VP zero ackermann knuckles

[KC_JoNeS]

So, a couple days ago, I placed an order for some zero ack knuckles. Right now, my rig is setup Sportsman, so good steering is a must. Standard knuckles (stock and aftermarket) have a really bad reverse ackermann, causing the outside tire to turn sharper than the inside tire. Well, I just could not take it anymore, and I ordered a good set of knuckles.

Question: I found a BTA "kit" on RPPHobby that is for BTA and 4 linking...however, it says it does not work with the zero ack knuckles. Could someone explain to me what the difference is? is it because the tie rod is not set for that length? Is there some other issue?

Am I going to have trouble setting up BTA with these VP zero ack knuckles?

Discuss.

Casey

[romulus22]

you can make anything work if you want it to

[KC_JoNeS]

Originally Posted by romulus22

you can make anything work if you want it to

I totally agree with you...I was really just asking the reason the kit is listed as not working with the VP 0 ack knuckles. I plan to make my own plate, tie rod, and drag link anyway.

Casey

[romulus22]

If it's this kit I would say the reasoning is just because of the tie rod isn't long enough to reach from knuckle to knuckle.

http://www.rpphobby.com/product_p/ldrste001.htm

But if you plan on redoing it all anyway why buy the kit?

[KC_JoNeS]

Originally Posted by romulus22

If it's this kit I would say the reasoning is just because of the tie rod isn't long enough to reach from knuckle to knuckle.

http://www.rpphobby.com/product_p/ldrste001.htm

But if you plan on redoing it all anyway why buy the kit?

I dont plan to buy the kit....it is just that I read that, and wanted a little feedback, seeing as how those knuckles are on their way. I also assumed it was the tie rod, but in case it was something else, it couldnt hurt to ask.

Casey

[romulus22]

I gotcha. kinda missed what you were asking at first

[Offroader5]

It's because when there is no ackerman in the knuckle, the hole in the arm is the same distance apart as the knuckle kingpin (pivot). This makes the holes a bit further apart on the zero ackerman knuckles and if you used the tie rod for ackerman knuckles (shorter), you'd end up with a bit of toe-in since a knuckle with ackerman has a kink in the arm so that it puts the hole on the arm inboard of the knuckle pivot point. Vise-versa, if you used a tie rod meant for zero ackerman knuckles on knuckles with ackerman...you'd get some toe-out.

[DickyT]

Originally Posted by Offroader5

It's because when there is no ackerman in the knuckle, the hole in the arm is the same distance apart as the knuckle kingpin (pivot). This makes the holes a bit further apart on the zero ackerman knuckles and if you used the tie rod for ackerman knuckles (shorter), you'd end up with a bit of toe-in since a knuckle with ackerman has a kink in the arm so that it puts the hole on the arm inboard of the knuckle pivot point. Vise-versa, if you used a tie rod meant for zero ackerman knuckles on knuckles with ackerman...you'd get some toe-out.

Unless running BTA, the pulling in of the zero ack knuckles in a BTA will create toe out

[gunnar]

Offroader5's statement is correct for a front mount tierod setup. DickyT's response is correct for a BTA setup- the toe-in, toe-out is reversed. I think KCJones has the tools and smarts to make his own stuff, but if he wants to save some time, he could just buy a battery/servo plate with 4 link holes, and fab up the rest.

If you have Ackerman knuckles, you can use toe-out in a front mounted tierod to help correct the angles at full turn, conversely, you use toe-in to correct in a BTA setup. Tie rod needs to be spaced/fabbed so the tires are parallel at full lock.

[Offroader5]

Originally Posted by DickyT

Unless running BTA, the pulling in of the zero ack knuckles in a BTA will create toe out

Originally Posted by gunnar

Offroader5's statement is correct for a front mount tierod setup. DickyT's response is correct for a BTA setup- the toe-in, toe-out is reversed. I think KCJones has the tools and smarts to make his own stuff, but if he wants to save some time, he could just buy a battery/servo plate with 4 link holes, and fab up the rest.

If you have Ackerman knuckles, you can use toe-out in a front mounted tierod to help correct the angles at full turn, conversely, you use toe-in to correct in a BTA setup. Tie rod needs to be spaced/fabbed so the tires are parallel at full lock.

Well yeah...if you want to be picky about tie rod placement

[KC_JoNeS]

Originally Posted by gunnar

I think KCJones has the tools and smarts to make his own stuff, but if he wants to save some time, he could just buy a battery/servo plate with 4 link holes, and fab up the rest.

