DIY Scooter Idea?

[mohave_steve]

Hello All,

I have been watching the discussions of DIY scooters with some interest and considering using a Minkota trolling motor for this application.

I have read that the Minkota motors "MAY" be usable with no modification down to 130fsw. I am not sure I want to be the one to test this

My thought: place the motor, controller and batteries in a PVC housing with a relatively low friction O-ring seal on the motor shaft and preasurize the housing with a pony bottle and reg. Reg would adjust preassure inside the housing proportionate to depth keeping the preassure inside slightly higher than the outside water preassure.

What do you think?

Also, does ayone know what the thrust of the popular scooter are? I have a Minkota 30lb motor available but I am not sure if that would be adequate.

Thanks

Steve

 

[marchand]

Make sure you put an overpressure valve on it.

I have no idea on thrust, but if you could find someone to open up their scooter and grab the part #'s off of the motor I'm sure you could find specs somewhere on the web.

 

[Gary D.]

Hello All,

I have been watching the discussions of DIY scooters with some interest and considering using a Minkota trolling motor for this application.

I have read that the Minkota motors "MAY" be usable with no modification down to 130fsw. I am not sure I want to be the one to test this

My thought: place the motor, controller and batteries in a PVC housing with a relatively low friction O-ring seal on the motor shaft and preasurize the housing with a pony bottle and reg. Reg would adjust preassure inside the housing proportionate to depth keeping the preassure inside slightly higher than the outside water preassure.

What do you think?

Also, does ayone know what the thrust of the popular scooter are? I have a Minkota 30lb motor available but I am not sure if that would be adequate.

Thanks

Steve

Stop right here, you're over thinking it. I have built several different styles with power from 34# to 128# of thrust.

Minkota and Motor Guide will both go to some real deep depths, well beyond 130'. There is no reason to put the motor inside housing and NO reason to pressurize a housing to contain the battery.

Start out here: Do it yourself construction plans
Do the Scuba Tow on the top of the page. I made a lot of modifications which I can help you out with. Once I worked the bugs out it is the best DPV I've ever had.

Gary D.

 

[mohave_steve]

Hey Gary,

Thanks for the reply. Maybe I can take a look at yours?? I have (finally) arranged my escape from Purgatory... I am moving to Walla Walla next week to start a new job.

To make certain I understand: The Minkota motors can be used to depths of 130fsw without modification?

That will make things MUCH simpler. Do the plans on the sit you referenced call for Minkota or similar trolling motors? Also, what kind of mods did you make?

Thanks

Steve

 

[Gary D.]

Kuel on the move.

The plans are well worth the money. But remember they are mid 70 technology. I modified about everything to bring it up to the 90’s. Not much has changed in the 2000’s.

About the only thing I kept was the basic shape which I even extended 6” for added space in the battery compartment.

Kent made it with basically one long side and I changed it to two pieces to separate the ballast tank from the battery box. Works very well.

I changed the removable wing to a fixed wing and a hatch to access the battery box which made everything much simpler.

My trigger is a magnetic door switch for an alarm system and it has proven to work flawlessly.

Lots of little changes to make it the fastest and most maneuverable submersible F-14 Tom Cat around. It will pull two divers slightly faster than most of the commercial units. Around 3.5 mph with two on it.

I had one with 60# and twin batteries. Keeping a mask on was a trick. Keeping it between 30# and 50# of thrust I have found to be the best.

Minkota and Motor Guide work equally well. Motor Guide I have had to 160’ Minkota to 140’ and they worked equally. I don’t know for sure but I have been told that Motor Guide, which is sometimes less expensive has a finer machining or polishing on the power shaft then Minkota has.

Making the case longer gives you room to add the speed controllers, relay and continuous use solenoid in a nice package.

I use Sears 33ah gel wheelchair batteries. The garden tractor size. I works out to 1ah = 1# of thrust. So with 30# of thrust you get around an hour of run time.

I can take some pics and post them later. It is a fun project and they do turn a lot of heads.

Here are a couple of pics on an early model during testing: ScubaBoard Gallery - DIY_DPV_F14 - Powered by PhotoPost

Gary D.

 

[Kingmob3]

look around the U. Cal Eng and Bio department websites, last time I was in SF, at the pier they had a 1ATA sub that a group of students had built, using trolling motors for propulsion. They had taken it well past 100 feet, multiple times.
Allen

 

[eclipse785]

I gotta quick question. I have an opportunity to pick up a working 17lb-thrust Minkota motor for super cheap. Can anyone tell me if this is enough to pull me around? I'm about 190lbs, medium build. If you guys think this could work, I'll pick it up and build a PVC housing for it.

Thanks for the help.

 

[Gary D.]

I gotta quick question. I have an opportunity to pick up a working 17lb-thrust Minkota motor for super cheap. Can anyone tell me if this is enough to pull me around? I'm about 190lbs, medium build. If you guys think this could work, I'll pick it up and build a PVC housing for it.

Thanks for the help.

17 isn't much but why not get it and look for another one to pair it up with. Most of the better commercial units are 30# or higher. 17 will work but don't expect to be fast. You could use it as an assist and be ok and you should get almost 2 hours off a 33ah battery.

The problem with a PVC housing is they don't fit a wheel chair battery very well. Just about 1/2" to small in most cases. I'm doing a one now we should be able to water ski behind and I'm going to notch the PVC interior and beef up the exterior which is a pain by the time I get done. It's going to be an 80 pounder thrust wise.

Gary D.

 

[DA Aquamaster]

I remember that particular design way back when in a popular mechanics article. Still kinda cool.

The Tekna scooters are reported to have about 50 lbs of thrust which is a bit more than the slightly less powerful but cooler running Oceanic Mako scooters.

50 pounds of thrust is probably enough to get the job done and any more than that is over the point of diminishing returns. Drag increases as the square of the velocity so it takes 4 times the power to double the speed of a scooter in the water. All that extra power has a proportional effect on run time so unless you have really large batteries, you may go a bit faster but you won't go nearly as far with a larger motor.

On the other hand, half the speed requires only 1/4 the power so 17 pounds will produce a bit more than half the speed of a 50 lb motor which while not blisteringly fast may still give a usable asist.

 

[eclipse785]

17 isn't much but why not get it and look for another one to pair it up with. Most of the better commercial units are 30# or higher. 17 will work but don't expect to be fast. You could use it as an assist and be ok and you should get almost 2 hours off a 33ah battery.

The problem with a PVC housing is they don't fit a wheel chair battery very well. Just about 1/2" to small in most cases. I'm doing a one now we should be able to water ski behind and I'm going to notch the PVC interior and beef up the exterior which is a pain by the time I get done. It's going to be an 80 pounder thrust wise.

Gary D.

I don't expect it to be fast, just something that will assist in long kicks out from the beach. And if I had my way, I'd get a bigger one, but I can get this for about $30 and it seems like a steal to me. I figure, if I can get this to work properly, I can upgrade to a bigger motor later.