4wd Corr/Pro-4 Truck REDESIGN POSTED 12/23/09
 

Just this past weekend I acquired a Stampede rolling chassis, but knew the 'Pede isn't for me, especially since the new rage is the Slash. I tend to not like conventional/stock things, though. Right away the thought of a 4wd Slash (non-Slayer) was running through my mind, since I have a Rustler I can steal stuff from. But even a simple 4wd Slash would be too easy considering I made a 4wd Stampede ("4x4 'Pede") several years ago.

Then I read about a member's dislike for the Slash's lack of solid-axle rear suspension. This led me to the ultimate RC Corr truck - a 4wd independent front and solid axle 4-link rear suspension truck. I've been working with solid axle/4-link suspension on crawlers for well over a year now so I have plenty of parts to work with and a pretty good understanding to go off of.

Right now I am stuck on what exactly to do with the rear - use a Wheely King or AX10 axle like you would normally see, or go with a Slash rear end, modified to have locked suspension arms and with an added 4-link? The former option would more than likely require a chassis-mounted motor/gearbox along with a motor in the front transmission. The latter option would decrease ground clearance and would probably increase complexity (because the Stampede/Rustler/Bandit/Slash tranny is not at all designed with 4-link suspension in mind).

What do you guys think?

Sounds very interesting. I've loved solid axle since my TXT1 but parts were too expensive back then . Though the motor/transmission would be a bit of an obstacle IMO. But hey we all know you always find a way to fit things no matter how hard it is :lol:

Hope to see more into this project :yes:

Something like a tamiya pajero/wrangler? Can't remember the chassis number, but it has independent front suspension, with a live axle rear and awd. Hopefully you can make it a bit simpler than that chassis...

How about a flat chassis with the rustler tranny in the center, with one output going to a real live axle, and the other output going to a front diff, like a crt.5, or touring car diff. Finding the correct diff to match the rear gearing may be fun...

Use rpm rustler rear arms and traxxas rustler sliders all around, with the rpm bearing carries and hubs. That way you can run 12mm hexes and 2.2 wheels/tires.

You could raise the center tranny up for more clearance if you like. Not sure what to use for center drives...

A buggy front end, centre diff and motor mount and a solid rear axle would be sweet. I would use the strongest axle you can find that is closes to the width of the buggy front end. I'm not much of a fan of dual motor set ups. Dual motors could give some interesting power delivery though.

Different diff ratios front and rear would make for some interesting torque split options front to rear. It would make the centre diff work hard but it would be interesting especially if you could change the ratios easily.

A std buggy front end and a narrowed xtm x-factor rear axle would be the ticket. Both use 13/43 gear sets, and plenty of people have narrowed the xtm axle.

Unfortunately the X-Factor parts are discontinued and difficult to obtain even for a guy like me who works at Hobby People... Not to mention I've heard of differential problems with the stock nitro motor.

But even then the X-Factor axle would be difficult to narrow without sacrificing a lot of strength, and with the use of a 1/8 buggy front end the whole truck would be quite a bit heavier than what I'm shooting for.

You guys are providing great ideas, and have made me think more about this. Previously I had not considered the front/rear differential ratio issue. Here's another idea - Wheely King or Axial rear axle, and MT2 front end. This setup can be made to take a lot of abuse, is much closer to the weight I am shooting for, and the front/rear end would have the same differential ratio.

Thoughts?

Sounds good, both have the same diff ratio? Whatcha think about my pede tranny in the center idea?

I have built a few crawlers that use the pede tranny for the center trans. Question is, do you know where to scare up a locker for the pede diff? I once saw one on ebay that had a solid center shaft that connected to a piece of al that replace the cover of the diff. It eliminated the spider gears and outputs. Wish I could find that item agin, my slash has terrible diffing out problems.

I like the idea of the stampede tranny, How about a goliath axle case? you should be able to use TC3 diffs and use a TC3 front case

Buggy front end , Axial rear with 4 link and SS or any aftermarket lockers , straight axle conversion and go with a Ae stealth tranny .

The Wheely King and AX10 use the same differential gear ratio as the MT2, 38/13. And now that I think about it, I could unbuild my not-quite-so-successful "direct-drive to diff" MT2 18SS for its front end and hardened differential gears.

As for the Stampede tranny idea, it'd work if I were planning something more conventional... Which just isn't me. When I can help it I don't use transmissions for 4wd (of all my 4wd vehicles my Dark Impact has the closest thing resembling a transmission).
But if I were to use one and lock the diff, I'd go straight for JB Weld. One time I locked a 'Pede diff using JB Weld and left a little grease in there. When I went to remove the JB Weld "locker" it pulled right out, thanks to the grease.

