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Polar Airboats


Hi all.
Another newbie here. I just bought a 17 foot Polar airboat without power.
Since I live in Canada, this thing is meant more for ice than water. (it even has a heater, he, he)
I am planning to build a long belt drive powered by a 330 HP Chevy.
Are there any Polar owners (or others) out there who could give me some info on the long belt drive. I'm not sure if Polar builds their own drives or buys them from Airboat Drive units.
Thanks in advance
From the looks of it Polar builds their own long belt drive. Do a search on long belts on this forum and get others opinions of them. I originally really wanted a long belt but! :lol: Your boat has a 8' beam, it can handle a SBC with a 2.68 grarbox up there. 8)
Cold-eh and barhopper - thanks for your replies.
I have already searched on "Long Belt". It seems there are 3 major drawbacks; Price, weight and oil change difficulty.
I think I can put it together for under $2K - belt, pulleys, bearings and tower. A bit less than the CH-2
As for weight, it shouldn't weigh much more than the CH-2. Both need belt, pulleys and bearings. The Ch-2 has an aluminum housing, the long belt drive has a tower. The tower would be maybe 40 lbs heavier than the CH-2 housing. If I have an aluminum driven pulley made that could shave 40 lbs. (the Gates driven weighs 56 lbs.)
For oil changes, I would either pump it out through the dipstick tube or install a fitting and hose to the oil pan drain as someone suggested on another thread, and pump it out through there.
Is there anything else I am missing?
I value your input. This forum is a great place to learn.
PolarBear, I couldn't agree more about the upper (driven) pulley on the Franklin drives. They're much heavier than they need to be.

Part of the reason of course is that they're supported on only one side, so the bearing up there is huge too.
If you design your support frame to accomodate a bearing on both sides of it, you should be able to take a lot of weight out of it.
You have to disassemble the current design anyway to change the belt.

You might want to consider making a half scale working model of it first,
and then when you have the bugs out of the design, build the one you'll actually use. Changing/modifying will be cheaper too.
Also, if something fails in half scale it would be safer to be around.

The oil change problem is easy to solve.

Another solution for the oil drain is a ball valve on the oil pan with a hose that will fit through the hull drain hole.

Or, at work we use "FEMCO" Drain plugs, Part # 1/2"-20-UNEF-LB-T10. It has a spring loaded oring valve that opens when you screw the drain adaptor on that would have a hose out the boat drain. Also comes with a screw on cap as a secondary safety.

For the upper bearing assembly I was planning on using a Wheel hub off like a full floating 1 ton rear end and bolting the studs to the housing. Just have to build a seal plate and prop shaft. Would have followed it furhter if my buddy with the machine shop wasn't so busy making money! :lol:
I'm with you on that one, Cold. A stainless ball valve in place of the drain plug, with a piece of tubing that will reach the hull drain hole.
It can be Tyrap'ed up out of the way most of the time.
When you want to drain the oil, just stick the tube through one of the hull drain holes and open the cock.

I'm thinking about putting one on my boat, and I have a regular engine stand. I could shove the hose on the valve when I want to change the oil and let 'er rip.

If you design your support frame to accomodate a bearing on both sides of it, you should be able to take a lot of weight out of it.

Olf, that's exactly what I had in mind. There can be upwards of 2000 lbs of pull on the shafts and with an overhung pulley (ie CH-2 or 3) that's gotta be hard on the shaft and bearings.
I'm not knocking Franklin, they obviously know what they're doing, but I would mount the pulley between bearings. You may have noticed the drive pulley IS between bearings.....

Cold-eh, all great stuff on the oil changes. I would be careful with the truck wheel hub though. There are some scary forces at work in this application (radial, thrust, momentum), make sure your bearings can handle them. Gotta love it though, when you find something off-the-shelf that can work in a totally different application.

I would have posted the Pic but don't know how. Pretty light stuff including bearing size compared to the truck hub I was going to use. Let's see, 7000 lb truck with a fulcrum (wheel) bolted to it going around corners and over bumps. Anyways I have my rotator now so the long belt parts are on the bottom shelf! 8)

Thanks for the picture, Cold-eh.
Those look like SealMaster bearing cartridges by the writing on the box- top-of-the-line stuff. $$$
I'd really like to know how the pulley and prop flange are fastened to the shaft. Kinda looks like there's a keyway there.
Olf, you've had yours apart, can you shed any light on this?
Looked like just a key-way for the prop hub. Gates uses Taperlock on all their pulleys. I checked with the local gates guys and their computer program didn't like the drive pulley RPM. It kept telling us to get in touch with their engineers. I'm sure it had something to do with the pulley. If you use a tensioner pulley they want it on the inside of the belt.
OR! :wink: Use a gear box at the bottom of the boat and use a 1/1 belt just to get the prop up there. Reduction of torque roll, longer belt life. :roll:
They are SealMaster. I can't criticize Franklin. Their units are virtually bullet proof, but damn if they aren't heavy.

Mine is a CH3, which is even heavier than the CH2 because of the 5" belt and larger pulleys. When I recently mounted mine on the new engine (working by myself) I used my shop crane to lift the upper drum into place so I could have two hands free to align the belt and bolts.

They're a lot heavier than they need to be IMO.

Cold-eh, you can download the software your Gates dealer uses - its called Design FlexII. Its on the Gates website. Its pretty neat, you plug in the #'s (HP, RPM, Center distance, etc.) and it tells you which belt/pulley combinations will work. Even has prices.
Speaking of prices,
I just got a price on a custom made, aluminum Polychain driven pulley. Its hard anodized and tapered for the Gates hub, AND its cheaper than the Gates cast iron pulley! Bet it weighs less than 15 lbs. Looks like I may be starting on my long belt drive real soon.
Now, if I could only figure out how Franklin fastens the prop flange to the shaft.......anyone???
Maybe I should start a new thread on the CH-2/3.
BTW, Cold, that truck that's going over bumps and around corners is doing over 200 MPH (assuming 2500 RPM), if I figured it right. That would make a big difference.
PB, the prop flange is pressed on.
Anytime you talk with those folks on the phone (nice, every one) they will tell you that the hub needs to be returned to them for dissasembly.

Obviously that's not completely accurate, but what they're saying is that they have the fixtures and experience to do it right.

I hear ya, olf.
Somehow I can't imagine an aluminum hub pressed on a steel shaft holding (minimum) 800 ft lbs of torque, but like we all know, they work!
I think I'll go with a spline/nut or a keyed taper bushing, the latter being way cheaper.
Thanks for the info
They're keyed and pressed. I like the idea of a spline, but of course that increases the cost/difficulty of making one big time.

You have a clean sheet of paper.

Yes, thought I saw a key slot in that picture. Now we're getting somewhere.
Simple and cheap.
Clean sheet of paper getting more cluttered by the minute..........

Ya'll got some nice boats up there :wink:
Sure would love to bring the boat up there some time if i had about 30 layers of clothing!

Ya'll lost me above on the subject of oil change :roll: I've got the CH-3 long belt and there's plenty of room to get a large sized dish-pan to drain the oil in the engine.

Basket, you're just the man I need to talk to.
Any chance of you emailing me some pictures of your long belt drive?
I am especially curious as to how the tower is attached to the engine.
It would seem to me that a 4 foot tower, bolted to the back of an engine block, with about 1000 lbs. of thrust coming from the top of the tower (4000 ft lbs at the block) would do some serious damage to the block.
I was planning to use struts from the top of the tower to the front of the engine mounting rails to keep everything "happy".
Nobody else appears to be using struts - can't figure out why.