cboggs' 5th D Sucker Punch

[Erik D_lux]

From everything Ive read about ackerman my understanding is we are wrong on our thinking of what zero ackerman is.

I agree its gotta be an ackerman difference between the hub/knuckles. Having the kingpin and steering arm mount aligned with each other isn't what makes it zero though. BTA and FTA make alter what actual zero is from my non engineering understanding.
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I guess what I should be saying is that mine might not meet the definition of zero ackerman but what my arms do is make it so both tires steer the same amount during throw where as the Wraith knuckles make it so the outer tire turns more than the inner. Whatever terms we want to throw on that.

Good points though that should be understood.

Im thinking the non zero arms would probably feel better ;-)

I am guessing they would too but my thought is "is what feels better actually working better"?

I can think of multiple things that make people feel better when driving but actually make the car work worse. 8* and non is a good example IMO. Sporty could be totally different though because if youre pushing and cant turn, thats a big deal in this class. My guess is that youre getting some turning radius back at the cost of traction say on a uphill climb and other points.

All I know right now is I'm back to winning again and I'm happy with how the rig is performing."thumbsup"

And after the "blah blah blah" thats what its really about. Feeling good and winning. "thumbsup"

 

[Robbob]

I am guessing they would too but my thought is "is what feels better actually working better"?

I can think of multiple things that make people feel better when driving but actually make the car work worse. 8* and non is a good example IMO. Sporty could be totally different though because if youre pushing and cant turn, thats a big deal in this class. My guess is that youre getting some turning radius back at the cost of traction say on a uphill climb and other points.

And after the "blah blah blah" thats what its really about. Feeling good and winning. "thumbsup"

I think your're right on the sporty part. We could be seeing a spot in tuning drivers tend to overlook or could tune differently to benefit. "thumbsup"

 

[Erik D_lux]

Yeah, it would be cool to have something more scientific.

Too bad Chris already took the setup off. It would be cool to have zero ackerman on, measure the turning radius and then non zero and measure the turning radius.

I would actually place my bets on the zero ackerman turning sharper, even though it feels like it pushes or should I say does push. This is how I felt with my sporty and the non zero arms I ran. I felt like it didnt push but it turned really wide because of it.

 

[cboggs]

I got the old axle still here all ready to go if we want to try an experiment."thumbsup" Just throwing this out, in my thinking if the inside tire turned sharper wouldnt that pull the car tighter through a turn and keep the most traction vs having the outside tire turn more?

 

[CM9000]

I would think so. but the rear outer tire dragging would counter act it? < this is something im trying to solve and be legal in shafty class and in any scale class.

 

[Robbob]

I got the old axle still here all ready to go if we want to try an experiment."thumbsup" Just throwing this out, in my thinking if the inside tire turned sharper wouldnt that pull the car tighter through a turn and keep the most traction vs having the outside tire turn more?

YEs and No? Maybe lol.

In my thinking with the caster we run we are always jacking the weight to the outside tire so I think I would want more or equal angle.

 

[VMGontheRocks]

I got the old axle still here all ready to go if we want to try an experiment."thumbsup" Just throwing this out, in my thinking if the inside tire turned sharper wouldnt that pull the car tighter through a turn and keep the most traction vs having the outside tire turn more?

Us scaler guys try and get the inside tire to turn sharper. :mrgreen:

 

[TSK]

FWIW, I think "zero ackerman" is being misconstrued, and should be coined "parallel ackerman" as far as what we in the crawler community are talking about. I had to do a lot of reading when I was making the wide angle seering rack for the TC-FD ddrifter.

Ideally, on a crawler, I think I would prefer non 8* with just a tad bit of true ackerman, where the inside turning tires would lead in with a bit more angle than the outside. Unfortunaly, with conventional "front of the axle" mounted tie rods, this would reuire the knuckle arms to be positioned out further than the kingpins, thur requiring wider offset wheels

THat's is why with conventional non-zero ackerman knuckles, the outside would turn sharper than the inside. Which is hy zero ackerman knuckles became so popular, because steering improved due to better, although not ideal, geometry.

