Kraton Who here has honestly played with CASTOR on there Off Road ARRMA's ?

[Big Kid]

While I'm working out getting the Kraton to Track bash with the best control, I've been pretty successful getting turn in, on/off power steering etc sorted, just recently with some new tires a bit of finer set up has prompted me to start experimenting with FRONT Castor adjusting.
The Kraton with the top upper A-arms generally centered on the pivot pin they have pretty severe negative castor rocking the wheels when turned severely on edge. While we know this helps dig in the front tire to aid tuning, there comes a point where there is NOT enough tire biting the ground and the front end pushes out more and more faster you corner.

So being able to fabricate round thrust shims ( used in lieu of the factory slip on clips ) we're able to make precise shifts in position of the upper a-arms forward or back on the pivot pin.
* Measured we have .155" of forward/back distance that indeed does change the castor quite a bit. So with a washer at each side of a-arm we simply use a combo of 2 washers who's total combined width equals @ .150" as to not create bind with pivot pin is secured tightly.

Picture is my latest setting being .050" on forward position & .100" at rear position. This places the castor angle more vertical ( Pivot ball to Pivot ball ) having wheels not tilt as severely.
Tire tread is still on edge when turning, but slightly more bite on the ground and it shows as less front end push / slide while cornering at speed.

At the same time also needed to shim the Lower A-arm ball link outward another .030" to maintain the @ 3 degree Front wheel CAMBER angle.

Done together the Kraton is really becoming a lot better planted and driveable throwing it around on a track surface.

Just sharing what I'm chasing .. and wondering if others have any input ?

Thanks,
BK

 

[Big Kid]

Another couple sets for testing at .120" X .030" & one more set at .140"x .010" which w/o cutting/notching the a-arm will reduce Castor angle further yet.

** To make note, any width combo can be installed reverse INCREASING castor angle ... FYI

 

[Tex Koder]

I use a combination of 3D printed clips and stainless steel washers on mine..

A bit more planted -bashing over loose dirt and rocky grounds ,IMO than before..
But it seems to have more understeer. Which maybe because I'm still on stock (weak) steering servo.

 

[Big Kid]

Am also noticing that .... As Castor angle moves more vertical, the Ackerman effect of having inside wheel turning sharper than outside IS INCREASING as well

 

[DLK83]

Am also noticing that .... As Castor angle moves more vertical, the Ackerman effect of having inside wheel turning sharper than outside IS INCREASING as well

Yup, and this is where tires make a huge difference.... try getting into a set of pin tires or something less aggressive as this will allow the tight turning angles, but also allow the tires to "push" into the turn a little. The more negative caster with aggressive tires can make for some funny handling... now, after you get all that hullabaloo figured out, start messing with scrub radius and roll center

 

[Dan B.]

Never played with CASTOR (that’s the horrible oil that sadistic grandmothers used to pour down your throat to make you puke) but I’ve played with caster extensively. However, your timing is great because that’s exactly what I’m working on today!
The design of the front suspension on all of the 6s Arrmas is going to give more caster angle than anyone is ever going to need or want. Like you, I want less. And like you, I also hate those cheesy plastic caster clips. To get the least amount of caster available, I do this:

Fit the front upper a-arm with no clips installed. If using a spacer (which I do) I use a caliper and measure the total distance (where the clips would normally be) of the extra space. Then I subtract 1.5mm from the total to compensate for the three M4 0.5mm PTFE/Teflon washers that go on the pin on either side of the upper arm and the rear outboard side of where the spacer will be up against the rear pin block.
That left me with a measurement of 2.03mm. So I was able to fit an aluminum M4x2mm spacer and when all tightened up she’s smooth as a baby’s arse and exhibits no slop at all. It feels like it’s on precision bearings, and life is good. Nylon bushings could also be used of course, but you’d have a higher wearing surface.

