Notices
RC Tanks Discuss all aspects of rc tank building and driving here!

1:8 dukw

Old 10-08-2021, 08:19 AM
  #1  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default DUKW in 1:8 Scale

Where to put this thread? It's a 6x6 but not a rock crawler, it's military but not a tank. Most folks don't know how to categorize it, it's just an odd DUKW. So I'll put it here.

"It's not very fast in the water, but it'll beat any boat on the highway!"

You can read a lot of DUKW history, but absolutely the single best reference is Doyle's "The Complete DUKW", though his smaller "The GMC DUKW" is also useful. The TMs, particularly TM 9-802 are super useful. But none of them have dimensioned drawings, beyond the little snippet I show below. Enough to get started on.

Other reference sources? I've visited DUKWs in museums and taken scores of shots. A lot of pics on the web, including a few FB and other military groups. And there's the Italeri 1:35 kit, which seems fairly accurate.
You can still find modified DUKWs in the tourist trade, handy if you can get close to measure things. I wish I had an original museum DUKW close now, I really need to measure some things!














Last edited by patmat; 10-08-2021 at 12:50 PM.
The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 08:22 AM
  #2  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

You can get a 1:10 DUKW kit from Deans Marine, but you need to source your own axles from other RC trucks, which costs as much again as the kit, which has a fiberglass hull. Many of these have been built.
I thought I could save $$ by building my own ca. 2004. It was made from wood in 1:12 scale, with self made axles. But I didn't have the tools I have today, so it wasn't very sophisticated and I never completely finished it.



Deans Marine 1:10 kit with Robbe axles

Me and my DUKW around 2004
The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 08:25 AM
  #3  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

I really want to build a bigger one in 1:8 scale (1:6 would be a bit too much!). But one of my major problems has been tires. Available RC truck tires are just WRONG- too wide, wrong tread. No one makes a decent DUKW tire, and that was enough to put my project on hold for years.
The Deans DUKW has you using large scale airplane tires... oh so wrong!


My DUKW with airplane tires. Ugh.




DUKW's complicated driveline, and NDCC tires




Full scale tires can still be had. Two flavors- one has those sharper shoulders on the tread, the other is more rounded.
The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 08:30 AM
  #4  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

But now, I have a 3d printer.

I'm in process of trialing two methods:

1. Directly print the tires in a rubber-like resin. Can be made hollow, which need foam cores added.

2. Print a hard shell mold, and pour urethane rubber into that. (Could also print a solid master and pour a silicone rubber mold around that... still possible too...).

I'm not so sure about the tear strength of the printed rubber, it might fall apart on the road.
The poured tire is solid- a lot of rubber! But it doesn't need a core, it can surely hold up the heavy model (I expect 28 pounds), and since this is really a boat, it needs the weight for ballast.


Printing a 5" OD tire in flexy resin




Printed



Squishy!



Printed rim



Tire on rim



Shell mold design




First pop... we got the bubble issue worked out later
The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 08:48 AM
  #5  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

With the tires looking feasible, it's time to get back to the axles.
My self made axles were cheesy with 1:1 bevel gears and simple housings. All the gear reduction was in drive gearmotor, not ideal.

Years ago, I decided to print a banjo style housing to fit around Traxxas Revo difs... that is still the plan. Axle ratio is about 2.7 or so to 1, and the units have functioning differential gears.


My old front axle




Printed banjo on Traxxas dif, and Traxxas drive shafts, from a few years ago... Shapeways nylon SLS.




Now my own printed housing


The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 08:50 AM
  #6  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

And what about the entire driveline and suspension?
I'm figuring this all out in CAD, as we speak. But so far it looks feasible.

Most 6x6 models have a through-drive axle in the middle, with a short driveshaft connecting the mid and rear axles. Real DUKWs (and the CCKW 6x6) didn't do that- they have an over-the-shoulder pillow block for a second rear driveshaft mounted on the mid axle, see the pic.


Over the shoulder driveshaft holder




CAD layout
The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 08:51 AM
  #7  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

The real rear suspension is with a single leaf spring set per side, actually mounted on a pivot, with additional stability through torque rods.
I'm going simple with a parallelogram linkage on both sides, and probably a faked solid leaf spring up front. This model doesn't need the flexibilty of a rock crawler, it will just trundle along on fairly smooth roads and sand.


Rear spring has a center pivot at "G"




My original parallelogram suspension, works fine. Requires rubber bushes in the rod ends, or real RC rod ends maybe.
The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 08:53 AM
  #8  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

And what about that transfer case??

I looked at available t-cases, like the one in the HG P602 MRAP, but no one has two rear outputs.
Time to design my own.
I salvaged the gears (Mod1 sintered steel, nice) from the P602 t-case, and will add a couple more from SDP-SI. Case will be printed, and I'll use simple flanged Oilite bushings. No need for a lot of ball bearings at this speed!

My design has 1.9:1 reduction, and I'll mate it to a gearmotor with 11:1 reduction, along with 2.9-ish at the axles. And it's set up with both rear outs turning the same direction.


HG P602 t-case



2-speed, which I won't bother with



My layout with 2 rear outs. Need to add case screws and mounting flanges.
The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 09:16 AM
  #9  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

And the propeller drive?
A separate gearmotor for that, I don't want to try to duplicate the DUKW's complicated multi-t-case set up.
Prop is a Federal Mogul "weed" style, looks just like the Monterey Clipper Hicks prop I've previously cast in bronze- perfect!


