RCBasher.com - HPI Wheely King Mods

Wheely [sic] (hwee-lee) -noun: A stunt in which the front wheels of a vehicle are raised so that the vehicle is balanced momentarily on its rear wheels
King (king) -noun: a person or thing preeminent in its group or class

HPI Wheely King Modifications

[Wheely King Info] [Wheely King Hop-Ups] [Wheely King Mods]

Wheelbase Extension

As with many R/C modifications, the WK wheelbase extension isn't difficult, it just takes some parts sourcing and some time. Please read this entire write-up before buying parts or even planning out your own project so you know what you're up against before you begin. I know the write-up is long, but I did it that way to maximize clarity.

There's a little bit of missing info on this page, and it's something I'm continuing to work on. Thanks for your patience!

Lower Links

Creating new lower links is the most time-consuming part of the wheelbase extension project, so let's jump right into it!

Disassembly: Remove the rear tires, stock rear lower links, and the screw securing the upper rear link to the axle housing. The lower links are attached by screws at the transmission and by pins with e-clips at the axles. It's easy enough, but here's a tip: slide a small hex key through the center hole in the plastic tube into which the link screws thread. This hex key will prevent the tube from rotating as you remove the screws.

Link Length: Based on input from others, I wanted my rear lower links to be 148mm from eye to eye. This will keep the truck within the 12.5" wheelbase limit for competition purposes should you decide to go that route, and it also gives a good appearance considering the scale of the truck without getting too crazy.

Rod Ends: I recommend using the Traxxas #5347 rod end kit for a few reasons: they're easy to obtain, they're cheap, the kit is rather large (12 rod ends and 12 pivot balls), and they're sized great for 8-32 thread. I've managed to bend links made of 6-32 rod a couple times, so I'm all for a little more beef! If you wish, you could use two HPI #85230 sets or two HPI #85050 sets which contain rod ends that will work, and use HPI #86059 for the pivot balls. More parts and higher cost than the Traxxas set, however.

One other option I just tried is Traxxas #5139 steel turnbuckles. They're probably not the exact length you want if you're going for competition, but they're fine for a play vehicle. They come two to a pack for under $10, and they're pre-assembled with the rod ends and pivot balls. They're also chrome-plated so they look nice, and they're turnbuckles rather than threaded rod so you can easily adjust their length should you desire to do so. They're not as beefy-looking as the sleeved custom jobs mentioned above, but I bet they'll be adequate. I'll definitely post here if I find out otherwise.

For reference and calculation purposes:
Rod ends from Traxxas #5347: 17mm long, 11mm thread depth, accept 8-32 threaded rod
Rod ends from HPI #85230: 23mm long, XXmm thread depth, accept 6-32 threaded rod
Rod ends from HPI #85050: 32mm long, 15mm thread depth, accept 8-32 threaded rod

Traxxas #5347 HPI #85230 HPI #85050

**The rest of this write-up will be based on using the Traxxas #5347 rod end kit. If you use the HPI parts (or something else entirely), adjust your measurements accordingly (most of the necessary numbers for the HPI rod ends are in parentheses).**

Tubing and Threaded Rod: Other necessary materials for the links include two feet of 8-32 threaded rod (Home Depot) and a couple feet of 1/4" O.D. x 0.031" wall aluminum tubing (K&S brand is available at most hobby stores). If you use HPI #85230 rod ends, use 6-32 rod and 1/4" O.D. x 0.049" wall aluminum tubing.

Aluminum Tubing: Start by measuring the length of the rod ends from the center of the eye to the end where the threaded rod is inserted (or use the figures stated above). Multiply that by 2 (two rod ends per link) and subtract that from the total desired rear link length (148mm). The result is the length to which you need to cut the aluminum tubing (114mm for Traxxas #5347, 84mm for HPI #85050, 102mm for HPI #85230). Cut two lengths of aluminum tubing, preferrably with a tubing cutter, although careful use of a Dremel or hacksaw will also work. Clean up the ends of the tubing and set them aside.

Threaded Rod: Next, measure the depth of the hole inside the rod end where the threaded rod will be inserted (or use the figures above), multiply that by 2 (two rod ends per link), add that to the length of the aluminum tube you just cut, and then subtract 2mm to make sure the aluminum tube gets snug before the threaded rod bottoms out inside the rod ends. Cut two 134mm lengths of 8-32 threaded rod (112mm of 8-32 for HPI #85050, or XXXmm of 6-32 rod for HPI #85230).

Assembly: First, rotate one of the threaded rods into a rod end. Ideally you'll hold the threaded rod with pliers wrapped in a rag or something so as not to damage the threads on the rod, but only the threads at the ends of the rods will be used and the rest will be covered by the aluminum tubing, so feel free to use a pliers without protection. Sure is easier! Thread it in the rod until it gently bottoms out, then unscrew it one revolution. Next, slide a length of aluminum tubing onto the the rod and screw on the other rod end until the aluminum tubing is snug.

The Other Three Lower Links: Repeat the above procedure for the other lower rear link. For the front lower links do the same thing, but my goal there was 136mm from eye to eye, so the threaded rod should be 122mm long (100mm for HPI #85050 and XXXmm for HPI #85230) and the aluminum tube should be 102mm long (72mm for HPI #85050 and 90mm for HPI #85230). Assembly is the same as it was on the rear.

I've got some more Traxxas turnbuckles I'll be trying for the front, slightly shorter than the #5139 set I used in the rear. I'll post up some pics when I'm done.

Installation: The mounts at the axle are exactly the same as before, so they're easy (other than those infernal e-clips!). The mounts at the tranny need to be modified slightly, however. The plastic tube into which the screws fastened needs to be shortened because these rod ends and pivot balls are wider than the stock pieces. I simply cut them at the necked-down point on each end and used some M3 flat washers to fill the gap, placing the same number of washers at each link to retain the symmetry of the mounting system. Turn the screws in snug and you're done!