 

[Erik D_lux]

in my thinking if the inside tire turned sharper wouldnt that pull the car tighter through a turn and keep the most traction vs having the outside tire turn more?

I guess it depends.

Just because I think we already think of it as 0 ackerman being where both tires turn the same, I am going to keep using that terminology.

My thinking says that the most ideal situation is to have both tires turning as much as possible (0 ackerman). I think the thing thats easy to forget is that we simply dont have our tires at a maximum, get different steering arms and then have the ability to have one tire turn more than the other. What really happens is that one tire turns more while the other gets restricted on anything but 0 ackerman.

On 0 ackerman, ideally you want to have your car setup so both the inner and outer tires turn 70*. I think this is the best setup and going to be the tightest turning. We are limited at 70* right now because of the universals. If your car limits you to a lesser degree, this could throw the whole theory off.

On NON 0 ackerman, like Chris just went to, you now have the outside tire turning sharper than the inside. Just to help discussion sake, lets put numbers on them and say that the inside tire now turns 50* while the outside tire turns its full potential of 70*.

Obviously the NON 0 ackerman will cause less push because while the outside tire at 70* is still struggling to turn as much as possible, the inside tire was at 70* on 0 ackerman but now at 50* its much less and this will cause less pushing and my guess, less turning radius. Imagine if we just took 0 ackerman, turned our EPA's down so we get 30* on both sides. Now we are really having a easy time with little pushing BUT, the turning radius just went down the crapper.

I think even in TSK's post where the inside tire turns a hair more than the outside, say 70* inside, 60* outside, I think it will turn less because both tires are not at a maximum. I do however think this will cause less pushing because there is less steering angle again on one of the tires and it will want to follow a natural path.

Now, if you were only getting 55* on 0 ackerman before on both tires but going to NON 0 ackerman gets you 55* on the inside and 70* on the outside, I think the NON 0 ackerman will win in this situation BUT IMO, you should be able to get a better performing steering setup with 0 ackerman in an ideal situation. Whether or not your car physically allows is a different story.

Chris, is your caster the exact same from before and after? Same question with toe in/toe out. Both of these could really effect the overall turning radius and pushing too.

 

[Erik D_lux]

Here is a picture of when I was running non 0 ackerman.

I had to cheat on this axle a lot because I was trying to run too narrow. Outside tire was fully stuffed, say 70* and outside tire was closer to 55*? This car never did please me with its turning capability but it never did feel like it was pushing either.

 

[cboggs]

Castor is the same on both, 20*, and toe is the same also. I'll get a pic later after work. On a pro I like non 8* (probably cause of the dig if needed) but just wasn't ever satisfied with it on the sporty.

 

[Robbob]

Here is a picture of when I was running non 0 ackerman.

I had to cheat on this axle a lot because I was trying to run too narrow. Outside tire was fully stuffed, say 70* and outside tire was closer to 55*? This car never did please me with its turning capability but it never did feel like it was pushing either.

Were those 8* or non?

I had to play a lot with the arms I have on my sporty to find equal throw and ran into similar problems. I found running shorter arms, think like Losi knuckles vs Axial with the stock ears, I got more steering then running the longer racing arms.

Quicker steering - stronger steering - less servo throw needed, actually turned epa's down ..... if that makes sense.


Different axles then me but Im wondering if you were to take and move your left front tie rod in towards the king pin ... you think you would actually get more throw into that lf tire?

Have to bend the tie rods to clear the pumpkin but you could get more angle to the inside tire with out sacrificing the outside. I don't have experience though with AR60s so I cant say Ive done anything to them.

Ill have to take a picture tonight of my AX axles with the Destroy plate. I almost feel like it has more steering them my Pro rig lol.

 

[Robbob]

FWIW, I think "zero ackerman" is being misconstrued, and should be coined "parallel ackerman" as far as what we in the crawler community are talking about. I had to do a lot of reading when I was making the wide angle seering rack for the TC-FD ddrifter.

