Hot bodies 1/8 diffs - Page 21 - RC-Monster Forums

JERRY2KONE · **Amazng -** 09.25.2011, 04:43 PM

Your truck looks amazing. You did a great job and you have somethng to be proud of for sure. The issue you are having seems to be pretty common and I am sure that most of us have run into this issue at one time or another. How about trying to use just one servo and then the other to see if it is one servo or both that are giving you the problem. Are you using a BEC, or just running both servos off of the ESC? Running two servos on the ESC might just be too much servo draw to deal with. Especially if they are high torque servos. I have had servo issues myself and still do not quite get how different some servos are when all the specs seem to be the same. The other thing that I believe you are going to have a problems with is using aluminum rims under power. Super-glue just does not stick too well to aluminum, and they will seperate fairly easy under load. There are several threads inhere about using beadlock rims, balancing wheels, and also taping the tires to prevent balooning whih yu will more than likely see if you use a good range of power, torque, and speed.

cmac · 06:48 PM

Quote:

Originally Posted by JERRY2KONE

Your truck looks amazing. You did a great job and you have somethng to be proud of for sure. The issue you are having seems to be pretty common and I am sure that most of us have run into this issue at one time or another. How about trying to use just one servo and then the other to see if it is one servo or both that are giving you the problem. Are you using a BEC, or just running both servos off of the ESC? Running two servos on the ESC might just be too much servo draw to deal with. Especially if they are high torque servos. I have had servo issues myself and still do not quite get how different some servos are when all the specs seem to be the same. The other thing that I believe you are going to have a problems with is using aluminum rims under power. Super-glue just does not stick too well to aluminum, and they will seperate fairly easy under load. There are several threads inhere about using beadlock rims, balancing wheels, and also taping the tires to prevent balooning whih yu will more than likely see if you use a good range of power, torque, and speed.

Jerry, I have tapped the tires. I'm hoping that they wont separate. I took extra time to sand the wheels and clean the release agent from the wheels. No I'm not using a separate BEC, but these servo's are not super high torque. I'm hopping the Hitec 9380 brushless servos with the low power draw will fix the problem of using high torque servos without a separate BEC. As for balancing I found a solution for my Dynamite wheel balancer.
Dynamite makes an 12mm axle, and I just bought a 12mm to 14mm adapter so I will be able to use the Dynamite balancer with these 14mm wheels. Balancing all my 17mm wheels has made such a dramatic difference in how my other truck ran I will not drive a truck/car without having the wheels balanced. I'm hoping all the extra time and care that I took gluing the tires on will result in no tire blow outs. Only time will tell. I was not planning on any real high speed runs until I balanced the tires. Just like everything else I have done with this build I will take my time and think things through before proceeding on. Thanks for the advice, input, and kind words.
Mike.

George16 · 09.25.2011, 09:35 PM

The 5625's has about 164 oz.in of torque and should be adequate for your truck. In fact, it should be able to center itself easier when it's running compared to when the truck is at a standstill. Less torque is needed when the vehicle is in motion.

If I were you, I'd try with just a single servo. Two servos are more of a liability and headache if they are not synchronized together. It seems to me that they are fighting/canceling each other a little bit.

Great-looking truck you got there! Don't be scared in running it up to speed. Just find a wide and clear area to run so you can minimize the chance of hitting something.

cmac · 08:32 AM

Thanks,
I'm not afraid to bring it up to speed. I was going well of excess of 55 to 60 with my old brushless Emaxx. This truck won't go straight and I'm fighting with the steering. I will try one servo at a time in the next few days. I can already tell that this truck handles much better than the stock brushless truck, and should be a missile when I can steer it straight. I think you are right they might be fighting each other. I'm sure I will work this out. I knew it was not going to just fire right up and be perfect. I have not come this far to give up or mess this up now. It's just going to take some time to work out all the little kinks. I guess this is just part of the fun.

Overdriven · 01:10 PM

As far as the servos go, using dual servos is a bit of a pain. The links from the servo horn to the bellcrank both have to be the same length on both sides or they will be fighting each other. If you can hear the servos buzzing with the front end off the ground they are fighting each other. Btw, I like to keep the radio and servos powered up when centering the linkage so I know nothing is moving around on me. First setup the bellcrank to center, then adjust the subtrim (not regular trim) on your radio to center the servos. Subtrim doesn't affect total servo travel like the regular trim does. With the bellcrank and servos centered them you can adjust the camber, then the toe in after that.

I know you have the dual servo saver linkage, but the Traxxas manual should have diagrams telling you the exact length the linkages should be. They are actually real size too, so you can just match your linkage to the manual. Also, just double check the servo savers to make sure there isn't excessive play in them as that can cause the off center issue you mentioned. If they are a little loose, see what spring you have in it, the black one is stiffer than he chrome spring and will have less play.

cmac · 10:47 PM

Quote:

Originally Posted by Overdriven

As far as the servos go, using dual servos is a bit of a pain. The links from the servo horn to the bellcrank both have to be the same length on both sides or they will be fighting each other. If you can hear the servos buzzing with the front end off the ground they are fighting each other. Btw, I like to keep the radio and servos powered up when centering the linkage so I know nothing is moving around on me. First setup the bellcrank to center, then adjust the subtrim (not regular trim) on your radio to center the servos. Subtrim doesn't affect total servo travel like the regular trim does. With the bellcrank and servos centered them you can adjust the camber, then the toe in after that.

