Author Topic: Trailling A-arm design  (Read 11138 times)

0 Members and 2 Guests are viewing this topic.

Offline BDKW1

  • Hero Member
  • ****
  • Posts: 896
Re: Trailling A-arm design
« Reply #15 on: November 17, 2012, 10:31:36 PM »
If it has camber change as it cycles it will also have toe change.

Only on a trailing arm car. A-arms not afflicted this way.

ironknot

  • Guest
Re: Trailling A-arm design
« Reply #16 on: November 18, 2012, 12:51:26 AM »
It needs a lot of tuning, I should explain the original idea was for a 5 link design and I was working on the driven line to get the maximum amount of travel. Now with the double single sprocket I could maybe put the cvs bolted to it so the forward link, Hub into chassis wouldn't fit how I wanted it so this is the solution. Its hot of the bendtech by a couple of days and I was wondering if it was as practical as it seems and by the sounds of it, might be the answer.

I have Grey Area 4 piston/Combo front brakes/hubs, 2 x 16 fox 3 tube by-pass, 2 x 16 fox air, 2 x 18 fox res coil overs, RCS with 300m stars, budgeting for welder, thinking small tig. Then learn how to weld, have some experience and doing night course in the new year. Hopefully by the time I'm welding Ok I'll have the design workable

Not in any hurray I'd rather get things the way i want than have some thing tomorrow.

Offline fabr

  • Administrator
  • *
  • Posts: 93126
Re: Trailling A-arm design
« Reply #17 on: November 18, 2012, 07:26:28 AM »
Only on a trailing arm car. A-arms not afflicted this way.
I haven't taken time to think that through but are you sure about that with this idea? This isn't a regular a arm geometry is it? If it were there would not be any wheelbase change when cycled through the range of travel. Since there will be a wheelbase change would there not be a toe change ? Just talking without thinking this through.
"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 fabr

  • Administrator
  • *
  • Posts: 93126
Re: Trailling A-arm design
« Reply #18 on: November 18, 2012, 07:35:51 AM »
Thanx Bdkw1, the front is long for a fuel tank infront of the pedal box and as the rear assembly has just come up so its a bit of a mess. Might take a good while to get some parts and start measuring. Everything is relient on something else its a jigsaw starting with the spool cv distance so I'll start with those parts and if that works move from there.

I post the progress down the track a bit.
Just a suggestion that will help prevent issues later,build from the wheels in. Everything really revolves around that . First step of any build is to determine the wheelbase and track dimensions.EVERYTHING is dependent on those 2 things and cannot be compromised.
"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 fabr

  • Administrator
  • *
  • Posts: 93126
Re: Trailling A-arm design
« Reply #19 on: November 18, 2012, 07:37:12 AM »
Also curious as to why you are considering using a double single sprocket.
"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 dsrace

  • VIP
  • *
  • Posts: 8581
  • my one true weakness
Re: Trailling A-arm design
« Reply #20 on: November 18, 2012, 08:06:16 AM »
with the arc they will be pivoting on I don't think there will be a toe change if it's done right but if it's a true daully and has a tie rod getting the bump out could be trying!
« Last Edit: November 18, 2012, 08:08:45 AM by Dsrace »
Don't never argue with an Idiot!
Because he will drag you down to his level and beat you with experience

Offline fabr

  • Administrator
  • *
  • Posts: 93126
Re: Trailling A-arm design
« Reply #21 on: November 18, 2012, 08:13:19 AM »
The arm mounts are not parallel to the cars centerline. If they were I'd agree but they are skewed. Honestly,CAD would prove whatever is correct and at this time I feel we only have WAG's.
"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 #22 on: November 18, 2012, 09:18:23 AM »
Double single sprocket should give the strength I'll need for a reduction from cs to jack. Width 86 inches wheels base 118 inches. Also need to determine the mounting face/centre cv distance because the A-arm mounts will have to be inline to eliminate plunge.

Not a new idea: http://www.offroadfabnet.com/forums/showthread.php?t=10011

Have looked at this idea a while ago and the theory is good. Toe variation is a percentage of the inlines a-arm. In-line 100 percent 45 degrees 50 percent as the toe variation will move the hub clock wise and anti clock wide viewed from the side. Or if this was a double trailing arm (two trailing arms) the toe would affect caster. That's it as the angle is moved from the inline position the toe starts affecting castor.

