Custom made volkswagon powered 8x8 with sea doo pump

[Adondo]

I just found this thread. NICE machine!

As for water speed, you're going to find that 5 ~ 6 MPH is going to be a "brick wall" for maximum speed. You're dealing with a displacement hull, much like a sail boat or barge, in other words something that cannot get up and out on top of the water. (i.e. get up on plane) You can only push the water so fast, and adding power is just going to make a bigger wave, and take more fuel. There's probably no way to get it on plane with tires etc. and it would be horribly unstable if it did.

Boat owners who fish no doubt notice that same 5 or so MPH is max kicker motor speed, be it a 5 or 15 HP, you can't get more out of them. When the boat's down in the water, you just can't push them any faster. A 6x6 or 8x8 is the same way.

[chris davison]

Ive done the fixed hull speed math and your right about 5.6 mph is max for me. right now I have 55 hp and I just dont want to do 1.5mph thats the best Ive done with a seadoo pump or tires.

[philipatmaxfour]

vw powered...

Ive done the fixed hull speed math and your right about 5.6 mph is max for me. right now I have 55 hp and I just dont want to do 1.5mph thats the best Ive done with a seadoo pump or tires.

Chris,Do it. Try the arm,but if need be try your next idea.You have already done what doubters like me thought was impossible.If you can get your wife/photographer to take a pic. or Can you imagine a video? of the machine on gravel going sideways for 10 feet in a turn. and a pic. going 13 mph. into the water! Please don't get discouraged now buddy, you have already climbed the mountain, and if it takes hydraulics ok but I hope not.For sure 1.5 mph in the water isn't going to be acceptable. Congrats on where you're at and best wishes.

[chris davison]

Thanks for the Kudos and encouragement. We all need it every now and then. Its below freezing here right now so I'll have to wait for warmer weather.

[chris davison]

Hey guys check out the Surplus center Surplus Center it has all kinds of neet stuff Bearings chains belts hyd pumps and wheel motors bilge pumps gearboxs and the tranys from 0 turn lawn mowers. ask for the catalogue to be mailed to you. also diesel engines and gas.

[chris davison]

Hi guys I've started to run my machine now had to buy a new battery as mine was used when I put it in. I have been pushing my maching to see if I can get stuck anywhere no luck so far. All my parts are worn in now and its working real good. I can do almost a zero 180 degree turn in the middle of a single lane dirt road. I climbed over a bunch of big rocks and concrete hearing my hull hit, went thru a field of thick weeds 4 and 1/2 feet tall that was weird hearing all that brushing on the hull, drove into a pit of water propelled across it with tires only turned around and climbed out with the front end sticking 4 feet into the air then coming down hard. I drove sideways on a hill of grass drivers side down and slightly sliding down hill then came to a 4 foot drop off into a stream. I rolled over the top and my nose hit the stream bed about 4 inches under the water with the two rear wheels in the air.
Gave it gas and the nose just scraped across the bed and came up as the rearend came down. That was fun and the foot brake pedal works great for that. I looked around and thought ok dummy how are you going to get out with that front end sticking out so far? I turned walley around and in first hit the hill at 2 mph nose first and it just pushed the nost up hill untill the front tires hit then I gave it some more gas and it climbed right over no problem with 4 front tires in the air as I came over that was a blast.
I will start on the prop drive shortly and post some pics. I have run it in 4th gear some but the lack of suspention makes 35mph real scary. 25 in 3rd is just fine. I havent run into any deep mud yet not sure how it will do maby high center in the muck.

[Mike]

Good to hear that it is working as well as it looks. We need some more video of your "testing"

[JoeMeg]

Glad to hear your having fun with your unit! I'm watching the pump part of this build for ideas as I plan on installing the pump in my Hustler rebuild. (when/if that ever happens,lol).

[chris davison]

I trailered my rig to a place under a big bridge where its more flat and wide on the white river. Had a blast running it in 2nd thru 6 inches to a foot of water splashing it 10 feet in the air and all over me. Took it to the rapids and it just blasted thru to the other side just floating sideways a little. It will not come out of the water where the nose hits first and the wheels are not touching yet
bummer. Maby with a little momentum from a prop drive the nose will hit and slide forward till the wheels hit. What a difference from driving say a jeep you just point it in the direction you want to go and fearlessly go for it. over tree stumps rocks deep water gullies in 2nd at 18 mph the front end hits slides up over till the front tires hit and on you go splashing all the way. I hit a rock so hard that it bent over the bead on a front tire it went flat and I didnt even know it. I played for another 20 min. and finally saw it as it was up on the trailer. Out in the wet sand and gravel I have been able to do a sliding 160 degree turn with the wheels spinning to go forward and hit a bump hard enough that only the 2 rear wheels were on the ground. Parked it on a slight hill turned on the bilge pump and pumped out about two gallons of water that had splashed in to the hull.

