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Old 09-24-2014, 07:06 PM   #1
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Default Bringing back the dead (ish) Crawler King

I thought I'd do something like a build thread for my new HPI WK. Except..that its NOT new at all. In fact its well used and abused. Oh, and I know NOTHING about modding RC crawlers. I do have a little mechanical aptitude, so I'll hopefully learn by trying.

Anyway, in my excitement to pick up a crawler, I traded a really nice lipo powered buggy for what turned out to be this heap of a crawler. It was covered in mud, ran (sort of), but wouldn't steer (at all). It came with two extra axles, one having been modified with an offset over axle servo mount made out of something like aluminum foil. I spent the first evening swapping out the axle bits to get the servo on the front axle.



Rear axle wasn't straight..used a bit of plastic from one to lock it mostly straight.



With that done, it would sort of turn right, but not so much left. Could be that its a craptastic servo or that I have to get the arm just right to make it work. Could be that the arm is plastic and flexing. Could be the crappy tinfoil mount flexing around...or it could be all of it contributing equally.



Either way, it moves under its own power now. Mostly just turns right, and falls over at the slightest hint of an incline or off camber slope. That will have to be addressed. SO top heavy. Battery box seems in a terrible location for COG. I'll try to get it on the front or rear axle I suppose.

Either way, its a shameful climber. Both axles have been locked up and the motor doesn't have enough going for it to get it up some of the stacked stone piles I have wen I approach it at an angle. If I approach anything straight on it just flips over backwards. A bit of an angle at speed, and I can sort of get up a few things. Only room for improvement here, but I'm still excited to have this antiquated beast of a crawler.

Feel free to offer constructive advice or humorous comments. Do keep it light and if you see I've made a huge mistake - go easy on me. First crawler with mods!

Oh yes..the 10 year old nicknamed it the "Crappy Crawler"...I thought about arguing..but it kinda fits the bill.

Last edited by Snarf77; 09-25-2014 at 10:33 AM.
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Old 09-25-2014, 02:29 PM   #2
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Default Re: Bringing back the dead (ish) Crawler King

I got to work on this thing and immediately decided the vertical shocks on this beast looked nothing like the shocks you’d see on a “good” crawler. SO…I chopped off the mounts and reduced the size of the frame in the back. Cut off this bit, basically the last 20% of the frame that seems useless anyway.



This of course, made the frame wobbly, having just lost some structure. I used the rear bumper/crossmember, shaved it down with a hobby knife, and used it as the new rear crossmember and shock mount.



Well..the lower shock angle pushed the rear axle/pinion angle way out of alignment. I moved the lower links and shocks on the axle to about correct levels..but that pushed the axle out from the upper wishbone about ¼ inch. I remedied that with some spacers cut from the old rear steering linkage ends, and of course, a longer screw from the old scrap screw box. It brought the angles back to about as good as they were.



I moved the shocks to the screw holes with the crossmember I made, added some spaces to move them away from the frame and got her going. Result..lower rear ride height, slightly longer wheelbase..and plenty of flex. Not more than I had, but definitely not less. I also used a black zip tie to pre-load the springs a bit more as they had a tendency to fall off when flexing or bouncing. New shock oil definitely in my future.

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Old 09-25-2014, 07:01 PM   #3
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Default Re: Bringing back the dead (ish) Crawler King

Nothing wrong with a Ck/Wk as a crawler. Tires and foams play a huge role in how the truck does on the rocks. As you have noticed the cg is really high on these trucks and the gearing is to tall. I like 96\14 gearing on a otherwise stock truck. Scx10 gear sets fit in the axles. I have home built 6 different chassis so far. Best mod is a new chassis in my opinion. With a new chassis you can correct the link geometry and mount your battery much lower. Not to thread jack but...
Here is what I did with 4 Wk axles...