On the topic of what will go on the center, what are your guys' thoughts on direct-drive to diff? I ran the numbers and it looks like a 2826/05 (900 kv) would work almost perfectly with 4s2p A123, giving a top speed of 40-45mph. This would be super lightweight, with great overall efficiency (which as we all know means longer runtimes).

I haven't looked into the Goliath axle, do you have any specs on it? But to me it seems like plastic TC3 diff gears might not hold up to the abuse of almost 4.5" tall tires.

Buggy front end, as in 1/8 buggy? If I went that route the front end would be under-driven which wouldn't be easy on the front or rear end (3.31:1 vs. 3.92:1). The AX10 axle in the rear is currently a possibility, depending on its track width, since I want to match the Slash's track width to fit the Slash body (actually the Proline Hardcorr). I commented on the center tranny idea above.

The MT2 front end option is becoming more viable... Turns out the track width of the MT2 front end is almost EXACTLY the same as that of the Slash's. If anything it's no more than about 1/8" narrower than the Slash. PERFECT.

Onto the rear solid axle: The AX10 axle is WAY to narrow, it needs to be about 2 1/4" wider. I'm gonna find out the comparable width of the Wheely King axle soon.

I really like this idea. I have a fondness for scale type builds. Have you ever poked around on scale4x4rc? There are lots of good builds there on prerunner type trucks, with live rear on 4 links, and IFS.

I have this tamiya cc-01 touareg that I have modded pretty heavily. I've had thoughts of building a 4wd corr truck using that and 1/8 buggy front end. Again, the diff ratio's are what always held me off....

Sounds awesome :). I'll keep an eye on this one...

Actually I have never been on Scale4x4RC. When I get some more time I'll see what the members there have done.

The Wheely King axle is about 3in. narrower than the Slash rear end. There are some axle widener things for the WK that I will check out when I go into work tomorrow.

Since you're solid in the rear, and IFS up front, you could also probably use 1/2" offset rims in the back, and no offset up front. That'll get you an inch closer....

It's a possiblity, but it wouldn't quite fit the Slash/Hardcorr bodies properly IMO.

Yeah, i guess you're wanting to use the narrow rims. I would too...

Sounds like this is gonna be a sweet project! Best of luck with it MetalMan, I'll be watching for sure. IFS with a solid rear axle is always very cool on scale trucks IMO. I'd cetainly go for a single purpose-built axle in the rear, for durability and realism over a more complex and possibly-fragile conversion of the Slash gearbox/suspension.

Incidentally, have you ever seen Thorbob's 4WD CORR-ish truck that he built a few years ago? It's an awesome truck that also used IFS and a solid rear, so you might find it useful: http://www.thorbob.com/baja_project_intro.htm. :smile:

I had seen Thorbob's custom baja truck, although I failed to remember about it until you reminded me :whistle:. He's got more resources than I do, and apparently more motivation as well. His truck is of a different level than mine, as his probably weighs at least 16lbs. I'm shooting for ~6lbs with mine... Although I thank you for the link, it has definitely helped with some ideas.

so waht happened metal man? you still gunna do this project? really seems cool!

This project is still on, just been waiting for the time. Truckbasher's E-Revo outrunner project comes first, although I have put a lot of thought into the Corr truck while at work. For example, last Saturday while I was at work (the LHS) a customer came in, got some parts, pointed at one of the images of a CORR truck on a Slayer box, and said he had that truck outside. :surprised:
It was Scott Douglas's truck, straight from being repaired after his recent bad crash.

The guy gave us a nice tour of it, so I got some pictures :party:.
http://img.photobucket.com/albums/v1...1018081727.jpg
Front suspension/driveshaft:
http://img.photobucket.com/albums/v1...018081727a.jpg
Rear suspension:
http://img.photobucket.com/albums/v1...1018081728.jpg
http://img.photobucket.com/albums/v1...018081728a.jpg
http://img.photobucket.com/albums/v1...018081728b.jpg

The rear suspension was definitely the most interesting part of this truck to me :whistle:. They designed it unlike other suspension setups out there, with parallel upper links mounted next to the shocks on the axle housing, and chassis-triangulated lower links. From what the technician guy said this suspension setup drastically reduces or eliminates the axle steer typical 4-link setups have when the axle articulates. And it's just as effective as a normal 4-link.

That does mean I will be trying to imitate this suspension design on my CORR truck project :yipi:. Before I build it though, I will have to play around with the geometry.

oooh! thats nice! cool just glad to here that its still going! cant wait to see pictures of it.

