777 HAUL TRUCK (1/12 size)

[DADSGARAGE]

Originally Posted by Espeefan

This is such a cool build to watch, and you are making incredible progress! I'm glad you got some larger photos up. I like your drivetrain and that steering system is pretty cool. I hadn't seen that style servo rack on servocity before. Those guys are constantly coming up with lots of new products. Genius idea on limiting the rear suspension travel, with those new arms and the set screw stops too.

I hope you don't mind, but I'd like to offer a suggestion for your steering knuckle drag links are set up. I've tried an identical system just like that before and I found that you can't get the proper ackerman geometry with it. The inside (of the turn) tire should turn in sharper than the outside. It makes a huge difference in steering. Right now, yours is the opposite. On a heavy truck like this, you might notice an improvement even more so than smaller models. It will 'plow' less in the turns.

It looks you could pretty easily fix the geometry, if you wanted, without changing anything but the way your drag links are bolted to the center steering arm. You just need to swap the right and left side drag links, where they mount to the center arm, with each other. Obviously you can't do that without interference, unless you bolt one drag link on the top of the arm to the top of the steering knuckle, and one on the lower side of both the arm and the knuckle. Picture worth a thousand words....


I don't know if you have the room for changing the drag links to one under, one over, but if you do, give it a shot, and then take your truck for another drive to check how much better it steers. Like I said, I've been there, tried that! Just wanted to share my experiences. I hope you don't mind me suggesting this, and my intention is not to offend you. I can't wait to see this truck all finished up!

The pics of the steering are deceiving...I didn't have the tie rod lengths set up properly when I took the pics.... one side is longer(oops), which means the steeing arms are not parallel to each other or the frame when pointed straight. I think I know what you mean about the steering geometry when turning the inide tires always have a smaller turning radius which is why the inside front tire need to turn at a sharper angle than the outside tire...this is also the reason why a differential is needed....

Best part of being on here is learning from others...thanks for the input!!

Here is a screen shot of what I used to set up the steering on the truck at full lock....maybe I did this wrong??

[IMG][/IMG]

[RCP57]

Originally Posted by DADSGARAGE

The pics of the steering are deceiving...I didn't have the tie rod lengths set up properly when I took the pics.... one side is longer(oops), which means the steeing arms are not parallel to each other or the frame when pointed straight. I think I know what you mean about the steering geometry when turning the inide tires always have a smaller turning radius which is why the inside front tire need to turn at a sharper angle than the outside tire...this is also the reason why a differential is needed....

Best part of being on here is learning from others...thanks for the input!!

Here is a screen shot of what I used to set up the steering on the truck at full lock....maybe I did this wrong??

[IMG][/IMG]

Oh come on now that's just cheating! What happened to the build it wrong ten times, get p'd off, forget about it and have the solution come to you when you are thinking about something completely different way of building? I need to get more computer savvy!

[DADSGARAGE]

I need all the help I can get.....I still make things wrong ten times...I just make more mistakes faster....

[Espeefan]

Originally Posted by DADSGARAGE

The pics of the steering are deceiving...I didn't have the tie rod lengths set up properly when I took the pics.... one side is longer(oops), which means the steeing arms are not parallel to each other or the frame when pointed straight. I think I know what you mean about the steering geometry when turning the inide tires always have a smaller turning radius which is why the inside front tire need to turn at a sharper angle than the outside tire...this is also the reason why a differential is needed....

Best part of being on here is learning from others...thanks for the input!!

Here is a screen shot of what I used to set up the steering on the truck at full lock....maybe I did this wrong??

That CAD drawing of the truck turning is exactly what you want. Perfect, in fact! I think the problem is your steering drag links do not travel equally, nor in a parallel / linear fashion, if that makes sense. Take a look at this picture.



Because your center steering arm swings in a substantial arc, the drag links do not maintain much parallelism with each other. With the wheels turned to the left, the more steering throw you add, the more out of parallel the right side link becomes. The result is the right link pushes the right knuckle more than the left link pulls the left knuckle. The knuckle on the right is at a greater angle, which is exactly the opposite effect you are after. Does that make sense, or am I barking up the wrong tree?