Real DUKW




My bronze props




FederalMogul "weedless"




with gearmotor drive



Prop & Strut
The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 09:17 AM
  #10  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

What's next?

I'm still designing. The hull I show here needs a lot of work, but it's straight-forward. I'll probably build in wood again, but I'm open to ideas.
Once that's worked out, I can start fabricating drive hardware in earnest.

All the rest is just decoration on top, and with my own printer, that should be easy.


Initial hull outline, much to do
Old 10-08-2021, 09:19 AM
  #11  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

Working on the basic hull layout now. I'm still not sure how I'll build it this time... maybe plywood again, but it sure would be a neat metal working project! If only I had the tools...

A lot of models miss some subtle features of the DUKW:
- The hull is actually wedge shaped, tapered in the profile view. It's hard to see this in photos which are almost always at some angle.
- There's a deadrise angle running along the side of the hull, which wraps all the way up the flat bow, Italeri even missed this at the bow.

Italeri also missed the width of the hull... they took the dimension "D" (98 inch), which is overall including the hoisting loops, and applied it to the hull proper. A too fat DUKW!



Deadrise angle
The following 2 users liked this post by patmat:
herrmill (10-09-2021), Will01Capri (10-13-2021)
Old 10-08-2021, 09:21 AM
  #12  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

That hull, it's just a big tub... shame not to beat it out of metal...








The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 09:23 AM
  #13  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

But I like plywood- easy to work and join, way stiffer than plastic. I coat plywood with resin, no glass needed, and sheath it in 0.020" styrene.








The following users liked this post:
herrmill (10-09-2021)
Old 10-08-2021, 09:24 AM
  #14  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

I put off this project for years, because I had no confidence in getting decent tires. But now, thanks to cheap 3d printers, I have a set of 1:8 rubber!
One tire is printed directly, the others are urethane rubber molded in a hard shell printed mold.
Wheels are all printed, and the axles are coming along too as prints, plenty strong so maybe I don't need to machine them out of metal.


Molded tires, printed wheels & axle housing
The following users liked this post:
Will01Capri (10-13-2021)
Old 10-08-2021, 10:39 AM
  #15  
RC_BobM
 
Join Date: Jan 2017
Location: Seattle, WA
Posts: 404
Likes: 0
Received 42 Likes on 40 Posts
Default

Very cool project! Thanks for posting the details. I love the driveline development and the fabrication of your own tires. This will be a great follow along project.
Best regards,
Bob
Old 10-08-2021, 05:20 PM
  #16  
Rjag
 
Join Date: Mar 2017
Location: Barrie, Ontario
Posts: 50
Received 1 Like on 1 Post
Default

This is the most interesting project build that I've read. Excellent pics as well. Thank you.
Old 10-08-2021, 09:54 PM
  #17  
RichJohnson
 
RichJohnson's Avatar
 
Join Date: Nov 2014
Location: San Diego
Posts: 2,305
Received 130 Likes on 89 Posts
Default

Nice project. Good luck, that is going to be a big undertaking.
I made some tires myself from a mold using black commercial silicone caulk.





The following users liked this post:
herrmill (10-09-2021)
Old 10-09-2021, 09:50 AM
  #18  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

Nice touch with the lettering, I was too lazy!
Old 10-09-2021, 10:59 AM
  #19  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

Thanks all. Today's progress: First fit up of the driven front axle.
Using Traxxas Revo parts for the guts. Big, strong, well made, widely available.


Last edited by patmat; 10-09-2021 at 11:02 AM.
The following 2 users liked this post by patmat:
herrmill (10-09-2021), Rjag (10-14-2021)
Old 10-09-2021, 11:01 AM
  #20  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

And the transfer case is coming along too.


T-case



Front axle trial fit up




Axle parts
The following 2 users liked this post by patmat:
herrmill (10-09-2021), Will01Capri (10-13-2021)
Old 10-09-2021, 07:07 PM
  #21  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

Got the transfer case assembled. 1.87:1 ratio, 2 rear outputs & 1 forward, steel gears, ball bearings, printed case with machined bores.



Assembled t-case, with 2 rear outputs



...and 1 forward output
The following users liked this post:
herrmill (10-09-2021)
Old 10-11-2021, 06:30 PM
  #22  
spinnetti
 
Join Date: Oct 2002
Location: Verona, KY
Posts: 119
Received 17 Likes on 13 Posts
Default

Great project! I've stalled on several projects due to the tires. Can you elaborate a bit more on that? I was thinking to print hard molds too, but which urethane did you use, and at what ratio fill to the mold? For some reason chicken to try and make tires lol.
Old 10-11-2021, 07:39 PM
  #23  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

Elaborate? Design mold, print mold, pour urethane in. 30 duro in this case. Not sure the brand, a friend poured them for me. Ratio? Um, fill it all the way...
Another way: Print a solid tire, and make a rubber mold from that.
Old 10-11-2021, 07:41 PM
  #24  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

Tonight's progress: All three axles assembled for the first time. And only one oops. Well, I can just print a new axle housing, no prob!


Parts for three axles and a t-case



All three assembled. Only one was epoxied backwards!
Old 10-12-2021, 08:14 AM
  #25  
patmat
Thread Starter
 
Join Date: Nov 2004
Location: Temecula, CA
Posts: 244
Likes: 0
Received 24 Likes on 19 Posts
Default

A hand for scale:



Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.