Thats one sweet truck...

Man, if you can copy that suspension then it will be one heck of a scaled CORR truck....

Me thinks you need to look at this thread.

http://radiocontrolzone.com/showthread.php?t=167129

Nice find but DaggerTrasher did post the main site of Thor Bob same project

http://www.thorbob.com/baja_project_intro.htm

aw crp,
I really should read the entire thread. :lol:

Thorbob is definitely an inspiration for my truck, but his is nitro... Imagine if he'd made it electric.

A company did make a copy of his design and made it electric.
It was nowhere near as good and died out.

Despite what it may look like, this project has been more alive than ever. I've been putting lots of time into it (too much!) just about every day, just wish the results were more indicative...

So far I have the MT2 front end built-up, the front (independent suspension) portion of the chassis is near completion, the upper deck for the front is being worked out, the Wheely King axle has been widened and has custom c-clamps to hold the shocks and upper/lower links, the link lengths have been determined, and I have come up with a viable suspension geometry (after much playing around with various mounting positions). Here are side views of the 4-link geometry:

Fully extended/uncompressed:
http://img.photobucket.com/albums/v1...nkextended.jpg

Compressed/maximum travel:
http://img.photobucket.com/albums/v1...compressed.jpg

And a comparison of the two:
http://img.photobucket.com/albums/v1...4-linkboth.jpg

The rectangle to the left of the links represents the c-clamp, and where two lines cross that represents a hole on the c-clamp where something can be mounted. The very middle of that c-clamp is in line with the center of the axle. The most-vertical member is the shock.
When I came up with this geometry, I was trying to keep a good pinion angle, as this will be very important. Another important factor was the change in wheelbase that occurs as the suspension cycles. This geometry causes the wheelbase to change only 0.05" from fully extended to fully compressed. Overall wheel travel is about 2 inches.

This truck will use an outrunner in direct-drive-to-diff fashion, and is a KMS 2826-06 (730 kv), a cheaper version of the Axi 2826-12. I bought the Axi "Cooler" fan for the motor to potentially reduce temps. The ESC will be a MM (on its way to me from CC), and for batteries I will run 3s at the track for ~35mph top speed and 4s for about 45mph when this truck is in Slayer-killer mode :yes:.

this project looks awesome!
looking forward to seeing more pics.

I have a question.

http://i87.photobucket.com/albums/k1...compressed.jpg

the parts circled in blue....how far apart are they in the 3rd dimension

not sure if the way I'm asking is making any sense....

what I mean is... I know they all cant be on top of each other, and im wondering if using different angles offsets the .05" you got out of the 2d geometry.
....just curious....I have never done a project like this and it got me thinking.

in any case. great looking idea!

In 3-D the upper links are about 2.75in. apart from each other, and the lower links are about 1/2in. apart at the blue circles. These angles do affect the lengths of the links (for example it makes the lower links seem shorter and I had to account for this in the above pictures), but the angles have more to do with what happens as the axle articulates.

That 0.05in. in wheelbase change is very minimal, and I'm not worried about it for now. If I did want to correct it, however, it would require quite a bit of trial and error in working with the length of the links and their positioning on the chassis. The current suspension geometry took me about an hour to come up with, and that was with fixed upper and lower link lengths!

And BTW, this is more than an idea :wink:. Thanks for the compliments.

Success! I maidened the truck today: first impression was that this motor is very loud! The tones it emits due to the ESC attracted quite some attention, but once rolling smoothly this truck is rather quiet.

Specifications:
-entire polycarbonate chassis, heated and bent with a propane torch. The two side plates were made together to ensure exact precision.
-HPI MT2 18SS front end with aluminum differential housing, aluminum knuckles, carbon fiber shock tower, and GS Storm 1/8 buggy front shocks
-HPI Wheely King rear axle with RC4WD straight-axle adapters, custom c-clamps for mounting of the 4-link suspension, STRC widener kit, and Ofna Super Shocks
-front body mount was cut from 3/8" thick polycarbonate and the posts are cut-down Slash front body posts
-rear body posts are for the Duratrax Nitro Quake
-the FLM aluminum bellcrank for the Rustler was fitted, along with 5x8mm bearings
-Airtronics 357 servo and Kimbrough Gas Truck servo saver
-any colored standoff/post on this truck was made by Axial (these things are awesome!)
-clear standoffs/posts are 1/8" ID and 3/8" OD polycarbonate tube tapped to 4mm
-front bumper mount is an aftermarket piece made to allow the MT2 to accept a Revo bumper, so I fitted a Slayer bumper which required minimal spacing
-the rear bumper is from a Slash, but the bottom mount was bent with a propane torch and the top mount was flipped
-lower links are T-Maxx or Revo steel steering turnbuckles, upper links are Revo steel pushrods
-the driveshafts are cut-down Maxx driveshafts
-Slash nerf bars
-STRC 14mm hex conversion for the Rustler/Stampede, with the wider hexes in the rear
-Slayer wheels/tires all around
-Proline Hardcorr body
-MM ESC straight from CC with CCBEC
-initially using 2x 3s 2100mah Impulse 16C packs in parallel
-2x Neu 4s 2100mah 30C packs just came in, and those will be in parallel for 4s 4200mah 30C