Upper Links

Disassembly: The attachment at the axle has already been disconnected, so you're ready to start working.

Link Length: Take a long (2" or more) 4-40 or M3 screw or threaded rod and slide it through the screw hole on the axle housing bracket and into the end of the upper link until it bottoms out, then back it off one full turn. Now pivot the axle housing on the lower link pins while sliding the upper mount hole along the screw or threaded rod until the axle is rotated to the pinion angle you desire. Measure the distance from the end of the plastic upper link to the bracket on the axle housing.

Tubing and Threaded Rod: Cut a length of aluminum tubing to the length measured above. The tubing you used for the lower links should work, but it is a bit oversize for this task. Consider buying a foot of 3/16" x (0.02" to 0.03") wall thickness aluminum tube for this application, but it's not necessary. For the record, the upper link tubing on my front end was 19mm long, my rear upper link tubing was 20mm long.

Installation:

If you're using a screw, simply put the tube into position, slide the screw through the bracket, through the tube, and into the upper arm, then tighten. If the screw bottoms out before the head seats on the axle bracket, thread a nut well onto the screw, cut an appropriate amount off the threaded end of the screw, and remove the nut and reinstall (removing the nut over the cut threads will help to clean them up).

If you're using threaded rod, do the same thing as with the screw but once it's in position, mark a spot on the rod about 3/8" past the bracket. Remove the rod, thread on two nuts, cut the rod to length, and turn the nuts off the rod to clean up the threads. Put the nuts back on the very end of the rod and tighten into each other so they're locked, then use them to turn the threaded rod into the end of the stock upper link. If the double-nut isn't at the correct final position just separate the nuts, turn one until it's holding the axle at the proper angle, and tighten the second one against it to lock them into position. Oh, and a little threadlock on the threaded rod wouldn't hurt.

Durability:
I'm finding that the longer the upper link, the looser and more flexible the assembly is. After doing the initial LWB project, I rotated the lower shock mounts for better ground clearance which moved the lower link mounting point closer to the center of the truck, which meant that if I wanted to keep the same lower links, the upper link would have to be lengthened. It got to a point where it there was just too much length there so it was more able to squirm around and get out of shape. A good option for the upper link is a pair of links like the lower link setup, mounted to the bracket on the axle housing. I haven't done this yet, but I likely will.

Driveshafts

Parts: The Wheely King uses sliding universals rather than dogbones or CVAs, so as long as you can find replacement sliders that are longer than needed and will connect to the tranny and diffs, you're set.

If you're a hard-core HPI fan, the HPI #82008 E-Savage driveshaft set will work, but I strongly recommend the Traxxas #4951X long halfshaft set for the T-Maxx. They're MUCH smoother than the E-Savage parts and don't get sticky at the limit of their sliding travel. Since they're sliding universals and made of plastic, we can just cut them down to the length we need. The ends that connect to the tranny and diff are different from the WK's, however, but we can simply remove the ends from the new sliders and put the WK ends on, using the Traxxas (or E-Savage) universal joints.

Universal Joint: The univeral joints from the T-Maxx and E-Savage are slightly larger than the original WK universal, but it works fine for the low-speed operations this truck will see. Simply (and gently) pry the flange off of the T-Maxx/E-Savage's universal pin while keeping the sliding portion of the shaft attached to each u-joint. After the first flange is off, the other comes off easily. Do the same for the original WK u-joints, keeping the joint attached to the sliding portion. Then carefully drill out the holes in the flanges to match the T-Maxx/E-Savage's universal pin and pop the WK ends onto the T-Maxx/E-Savage sliders.

Installation: With the WK upside-down, hold one half-slider assembly to the tranny and the other to the diff and put the sliding sections side-by-side to determine how much to shorten the sliders so they'll fit the WK. You don't need much sliding action due to the way the WK suspension works, but you do need some amount of engagement to spread the load. Keep as much engagement as you can while maintaining smooth movement and no bottoming. Repeat the procedure for the front, but keep in mind the overall length will be shorter. Then disconnect the upper suspension links and install the driveshafts, making sure they move freely. Reconnect the upper links and test the vehicle to make sure everything works properly and there's no binding.

Steering Link

Parts: Just some more 4-40 threaded rod to replace the stock linkage wire and another rod end, this time from HPI #85230.

Assembly: I cut my steering link's threaded rod to 120mm and it works great. Just turn the threaded rod into the stock rod end at the servo and use a small rod end from HPI #85230 for the axle end. Feel free to cover it with aluminum tubing if you wish, but it'd only be for looks, not for strength concerns.

To do a custom length for your truck (might be smart to measure, just in case), just center your steering servo, point your wheels straight ahead, and do like we did for the lower links:
1) measure from center-of-eye to center-of-eye of each rod end (where the screws go through)
2) measure the length of each rod end from the center-of-eye to the threading end
3) measure the thread depth of each rod end
4) Take the #1 measurement minus the #2 measurement of both rod ends plus the #3 measurement of both rod ends. Subtract 2mm from the total and cut the threaded rod to that length.

Trim the Body

Not difficult, but necessary if you want to take advantage of the extended wheelbase and impressive articulation. Essentially I just extended the top of the wheel opening to the rear, nearly to the corner of the body, then turned it down so it still kind of looked like a wheel opening. I also trimmed the lower half-inch all the way along the tailgate. See the before and after images below. Additional trimming might be advantageous depending on what wheels and tires you're using and how much articulation you have.

Feedback is always welcome, please click the "Contact Me!" link if you'd like to leave some.