« previous next »
Pages: 1 2 [3] 4   Go Down

Author Topic: Trailling A-arm design  (Read 11305 times)

0 Members and 1 Guest are viewing this topic.

Online fabr

  • Administrator
  • *
  • Posts: 93168
Re: Trailling A-arm design
« Reply #30 on: November 19, 2012, 10:27:53 PM »
What a great way to explain it.  8)
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline Yummi

  • Grumpy, Sneezey and Dopey all rolled into one.
  • Administration
  • *
  • Posts: 238
    • Jeeping With Dogs
Re: Trailling A-arm design
« Reply #31 on: November 20, 2012, 05:32:22 AM »
Quote from: BDKW1 on November 19, 2012, 08:10:10 PM
For something fun.....

A class 1 buggy weighs 3500-4000#'s. Lets say 3750 average. They usually have around 20" of wheel travel. say 40/60 weight bias and you get 1500#'s in the front. 1500/20 inches of travel=75#'s per inch. Now if your motorcycle powered car weighs 1500#'s with the same weight distribution you get 600#'s in the front /75 = 8" of travel. I could make the 1500# car handle the same with under 10" of wheel travel.........

More mass needs more time to decelerate transfer the same amount of force. Wheel travel = time. The lighter the car the less wheel travel is needed. Granted, this assumes that a lot of things like unsprung weight will decrease proportionally so it's not exact but more of a fun observation.

Wow, very insightful.  About 5 / 6 years ago I asked the question on another forum and got crickets.  My question was is a well thought out 12" better than a poorly thought out 16" or some variation of that.  My underlying concern being that so many folks had tunnel vision re: Total travel vs. Quality of Travel.  You just kind of hit the nail on the head. 
Logged
**********************
I like things that move.   Pretty much limits me to cars and strippers

Did you know I have a blog?  Come on now, it is 2016, everybody does.  http://www.jeepingwithdogs.com

Online fabr

  • Administrator
  • *
  • Posts: 93168
Re: Trailling A-arm design
« Reply #32 on: November 20, 2012, 07:08:06 AM »
He sure did!
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline Carlriddle

  • Another build? What are you thinking?
  • Hero Member
  • ****
  • Posts: 4593
Re: Trailling A-arm design
« Reply #33 on: November 20, 2012, 07:20:33 AM »
Quote from: Yummi on November 20, 2012, 05:32:22 AM
Wow, very insightful.  About 5 / 6 years ago I asked the question on another forum and got crickets.  My question was is a well thought out 12" better than a poorly thought out 16" or some variation of that.  My underlying concern being that so many folks had tunnel vision re: Total travel vs. Quality of Travel.  You just kind of hit the nail on the head.

Are we still talking about suspension? Or something else  rofl

So I'm trying to soak this in, and seems to me that any type of suspension that has a forward arm (trailing, semi trailing, 4/5/6 link) that once that forward arm reaches level any additional up travel will result in the tire also moving toward the front of car.  And if your running 30" tire and 3" ground clearance then 30"/2=15"-3"=12"  so the last 12" of travel the tire would move forward. 

And thats a sweet example of the wheel travel vs weight.
Logged
You can keep your CHANGE, I'd like to keep my DOLLAR.

ironknot

  • Guest
Re: Trailling A-arm design
« Reply #34 on: November 20, 2012, 08:25:52 AM »
Quote
So I'm trying to soak this in, and seems to me that any type of suspension that has a forward arm (trailing, semi trailing, 4/5/6 link) that once that forward arm reaches level any additional up travel will result in the tire also moving toward the front of car.  And if your running 30" tire and 3" ground clearance then 30"/2=15"-3"=12"  so the last 12" of travel the tire would move forward. 

And thats a sweet example of the wheel travel vs weight.

Wheel moving forward toward the chassis pivot line but back at the angle the pivots are angles up at the front. I thing the bump is at about 16 degress so if the pivots are angled up at the front more than that its still moving back.

I'm working out why sometimes these ideas move more slowly than others, but I think I've got it.

Next question; would the wheell moving back make that much of a difference maybe comparing it to wheel size. With the wheel moving out from the below holizontal and back at the (umm) pivot angle the combines effect from hitting a bump and the wheel moving would be a big combines rearward movement that could smooth things out.

If the approach angle of a bump is 40 degrees and the initial movement of the wheel is 20 degrees back does that back the effective face of the bump 20 degrees compared to an a-arm design. This is an oldy, but a goody.
Logged

Online fabr

  • Administrator
  • *
  • Posts: 93168
Re: Trailling A-arm design
« Reply #35 on: November 20, 2012, 08:38:46 AM »
Opinion only as I have no way to prove it. The question you pose has a time component that would be involved. At slow speeds it is irrelevant. At high speeds it could become a factor. Just an opinion.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

ironknot

  • Guest
Re: Trailling A-arm design
« Reply #36 on: November 20, 2012, 08:50:07 AM »
Bit off topic but along the lines of what we're talking about, found this pdf with some interesting observations on G-forces at impact, time and the use of suspension:

www.highspeedcraft.org/pdf/7Ullman_HSC_Suspension_Seat_Design.pdf
Logged

ironknot

  • Guest
Re: Trailling A-arm design
« Reply #37 on: November 20, 2012, 10:46:31 AM »
Still not impress, the Shamwow chassis got it all.

