HEMTT Wheely King-Based Tandem Axles!

[killbucket]

http://www.youtube.com/watch?v=6u0kZJY4uHk



...First Look at my HEMTT chassis, made from at least two Wheely Kings.


Using the control arms designed for the MegaWilly, I can now make up shorty tandem setups using the HPI Wheely King parts. for size reference, the frame rails are our standard Steelworks #2780765 aluminum channel, 26.5" long each.


Each wheel has its own shock absorber, and each pair of axles has two leaf-spring packs that pivot on bogies.


Unlike most Bigrig axle setups, this one allows a ton of articulation, something an off-road Military vehicle kinda needs...


A simple bulkhead bolts around each pinion gear boss, and carries control loads, but not the weight of the vehicle.


Note that each axle gets only TWO ball ends (Traxxas 8-32 size shown), and the whole vehicle uses only 8.
Should save more than a few pennies for my 1/10 scale Pentagon Budget.


Sorry about your eyes, I got a bit artsy-fartsy late last night...


Drop a WK trans in the middle of this, and it's a go-er.
Actually, I'm going to use a Tamiya Lunchbox transmission, cut-down, to drive a custom-made transfer case.
Or I may go the EASY route, and drop in another hapless Harbor Freight drill:

BTW, these are the 5.75" tall tires depicted in the CG. This is a MONSTER Big Rig.


Hey, you can actually see what th heck's going ON in this shot...Can you tell this is a basic crawler suspension, on 1/4-elliptical buggy springs? Also note how a sinmple cradle made of sheet hold the lower links and upper arm mounts. In the final parts, I'll likely merge the leaf-spring pivots onto them, and maybe even those upper shock mounts, too.

That will make for a fully 'modular' tandem axle., that could be dropped into a multitude of vehicle types...


Sorry about the artifacting in this one. I compressed it a bit too much in post-processing. But it does show clearly how the shocks mount, and that they damp the lower arms right up tight to the suspension pivots.

Who said anti-roll / swaybar? Take a seat up front. Because yes, this would wallow like crazy, as it is right now.

mmore ccoming...

[killbucket]

CAD saves you SO much time in cobbling, bodging, and just plain do-overs.
I draw the parts in TurboCAD to size, then import them to an ANCIENT version of StudioMax, where I 'loft' the outlines into 3d shapes.

Because everything's actual-size, I can then re-arrange things as needed, and it's easy to see where parts want the same space (THAT never happens, right?) and move or change them as needed. The GREAT thing about CAD is, I can have TEN WK axles (a thousand dollars' worth) all sitting together if I want.

The Vee-shaped control arms are a good example of a part that would take some trial and error to get 'right'. They aren't in the CAD file yet, having been drawn-to-fit on the MegaWilly chassis:

(Deceptively simple geometry has built-in counter steering) The control arms are all identical- I hate making unique parts, or overly-complex ones. Ditto re-inventing wheels: I love it when a part can be 'universal', and go on more than one application.

You're looking at the fruits of two 10-hour days' work here so far. Admittedly, I'm not the fastest 3D animator out there, and my imagination got beat up pretty good while partying through the 1990's in Santa Clara (I was a Biker for over 20 years). But I just love taking the seed of an idea, and fixing what's wrong with it.

Like the Wheely King's complete LACK of Caster angles as it comes out of the bow, even though 18 degrees is designed in (note the slant to all my king-pins here, with the pinions parallel to the ground).


VIDEO OF THE AXLES:
http://www.youtube.com/watch?v=0TJkAXrwc1Q

[DEVROCK]

Wow! Excellent work! I can't wait to see how this turns out. Any plans for the body yet? And what kind of material do you plan to make it out of? Keep up the good work!

[killbucket]

.063 ABS sheet, not Styrene. Because ABS will take a beating and a half, and shock loads don't split bonded seams.

It'll be a giant dumptruck, I've decided.


Darn- I forgot the jack-stand!


"Artsy-Fartsy"...(add to dictionary)- Bill Gates, why do we still hafta clean up after you?


Heavy Metal. If the rails look skinny, it's because all the other stuff is bigger than you usually see with them. axles are over 8 inches wide at the hub centers.


This is the cab end, I think a dump bed would be the best option for this, so it's easy to haul odd items..(and do I own a few...).


Time for some steering gear...wait til you see how SIMPLE those blocks will mount to the axle tops...you're gonna slap your head.


On those leaf-springs: Not gonna be metal.
They will be fiberglass. Onc the shape is final, I'll carve a master using the ShopBot, and then pull a silicone mold.
Then using this wonder-product:


I'll attempt to cast a pile of nice, flexy replicas.


