Making non-swimming tires swim?

[great white]

No, not another typical tire question about what swims and what doesn't!



I'm wondering if anyone has ever tried the "fender trick" that you used to see in SAE Baja water events?

For the uniformed, it's basically a fairly close fitting fender on the rear wheels that have a "jet" pointed out the back. What it does is prevent the tire front throwing water forward and essentially "scrapes" the water off the tire and forces it to be thrown rearward, creating forward thrust.

Here's a vid:

https://www.youtube.com/watch?v=m6qN3qgpLpQ

They don't have the water event (got rid of it in 2012) but as you can see it seems to be quite effective. Some even have had "non-swimming" tires work reasonably well, with semi-swimming tires showing great gains.

But they may be a problem in swamp or deep mud if that's what you normally travel.

I was just curious if anyone had tried it as my argo currently has 8 "knobby" tires on it and doesn't swim a damn with them. You get in water and it just goes around in circles if you are trying to use the tires for propulsion (I currently have an outboard for any length of water travel).

I thought I might make a temporary scraper of some sort and see if it makes it swim at all, for curiosity's sake as much as anything else. With no suspension on the argo, it would seem a relatively easy thing to try, just bolt it on a give 'er a go! Doesn't work; pull 'em off again.

I also ran across the "penguin" amphib, which apparently used "paddles" on the rims:

https://www.youtube.com/watch?v=8qRmJ2NNNxw

That's an interesting method of getting water propulsion as well and would seem to be a reasonably easy modification....

[pinestumps]

It is worth a try, I know the stern redirection chutes have been used successfully on tracked amphibians since the LVT days of WWII. Russians used them on the BMP with good effect.

Here is a good read on some water performance improvements for LVTs in the late 60s: https://deepblue.lib.umich.edu/handle/2027.42/91649. I know they are tracked vehicles but the 'paddle wheel' is similar.

There are many other DoD papers on DTIC relating to improving amphibian performance in water via wheel/track propulsion during the Vietnam conflict.

[monkstr6100]

I like the simple idea of the scraper on at least just the rear tires. And I am not sure about space, but those paddles on the INSIDE of the rim is a good idea too and would/should not cause any issue with being in the way of anything for normal trail riding. Cant picture of the top of my head though the clearance that my max II has in the inside.

[great white]

I'm going to say the principal at play is the fact that a round body spinning in a fluid produces thrust all around it's circumference equally. Basically cancelling out any intent of a directed thrust.

I can't say for a max, but with an Argo floating with it's rear tires partially out of the water, there's likely enough of a rear thrust vector to give propulsion. Meaning the front 2 (or 3) tires contribute very little in the way of thrust.

But by fitting a "fender" over the top half of the tire, the upward and forward vectors are minimized in the amount of water the tire can move leaving just the rearward thrust components.

That's my thoughts on it anyways...

[great white]

I like the simple idea of the scraper on at least just the rear tires. And I am not sure about space, but those paddles on the INSIDE of the rim is a good idea too and would/should not cause any issue with being in the way of anything for normal trail riding. Cant picture of the top of my head though the clearance that my max II has in the inside.

I think with just a paddle alone you would run into the same issue as you would with a bare tire. As it rotates, it generates force in all directions, effectively nullifying any thrust you might be expecting from it.

With it totally submerged, you would need some way of destroying any thrust it develops that isn't in a rearward direction.

Basically, you would need to run it inside some type of impeller housing with a rear exit or perhaps a "half housing" on the top and front areas of the paddle wheel. So you're probably still stuck with some type of fender arrangement, even if it is small and between the rim and body...

[Tour1]

Speaking as a boat guy w/o AATV experience, the first thing I would try is to get the whole thing higher in the water, maybe by having an inflatable bladder between the skid plate and the tub, a rubber boat bolted to the outside, or an inflatable skirt that adds some hovercraft to the machine. The under-tub hovercraft skirt might help in mud, too, but you'll need some fancy fan duct stuff. Maybe build the skirt out of an old skid plate (inverted) and use a mechanically lowered flap in the back with dryer ducts to the fan. It all adds weight too.
The ideal amount of tire in the water is likely the same as a side wheeler or stern wheeler riverboat. I'll bet there was a lot of research done to figure out what is most efficient, especially for the ones that have adjustable depth. Don't go by a diesel driven fake, though.
For your purposes the "jet" diverter-scrapers sound good. One in the rear and between tires if you can.

[great white]

Speaking as a boat guy w/o AATV experience, the first thing I would try is to get the whole thing higher in the water, maybe by having an inflatable bladder between the skid plate and the tub, a rubber boat bolted to the outside, or an inflatable skirt that adds some hovercraft to the machine. The under-tub hovercraft skirt might help in mud, too, but you'll need some fancy fan duct stuff. Maybe build the skirt out of an old skid plate (inverted) and use a mechanically lowered flap in the back with dryer ducts to the fan. It all adds weight too.
The ideal amount of tire in the water is likely the same as a side wheeler or stern wheeler riverboat. I'll bet there was a lot of research done to figure out what is most efficient, especially for the ones that have adjustable depth. Don't go by a diesel driven fake, though.
For your purposes the "jet" diverter-scrapers sound good. One in the rear and between tires if you can.

I'm going to try a simple sheet metal "fender" on the top half of all eight tires. I'll start by testing just the rear, then add the fenders moving forward 1 at a time. If adding fenders to the fronts adds thrust, I'll make a more permanent installation. Probably make a form and fiberglass the fenders up. That woudl let me produce 8 of them all the same.

Attaching them to the body would be fairly simple while I still have the fixed axles, might be a different story when I build the suspension. Guess I'll have to put some kind of mount on the wheel hub when I do the CV shafts and A arms.

But, that's a looong way off. For now, I have to just replace the bearings, seals and chains with new ones so i can use the rig at all.....