R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Like Tree1Likes
Reply
 
Thread Tools Search this Thread
Old 06-13-2013, 05:55 AM   #1951
Tech Addict
 
Join Date: Mar 2007
Location: Melbourne
Posts: 734
Trader Rating: 37 (100%+)
Send a message via MSN to slyts6
Default

Quote:
Originally Posted by Caseymacgyver View Post
Yeah, the KPI topic has gotten a bit muddled, which I'm sure that I contributed to. I'll try and consolidate some of the info here in hope of clarifying:

The KPI mod is a complete and fundamental change of the D3's front suspension. It swaps out the steering knuckles and CVD's, deletes the C-hubs, replaces the upper double-ball links with vertically constrained arms (Yokomo Type C) and modifies the lower arms (Chopping and drilling) to attached ball cups for the lower link. In essence, all of that is to convert the upper and lower steering knuckle pivots to simple ball joints, with fore/aft stability coming from the upper and lower arms themselves, rather than the C-hubs.

The real key to being able to do KPI is using steering knuckles that have the ability to offset the steering axis from the wheel axis normal. MST is one of the few companies that currently offer that. So to be clear, the "KPI" part of the mod comes from the knuckles, and only the knuckles. The other steps are just prerequisites, with other worthwhile benefits.

The most common method uses:
  1. Yokomo Type-C 'Parts' Upper Suspension Arms - part number SD-008UC Banzai Hobby
  2. MST I PARTS-wheel hubs 210008 (Plastic) OR MST Short Arm Steering Hub, 210239 (Aluminum) - Ebay
  3. MST CVA wheel axle (2 PCS) 310006 - Ebay
  4. SQUARE Universal Shaft 46mm:OTA R31 from Broadtech.hk, Banzai, RCMart, etc...
  5. (2) 20mm set screws
  6. (2) 10X15X4mm bearing (same as the large diff. bearings)

The Yokomo arm really just replaces the inner ball stud and ball cup of the upper link. The turnbuckle threads into it, with the outer ball cup still attached. You cut/file a nice tight slot through the pivot of the Yokomo arm so that it forks around the front shock tower. You then use screws or a hinge pin through the holes in the Yokomo arm and your preferred roll center hole (existing) in the shock tower. The arm should be tight fore/aft, but free to pivot up/down.

The lower arms get cut off square at the crossbar, about 1/3 of the way inboard. You then drill a 0.100" hole roughly in the middle. The location depends heavily on where you cut the slot in the Yokomo arm. Fore/aft on either changes the caster. Do the Yokomo arms first, both at the same time if possible, and install. Then decide where you want to drill the lowers, and do them both at the same time as well. With the hole drilled, you then thread in the 20mm set screw, screwing a ball cup to that. Again, do both at the same time, holding them side-by-side. Make sure the cups extend the same distance and point in the same direction. Once you put them back on the car, count how many turns you make when finalizing the trackwidth then match on the other side.

Cutting the lower arms as described above will eliminate the outermost shock mounting position, and most likely make the 2nd outermost unusable (Chops right at the edge). This is not generally a problem, as with the significantly increased steering angle enabled by the other aspects of this mod, those 2 mounting positions become unusable anyway because the wheels would hit the shocks. The 3rd (innermost) mounting hole is unaffected by the mod and presents no interference issues. However, the increased leverage to the spring will require something correspondingly stiffer (Blue or Purple).
This is such a great help! Now I know how to finish it!

I've bought pretty much everything now... But what CVD rebuild kit do I need for the 46mm square driveshafts and the MST axles? Can I just use the stock D3 ones or do I need the square ones or MST ones???
__________________
Axial Wraith -- Scratch Built -- Vanquish -- Motoworx -- Rc4wd
Axial XR10 -- Hitec 7955tg -- Vanquish -- Airtronics -- Tekin FXR's


If it's got wheels or tits, you'll have trouble with it.
slyts6 is offline   Reply With Quote
Old 06-13-2013, 07:36 AM   #1952
Tech Regular
 
Join Date: Sep 2012
Location: Gilroy, CA
Posts: 477
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by FoiVoS_ View Post
Guys where would you reccomend me to buy the 55o mods and the FOW ? The best prices i found where in rcmart ... Anything else ?
If you are in the US tqrcracing.com is fast.
But outside of US...probably rcmart is best best
eunique is offline   Reply With Quote
Old 06-13-2013, 08:53 AM   #1953
Tech Master
 
pettyeagles's Avatar
 
Join Date: Jan 2010
Location: East Central, Il
Posts: 1,644
Trader Rating: 81 (99%+)
Default Shock Mod???