Ideally, on a crawler, I think I would prefer non 8* with just a tad bit of true ackerman, where the inside turning tires would lead in with a bit more angle than the outside. Unfortunaly, with conventional "front of the axle" mounted tie rods, this would reuire the knuckle arms to be positioned out further than the kingpins, thur requiring wider offset wheels

THat's is why with conventional non-zero ackerman knuckles, the outside would turn sharper than the inside. Which is hy zero ackerman knuckles became so popular, because steering improved due to better, although not ideal, geometry.

Also why we saw/felt a sharper steering in the XR over traditional setups of the past.

True(er) zero ackerman because the steering was bta. ;-)

So glad we don't have to factor in bump steer and camber gains in crawlers ...... my head explodes when touring car/12scale season comes around and tuning those. :lmao:

 

[TSK]

In my "ideal" description, I think it will push less because in the tires won't be fighting each other (scrubbing) as the inside tire ALWAYS turns a tighter circle than the outside will. Thus the outside tire needs marginally less steering angle to help guide the car around the same turn as the inside needs.

A) 0 kingpin inclination = more traction
B) True Ackerman (inside turns sharper) = less scrub

A + B = best steering

All just my personal opinion of course.

 

[WHITE-TRASH]

In my "ideal" description, I think it will push less because in the tires won't be fighting each other (scrubbing) as the inside tire ALWAYS turns a tighter circle than the outside will. Thus the outside tire needs marginally less steering angle to help guide the car around the same turn as the inside needs.

A) 0 kingpin inclination = more traction
B) True Ackerman (inside turns sharper) = less scrub

A + B = best steering

All just my personal opinion of course.

I am 100% in agreement with that train of thought. If we had a center differential and unlocked axles to allow for different tire speeds through the turn arc equal inside and outside turning may be the ticket. But will everything locked functional ackerman is the key since which ever tire has the most traction has the most say in direction of travel.

 

[WHITE-TRASH]

After having another 5 hours on the road thinking on this subject I'm pretty sure dlux is right. And wrong. :lol:


Equal steering can turn better ie in a tighter circle when on a moa which he is far more used to driving so that's the go to place for his thought process. MOA can front dig with the rear locked or going reverse of the front. 2 things a sporty rig are incapable of. Sporty has no dig and the rear is driving even if in a reduced speed due to offset gearing. No matter what there is some push straight forward on a sporty which is doing its best to make the rig travel in a straight line. Running something closer to true ackerman helps the shafty turn since the inside tire can turn in a tighter circle helping the front end come around.

If someone hasn't beat me to it next weekend I'll take a few hours and try multiple setup as far as steering arms, toe, knuckles, even bta since I have 3 rigs with different setup to poach parts from to do a semi scientific test on this.


My bouncer runs vp knuckles with axial shorty steering arms and a vp 0* arm on the backside of a knuckle connected to the drag link. It steers well due to the leverage factor of a longer steering arm and shorty tie rod arms. Robbob is 100% correct in that idea, I'm proof. :lol:

 

[Robbob]

Didn't want to blow Chris's thread up with my pictures so I posted them in my build. I do have this though showing my ackermen.

Sporty can def benefit from the steering where we don't have the magic stick to lock an axle up. :ror:

 

[Erik D_lux]

Castor is the same on both, 20*, and toe is the same also. I'll get a pic later after work. On a pro I like non 8* (probably cause of the dig if needed) but just wasn't ever satisfied with it on the sporty.

Man, I dont know about you guys but its starting to feel overwhelming with all the things to think about in sportsman and their steering. Can you guys just install dig in these cars and call it good?

I feel a bit out of my realm because I dont drive sporty and dont have much experience at all with them.

I know I felt steering was very important with these cars but I think the question coming up in this thread and what Chris is stating (at least for himself) is that steering is more important than traction and other benefits? Seems a bit wild but I guess I can see it.

Were those 8* or non?

Non

I had to play a lot with the arms I have on my sporty to find equal throw and ran into similar problems. I found running shorter arms, think like Losi knuckles vs Axial with the stock ears, I got more steering then running the longer racing arms.

Quicker steering - stronger steering - less servo throw needed, actually turned epa's down ..... if that makes sense.