Extradition
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Old 09-25-2014, 08:10 PM   #4
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Default Re: Bringing back the dead (ish) Crawler King

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Originally Posted by lonleycreeper View Post
Nothing wrong with a Ck/Wk as a crawler. Tires and foams play a huge role in how the truck does on the rocks. As you have noticed the cg is really high on these trucks and the gearing is to tall. I like 96\14 gearing on a otherwise stock truck.
The CG is super high...it wasn't helping with the huge NIMH battery that was sitting in that thing. I read in another thread about the 96/14 and want to go that way. Where can I get a 96 tooth spur? I searched on fleabay and found two..but not sure how to tell if they will fit. There is a robinson racing one, but its "half thickness" to reduce friction. Seems like I'd want more pinion/spur contact for longer life. THe other is a Kimbrough products spur...not much more said about it. Other options? Recommendations?

Your ride looks amazing. I'm not there yet. Still modding this chassis as I learn how it works and how changes affect off-road ability.
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Old 09-25-2014, 08:27 PM   #5
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Default Re: Bringing back the dead (ish) Crawler King

So I got into some more frame chopping and realignment of suspension. Lost the other end of the frame.



Battery box had to go once that was out so I had room for electronics and whatnot.



I reused the crossmember that mounts the on/off switch (why not..its convenient) to stiffen her back up a bit. Spaced out the reach shocks from the body and mounted at a slight angle. The frame isn't symmetrical so the front shocks are more vertical than the rear....anyway, the electronics are nice and compact now.



Crappy Crawler Version 2.0!



It actually wheels about 10 times better. I seriously think it was that huge brick of a NIMH mounted up so high in the chassis. Losing that helped. It now will stand mostly vertical without tipping.
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Old 09-25-2014, 08:34 PM   #6
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Default Re: Bringing back the dead (ish) Crawler King

I did mount a small 2S lipo on the front above the servo. Temporary until I fab a better plate, but it works well enough and doesn't fall off. The battery doesn't contact the springs under any amount of articulation. Keeps some weight low and forward too.



She now drives worlds better with the COG a bit lower. The lipo, though small, livened up the driving a bit too. It still likes to stall if you squish a tire into a rock. This 55t motor is at the end of its days, but no upgrades for now.

Flexes out pretty well:





Oh yeah, then I found the perfect body for it. Totally scale.

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Old 09-25-2014, 09:23 PM   #7
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Default Re: Bringing back the dead (ish) Crawler King

Haha now we are talking!
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Old 09-26-2014, 02:57 PM   #8
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Default Re: Bringing back the dead (ish) Crawler King

I added the gear reduction unit. The thing is now INCREDIBLY slow..scary slow. But, it will crawl up anything. Mine is performing much better. crawling up this vertical stacked rock wall about as tall as the CK that used to laugh at it before i moved everything around. This climbing is at full throttle in the video!

Link to video (couldn't figure out how to embed) : https://flic.kr/p/pps1TG

Either way, can't keep the GRU unless I get a much lower turn motor I suppose.
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Old 09-26-2014, 03:16 PM   #9
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Default Re: Bringing back the dead (ish) Crawler King

Should my driveshaft look like this? Doesn't seem to work as well this way.



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Old 09-26-2014, 07:00 PM   #10
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Default Re: Bringing back the dead (ish) Crawler King

No slipper?
Looks like it is time for upgrades.
One option is to run Mip's, then you will find the next weak link. Either axle shafts or the plastic gears in the gearbox. Or install a slipper unit, should be a sticky at the top of the page. Or best bet is swap out the transmission. Mine currently is running the hpi gru, coupled to a axial transmission used as a transfercase.
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Old 09-29-2014, 09:47 AM   #11
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Default Re: Bringing back the dead (ish) Crawler King

Quote:
Originally Posted by lonleycreeper View Post
No slipper?
Looks like it is time for upgrades.
One option is to run Mip's, then you will find the next weak link. Either axle shafts or the plastic gears in the gearbox. Or install a slipper unit, should be a sticky at the top of the page. Or best bet is swap out the transmission. Mine currently is running the hpi gru, coupled to a axial transmission used as a transfercase.
I did some reading here on the forums and actually went with the el-cheapo traxxas max driveshaft. Less than $10 shipped and apparently strong as can be. Just cut to length.