Yeah, I am trying to make full use of the cheap labour that surrounds me each day. Also, I can design, and get a prototype in about 24 hours, where as if I order up something from the states, it take nearly 3 weeks to get here.

I think I will fab up my own.

[thomas]

i used the stock battery tray form the AX10 and drilled holes and cut it up for the front 4 link, battery, and servo... so it was free for me.

[sourdojack]

The tierod length (eye to eye) for zero ackerman knuckles is right at 6". You can build your own BTA set-up fairly easy. If your running the tie rod in the front, you can get away with a Lundsford 140mm Rock Grinder link.

TOM

[TSK]

Ideally, for a BTA setup, you'll want to use standard high clearacne knuckles as opposed to zero ackerman knuckles. Using the standard knuckles in a bta setup will give you "true" or "correct" ackerman in which the indie tire turns sharper than the outside tire.

So rule of thumb is zero ackerman for standard steering, and standard knuckles for bta steering.

[sourdojack]

Originally Posted by TheSCorpionKing

Ideally, for a BTA setup, you'll want to use standard high clearacne knuckles as opposed to zero ackerman knuckles. Using the standard knuckles in a bta setup will give you "true" or "correct" ackerman in which the indie tire turns sharper than the outside tire.

So rule of thumb is zero ackerman for standard steering, and standard knuckles for bta steering.

I'm going to have to disagree with ya on that one.

With the axles being locked, you want BOTH wheels turning to full lock on the CVD's. There is no reason to have the outside tire not turning as sharp as the inside tire. It's not like with a crawler your trying to reduce tire scrub (which correct ackerman does).

And like Casey said, in Sportsman class, every bit of steering is a must.

TOM

[TSK]

Originally Posted by sourdojack

I'm going to have to disagree with ya on that one.

With the axles being locked, you want BOTH wheels turning to full lock on the CVD's. There is no reason to have the outside tire not turning as sharp as the inside tire. It's not like with a crawler your trying to reduce tire scrub (which correct ackerman does).

And like Casey said, in Sportsman class, every bit of steering is a must.

TOM

What ever floats your boat buddy. Tire scrub will play a bigger role on a locked axle because tires don't have the benefit of rotating independantly. the tires will fight each other less. The amount of steering angle between the two wheels is like 2-3*, i doub;t that much angle makes a noticeable difference in your turning radius. It's like when you ahve a standard steering setup with standard knuckles and do a dig turn. the wheels fight back and forth with each other. he minute the zero ackerman knuckles go in 9which reduce the scrub angle in a standard linkage setup) the tires don't fight anymore. therefore havig correct or true ackerman will benefit the setup even more.

And as far as a tie rod. The 5/1" long revo stainless tie rod will work. Dubro rod ends are a better choice than the revo ends for that application though.

[flapjack]

ive built up a system that works well....it will be shown soon in my fastback thread.......ill give you a hint stock axial links a couple spacers a few bends poof mine works great for me....sporty rig too

[KC_JoNeS]

Originally Posted by TheSCorpionKing

Ideally, for a BTA setup, you'll want to use standard high clearacne knuckles as opposed to zero ackerman knuckles. Using the standard knuckles in a bta setup will give you "true" or "correct" ackerman in which the indie tire turns sharper than the outside tire.

So rule of thumb is zero ackerman for standard steering, and standard knuckles for bta steering.

You ARE correct in that true ackermann will come by using standard knuckles in BTA. It took me a minute, but yeah...you are right. But, let us imagine the times where you blip throttle a few times to get your front to turn even sharper, basically asking your front tires to slide a bit. If you have no ackermann, you effectively have two tires pulling in the same direction...thus giving you better turning ability. The ackermann, in theory, just wont pull you as hard in the direction you want to go.

[sourdojack]

Here is just one quick example of where you want both of your knuckles turning to full lock with VP Zero Ackerman knuckles.

This is Chris the Battery Man at the AWCC Last Chance Qualifier.



If the outside tire didn't turn that extra 2 or 3 degrees, Chris wouldn't have been able to hook his right front tire on the rock and clear the gate without a reverse.

[TSK]

Originally Posted by sourdojack

Here is just one quick example of where you want both of your knuckles turning to full lock with VP Zero Ackerman knuckles.

This is Chris the Battery Man at the AWCC Last Chance Qualifier.



If the outside tire didn't turn that extra 2 or 3 degrees, Chris wouldn't have been able to hook his right front tire on the rock and clear the gate without a reverse.

I thought we were talking about no dig sportsmans? Having dig in that moment would have allowed him to complete the gate. We're talking about a sportsman having optimal steering in most situations. Not just one.