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MacMan
02-03-2004, 08:26 PM
So after building the truck, I noticed that the rear axle has more travel than the front, because of the servo hitting the chassis. Went to the hobby shop, picked up a super small servo. It puts out the same torque that the standard Futaba servo does, but it's half the height. Steering is quick and precise, and I've got a lot more travel too.

I had to take the dremel to a number of pieces, but it worked great.

I was going to throw a rear servo in to, but if you only have a two channel radio it's lame because the steering arm goes right up against the rear of the chassis and again blocks the travel. :P

Tonight I'm going to pull out the center diff and put the Traxxas friction pegs in. I can't believe that Tamiya designed it this way. As soon as one wheels looses traction, your rock crawling ascent is over. :P

pkh
02-03-2004, 08:52 PM
I'm planning on adding a RWS servo to mine in the near future. To solve this problem, I'm planning to resolder the pot and the motor to reverse it (swap the polarity of both), so I can point the servo arm down, like the front servo :D .

MacMan
02-04-2004, 12:21 PM
sweet! Please let us know how it goes. I'd really like to do this as well. Maybe take some pictures so everyone else knows what to do. :)

MacMan
02-04-2004, 02:34 PM
So yesterday I finished the body, put in friction pegs and new wheels/tires. I bought the Wild Willy 2 wheels and they're perfect! They have more offset than the stockers, so the larger tires don't have any rubbing problems.

The friction pegs are great. They work just like a slipper clutch. My truck pulls some nice wheelies, even with the big tires.

I'll post pictures when I get home.

pkh
02-04-2004, 03:16 PM
Originally posted by MacMan
sweet! Please let us know how it goes. I'd really like to do this as well. Maybe take some pictures so everyone else knows what to do. :)
When I hack into my servo to reverse it, I'll definitely take some pics! For those who don't care to go to this trouble, here's a couple of other options:

A Y harness with a built-in reverser on one side:
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXAFN1&P=7
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXAFN2&P=7

A larger & more complex reverser with a trimming/centering adjustment:
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXANF2&P=7

These are $10 - $25 more than just buying a Y-harness (~$10). I'm a cheapskate, and like to hack into things, so I'll take a crack at modifying the servo itself to save some $$!

MacMan
02-04-2004, 04:59 PM
Hmmmm, I bought a y-harness, but it doesn't have the built in reverser. Maybe I'll see if I can return it and get the other.

Thanks for the link!

-Chris

pkh
02-05-2004, 12:45 PM
I took a closer look at the EMS reverser on Tower's website, and it appeared to have a centering adjustment on it as well. When I called Tower, their tech support said it didn't have the center trim, but the picture shows a small adjustment pot on it... so I ended up calling EMS to find out for sure, and they verified that it *does* have a center trim on the reverser.

So, I'll probably get that instead of hacking into the servo afterall. If I just reverse my servo, I'd have to adjust the center trim (w.r.t the front servo's center) mechanically, which will be a pain in the a$$! Especially with servo savers installed! With a good hard impact, the center seems to get skewed a little with the servo savers! It would be very useful to have an electronic trim to make minor adjustments.

I might be able to put a trim into the servo when I hacked into it, but getting access to the pot from outside the case would be a pain, and any holes I'd drill to get access to it would allow dirt/dust/mud etc. into the case!

So, for $9 more than a regular Y-harness, the EMS reverser may be the best bet afterall!!

Darn, and I was looking for an excuse to hack into something, too!!

MacMan
02-05-2004, 01:39 PM
you know what I'd like to figure out how to do? I've got a 3-channel hpi controller from a savage. The third channel is just a switch though, so it can't be used for rear steering. Seems like I should be able to use the third channel to set the rear steering to full lock right, or full lock left, but the problem comes in when I want to let it be centered. :(

MacMan
02-05-2004, 01:53 PM
BTW, I just posted pictures under the gallery thread.

pkh
02-05-2004, 01:55 PM
I think it'd be cool to use the 3rd channel to select either:

1) Center-locked rear servo
2) Active (reversed) rear servo

Then at high speeds, you could center lock it, and at low speeds you could steer it. I'm not sure if I'd have the coordination to turn the rear separately from the front with a third channel!