Offline BDKW1

  • Hero Member
  • ****
  • Posts: 896
Re: Trailling A-arm design
« Reply #23 on: November 18, 2012, 02:05:23 PM »
Also, you either need to move the roof bars out where they meet the B-pillar or move the rear diagonals in. They should meet at the same spot on the B-pillar.

ironknot

  • Guest
Re: Trailling A-arm design
« Reply #24 on: November 18, 2012, 05:29:46 PM »
Thanx Bdkw1 I should have checked a few precidents but I liked the look of it, I'm going to submit the plans to Cams (Australian Motorsport governing body) before I start.

What I want to know is what is the ideal diamensions for a single buggy if Im left with an 86 inch outside rear wheel measurement. 112 seems popular for smaller buggies and would give a better turning circle but I really want to be able to hold top speeds over whoops and 118 seems like the next step and would give me a bit more straightline stability. 26

If your have a theory I'd like to hear it and spec on suspension travel would be very welcome I'm thinking if the back comes together I could get 26 inches of wheel travel (with MT Baja belted 31 inch) sounds huge but I shooting for the sky. Preload anyone? Another guess 8 inches. . . thoughts pls.

Offline fabr

  • Administrator
  • *
  • Posts: 93126
Re: Trailling A-arm design
« Reply #25 on: November 18, 2012, 05:42:51 PM »
ride height ,IMO,should be 1/2-2/3 of travel depending on a lot of things not the least of which is just plain personal preference
"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 BDKW1

  • Hero Member
  • ****
  • Posts: 896
Re: Trailling A-arm design
« Reply #26 on: November 18, 2012, 09:04:45 PM »
I'm going to submit the plans to Cams (Australian Motorsport governing body) before I start.

They will actually review plans and OK them before being built? What a strange concept...........  rofl

That was a joke that would only make sense if you had run a car through SCORE tech.......

As for wheel travel, Is this for NZ tracks or Ausi tracks? Either way 26" is way too much. A well done 16" would handle either. 12-14" would be better in NZ.

Also, fuel tank in front? On a light car this will create a lot of weight bias change from full to empty. Getting mounted near the center of the car would be the best. I'm all for weight in the front of the car, but it needs to be something that doesn't change like the battery.......

ironknot

  • Guest
Re: Trailling A-arm design
« Reply #27 on: November 18, 2012, 10:41:09 PM »
Buggies for Aussie and the suspension numbers are a matter of casing an idea for a very long time. Its the 26 inches is too much that I want to work out, like how much is too much pre-load.

Class one buggies and some TT are using 24 inches front suspension, maybe that's the magic figure I'm after even with smaller wheels the centre of gravity is still the same after preload and too much preload will make for huge body role and pitching into corners and maybe whoops.

I had an old Type 4 vw and I remember with a full tank of fuel it was impossible not to get a big off putting dip in the front end braking into a hard corner. So move the driver forward and put the tank behind the driver as low as is possible.

Still having trouble with the too much suspension and preload idea, lol  LMAO LMAO, its an unexpected change of perspective I'm going to do some more research from this new perspective and see what were I get. I could probably put a rear sway bar but I think a front sway bar would be out of my league.

So if you have an idea of the ideal amount of pre-load or just care to tell me what you reckon, I'd appreciate any ideas.

Offline fabr

  • Administrator
  • *
  • Posts: 93126
Re: Trailling A-arm design
« Reply #28 on: November 19, 2012, 05:48:47 AM »
preload IS ride height.

ride height ,IMO,should be 1/2-2/3 of travel depending on a lot of things not the least of which is just plain personal preference regardless of travel .   Trophy trucks and small buggies are 2 completely different animals. A big and heavy TT needs a huge amount of travel. A light buggy will not likely even be able to cycle the suspension through 24" or more travel. To do so would require a very soft valved shock. That soft valving will do almost nothing to control the car through whoops and the body roll would be horrendous. If massive jumps are the only thing you would do then MAYBE a smaller,lighter buggy could use huge travel numbers. Don't get tunnel vision when it comes to numbers.  As BDKW said,sometimes less is better.
"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 BDKW1

  • Hero Member
  • ****
  • Posts: 896
Re: Trailling A-arm design
« Reply #29 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.

 

SimplePortal 2.3.7 © 2008-2024, SimplePortal