Re: [Electric Boats] Scooter Motor

 

agreed, and I'm a fan of those little scooter motors, they provide a lot of bang for the buck. 500w peak minus typical electric motor inefficiency might be 400w actual work, and barely over 1/2hp. it might equate to two very athletic persons with oars, just not enough power.   I think the guys here are absolutely correct with the 1kw per ton minimum powering, is about 1.3hp per. that scooter motor would be pretty darn good for powering a tender.   how heavy is the sailboat? (big factor!) for quick rough estimates I like using: http://go-fast.com/boat_speed_predictions.htm  an online calculator. plug in the boats weight, and 0.5 for the horsepower of that scooter motor.. honestly, you might attain 1/2 to 2/3 of the speed it'll indicate, for prop slip etc. the calc also works other directions, plug in weight, desired speed, and hit the calculate button under the horsepower slot, where 8-9 mph might be a good startpoint for speed. prop slip is very high (30-35-40%?) with small power and low speeds! 9mph projected might be 5-6 in real world application.   disclaimer: I'm no pro at this stuff btw!   monsterscooterparts.com site has some 36v 1000w motors pretty cheap, chaining a couple of em together might wring up about 2.2hp worth of output. whole lot cheeper than a similar power output electric outboard, how really strong and reliable may be another story entirely! could also maybe be real nice (and cheep) if the sailboat is about 3-4000 lb range.   Arby is right on about free spin vs under load rpm too, my experience is more small scale electrics, model cars and boats (extreme demand-output for their size!). we'd typically gear em for 80-85% of free spin rpm, gives best speeds and acceleration without big risks of cooking the brushes and armature winding "painted on" insulation. you'll need to know your prop pitch, (how many inches per rev) then about 88 ft per minute per mph (not counting prop slip!) then calc a reduction ratio for a typical 25-2600 rpm free spin of a scooter motor.. 80-85% being in the 2000-2200 ballpark. (fun with a calculator!) definitely need to run all the numbers for fairer estimations, better to end up being a little over-geared than under-geared where you might fry the motor(s).   disclaimer again: I'm a low budget tinkerer-rookie to this stuff, but hope its all helpful.   --- On Sun, 4/1/12, Arby bernt <arbybernt@yahoo.com> wrote: From: Arby bernt <arbybernt@yahoo.com> Subject: Re: [Electric Boats] Scooter Motor To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com> Date: Sunday, April 1, 2012, 3:49 PM   500 watts, peak (350 continuous?), before reduction will be about as effective as an oar. I got schooled on 2kw in about the same size boat (Thanks Myles and Scott), so you might consider holding off until you get hold of a little more power. 5kw seems to work at the 80% functional point. If you do choose to stick with your motor, invest in thermal monitoring with a probe in your motor.  Or do it anyway. Nothing like a little experience. Run your motor at no load and measure the shaft speed. Hooked up on you boat, tune your reduction so the motor can hit about 70 to 80% of the no load speed. This will maximize your power output. Most people under-speed their motors, resulting in high thermal loads, increased brush wear, and under-performance. A well lubed chain drive is noisy but easy to tune. Once you have the ratio, order a HTD timing belt and pulleys from Small Parts/Stock Drive Components or Grainger. Use a 1/2 belt to reduce parasitic losses, but understand a larger motor will require a bigger belt. A pair of deep-cycle group 31 batteries from Kmart and two 12v chargers or solar panels, and you're good to go. And snap a few pictures along the way too,  Arby Advanced Marine Electric Propulsion  From: artworxz <no_reply@yahoogroups.com> To: electricboats@yahoogroups.com Sent: Sunday, April 1, 2012 7:26 AM Subject: [Electric Boats] Scooter Motor   I'm new here, and would greatly appreciate any help anyone can give me. I recently purchased a 27' Sailboat, that had the Inborad missing. Has the shaft waiting for whatever. I have a 24 volt 500 watt Scooter Motor, thats been sitting around for a couple of years, and was wondering if I could hook this up to my shaft, and use it only for getting out of the Marina, and returning into my slip. Not looking at performance. If this is possible, could anyone tell me what I would require to make this setup. Just looking for a basic simple way to turn the prop. Thanks

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