Looking for a picture of the shock mod where the dampening remains the same but the rebound is slowed down.
__________________
A bad day racing beats a good day at work. My RC fleet:
SC5M(x2), B5M, SC10.2, FT SC10, FT TC5, FT TC4, 12R5, AE Rival MT, RC10 Classic, RC10 Worlds, CW Pro Comp Outlaw, F104 pro v2, RJ Speed Legend, Traxxas Slash(x2), 4x4 Slash VXL, Vendetta ST, Axial SCX10, Yeti, Smt10, G-Made/AX10, Tamiya Super Clodbuster
pettyeagles is offline   Reply With Quote
Old 06-13-2013, 01:09 PM   #1954
Tech Apprentice
 
FoiVoS_'s Avatar
 
Join Date: Jun 2013
Location: Thessaloniki/Greece
Posts: 92
Default

Hmm i got to the point where i need to position the driveshafts and i dont know how much rear camber should i give it .. Any suggestions ?
FoiVoS_ is offline   Reply With Quote
Old 06-13-2013, 04:14 PM   #1955
Tech Initiate
 
Join Date: May 2013
Location: Carlsbad
Posts: 43
Default

Quote:
Originally Posted by DMSewell27 View Post
Thanks for putting the KPI mod in black and white.

But, I would like to know a little more about the horizontal shock you have mounted behind your front shock tower. from what I can see it offers some more adjustment to the KPI, but in truth... I am befuddled.
Here's another long one for any fellow gear heads out there

The horizontal shock mounted on the front tower was mostly driven by my high caster angle, but is certainly magnified by KPI. The purpose of the shock is to allow the left/right front suspension arms to move up/down to accommodate the up/down effect that the massive camber changes have on the wheel contact patches as they steer lock to lock. With positive caster, the leading front wheel will want to push down into the ground, while the trailing front wheel will want to lift up. This "jacking" effect can be desirable, but as caster, steering angle and KPI increase, the negatives start to quickly outweigh the positives. IMO, this would not be worth considering at 10 of caster or less. For reference, I'm running about 20 of caster and ~10 of KPI at a 2.52 CS ratio, and drive almost exclusively on residential asphalt.

Without this shock setup, the entire chassis has to roll and twist to accommodate the wheels as they steer. At high caster/KPI, the chassis will dramatically roll in the opposite direction of the drift, giving it a very unnatural, hovercraft-type movement, and very twitchy rear traction. The jacking effect also increases the weight carried by the leading front and trailing rear wheels, making those wheels less able to absorb minor bumps and thus more prone to traction upset during a drift.

With this shock setup, the chassis stays nearly flat as the wheels steer, even allowing the chassis to roll in the direction of the drift for a more natural look and (More important to me) more intuitive, predictable weight transfer during transitions. Ideally, both front contact patches are the same and the rears are the same too, independent of the steering angle. Further, the weight transfer is not abruptly forced around by the steering wheels, but rather the result of inertia, consistent traction and gravity.

The horizontal shock carries about 75-80% of the front end weight. The vertical shocks are to adjust how much and how fast the body rolls, because the horizontal shock provides no roll resistance. The vertical springs are softer than the softest D3 springs (white). The horizontal shock is mounted to the left and right pivots that are also functioning as the upper arms. When I compress the front of the car, both ends of the shock move towards each other. The suspension still behaves as independent, with the effective spring rates of the left and right sides referencing the position of the opposite side, rather than the chassis. The result is essentially the opposite of an anti-roll bar. Specifically, when one side is compressed, the opposing side extends.

Here is the design and explanation that started me down this path.
http://www.drccentral.com/forums/ind...dpost&p=219636

I had originally copied the design more completely, with both the horizontal shock and vertical shocks actuated through their own sets of pushrods and pivots. They may appear to serve redundant purposes in the above linked pictures, but the progressive nature of the pivots does in fact yield different tuning results. On the D3, the front end was too cramped to get the geometry "true" enough to perform as I wanted. It stayed flat while steering, but had too little resistance to body roll and would sort of "Flop" back and forth. Also, without anything to help return the chassis to neutral after a drift, except a roughly corresponding drift in the opposite direction, my car would tend to get stuck leaning where it was left. I eliminated the pivots for the vertical shocks and mounted them to the front tower with some very soft springs and lightweight oil. They help return the chassis to neutral, without adding much resistance to the moving arms while steering. The Yokomo had been flipped to move the motor to the rear, and has some different dynamics, so I had to adapt the concept to work for me.

Actuating the horizontal shock directly via the pivots was my own idea, but I'm sure it's been done before. I couldn't find the same single pivots as the gold Yokomo, and once I mounted the ones I used, it seemed too obvious to not do, especially since it eliminated a lot of clutter and a bit of unsprung weight. The result is very linear too. Getting the spring rate, ride height and damper travel right took a lot of trial and error, and the interdependance does complicate adjustability.

