11 April 2004

Amphibear II

Thanks to Deryck Shewchuck interest I designed second generation of Amphibear. Now universal for any ATV with front and rear metal frame racks. Also: rear and front kits are similar, waterline is lower on ATV and some more updates.

Folded easily

Pontoons now horizontally

Raised position

And I concluded two floating tests also

First floating test

First one revealed, that load strap around float is still needed (not in pictures above). Entering the water, rear pontoon was trapped by shore edge and turned around the fixing. It caused much higher waterline (ATV exhaust was below water, when rear pontoon turned). So I felt like captain of Titanic. But at this strange position everything was stable, and I could make small circle and exit again.

Second floating test

It was success. ATV floated, no problems. A bit disturbing was high degree of pontoon deformation with full ATV load on it, but to rubber it does not matter.

I tested at Pirita river in Tallinn. Water was about 3 degrees C, still some ice at shadow places.

One of things I wanted to see was sideways stability. Easiest to test it is to stand on one footboard. As logic suggested, with elastic pontoon it does not too much trouble. ATV just declines a bit and moves its centre of gravity to opposite.

I was exited to test purchased mud paddles. For my sadness it did not increase the travel speed of ATV, it is still about 2 km/h. However it increased the torque. Against the quite heavy wind meanwhile the movement was slow, but firm. Mud Paddles at work and on ground.

To have more power for mud paddles I raised rear axle by winch in water. It helped, but slightly only.

Stopper for pontoon height adjustment I am especially proud of. In right upper corner see kit fixing to carrier – no holes or other damage to ATV.

Stopper allows 7 positions in total, 5 of them have secured both sides movement for floating safety.

Load strap tensor can be fixed to carrier tube differently: to shorten strap, use otherwise hardly accessible places or not damage your carrier painting. (Before that you have to turn hook around on tensor)

Corner, that avoids side decline of frame and bag ends tensioned between two metal tubes

Just before second test. See load strap path and how kit position is lowered by positioning fixing below carrier tube (in upper right corner)

Third floating test

I tested Amphibear in different exit conditions in lake Peipsi. More interesting part of test was with 3.3 hp outboard installed. I raised rear pontoon for more room, then fixed outboard to rear rack. You see in the picture, that outboard angle is not the correct one.

Please see ATV moving in picture by waives. However it is only 1/3 of throttle, as otherwise due to not correct ange outboard sucks air into propeller and can not use engine power. Wheels are not used, as wheels tend to empower ability to suck air. Speed was 3,5 km/h with about 1 hp used. It is more than with wheels.

It seems I need to develop some simple propeller attachment to ATV to get it moving with tolerable speed in water (as 1hp with propeller was already helpful and ATV has 26 hp to use)

Amphibear I

11 December 2003

The one who has tasted the freedom to drive ATV on rough can hardly accept it’s only and one disadvantage–it cannot float. After three years drawing several schemas on paper, making wooden frame models and finally cutting it to hard metal this is not true anymore.

Yamaha Kodiak floating on

• Two inflatable pontoons

• Pontoons can be raised to travel position for more ground clearance for travels between floats

• Adjustable pontoon height for exiting in rough coastline conditions

• Keeping all cross dimensions of original ATV for allowing the same narrow tracks in nearby forest (pontoons deflated)

To honour the Kodiak, what has worked well in these wet conditions I named my baby Amphibear

Final result is simple. It consists two metal frames, hinged for float and travel position, two textile bags for pontoons and two truck tubes accompanied with portable tyre inflator. Pontoons position is managed and pontoons secured by several load straps.

Floating tests

For pleasant surprise Amphibear has enough side stability, so I could stand on one footboard and it did not try to turn upside down. With quite narrow floats and high centre of gravity I was grateful to see it.

Amphibear as driven by wheels moves real slowly in water. I reached some 2 km/h (1.2 mph) as maximum. For a small surprise, it shows more speed backwards as so the tyres meet more resistance in water. This is clearly not enough for river crossing or strong wind conditions.

Third, some tighter water plants on surface can make Amphibear stuck easily. As no grip in water, situation is quite tricky if also water not shallow enough or your direction is towards other shore. The winch with anchor can help you out of situation, but make sure it points the right direction before you get stuck:)

First test video is here (5.3 Mb). Look also at technical section, and let me know your experience.

