2021 - Traxxas Slayer

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Whew, it's been a long time since I wrote a Build Complete thread. I've barely had time to think for the past year, much less play with my toys.

About a year ago, I decided I wanted to build a nitro short-course truck. But I've become spoiled and lazy Traxxas nitro RCs that have reverse gears -- and electric RCs that can reverse without even needing reverse gears -- so I wanted my nitro SCT to have a reverse gear too. That certainly narrowed-down the selection a lot.

In fact, it narrowed-down the selection to...nothing. There are no nitro SCTs with reverse gears. Buuuuut, the Traxxas Slayer shares a lot of parts in common with the Traxxas Revo, so maybe I could drop a Revo transmission into a Slayer and get what I want?

Well...technically yes, but of course the devil was in the details. Since the Slayer doesn't have a reverse gear, it doesn't need a shifter servo, so it uses different electronics boxes than the Revo, and of course they were different enough that the side-bumpers on the Slayer don't fit the Revo's electronics boxes -- at least not without cutting the Slayer's side-bumpers to fit. (I could've gotten rid of the side-bumpers, but one good cartwheel would've mangled the SCT body shell without some kind of side support.)

Also the Revo and Slayer both have the weirdest throttle linkage setup I've ever seen, with the return spring on the outside of the electronics box instead of integrated into the servo linkage itself, so I cleaned that up too.

Oh, and then there was the elephant in the room -- the Slayer's oversized chassis that doesn't fit any aftermarket body shells. The "old" Slayer had a shorter chassis plate with the correct wheelbase, but the trackwidth was still too wide; fortunately I was able to cut-down the ends of the suspension arms by 9mm apiece, narrowing the trackwidth enough to clear a standard SCT body when running Pro-Line "ProTrac" narrow-offset wheels, without the wheels scrubbing on the suspension linkages at full steering lock.

Speaking of the suspension linkages, I fiddled with the lengths of those linkages to adjust the truck's maximum ground clearance, and eventually settled on a single set of 3mm spacers installed on the linkages (whereas the Revo has two sets of 3mm spacers installed), for the best compromise between ground-clearance in grass vs. stability when cornering.

In the picture above, you can see I'm still running the stock plastic driveshafts and wheel hubs; normally I would've upgraded those to MIP X-CVDs and Team STRC aluminum hubs, but the Slayer is already heavy due to the large complex transmission in the center and the extra servos off to the sides, making this an SCT that weighs as much as some monster trucks. So I opted to save a little weight and run the stock axles and hubs. I can always upgrade them later if I need to, but for now they work fine, even with the upgraded engine I had to install to haul this pig around in the grass:

You might be thinking this is not an upgraded engine, because it displaces only 3cc compared to the 3.3cc that the stock TRX3.3 engine displaces. But it definitely is an upgrade, not just in quality but also in power. OS doesn't need me to sing their praises, but I'll do it anyway: the 18TM is a significantly more powerful engine than the TRX3.3, especially when paired with the optional single-chamber exhaust pipe that pushes the horsepower peak lower-down in the RPM range where it's actually useful when driving in grass. I suppose the 21TM would've been an even better upgrade, but it also would've been louder and thirstier.

Oh, and that's not the original pullstarter. The 18TM is designed to use a Traxxas pullstarter, but I didn't like it, so I took a gamble and tried a backplate and pullstarter for an OS 12TG, and sure enough they fit! Of course those parts are discontinued, because why wouldn't they be? Hopefully it won't break any time soon. Not sure why OS never made their own pullstarter for this specific engine, but at least I was able to find one that fit, which is genuinely remarkable when trying to interchange OS engine parts.

So anyway, that's my Traxxas Slayer -- chopped down to a normal SCT size so it can keep my Slash company.

I just realized I never posted my solution for fitting normal SCT wheels to the Slayer. The Slayer comes with 14mm hexes designed for 6mm axles, but normal SCT wheels are designed for 12mm hexes and 5mm axles. Drilling-out the centers of the wheels by 1mm to fit the larger axles solves part of the problem, but getting hexes required digging around in Traxxas' parts bin.

The XO-1 touring car uses standard 12mm hexes that fit 6mm axles, but the included screw-pins are a little too narrow. Fortunately I had some 2mm screw-pins with 2.5mm heads hiding in my spare-screws jar, and I was able to use those in place of the screw-pins that came with the XO-1 hexes. If I hadn't been able to find any screw-pins that fit, I suppose I could've re-tapped the screw-holes in the hexes to fit 3mm heads, but that turned out to not be necessary.

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