The upper and lower suspension pins I’m using are the RamJam titanium ones and for speed run cars I highly recommend them. They’re light as a feather. I try to limit my use of titanium on street bashers though, because it wears more quickly.

Am also noticing that .... As Castor angle moves more vertical, the Ackerman effect of having inside wheel turning sharper than outside IS INCREASING as well

Yes, that is correct. Move your inner steering linkage ball to the forward most position (nearest front of car) on the Ackerman plate. That will help. Then after you adjust the toe setting play with the pivot balls when you adjust camber. That would be done with the car fully dressed, sitting on all fours with the batteries in it. You can make an improvement, but you’ll still have too much positive caster to get a decent scrub radius. Don’t let it keep you up at night. The reality is that a perfect alignment can never be achieved with either a pivot ball front suspension (you need c-hubs like a proper car) or with that much built in caster.
Arrma could remedy this by eliminating the stupid front kick-up and designing some proper upper and lower a-arms that don’t have an offset axis and use C-hubs instead of pivot balls.

 

[Tex Koder]

Never played with CASTOR (that’s the horrible oil that sadistic grandmothers used to pour down your throat to make you puke) but I’ve played with caster extensively. However, your timing is great because that’s exactly what I’m working on today!
The design of the front suspension on all of the 6s Arrmas is going to give more caster angle than anyone is ever going to need or want. Like you, I want less. And like you, I also hate those cheesy plastic caster clips. To get the least amount of caster available, I do this:
View attachment 361865
Fit the front upper a-arm with no clips installed. If using a spacer (which I do) I use a caliper and measure the total distance (where the clips would normally be) of the extra space. Then I subtract 1.5mm from the total to compensate for the three M4 0.5mm PTFE/Teflon washers that go on the pin on either side of the upper arm and the rear outboard side of where the spacer will be up against the rear pin block.
That left me with a measurement of 2.03mm. So I was able to fit an aluminum M4x2mm spacer and when all tightened up she’s smooth as a baby’s arse and exhibits no slop at all. It feels like it’s on precision bearings, and life is good. Nylon bushings could also be used of course, but you’d have a higher wearing surface.
View attachment 361867
The upper and lower suspension pins I’m using are the RamJam titanium ones and for speed run cars I highly recommend them. They’re light as a feather. I try to limit my use of titanium on street bashers though, because it wears more quickly.

Yes, that is correct. Move your inner steering linkage ball to the forward most position (nearest front of car) on the Ackerman plate. That will help. Then after you adjust the toe setting play with the pivot balls when you adjust camber. That would be done with the car fully dressed, sitting on all fours with the batteries in it. You can make an improvement, but you’ll still have too much positive caster to get a decent scrub radius. Don’t let it keep you up at night. The reality is that a perfect alignment can never be achieved with either a pivot ball front suspension (you need c-hubs like a proper car) or with that much built in caster.
Arrma could remedy this by eliminating the stupid front kick-up and designing some proper upper and lower a-arms that don’t have an offset axis and use C-hubs instead of pivot balls.

That looks like some high precision tuning right there sir.

I'm going to try to replicate your extreme setup... One of these days.

 

[Big Kid]

Yup, start messing with scrub radius and roll center

Was doing that a few weeks ago and found that moving down on inboard rear link while keeping connection at axle carrier on top holes added camber as suspension was compressed. Static rear Camber also @ 3 degrees negitive with battery on board.
Snapping a turn after landing off a jump resulted in a lower tendency to high side trip on outside edges of tires.

Or I'm imagining it ???

 

[Garcbomber]

Are you familiar with the Typhon TLR setup and adjustments?

 

[Dan B.]

Are you familiar with the Typhon TLR setup and adjustments?

I’ve been playing with it, but it still can’t overcome the front kick-up geometry and the built in (excessive) caster. The extra tuning positions get it closer, but it still isn’t near enough to perfect. It is indeed a better mousetrap from the Arrma perspective but not even close to what Hobao, for example, is offering.