I did a linkage version of the same thing in the rear, although it's not really needed to address jacking. It does however allow the chassis to roll more evenly side to side instead of twisting, and keeps both wheels flat and on the ground no matter what. The effect is a lot of rear traction, which fits my drifting style. The upper links attach to the caliper holes and then to the chassis just forward of the lower arm hinge pin. This makes the roll center very low. At ride height, both rear wheels stay completely flat on the ground, even while rolling the chassis left/right until the leading edge hits the ground. The dual rate springs worked out perfectly here, with the ride height just short of the transition point (soft spring fully compressed). The vertical dampers are mounted to the tower same as the front, but without springs, so they basically just affect the roll rate. I'm really happy with how the rear end is working, but it's still on my list to clean up the geometry a bit. I'll probably wait until I get something nailed down for Aluminum rear lower arms before revisiting though.

Caseymacgyver is offline   Reply With Quote
Old 06-13-2013, 10:14 PM   #1956
Tech Initiate
 
Join Date: Jun 2013
Posts: 22
Default

foiVos: i just did everything as close as stock spec i could, when its up and running ill make adjustments as i go, also making sure everything is as close as it could be by analysing with my eyes..

I was wondering with the one way axles, i have this one on the way:
http://www.rcmart.com/3racing-sakd32...=595_1419_1566

thats for the front, what about the rear? should i order the same one and just use smaller pulley? I have seen a similar one but it didnt state it was for rear, What do you guys use for the rear?

Thanks
Ace212 is offline   Reply With Quote
Old 06-14-2013, 08:45 AM   #1957
Tech Master
 
pettyeagles's Avatar
 
Join Date: Jan 2010
Location: East Central, Il
Posts: 1,644
Trader Rating: 81 (99%+)
Default

You use the spool that comes with the kit in the rear.
__________________
A bad day racing beats a good day at work. My RC fleet:
SC5M(x2), B5M, SC10.2, FT SC10, FT TC5, FT TC4, 12R5, AE Rival MT, RC10 Classic, RC10 Worlds, CW Pro Comp Outlaw, F104 pro v2, RJ Speed Legend, Traxxas Slash(x2), 4x4 Slash VXL, Vendetta ST, Axial SCX10, Yeti, Smt10, G-Made/AX10, Tamiya Super Clodbuster
pettyeagles is offline   Reply With Quote
Old 06-14-2013, 01:13 PM   #1958
Tech Regular
 
Join Date: Sep 2012
Location: Gilroy, CA
Posts: 477
Trader Rating: 3 (100%+)
Default

Caseymacgyver. Thanks for your recent posts dealing with the KPI and posican. Have seen those links in drccentral and driftmission a while back but never looked into it further for its benefits but that video sure highlights it.

Until my recent break of 1 of my dogbones, I didn't realize how much slop has developed in my front suspension. 1 bearing on steering wipers was almost disintegrated..so replaced that and semi rigged the post to mimmic yours until I can get your spacers in the mail. I put one added brace on the upper arm to tie to the top chassis support and that got rid of fore/aft play on the side.
I did some practice and wowed myself...so I guess I have been getting slightly better with driving my D3.

So...when I have more time, I will try out similar set up to your front posican. What weight oil, #of holes in shocks, and front horizontal spring (do we want stiff or soft)?



Last edited by eunique; 06-14-2013 at 02:40 PM.
eunique is offline   Reply With Quote
Old 06-14-2013, 10:16 PM   #1959
Tech Addict
 
Join Date: Mar 2007
Location: Melbourne
Posts: 734
Trader Rating: 37 (100%+)
Send a message via MSN to slyts6
Default

Quote:
Originally Posted by slyts6 View Post
This is such a great help! Now I know how to finish it!

I've bought pretty much everything now... But what CVD rebuild kit do I need for the 46mm square driveshafts and the MST axles? Can I just use the stock D3 ones or do I need the square ones or MST ones???
Can anyone help me with this one?? ^^^^^^


Also I have borrowed a setup station and I need a base to set it up. Anyone got a base height and camber I should start with??
__________________
Axial Wraith -- Scratch Built -- Vanquish -- Motoworx -- Rc4wd
Axial XR10 -- Hitec 7955tg -- Vanquish -- Airtronics -- Tekin FXR's


If it's got wheels or tits, you'll have trouble with it.
slyts6 is offline   Reply With Quote
Old 06-14-2013, 10:29 PM   #1960
Tech Regular
 
Join Date: Sep 2012
Location: Gilroy, CA
Posts: 477
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by pettyeagles View Post
Looking for a picture of the shock mod where the dampening remains the same but the rebound is slowed down.
I did it before..but don't have pics of it...got the details from csjunkies
I run on carpet drift track...but eventually went back since I improved with regular rebound shocks.
eunique is offline   Reply With Quote
Old 06-14-2013, 10:40 PM   #1961
Tech Regular
 
Join Date: Sep 2012
Location: Gilroy, CA
Posts: 477
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by slyts6 View Post
Can anyone help me with this one?? ^^^^^^


Also I have borrowed a setup station and I need a base to set it up. Anyone got a base height and camber I should start with??
If I remember correctly, you can't use the MST ones since they would be too big to fit...so you should use the square pins.
I am using Broadtech R31 CVDs so mine is a little different and in my case also used the R31 pins

for setting up..good that you got a hold of a setup station..I ended up buying a set since I could always use it.

