2009
    Posts: 1,475
    Likes: 178, Points: 63, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Here's some info on quieting metal gear noise toward the middle of document:

    http://machinedesign.com/article/more-than-a-lubricant-0823

    There may be a penalty of higher friction for the lower noise which maybe lessened with PTFE (teflon).

    Here's a pic of the teflon lube I have used with great success:

    http://www.amazon.com/Lubricant-Sup...ref=sr_1_6?ie=UTF8&s=hi&qid=1270609730&sr=8-6

    I believe it may come in various formulations. Triflon was sold to Krylon corp, but still a good product.

    Good luck, hope it works for you.

    Porta

     
  5. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 60, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    Many thanks for the advice, much appreciated. I believe that what was marketed as Triflon is now sold as Triflow. If so, then I can buy it locally here in the UK, as it seems to come from these people: http://www.triflow.co.uk/

    You're right, Rick, I will have to try it in the boat and see what the noise is really like. My expectations of totally silent propulsion may not be realistic! I ran it again yesterday evening for an hour or so and either it seemed to get a bit quieter or I'm getting used to the noise. It may be that, when it's fitted in the stern of the boat, under the deck and in it's own compartment, it will be quiet enough. I suppose the other factor is that it's bound to make a more noticeable noise in the workshop, outside on the river it may well not sound too bad at all.

    At least the gear noise is low frequency, unlike the high pitched whine that the Torqueedo unit makes. This will, I'm sure, make any noise less irritating.

    Jeremy
     
  6. Guest625101138

    Guest625101138 Previous Member

    Jeremy
    The attached is one of my Mars motors being exercised on the bench. It is very noisy here but gets quieter once encased and in the open air.

    Look at how ICE outboards can be silenced compared with the uncovered motor.

    I would be surprised if your drive is not acceptably quiet.

    The little PMSM I have with belts on a boat is quite a lot noisier than my rough and ready outboard using the Mars motor with aluminium hood.

    Rick
     

    Attached Files:

  7. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 60, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    That video is interesting, Rick, as the sound of the commutation pulses is really very distinct, far, far more so than on the 63mm diameter model aircraft outrunner motors I'm using. I can just about here that "clicking" noise of the commutation pulses at very low speed if I load the shaft down on my motors, otherwise it only seems to become noticeable when it excites a resonance somewhere in the motor/drive chain.

    The motors I have do become noisier if I run them at higher voltage/rpm. At 36V even the belt driven unit whistles a bit at full speed. However, one of the nice things about running them on 12V is that the rpm is low enough to reduce the raw motor noise (not anything from the drive train) to a gentle hum, even at full speed. I suspect that they are a lot quieter on the bench that your Mars brushless motor, though. I think one reason your Mars might sound a bit louder might be the Kelly controller. These have a fairly low PWM frequency I believe, which, coupled with the low inductance of the Mars, may be giving a fairly high torque ripple. Unfortunately, there isn't much choice when it comes to powerful brushless motor controllers, at least not at the budget end of the market.

    I've discovered that my camera will take short video clips, so I'll try and see if I can take some of the gearbox leg and also the belt drive unit, to give an idea of the noise level.

    I had a good day yesterday, albeit one with around 9 hours of driving, as I went over to see the boat builder to finalise the build details of the hull. Delivery is scheduled for the end of May, for the bare hull, ready for me to install the motor and control system. I think that we've managed to pare a fair bit of weight away, by changing some of the construction details and opting for 4mm ply for most of the hull.

    I need to sort out the final details for the seats. I had wanted to use some of these folding seats: http://www.porterswoodworking.com/accessories.html (the ones towards the bottom of the page, just above the folding tables). Unfortunately, Porters aren't trading any more. I've looked at other canoe seats but not seen any I like. I've also looked at some recumbent bike seats, but although I can buy locally made ones quite cheaply they are all a bit too narrow. I have access to some laminated birch ply seats, from damaged cafe seating. I think I may be able to trim these to fit and add some upholstery, although ideally I'd like seats with a folding back, so I can fold them down to fit a cover over the cockpit. If I can't find any ready made I may resort to having to make some from scratch.

    Jeremy
     
  8. Guest625101138

    Guest625101138 Previous Member

    Jeremy
    If you are using a windows system it should have Movie Maker bundled with it. This allows you to edit and compress video files if your camera produces avi or mpeg format. It will not do mov. It is handy for just cutting the most useful clip.

    If you have not already heard it this is my little PMSM with a belt reduction:
    http://www.boatdesign.net/gallery/data/500/V11JE_10kph.wmv
    It is much noisier on the boat than the Mars motor. However it has no enclosure. The motor is only 40mm in diameter. I could get up to 11kph with it at about half rated power. Before I got to full power it snapped the tiny toothed belt. I now have a larger motor but I have not bothered playing with it. Too many other things to do.