More artsy-fartsy. I have no idea what scale I'm hovering around, not my area of expertise...but I'll try up the math in a bit, based on actual HEMTT specs.


A nice thing about going Dump-truck is that swapping other body units on won't be a hassle.


This should be able to drive through a scale barricade or two.


Kinda (only kinda) reminds me of the (wipes tear away)

Landmaster.




Ohh,......I should build a 21st-century version of

Dobbertin's Surface Orbiter.

[karlos]

I'm still waiting for someone to step up and build the RC version of this.

I like what you got going so far. If your going to keep that wide of a tire on it, I think it would look better with the cab and bed a little wider.

[killbucket]

The Landmaster was reader's ride of the year a decade or so ago in RC Car Action Magazine. I'm pretty sure you can look it up, and it's a tough act to follow, to this day.

[HndsWthtShdws]

You should do a rollback style rear. Shouldnt be too hard to make and lets you have whatever rear body you want. What could be cooler than removing the dump bed and hooking up a service body...all under radio control?

[killbucket]

I've worked out an adapter, so I can put a second pinion into an axle- KEY to making this work.

[gapjr]

Wow, now that's alot of wheely king. Can't wait to see the finished product.

[The_REDRASCAL]

I'm likeing this project. Cool renderings.

[killbucket]

Pretty pictures and daydreams have a bad habit of staying...just that. Let's build something already!


strips of ABS plastic (www.interstateplastics.com): 24 inches long. Two strips 1/8" thick, 1.2" wide, four strips 1/16" thick, .50" wide. these were all made by scoring the plastic sheet and snapping it- just like that white 'styrene' stuff.
...but this can take a major beating, and stay together.


Oatey BLACK cement #30889 for ABS:
http://www.oatey.com/Plumber/Shared/...ck+Cement.html
In a Wilton cake decorating bottle for easy application. I should be wearing gloves....they save a TON of time on hand-cleaning.


Using your more familiar alum channel as a straightedge/block, I glued the 1/2" strips to the edges of the 1.2" ones.
I had to practice the "Just walk away, human*" rule, let them set up for about 40 minutes before lifting them free. Sometimes, TIME is the only tool you can use, darnit.


I snapped out two, 2.874 x 1.07" panels to go into each end from 1/8" ABS sheet, and glued them in, using a steel square as a guide.


Assembled rails. These are in severe danger of shortening...I may build a 'standard' truck to get my geometry right first.

Elapsed time: one hour.


A WK axle is bolted between two Coroplast sheets (again, interstate plastics) and the rails set in for a look-see. The outside rail dimension is identical to the Mega Willy's frame, so there IS some common work under both, even though part shapes will change entirely.

More to come today...making the mounts for the rear suspension, and robbing that 2WD straight axle back from RedWilly, to use in mocking this up.

*Lord Humongus:
http://www.youtube.com/watch?v=_TL4XZdyo3g
A sophisticated scene, actually. He's trying some Mind Control on them.

[killbucket]

http://www.youtube.com/watch?v=pWGQqrcAubA
CORRECTION: somebody mistook this for MY work?
No, somebody BEAT ME TO IT...I hate to copy, skipping this concept, keeping the CAD files fer now.
We're DONE with this idea...I'll have to do something else with these parts...

[jsj1982]

wouldnt you want it slightly flexible in the middle? otherwise it looks awesome.

[killbucket]

You mean the drill/ WK axle above?

It pivots at the U-Joint, and as long as the suspension is designed to pivot on the same center, that's all the drive-shaft it needs.

[killbucket]

Necro post warning...


Here's the lowdown: to make the middle axle for a six wheel drive truck, you need a center axle with an input shaft, and an output shaft to drive the axle behind it. To do that, we need to sand off the mating flanges on both axle halves, as seen in this first pic (this one still needs a tiny bit more sanding, but shows the process well. We want both halves to mate up flat to each other).

Step one: open two axle housings, and remove the diffs and bearings. If the pinion's good and greased, you can just leave it be, because of how we trim the housings.


To trim the housings, a sheet of 220 wetordry sandpaper is spray-adhesived to a sheet of rigid plastic. Holding the housing's mate surface face-down against the wet sandpaper keeps the debris mostly away from the greased pinion. Once I had the job done, I wiped out the excess, and put in new synthetic axle grease.



As you can see, the clamps hold everything in alignment nicely, and one side can be over-drilled at the four center screw holes to allow screwing the two halves together as one.