I dont think this should be trues unless you didnt/couldnt adjust the rest of your steering?

In my findings, if youre arm on your knuckles is 1", your servo should have about a 1" long arm to get full throw. On something like the Losi or B2, the arm on the knuckle is much shorter so you can run a shorter servo arm.

Basically you should be able to get the same throw/angle but the steering arm needs to compliment the knuckle arm.

So, I think the steering, all things being equal should have the same strength, same speed and same throw?

The only thing I really didnt like about short knuckle arms is that you need to have a short servo horn and it seems like things like to cam over much quicker that way where as a longer servo horn and longer knuckle arm seem to not want to cam over on themselves making it an easier system to setup.

Different axles then me but Im wondering if you were to take and move your left front tie rod in towards the king pin ... you think you would actually get more throw into that lf tire?

Have to bend the tie rods to clear the pumpkin but you could get more angle to the inside tire with out sacrificing the outside. I don't have experience though with AR60s so I cant say Ive done anything to them.

That setup just was what it was. I was trying to get both tires to get full throw and I did. The outer was scrubbing the diff cover and I dont think you can see it in that pic but the inner tire was rubbing the link mount. I even trimmed down the link mount but didnt eliminate the entire side of that mount because I insisted on double sheer.

Also why we saw/felt a sharper steering in the XR over traditional setups of the past.

True(er) zero ackerman because the steering was bta. ;-)

I have always wondered about this quote. I have heard it from many, many people and usually when I question, there is never anything but a blank stare. Maybe its because I am missing something simple? LOL.

I heard this pretty much as soon as the XR came out. "I went to the XR because it gets so much better steering that then Berg". I would hear that all the time. This is before almost anybody ran modified universals so I know their universals were only good for the same turning degree as the Berg, about 58*.

Maybe it just felt better or actually was better because like you were saying, the ackerman is a bit more true? Or, maybe its because the 8* brings less scrub and its able to turn with less force?

I feel we need some serious testing on 2.2s and 2.2P.

In my "ideal" description, ......

IMO, it might be worth hashing it out but seems there are bigger fish to fry at the moment.

I imagine having your or my "ideal" setup but making the tires so they turn 90*. What I am wondering now is if there is a point of diminishing returns? We are all shooting for more turning angle but should we? What if you had either of our "ideal" setups but found out that since the rear is a huge determining factor that 60* of steering will actually out turn 90* just because of the lack of push?

If you are on the same page as me above, now there are so many other things to be curious about.

I think you could almost chart out setups that allow the least amount of push/traction all the way up to the top end that makes the most amount of push/traction. Just for fun, lets say the bottom of that list would be 8*, no scrub, no caster and then the top would be non 8*, lots of scrub, lots of caster.

Now, I think you should tune each item individually until youre where you want to be. The bottom of the list (8*, no caster, no scrub) might get you the best turning radius but at what cost? Maybe now you cant make a climb or a side hill. Thats going to be a tough one to figure out.

Another example is that Chris might be able to choose which attributes he likes the best and tune from there? Say he likes the benefits of caster more than anything else so, keep the caster at 20*, go 8* and then scrub might be what it is since we are forced into that more than anything. OR another option might be that he likes non 8* so much that he wants to keep those traits but reduce the caster to 0*. Is 0* caster and non 8* going to be similar to 8* and 20* caster? Maybe? Now he also eliminated some push but can keep some of the good traits that non 8* offers. Much to think about and test.

which ever tire has the most traction has the most say in direction of travel.

I think this is the problem. I think the rear tires have the most traction and say in travel when youre tires are almost parallel to the housing.

After having another 5 hours on the road thinking on this subject I'm pretty sure dlux is right. And wrong. :lol:

Good pic.

 

[CM9000]

imagine a no dig shafty out turning another no dig shafty shaft with the same steering throw and ackerman setup. you wont get more from the front. its all in the rear.

 

[Erik D_lux]

imagine a no dig shafty out turning another no dig shafty shaft with the same steering throw and ackerman setup. you wont get more from the front. its all in the rear.

Man, if only somebody figured out how to make the rear under drive even more.... Oh wait... its been done.