whatcha think

[Magnethead]

Body dimensions 14" x 34" x 6"
overall dimensions 20" x 36" x 15"

top span of tracks: 36"
bottom span of tracks: 21"

Pontoons under body will hold up to ~35 pounds. So should allow for 15-20 pounds of payload.

---------------

Length: 401"
Height: 112"
Width: 96"
Wheelbase: 210"
Weight: 39,610 pounds

 

[Magnethead]

re-designed the bottom main pontoon. I didn't draw the side pontoons, but they'll be "inside" the track carriers.

My calculations before were flawed by 200%. Re-did the calcs, and it comes out to 25 pounds of bouyancy at 2" of sink. Safe to say I'm gonna be looking into any way I can waterproof those motors or get them higher on the chassis without effecting the cargo bay (which is impossible)

 

[Magnethead]

found these:

http://www.radiocontrolzone.com/showthread.php?t=261592

http://socalrcrc.org//threads/3521-SlowRoller-8x8

 

[SlowNeasy]

what are you building mag? poi, many years ago i worked at the tank automotive command (tacom) in warren, mi and worked on some tech manuals for the hemmt.

 

[Magnethead]

what are you building mag? poi, many years ago i worked at the tank automotive command (tacom) in warren, mi and worked on some tech manuals for the hemmt.

another robot design. This is about the most feasable one I have designed. Trying to design it to float and climb stairs.

 

[Magnethead]

Current Calcs say that the tanks in the track frames will hold 5.5 pounds each, and the main tank will hold 17 pounds, for 28 total. Not sure what it'll weigh, but gonna build it with HDPE rigid sheet where I can, and aluminum flat bar and sheet metal where I can't. minimal wood and steel.

Not sure I like the design of the rudders, but trying to stay simple. high speed motor will be up inside the belly tank, have a pass-through, and come down the slot to a carrier bearing, with a 2 blade prop on the end.

The whole belly is going to be one combined unit that will come off easily. Plan is to use a keyhole slot in all 4 corners, with a retaining bolt. Just remove bolt, slide back, unhook a pair of connectors, and it comes off clean. (adding 5.5" of ground clearance)

 

[Magnethead]

neat page about the DUKW's: http://telstarlogistics.typepad.com...around-san-francisco-by-ambphibious-dukw.html

 

[Magnethead]

I'll be using a 2 blade prop, but here's a mockup of what it'll look like. The rudders still fit within the outline of the tracks shockingly. The prop angle is around 12 degrees, which is considered average for a V-drive configuration (which is the closest spec for what I'm making). Purpose of the multiple rudders is to make a more complete rudder cross-section. They're mocked at 2.5" apart but I'm probably going to change it to 1.5". No effect going straight, but when turned, the point is to make the same effect as one huge rudder, completely blocking the cross section.

 

[Magnethead]

made tracks 1" taller, lengthened bottom span 1" and shortened top span 1"

height to bottom of front roller (max climbable wall) is 7.25", 8.5" to roller centerline.

side pontoons are 30" x 23" x 4.5 x 1.75", 7.5 pounds capacity each.
Belly tank is still 25.12" x 2" x 12" minus a 1/2" x 2" x 10" slot for the prop shaft, where I'd be comfortable with it- 21.3 pounds capacity.

total capacity of 36 pounds.

 

[Magnethead]

So I'm actually going to build this one.

HDPE is more expensive than I expected, so I'm going to short-term make do with some 1/4" plywood. Then when I'm done, I'll get the HDPE and transfer everything over. Should help clean things up, too.

Been working on some math with my friend in florida (He works in Siemen's Gas Turbine division) and we came up with numbers saying this thing will move about 70 feet per minute in water, and 140 feet on land, fully loaded at 30 pounds. Achieving this via a 3" prop with 4.2" pitch turning at 250 RPM.

Going to start the hull/pontoons this week and get those load checked, then I'll piece the body together. As much as I want to put doors on it, I'm probably just going to paint them on- I'd have to make a way to keep the doors closed and put hinges on them.

 

[Magnethead]

So I have a semi-final design done-

Belly tank will support 30 pounds @ 3 inch submersion
Both side pontoons inside the tracks will support 15 pounds
(net floating weight = 45 pounds )

Propeller will turn at 250 rpm, and with a calculated 80% efficiency, will move the vehicle at 70 feet per minute.

Preliminary numbers say it should generate about 10-12 pounds of thrust, and the hull will have a drag force of about 1.5-2 pounds, leaving 8-10 pounds of thrust for forward movement. My friend is going to look at the numbers and pul some info from people he knows to get a more for-sure number on that.

Yes, i know my handwriting is horrible.

 

[Magnethead]