I did some mental match and to get the WK right for actual use would cost mroe than an already made capable crawler. So..cheapo driveshaft, then removal of GRU and a 35 T motor instead. Just experimenting to see how she goes.
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Old 09-29-2014, 12:11 PM   #12
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Default Re: Bringing back the dead (ish) Crawler King

WK's have an internal clutch. that snapping sound you hear when it's bound up in the rocks is the clutch working. hopefully the previous owner didn't lock it up, it should be clicking before the emaxx shaft lets go, the stock shafts get very weak after a while.
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Old 09-29-2014, 03:36 PM   #13
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Default Re: Bringing back the dead (ish) Crawler King

I've heard the clicking..wasn't sure what was making the noise. I honestly thought it was the servo breaking or maybe the pinion stripping the spur.
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Old 09-30-2014, 09:20 AM   #14
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Default Re: Bringing back the dead (ish) Crawler King

I bought a 35T motor and a novak rooster ESC to go in her. I'm thinking about building a chassis for her of my own design. It won't be as cool as the ones people have posted up, but it would be a good learning experience I think. So the question is - should i first work with aluminum (and how thick) or delrin or cutting board (again--how thick) as some folks have done up. I don't have access to any nice shop tools - it will all have to be hand done with drill, jigsaw, and dremel.
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Old 09-30-2014, 06:50 PM   #15
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Default Re: Bringing back the dead (ish) Crawler King

I've made a couple out of 3/16"cutting board material. you just have to keep the rails a little more narrow than the width of an axial frame, so you can mount the shocks. the cutting boards are about $2 ea at walmart, so you can buy two, and cut both framerails at the same time so they match.
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Old 09-30-2014, 11:06 PM   #16
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Default Re: Bringing back the dead (ish) Crawler King

X2 on the cutting board.
Depending on the type of chassis you can use aluminum in the 1\8" flavor.
With cross bracing it is very strong. My 6x6 uses 1\8" aluminum, my 2nd and 3rd chassis were pure Walmart cutting board, my 1st was aluminum angle. Also built scale chassis out of 1/2" steel square tubing.
You can buy the 1\8" aluminum @lowes to $10 or so and a 4ft long sq tube for $4 or so. The steel is cheaper and stronger, but harder to work with.
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Old 10-01-2014, 06:52 AM   #17
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Default Re: Bringing back the dead (ish) Crawler King

Quote:
Originally Posted by makya View Post
you just have to keep the rails a little more narrow than the width of an axial frame, so you can mount the shocks.
I think i'll try the cutting board approach - $2 seems good. I'm a bit confused here though. How does the width preclude shock mounting. For instance, If I made the frame a bit wider, couldn't I just mount the shocks inboard of the frame? Not that its the best idea..I just want to understand why I have to limit the width.
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Old 10-01-2014, 04:44 PM   #18
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Default Re: Bringing back the dead (ish) Crawler King

I have had zero success with in board shocks.
Just saying. Anyhoo you need to keep the frame width narrow enough to mount the shocks on the out side and still clear the springs. There are a couple of options, first keep the frame straight front to rear, or bow it out in the center and keep it narrow on the ends.
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Old 10-02-2014, 07:23 AM   #19
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Default Re: Bringing back the dead (ish) Crawler King

Quote:
Originally Posted by lonleycreeper View Post
I have had zero success with in board shocks.
Just saying. Anyhoo you need to keep the frame width narrow enough to mount the shocks on the out side and still clear the springs. There are a couple of options, first keep the frame straight front to rear, or bow it out in the center and keep it narrow on the ends.

Ok - I have a vision of a chassis in my head that might work for me. I'll have to get the rule out to see if things will stick out the sides of the chassis though. I'm going to have to get better at making spacers with all thread as I'm sure the design will have to change regularly to figure out what will work for me. I've decided I want to make a reliable basher/crawler with relatively low COG, but larger tires. A crawler the kids can also play with, without destroying it.

I think the Level3 low COG motor mount will be necessary though. I can't build that myself really. I'll pick up some parts this weekend and start designing something.

Last edited by Snarf77; 10-02-2014 at 07:34 AM.
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Old 10-02-2014, 06:06 PM   #20
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Default Re: Bringing back the dead (ish) Crawler King

Check out R2 trans in a crawler king. I've had some fun with it and it works well.
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