    Rick
     
  9. BertKu
    Joined: May 2009
    Posts: 2,521
    Likes: 47, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi Jeremy,
    I bought the 3150 watt outrunner, which one are you using? the 2200 watt? or also the 3150 watt type. Did you had any problems with the magnets vibrating loose ?
    Thanks Bert
     
  10. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 60, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    Bert,

    I have a couple of old TowerPro 5330 2800 watt outrunners, 63mm diameter, plus a Turnigy Aerodrive 63/74 170Kv 3250 watt outrunner.

    I've not had any magnets come loose, but as I mentioned earlier in this thread, I strip the motors as soon as they arrive and re-glue the magnets in place, and replace the cheap Chinese bearings, before I use them. Magnets coming loose is a fairly common occurrence I've heard, which is why I add extra adhesive.

    The technique I use to strengthen the magnet bond is to clean and degrease the inside of the rotor, all around the magnets, using isopropyl alcohol. I then use Hysol structural epoxy adhesive to completely fill the gaps between each magnet, leaving the inside of the rotor smooth. To stop the Hysol from slumping whilst it cures, I put the rotor in the lathe and gently spin it at very low speed for a couple of hours. This tends to leave a pretty smooth inside surface that not only encapsulates the magnets in place but probably also reduces the drag from the spinning rotor slightly.

    I would guess that any thickened epoxy adhesive would do the job as well as Hysol, that just happened to be the stuff that I had to hand.

    Jeremy
     
  11. portacruise
    Joined: Jun 2009
    Posts: 1,475
    Likes: 178, Points: 63, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Jeremy, if you decide to rework the noise factor, cogged belts might be a consideration instead of gears. They have proven reliable in the Escapade and I think Rick has also experimented with these, using idlers that do away with any slippage- see the pedal boats section. Some advantages over gears in weight and lubrication, perhaps. OTOH, if you can get a big enough outrunner and run at low speed, that may take care of whine as you indicated- by running at low voltage.

    Wonder what the difference in efficiency between the old brushed motors and the top efficiency outrunners would be? I know the advantages as far as brush dust and perhaps stator torque and heat dispersal, but I wonder how much difference there is at full speed where the controller serves essentially only as a commutator.

    Porta


     
  12. BertKu
    Joined: May 2009
    Posts: 2,521
    Likes: 47, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    Thank you very much for the advise. Is Hysol a 2 component glue, or is it a "never get hard" glue type?.

    I also was planning to use belts instead of gears, not for the noise, but convience. The outrunner is only for experiments, the motor I need is much higher in wattage. What is unknown to me is the slip and strech of the belts after a some usage and I have to figure out what the maximum power one can transfer with the size of belts I had in mind.
    Bert
     
  13. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 60, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    I've built a toothed belt reduction drive and have it as a standby in case the gearbox is too noisy. Here's a photo:

    [​IMG]

    Running this motor on 12V with the belt drive is pretty quiet, as the motor and belt speed is pretty low. At cruise speed it's just a gentle hum.

    There's not much to choose in terms of efficiency between brushed and brushless PM motors, as far as I can see. The availability of high power brushless motors seems better than that of brushed motors, though.

    Jeremy
     
  14. Jeremy Harris
    Joined: Jun 2009
    Posts: 978
    Likes: 60, Points: 28, Legacy Rep: 711
    Location: Salisbury, UK

    Jeremy Harris Senior Member

    Hysol is just a two part epoxy adhesive, sold as a structural adhesive. It bonds pretty well to near enough anything. You could use any decent thickened epoxy just as well.

    Toothed belts of the HTD type don't really stretch much at all. Their power handling mainly depends on the torque being transmitted and the number of teeth in engagement. If you push it, then the design can be limited by the belt tensile strength.

    The belt manufacturers provide charts showing the power/rpm/belt size/duty/pulley size, but I found it easier to work out the maximum torque at maximum rpm and then work back to the belt and tooth loads for the smallest pulley.

    Jeremy
     

  15. portacruise
    Joined: Jun 2009
    Posts: 1,475
    Likes: 178, Points: 63, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Jeremy, thanks for the pics. Looks like quality work. So all your noise is coming from the topside reduction and nothing from the prop bevel it would seem.

    With no stretching of the belt, the simple direct hookup should work well.

    I like the wrap pulley because you can use a smaller under rated pulleys and belts, since you have a wrap around to engage more teeth to prevent slippage and lower tension stress on bearings. Also, replacing belts can be done in seconds and tensioning is always nearly correct with a spring loaded idler.

    What do you think of a stainless steel beaded cable system feeding directly to the prop? Sort of like the twisted chain used in hbp, it avoids gears for reduction, shaft and lower prop bevel, producing a lighter and simpler unit. Maybe not as good with electric, since the larger pulley would be at the prop area...

    Porta

     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.