I know you have the dual servo saver linkage, but the Traxxas manual should have diagrams telling you the exact length the linkages should be. They are actually real size too, so you can just match your linkage to the manual. Also, just double check the servo savers to make sure there isn't excessive play in them as that can cause the off center issue you mentioned. If they are a little loose, see what spring you have in it, the black one is stiffer than he chrome spring and will have less play.

Overdriven,
you are the man

the tip for leaving the radio and servos on when mounting the arms did the trick. The servos seem to center now. It now drives where I point it. Thanks so much

I will do some more testing tomorrow if I get some time. I forgot to locktite the pinion gear and kind of freaked out when it popped off. Neil, I also received the long screws. I went ahead and ordered 40mm, 45mm, and 50mm screws. Turns out the 45mm screws are the best,.... (that's what she said). The shock springs no longer touch part of the A-arms and overall just look so much better. As far as mounting the bellcranks, I always just turned on the radio/truck and let the servos center, then turned it off. Then I mounted the steering linkage. I'm sure I will have a few more bugs pop up, but it is reassuring to know that a real answer is just a few clicks away. All of you guys are the best. Remember that one year ago I had never owned an RC vehicle, and eight months ago I was afraid to change a shock tower out. I've come a long way in a short time. I would have been lost without you guys thanks again,
Mike.

Overdriven · 11:03 PM

Some stuff you pick up yourself from trial and error, other times little tips and tricks from others really makes things so much easier. I know I've had more than a few "Duh, why didnt I notice that..." moments myself after reading someones post. If you have any other little issues with the steering reread my last post and go from there. Can't figure it out? Then just ask!

Edit: I wouldnt worry about your current servos drawing enough to need an external BEC. It might be nice insurance, especially if your going to add lots of led's or something. I also think their combined torque is plenty for your truck as long as they're setup properly. Unless the brushless servo's are that much faster or you just really want them, I don't see a reason to upgrade to them.

cmac · 09.26.2011, 11:06 PM

Quote:

Originally Posted by Overdriven

Some stuff you pick up yourself from trial and error, other times little tips and tricks from others really makes things so much easier. I know I've had more than a few "Duh, why didnt I notice that..." moments myself after reading someones post. If you have any other little issues with the steering reread my last post and go from there. Can't figure it out? Then just ask!

Edit: I wouldnt worry about your current servos drawing enough to need an external BEC. It might be nice insurance, especially if your going to add lots of led's or something. I also think their combined torque is plenty for your truck as long as they're setup properly. Unless the brushless servo's are that much faster or you just really want them, I don't see a reason to upgrade to them.

Thanks again, I will....

cmac · 09.27.2011, 10:18 AM

Ok, guys I have another question. Now that my truck is tracking straight I'm now seeing that the steering is really sensitive. When I'm up to speed the truck will dart with every little input. Is there a way to "calm" some of that down? I'm also thinking about how to do a more permanant way to mount my batteries. I see I could use trays, but I'm looking to do something much better. I found a web site where you can make your own carbon fiber parts and I think this might be an option.
http://www.google.com/url?q=http://w...epBjOMPq8JIP2g
Do any of you guys have any experience this? I wonder if it would be strong enough? Watch the video and tell me what you think. There is a link on the web site. I'm at work and they block anything related to Youtube, but it's on the site under "kits".

JERRY2KONE · **Rcm -** 09.27.2011, 10:45 AM

RCM MonsterMike makes battery trays and sells them in his store. Carbon fiber is another alternative and yes it will hold up if you do it right. There are good and bad ways to produce items out of CF, and it can get a little bit tetious, and complicated if you have never done it before. We have seen guys in here who have manufactured some pretty good items right in their own garage, but it can be a costly gamble if you have no idea what your doing.

cmac · 09.27.2011, 12:27 PM

I think I'm going to give it a try. I think becase the shape is not too complex it should not be too difficult to make the parts. The basic kit is about 50 to 60 dollars US. Not too bad. Should be fun. If I go that route I will be sure to document the whole process.

George16 · 09.27.2011, 10:05 PM

You can program your Futaba radio for a less "sensitive" feel. The reaction times can be controlled electronically through your radio.

cmac · 09.30.2011, 06:29 AM

Thanks George I was hoping for a little explanation of servo speed and servo exponential-function. What do they do and how can they help me?

thirdcliff · 09.30.2011, 12:57 PM

Very nice turn out, Mike! That truck is beautiful. I really like how you left the other parts silver, they play off the red chassis nicely.

So how do you like the slipperential??? How well does it drive??

cmac · 09.30.2011, 01:14 PM

I love it. The truck weighs 13lbs with the batteries so I had to add an extra spring so it will hold up to the power and weight. I really have not had the chance to really flog it because I am still working out issues with the servos,the slipperential is highly recommended.
thanks
Mike.