Floating position

Travel position, after adjustments of fixing system

Travel position, pontoons partly deflated

Design

Construction task

• Put ATV float

• Stability enough to drag yourself out of water, without turning ATV around

• Not to extend width and height dimensions

• No more than 10 min. for gearing the pontoons and one man can do all gearing

• Can fit pontoons into my (cover closed) trailer

• As ordinary materials used as possible

• Keep as much riding quality and safety as possible

• I can make all works using my home tools

Based on the requirements, some things were clear immediately (or after a while for me:)

• It cannot be any Bigfoot solution. Bigfoot can be as easy solution to float your ATV, but it creates totally different riding and dimensions.

• Pontoons should be inflatable. I even bought 400 mm waste tube and tested pair of pontoons I made. However, they eventually are too heavy and increased ATV dimensions. Finally, they are not friendly at all. Also, some design tasks will be more complicated than with inflatable.

I did some drawing and some tests. As a result I decided

• Pontoons in sides are nice dream, as you cannot solve your riding safety and comfort. Pontoons (or frame) in raised position will make your life in danger at normal speeds of driving. Getting on the ATV turns to small exercise also. I carried these troubles in mind, but luckily friend from car shop asked simple question, why not pontoons in the ends? (Sure, you can try to overcome side construction problems with more complicated frame or using 4 pontoons). I decided for the pontoons in both ends.

Build

Supplies used

Pontoons

• Truck tubes 500/55 – 15.5, 500/60 – 15.5, 2p

• Fabric 1,5x4m for pontoons. Should be as strong as possible, also in wet conditions, stand sunlight and wear.

• Elastic pressure tube, internal diameter about 8 mm, 3 m for rear and 1,5 m for front pontoon, corks for tube, 2p

Frame

• Square tubing, steel 20x20mm (25,4mm=1inch) and wall thickness 2 mm, about 8m needed, for spare have 10m in total. This is the frame material I used.

• Square tubing, steel 25x25mm, and wall thickness 2 mm, about 0.5m needed. This was for quick fixing on ATV, as frame tubes fit into this tube. You can avoid need for this tube dependent on your own fixing used.

• Steel plate, 20x4mm 0.2m. I used it for fixing position regulation straps on frame.

• Bolts and nuts M8, 35…80, 22p. As all frame was assembled by bolting.

• Stainless steel wire rope, diameter 3mm, all together about 4m.

Position regulation

• Load straps, 40mm width, 2p, about 4m and 5m. These wider straps I used for position regulation.

• Load strap tensors for 40 mm width strap with handle, 4p.

Other

• Load straps, simple, 3p. These straps were added to bags just for security.

• Electrical portable tire inflator on 12V. Any type is good, but some rapid inflation will be welcomed later.

• Some more fixing small supplies as needed.

Work order

• Find appropriate frame fixing points on your ATV (dependent on your ATV model). Be sure that frame fixing points can carry the full load of ATV on float. Design the frames in paper and if needed build wooden model (avoids a lot of extra work later).

• Build the frames. I used drilling of lot of holes and assembling frame parts with bolts, but welding should be even more efficient solution. However, it is easier to relocate some holes if you need later, so first bolting seems good idea. If bolting, you can use some aluminium tubes instead steal tubes as well.

• Design, cut and sew the bags and or load straps, whatever are used for fixing the tubes. Again, sewing must carry the load of your ATV, so be sure about every material and method used.

• Finish all the rest of fixing and construction works (like distant inflation tubes, straps, etc.)

• Test it on ground and on shallow water. Be careful with stability test in water, do not have it alone.

• Only after testing, it is wise to make all painting and other finishing works, if it is clear that no adjustments are needed.

Please notice that most of the pictures show first version, some described improvements I did after photos were taken.

Front pontoon

Rear pontoon

Rear, pontoon in upper position

Adjustments

• Later on, I had to adjust the height of frame higher (and it can be even higher as current photos tell). As life shows pontoons can be fixed closer from their center, not from bottom-line and it will work as well

• I had also rigid frame fixing to underside of ATV of pontoons at float position (in pictures also). I gave it up for adjustable load straps. It allows adjust the position of pontoons, when floating also.

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