[Leighos]

Hi Chris,

Great to know you've been getting out there and enjoying Walley, what a blast it must be!

I've been working on a basic model of my Terrapin 1/2 scale project, drew it all up exactly half size to see what can fit in it (engine, driver etc) - turned out 35in inside the hull was just not enough so had to widen it to 48, will probably drive better having a wider track anyway.
So here is a render of the 3d model (the Stig driving to show scale)...


I intend to power with a Subaru EJ (horizontally opposed 4 cylinder) running thru a 5speed 4WD transaxle, the front wheel outputs driving the wheels via chains (as Walley does) and the rear drive output to run the propellers (yes the original Terrapin had 2 props, oh and 2 v8 engines!)

Its really only in the design and concept stage at the moment, getting a few ideas and seeing what will work well together.

I'm looking forward to seeing some pics of your redesigned prop drive.

[chris davison]

Leighos that looks really cool, are the two front tires higher than the others? it looks like they are. 48 inches wide will be very stable Will there be a way to disconnect the tires when the props are turning? how will you control the direction in the water? what will be your length and side height? what will be your tire sizes. 30 inch tall by 12 wide would be a good size. What will be your axle spacing? We all have a million questions when we like what we see. Do you know the tranny ratios? I would suggest a 2.5 to 3 to 1 reduction on your jack shaft. You will probubly never use 5th. Do you have a trailer for it? Chris

[Leighos]

Thanks Chris.

Yes as with the genuine Terrapin, the front and rear wheels are raised off the ground. In the half scale this works out to be 4" for the front and 1" for the rear, I'll have to come up with a raised bearing/sprocket carrier on either end of the chassis rails for that.

I'm still considering options for the prop drive, but so far I like the idea of the 4WD transaxle as it has a center differential, its possible I could use a disc brake on the prop shaft to stop it turning when the wheels are used, and vice versa - apply the park brake on the wheels to get the prop to spin.
There are a few different models transaxles that I could use, but the one I'll base my designs off is the one that is used in my Subaru Legacy RS, I know it well as have rebuilt it and it regularly sees the full brunt of the 300hp I have running thru it so I know its strong! Plus I have a couple of spares so makes sense to use what I already got.
Ratios are (1st) 3.454 (2nd) 2.062 (3rd) 1.448 (4th) 1.088 (5th) 0.825 with final drive being 4.111, you're right I probably wont get to use 5th much.
Again with Walley as inspiration, I was going to use 2.5:1 on the jack shaft with enough room to go to 3:1 if needed.

Direction in the water will be a large rudder in between the two props as with the full scale Terrapin. I may have to use some sort of servo assist for that as I intend to use a steering system like Walley's with the sand rail brake cylinders and I don't think I'll get enough travel with a conventional cable and pulley to get the required deflection.

As with the rest of the model I used the half scale principle on the wheels and tires, worked out at 25-8-12, which is a very popular size here with farm atvs and 4x4 Suzuki Carry's. Axle spacing is currently 28"
It might seem that I'm obsessed with the half scale concept but in reality I know I will deviate from this for practicality sense, as I already have with widening to 48".

I do have a really nice trailer to, a single axle tilt trailer built for a race car - I've had a 3500lb car on it and tows well.

[rodp]

Living no more than 15 miles from where Morris Commercial were built...................I don't think I would copy anything designed by them

I still remember some of the trucks they used to make

[chris davison]

From what you have said this seems to be well thought out will be very stable on land and on water. Good thinking on the spacing for 3 to 1 ratio do you know the HP and torq of your motor? This will look like a terripin on the outside, but inside it will have no resemblance at all. What have you planned for roll bars, wind shield, canvas top, or roof rack? Oh yes what is the ring and pinion ratio?

Chris

[Leighos]

Ring and pinion (final drive) is 4.111 if I go ahead and use the same tranny I have, but there are a few other ratios out there for the same case (3.9 to 4.44). I'll try and find a wrecked car to take the engine and trans out of.
I'm hoping to use the smallest of the EJ's, its a 1500cc with 94hp @5200rpm and 105ft/lbs at 3600rpm, unfortunately they are harder to come by as most Subaru's here are around the 2000cc.
I like the idea of the folding roll bar, that way I can fold it down when I go to military vehicle shows for that more authentic look.

Was looking at the pics of your axles, they are 1 3/8 with the ends turned down to 1 1/4 to fit the 2 bolt flange bearing and then drilled and tapped in the end for a locking bolt? What steel did you use for the axles?
Also are the frame rails mild steel or chro moly?