If I missed anything, just ask :angel:.

This truck has interesting handling thus far - the rear shock oil (45wt) is too thick, and the rear needs a sway bar BADLY. Right now when I pitch the truck the chassis leans, and leans for too long after pointing the truck in a straight line. This is no doubt the result of the shock oil not allowing for a quick enough weight transfer, and will be fixed. In the soon-to-come pictures you will notice the torn up overspray film on the body, please ignore that :whistle:. And now, for the build pictures:

http://img.photobucket.com/albums/v1...k/IMG_7861.jpg
http://img.photobucket.com/albums/v1...k/IMG_7864.jpg
http://img.photobucket.com/albums/v1...k/IMG_7865.jpg
(Note that these are older)

http://img.photobucket.com/albums/v1...k/IMG_7873.jpg
http://img.photobucket.com/albums/v1...k/IMG_7877.jpg
http://img.photobucket.com/albums/v1...k/IMG_7880.jpg
http://img.photobucket.com/albums/v1...k/IMG_7883.jpg
http://img.photobucket.com/albums/v1...k/IMG_7872.jpg
http://img.photobucket.com/albums/v1...k/IMG_7886.jpg

http://img.photobucket.com/albums/v1...k/IMG_7892.jpg
http://img.photobucket.com/albums/v1...k/IMG_7896.jpg
http://img.photobucket.com/albums/v1...k/IMG_7898.jpg
http://img.photobucket.com/albums/v1...k/IMG_7901.jpg
http://img.photobucket.com/albums/v1...k/IMG_7905.jpg
http://img.photobucket.com/albums/v1...k/IMG_7902.jpg
http://img.photobucket.com/albums/v1...k/IMG_7910.jpg
http://img.photobucket.com/albums/v1...k/IMG_7913.jpg

Quick comparison of the width between front and rear (almost exactly the same):
http://img.photobucket.com/albums/v1...k/IMG_7914.jpg

http://img.photobucket.com/albums/v1...k/IMG_7921.jpg

With 2x Impulse 3s 2100mah in parallel:
http://img.photobucket.com/albums/v1...k/IMG_7919.jpg
http://img.photobucket.com/albums/v1...k/IMG_7923.jpg

http://img.photobucket.com/albums/v1...k/IMG_7926.jpg
http://img.photobucket.com/albums/v1...k/IMG_7927.jpg
http://img.photobucket.com/albums/v1...k/IMG_7929.jpg

2x Neu 4s 2100mah 30C to be in parallel:
http://img.photobucket.com/albums/v1...k/IMG_7933.jpg
http://img.photobucket.com/albums/v1...k/IMG_7940.jpg

Underside!
http://img.photobucket.com/albums/v1...k/IMG_7932.jpg

Proline Hardcorr (to be painted):
http://img.photobucket.com/albums/v1...k/IMG_7942.jpg
http://img.photobucket.com/albums/v1...k/IMG_7946.jpg
http://img.photobucket.com/albums/v1...k/IMG_7948.jpg
http://img.photobucket.com/albums/v1...k/IMG_7949.jpg
http://img.photobucket.com/albums/v1...k/IMG_7953.jpg

The rear suspension looks almost the same as the real thing :yes:...

even got the fan :lol:

Travis, truly a masterpiece....hope to see the video...

Still need to make the rear sway bar, figure out how to keep the batteries from sliding forward/backward, work on ESC settings, paint the body, tweak the suspension, wire up the two fans on the body (both were pulled from MMMs BTW), and some other minor stuff. Just FYI, anything which on this truck is merely a film covering up clear polycarbonate. It WILL come off - in time. I just want to keep this truck as scratch-free as possible :no:. Advice, comments, whatever is appreciated!

Had to have the fans! Video will come when I get the truck more worked out. Thanks!

nice man!!! cant wait for the vid!!

:surprised: Masterpiece is right :surprised: That thing turned out amazing!