 

[Garcbomber]

I’ve been playing with it, but it still can’t overcome the front kick-up geometry and the built in (excessive) caster. The extra tuning positions get it closer, but it still isn’t near enough to perfect. It is indeed a better mousetrap from the Arrma perspective but not even close to what Hobao, for example, is offering.

If Tex printed you inserts more extreme than the kit, is it feasible to get perfect within the available block adjustment area?

Otherwise the upper hinge pin block could be custom machined if you knew the exact hole location based on the tower position.

 

[NitroK]

Never played with CASTOR (that’s the horrible oil that sadistic grandmothers used to pour down your throat to make you puke) but I’ve played with caster extensively. However, your timing is great because that’s exactly what I’m working on today!
The design of the front suspension on all of the 6s Arrmas is going to give more caster angle than anyone is ever going to need or want. Like you, I want less. And like you, I also hate those cheesy plastic caster clips. To get the least amount of caster available, I do this:
View attachment 361865
Fit the front upper a-arm with no clips installed. If using a spacer (which I do) I use a caliper and measure the total distance (where the clips would normally be) of the extra space. Then I subtract 1.5mm from the total to compensate for the three M4 0.5mm PTFE/Teflon washers that go on the pin on either side of the upper arm and the rear outboard side of where the spacer will be up against the rear pin block.
That left me with a measurement of 2.03mm. So I was able to fit an aluminum M4x2mm spacer and when all tightened up she’s smooth as a baby’s arse and exhibits no slop at all. It feels like it’s on precision bearings, and life is good. Nylon bushings could also be used of course, but you’d have a higher wearing surface.
View attachment 361867
The upper and lower suspension pins I’m using are the RamJam titanium ones and for speed run cars I highly recommend them. They’re light as a feather. I try to limit my use of titanium on street bashers though, because it wears more quickly.

Yes, that is correct. Move your inner steering linkage ball to the forward most position (nearest front of car) on the Ackerman plate. That will help. Then after you adjust the toe setting play with the pivot balls when you adjust camber. That would be done with the car fully dressed, sitting on all fours with the batteries in it. You can make an improvement, but you’ll still have too much positive caster to get a decent scrub radius. Don’t let it keep you up at night. The reality is that a perfect alignment can never be achieved with either a pivot ball front suspension (you need c-hubs like a proper car) or with that much built in caster.
Arrma could remedy this by eliminating the stupid front kick-up and designing some proper upper and lower a-arms that don’t have an offset axis and use C-hubs instead of pivot balls.

Can't find a single Arrma part in the pictures. Precision build...very impressive.

 

[Dan B.]

If Tex printed you inserts more extreme than the kit, is it feasible to get perfect within the available block adjustment area?

Otherwise the upper hinge pin block could be custom machined if you knew the exact hole location based on the tower position.

I think it’s definitely possible. I’ve given it a lot of thought since I’ve been shifting my focus to road cars. To get it perfect it would require redesigning the front bulkhead for fitting on a flat chassis with no front kick-up and changing the top and bottom pin blocks to accommodate this. Then, when the front upper and lower arms were redesigned to fit this new configuration it would be possible to have meaningful caster adjustment via the upper arm without totally screwing up the other adjustments, as the inner pivot axis would be 0°. But here’s the deal…why? Because you already get all of that when you purchase a Hobao VTE (SWB) or VTE-2. So…just go but a Hobao and be happy? Thats the rub, as they say.

Can't find a single Arrma part in the pictures. Precision build...very impressive.

Thank you, sir! I’ll have a build log up in the very near future.

 

[Big Kid]

For giggles set up Both the Typhon and Kraton on a flat surface resting on the belly pan.
Taking a machinists adjustable angle finder / compass took a measurement angle for Castor.

TYPHON with a centered Top a-arm = @ 33 degrees
KRATON with the .100" X .050" Top a-arm spacing as above post #1 = @ 24 degrees

FYI

 

[lautri]

Caster, not castor.