Another cool idea would be to cook up a circuit that would sense the ESC signal and back off on the rear servo rotation at higher speeds, or just center lock it over a certain speed, but now that's getting complicated! Would only require 2 channels, though...

Maybe someday a company like EMS will come out with a RWS circuit with these (or similar) features. Actually, just having a dual rate adjust as well as a center adjust on the reverser would be very cool. Then you could dial back the rear steering angle a little. That would let you reduce your turning radius only as much as you needed to, and make high speed steering a little easier!

MacMan
02-05-2004, 08:34 PM
Seems like some of this stuff would have already been designed for the clod and txt-1. I know that some people really make them scream, you'd think they'd be interested in finding a way to keep the rear servo centered at the flip of a switch.

GrEenGoBlIn
02-05-2004, 10:11 PM
i still cant figure out how the 3rd ch. would work on the rear servo...i have an M8 and i just threw a y-harness on it...so im using 2 channel and it works great...

Can someone help me out iwth the 3rd chanel?

pkh
02-05-2004, 10:37 PM
Originally posted by GrEenGoBlIn
i still cant figure out how the 3rd ch. would work on the rear servo...i have an M8 and i just threw a y-harness on it...so im using 2 channel and it works great...

Can someone help me out iwth the 3rd chanel?

Well, I believe there are two ways you could control RWS with the third channel, one of which is alluded to on page 25 of the manual (the second one below):

1) You need a TX with a variable 3rd channel control, not just an on/off or a +/- control. This would allow you to steer the RWS servo independently from the front. The only TX's I've seen that could do this are 4-channel stick TXs that are better off left to the fly-boys!

2) Using a servo mixer, you could mix the 3rd channel with the front servo's channel. This mixed signal would be sent to the rear servo. The third channel would be switched to either + or -, giving you a reversed rear servo, or one that turns in the same direction as the front. If you look at the pictures on Tamiya's website, you'll see some of the TLT-1 using both steering modes:

http://www.tamiyausa.com/product/item.php?product-id=47201

Actually, here are the pics...

Synchronized RWS:
http://www.tamiyausa.com/images/product/251/47201/gallery_10.jpg

Reversed RWS:
http://www.tamiyausa.com/images/product/251/47201/gallery_9.jpg

The reversed RWS will give you the tightest turning radius, but will be bad/unstable for higher speeds. The synchronized RWS will be better for high speeds. Some full sized vehicles with RWS actually make this mode switch based on vehicle speed.

MacMan
02-06-2004, 02:30 AM
Any way to use a y-harness for four wheels steering, and then use the 3-channel "switch" with a servo mixter? That way I could use the hpi controller to switch between normal 4wheel steering and crabbing. :)

Be-Jammin
02-06-2004, 06:41 AM
Why would anybody need a servo reverser? Isn't rear servo already turning the opposite as the front because it is facing the opposite direction? As previously stated, I would think only the Y-harness was needed.

GrEenGoBlIn
02-06-2004, 10:23 AM
Originally posted by Be-Jammin
Why would anybody need a servo reverser? Isn't rear servo already turning the opposite as the front because it is facing the opposite direction? As previously stated, I would think only the Y-harness was needed.

You only need a regular y-harness...but if you look at the setup on a "reversed RWS" tlt, you would notice that the servo saver points upwards and when the shocks unload partially, it hits the chassis....so getting a harness with a reverser would allow you to flip the servo and setup the linkage like in the front...so it would give you MUCH MORE clearance.


What would the +/- of going to a syncronized RWS....i just cant picture how that would work

pkh
02-06-2004, 10:31 AM
Originally posted by Be-Jammin
Why would anybody need a servo reverser? Isn't rear servo already turning the opposite as the front because it is facing the opposite direction? As previously stated, I would think only the Y-harness was needed.
With a Y-harness and the servo arm the mounted the same as in the front you get synchronized steering, not reversed steering (see pictures in my previous post). If that's what you want, then go for it!

If you wanted reversed steering (which I'd think most people would want) then you need a servo reverser, or you need to mount the servo saver up, where it gets crushed by the suspension!

Your choice!