Four Wheel Steering, Skid Plate and Locked Differentials
Mr. UPS delivered lots of neat stuff.
A New Era center skid.
A Cirrus Y-Harness with Servo Reverser (04581).
And a pair of Hitec 945 steering servos.
My goal here is to create a dedicated rock crawler. So I'm converting the truck to Four Wheel Steering (4WS), locking the differentials and adding a skid plate to protect the transmission. Here's all the new stuff I got including a New Era center skid, a Cirrus Reversing Y-Harness, a pair of Hitec 945 steering servos and a tube of Household Goop to lock my diffs.
Fist I wanted to tackle the diffs. I was trying to remove as few links as possible. Here's what I ended up with. Looks like the truck was run over by a train. After I had the diffs apart, I cleaned out the grease and filled them with Goop.
This pic shows the brackets in place for the New Era center skid.
This pic shows the skid itself in place (using plenty of loctite, of course).
Here's a pic of the Cirrus Reversing Y-Harness. It's the little black thing between the receiver and ESC. I used the Reversing Y-Harness in place of a straight Y-Harness and the complicated rear steering servo bracket suggested in the Tamiya TXT-1 manual. In other words, my rear steering servo is connected to the rear under guard using the same simple bracket arrangement used with the front steering servo. Then the Cirrus Reversing Y-Harness is used to operate the rear servo in the opposite direction from the front. By the way, instructions for the Cirrus Reversing Y-Harness are nonexistent.
And finally, a pic of the truck in its new 4X4X4 mode.
Well, I hit a few bumps in the road. First, I ordered the servos with the J connectors. These are not compatible with the Cirrus Y-Harness connectors. But I was able to trim the J connector with a knife and got it to fit without much hassle. Also, I'm not sure I hooked up the Y-Harness correctly because everything ran backwards. I thought that the non-adjustable output was the non-reversing output so I ran it to the front servo. I thought that the adjustable output was the reversing output so I ran it to the rear servo. But then it all steered the wrong way. As I mentioned above, there are no instructions with this thing. But the problem was no big deal. I just flipped the steering reversing switch on my radio and it all worked fine.
Then I stripped the front steering servo saver because I used the wrong part. Then I stripped out all the Household Goop that I was trying to lock my diffs with. Then I stripped the rear steering servo saver because, again, I used the wrong part. Grrrrrr!!!!
Didn't even get a chance to scratch the new center skid. Time to the get after those diffs with some J-B Weld. No more screwing around.
I fixed up the stock servo savers with the right parts so at least the truck runs now. But now the diffs are diffing without grease. That's probably not good. I like the 4WS, but it's going to take some getting used to. Going forward or backward, the trailing wheels seem to steer harder than the leading wheels. So it's like driving a forklift. But the 4WS makes a huge difference. I was having hill climbing problems with just the 2WS because as soon as I would veer off the vertical ascent line, the nose would slide off to the side and I'd end up heading back down the hill to try again. The 4WS takes advantage of the rear wheel's greater traction and kicks the ass-end around to point the truck in what ever direction I command. Once I get power to all four wheels I'll be invincible!
I tore down my diffs again. What a mess. The Goop cured to a rubber cement consistency. I didn't use enough Goop to lock the diffs, but there's enough so that all the parts are coated. I'll have a few more hours of picking and scraping before I'm ready to try the J-B Weld.
Took my first test drive today with my J-B Weld locked diffs. Interesting. The steering is quite wiggy. The inside wheels have little grip when turning so the truck seems to turn even tighter. Controlling this beast is going to take some getting used to. But oh when all four wheels dig into a steep hill... the truck will flip itself on its lid before it gives up. Cool!
Update, Summer 2003: Jeff's TXT-1 versus West Virginia
This was the first real test of my TXT. Had lots of mountain trail rock crawling fun. Check out the pics on my TXT-1 Gallery page.
I wasn't entirely satisfied with my four wheel steering set up. Regardless if I'm going backward or forward, the trailing wheels are substantially more responsive to steering commands. I guess the motion of the truck somehow gives the trailing wheels a mechanical advantage. Anyway, when I quickly turn from left to right or right to left, I get a momentary "crabbing" effect until the leading wheels catch up with the trailing wheels. It's a little unpredictable because the truck momentarily goes sideways before it begins to change direction. I'm running a pair of hitec 945s. Not the most powerful servos you can buy, but near the top and not cheap! My J-B Welded diffs aren't helping, but I like the extra traction. I don't think I want to spend even more money on another set of better servos. Or perhaps I just need stiffer servo savers. I'm still using the ones that came with the truck. Perhaps I'll buy a pair of the Kimbough #124 Servo Savers.
The plastic front axle guard distorted where the one bottom link connects. I'll be buying some aluminum axle guard replacements.
All the set screws on the drive shaft universals loosened up even though I loctited them. Fortunately one of the drive shafts popped out so I noticed the problem before I lost any screws.
Finally, I'm going to try rewiring the motors in series. The stock motors drive the truck at about a running pace. But all I need is a walking pace and I'd rather have the greater torque and longer run time.
Stay tuned for more mods and testing...
TXT-1 Mods: Part 2