Ride height will depend on where /what surface you run on...but 5 to 7mm is a good place to start...you will have to play with it and try flat/even front to back or slightly offset between front and back

here was my setup
http://forum.driftmission.com/Thread...t#.Ubv9vlKYjYU

For camber...again there are lots of variables...and you will have to try...practice, make small, one-at-a-time changes and practice...it will be a long process since even small changes could affect the chassis
eunique is offline   Reply With Quote
Old 06-14-2013, 11:34 PM   #1962
Tech Addict
 
Join Date: Mar 2007
Location: Melbourne
Posts: 734
Trader Rating: 37 (100%+)
Send a message via MSN to slyts6
Default

Quote:
Originally Posted by eunique View Post
If I remember correctly, you can't use the MST ones since they would be too big to fit...so you should use the square pins.
I am using Broadtech R31 CVDs so mine is a little different and in my case also used the R31 pins

for setting up..good that you got a hold of a setup station..I ended up buying a set since I could always use it.

Ride height will depend on where /what surface you run on...but 5 to 7mm is a good place to start...you will have to play with it and try flat/even front to back or slightly offset between front and back

here was my setup
http://forum.driftmission.com/Thread...t#.Ubv9vlKYjYU

For camber...again there are lots of variables...and you will have to try...practice, make small, one-at-a-time changes and practice...it will be a long process since even small changes could affect the chassis
Cool ill try that setup and see how she rolls/slides


So to expand on the CVD build I need to do... I don't know the ne of the part, but I need to get the piece in the driveshaft that the pin gets screwed into...which one should I buy?
__________________
Axial Wraith -- Scratch Built -- Vanquish -- Motoworx -- Rc4wd
Axial XR10 -- Hitec 7955tg -- Vanquish -- Airtronics -- Tekin FXR's


If it's got wheels or tits, you'll have trouble with it.
slyts6 is offline   Reply With Quote
Old 06-15-2013, 01:42 AM   #1963
Tech Regular
 
Join Date: Sep 2012
Location: Gilroy, CA
Posts: 477
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by slyts6 View Post
Cool ill try that setup and see how she rolls/slides


So to expand on the CVD build I need to do... I don't know the ne of the part, but I need to get the piece in the driveshaft that the pin gets screwed into...which one should I buy?
If you ordered the Square R31 CVDs, they come with those pins (and set screws)...you just use the MST axle and the rest of the Square CVD to make a hybrid MST axle/Square dogbones CVD...or also some have used the UWA D3 dogbones mated to the MST axle.

Pickled has the details in his post #48 here
http://forum.driftmission.com/Thread...5#.Ubwn5Wt5mK0
eunique is offline   Reply With Quote
Old 06-15-2013, 02:25 AM   #1964
Tech Addict
 
Join Date: Mar 2007
Location: Melbourne
Posts: 734
Trader Rating: 37 (100%+)
Send a message via MSN to slyts6
Default

Quote:
Originally Posted by eunique View Post
If you ordered the Square R31 CVDs, they come with those pins (and set screws)...you just use the MST axle and the rest of the Square CVD to make a hybrid MST axle/Square dogbones CVD...or also some have used the UWA D3 dogbones mated to the MST axle.

Pickled has the details in his post #48 here
http://forum.driftmission.com/Thread...5#.Ubwn5Wt5mK0
Champion mate thank you! Wasn't sure coz banzai don't advertise it coming with anything else other than the bone.
__________________
Axial Wraith -- Scratch Built -- Vanquish -- Motoworx -- Rc4wd
Axial XR10 -- Hitec 7955tg -- Vanquish -- Airtronics -- Tekin FXR's


If it's got wheels or tits, you'll have trouble with it.
slyts6 is offline   Reply With Quote
Old 06-15-2013, 07:05 AM   #1965
Tech Regular
 
Join Date: Sep 2012
Location: Gilroy, CA
Posts: 477
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by slyts6 View Post
Champion mate thank you! Wasn't sure coz banzai don't advertise it coming with anything else other than the bone.
Sorry correction on that...if you ordered just the R31 dogbones then they don't come with those pins. (just looked it up from Banzai for just the dogbones and don't think they come with the pins)
Pickled's thread on that is for the complete Square R31 CVD and will come with it as you will need to disassemble the R31 axle out of it and mate it to the MST axle.
eunique is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 08:25 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net