How about a limiting strap from the base of the hoop the top hub, a-arm mount to limit bump. Nylon donut between two washer mounting the clevis and the shamwow's got limiting bump stops.

Did you say grill, of course you can.
Logged

Offline BDKW1

  • Hero Member
  • ****
  • Posts: 896
Re: Trailling A-arm design
« Reply #38 on: November 20, 2012, 07:40:00 PM »
Running rake in suspension is a good thing. It does take a lot of shock load out. This is why VW's work so well for what they are. Just be aware the rake win the front will cause more dive in braking. Either stiffen up the springs and live with it or dial in a little anti-dive......
Logged

Online fabr

  • Administrator
  • *
  • Posts: 93168
Re: Trailling A-arm design
« Reply #39 on: November 20, 2012, 07:50:56 PM »
uh,oh,the anti-dive subject again.....................where's xxxxx? He'll argue 180 opposite. Personally I see no harm in anti-dive but others don't see it that way.




(xxxxx? I decided it wasn't a good idea to use his name without his permission) :)
« Last Edit: November 20, 2012, 07:52:40 PM by masterfabr »
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Online fabr

  • Administrator
  • *
  • Posts: 93168
Re: Trailling A-arm design
« Reply #40 on: November 20, 2012, 08:15:00 PM »
Quote from: ironknot on November 20, 2012, 08:50:07 AM
Bit off topic but along the lines of what we're talking about, found this pdf with some interesting observations on G-forces at impact, time and the use of suspension:

www.highspeedcraft.org/pdf/7Ullman_HSC_Suspension_Seat_Design.pdf
I just read this. Those boat seats would be the cat's ass in a monster truck or anything with enough room.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

ironknot

  • Guest
Re: Trailling A-arm design
« Reply #41 on: November 21, 2012, 08:52:49 AM »
I think I can live with the dive as the move in alignment for the front suspension tabs would loose the wheel moving backward through the suspension movement as I understand it.
Logged

Offline Engineer

  • Inquisitor
  • Global Moderator
  • *
  • Posts: 2657
Re: Trailling A-arm design
« Reply #42 on: November 24, 2012, 03:37:33 PM »
Quote from: ironknot on November 20, 2012, 08:25:52 AM
Wheel moving forward toward the chassis pivot line but back at the angle the pivots are angles up at the front. I thing the bump is at about 16 degress so if the pivots are angled up at the front more than that its still moving back.

I'm working out why sometimes these ideas move more slowly than others, but I think I've got it.

Next question; would the wheell moving back make that much of a difference maybe comparing it to wheel size. With the wheel moving out from the below holizontal and back at the (umm) pivot angle the combines effect from hitting a bump and the wheel moving would be a big combines rearward movement that could smooth things out.

If the approach angle of a bump is 40 degrees and the initial movement of the wheel is 20 degrees back does that back the effective face of the bump 20 degrees compared to an a-arm design. This is an oldy, but a goody.

I think that it really depends where in the travel the wheel moves forward.  On a 5-link or trailing arm the wheel moves forward at the very bottom of the stroke.  At that point it doesn't matter because the impact of an edge is already taken care of and if you reach the very bottom of the travel then you are absorbing a major vertical hit.

People get away with this A-arm design (non-parallel to the center of the car) on the front all the time.  The wheels travel forward as they bump up from ride height, so it either really doesn't matter that much, or in the sand the conditions aren't that punishing. IMO.

Throwing some anti-dive into this design would be great. ;D

I can't believe Fabr is the only one that sees the toe consequences of A-arms non-parallel to the center line of the car.  Toe change is inevitable with any camber change.
Logged

Online fabr

  • Administrator
  • *
  • Posts: 93168
Re: Trailling A-arm design
« Reply #43 on: November 24, 2012, 03:58:25 PM »
I'm in the minority many times.  rofl ;D ;D So was Columbus. ;)
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

ironknot

  • Guest
Re: Trailling A-arm design
« Reply #44 on: November 24, 2012, 08:41:14 PM »
I don't think toe will be a factor because the mounts on the hub are at the same angle as the mounts on the chassis. This the inner and outer mounts parallel, the centre point, top and bottom of the hub are moving straight up/down and not affecting the toe in any way.

If the mounts at the hub were in-line with the centre line of the buggy, or the line of the hub, the toe would change dramatically as the suspension cycled.
Logged
Pages: 1 2 [3] 4   Go Up
« previous next »
 
SimplePortal 2.3.7 © 2008-2024, SimplePortal