IRS Custom A arms

mustang3550

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Any input on this A Arm build for irs would be most appricated, Doing my own this with some DOM tubing and aluminum bushing.

1184898_703896849671286_1443947765_n.jpg
 

RichV

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Sounds like a lot of work. Why not use the stocker?
 

Win

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I'm with Rich. Why not use the stock arms. Are you trying to loose weight and go with Coilovers and ditch those A arms?
 

eqmdef8

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From a fabrication standpoint I would add some gussets in to help strengthen the arm. Not trying to down your work, and you may have known/done the rest of this. Ideally you are working with a 220v mig or tig welder and not a 115v, I don't know if you'll get enough penetration with 115v mig. The tube ends should be notched. You should make a jig up and bolt the stock arm down, that way when you fab the new arm it has the same geometry, or if your changing it for some reason its in a controlled enviroment and can be dialed in.

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mustang3550

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From a fabrication standpoint I would add some gussets in to help strengthen the arm. Not trying to down your work, and you may have known/done the rest of this. Ideally you are working with a 220v mig or tig welder and not a 115v, I don't know if you'll get enough penetration with 115v mig. The tube ends should be notched. You should make a jig up and bolt the stock arm down, that way when you fab the new arm it has the same geometry, or if your changing it for some reason its in a controlled enviroment and can be dialed in.

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220v yes for sure. Im leaving the unit completly assembled and weld 3 braces to the rotor to assure it would not move as I welded, Im kinda going off Kenny Brown set, Coil overs yes. Seeing price of good bushing from sat FTBR I decide to machine and turn my own. Machining career and background. Using dom and tubing bender for the 1" dom.120 wall tubing. When torqued the a arm is freely moving and gussets are in the work. Slot is there to chamver adjustment. Stock are ill drop right back in as this on will go in aswell. I removebraces that held rotor and still easy assembly.
 

eqmdef8

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Good deal. Sounds like you know what your doing :). Again, wasn't trying to down your work, just know that there's a certain skill level needed to make control arms but you appear to have it so should be good. The only thing I would worry about then is that a solid bushing won't allow any movement other then vertical. You might end up with some stress on other places under hard cornering. That is based on the assumption you are autox/road racing. Setting up a IRS for drag is kind of pointless :).

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mustang3550

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Street and nights to ride out and for use at VIR. ALOT to upgrade on this. No harm done im looking at to see what people think and get further input. It will be stiff but as I see movement is what kills these units. Upgrading it to all 31 spline will be next. Will have a 408 n/a driving it.

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Dalamar

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Hey 2550,
Looks like a fun mach up.
I'll try to explain my impression/suggestions based on that picture.

I agree with what eqmdef said.

Since you're going with coil overs, where will the coil over mount go?
I don't like how the right "A" arm is so far offset from the frame pivot. I would change that to more of a true A-shape for more even load bearing.
Also suggest adding a gusset for strength and possibly a flat bar o(on edge) along the opposing side of the tube for additional strength.
with coil overs, remember that all the weight of the car will be transfering up the coils to the pivot point.
you could also add an additional tube to reinforce the mount as well. That's my impression on it. i'm a fan of going the extra mile so I don't have to worry about things breaking later. hope it's helpful.

Look forward to seeing updates.
 

mustang3550

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Coilover mount will be on the lower.atm I have about 3.65 distance from the bare edge to the main subframe. Coilovers being about 2.8 o.d. doesnt give to much room. On second one I may try for more on an A bend but keeping clearance is key. Coil over tabs may be welded to lower when I put rear in car so that the tab if .250 or .500 off doesnt hit the upper or subframe. I always over do it. Under car matrix went pretty extreme but it surely helped chassis stiffness. Ill look into re design with second a arm this evening. Pictures will follow.

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white95

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Street and nights to ride out and for use at VIR. ALOT to upgrade on this. No harm done im looking at to see what people think and get further input. It will be stiff but as I see movement is what kills these units. Upgrading it to all 31 spline will be next. Will have a 408 n/a driving it.

We'll have to compare notes after we get these things built/installed since my IRS is FTBR spec and is behind a 410w.



...and I like to road race...
 

Dalamar

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Gotcha,
sounds good man, look forward to seeing your fab work.
I like stuff like this.
 

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Looks like your design is solid, just as long as you're using a good welder and everything is good quality. Hard to tell by the pics how consistent the penetration is but if you have a background in this stuff you know enough whether or not to trust your work haha. Love seeing custom stuff like this, not just bolt ons ;)
 

mustang3550

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Looking like if theres a bend or sharp angle theres s gusset by there specs. Thats probably best. Time start cutting some :p

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mustang3550

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4 gussets added to what I think are the critical areas of this...I have not shaped or deburred this yet so pardon the one gusset straight edge.
u6uduga9.jpg


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eqmdef8

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looking good so far. I question your spindle side bushing. Would be better if that was 1 piece bent to a C, as it appears to be three pieces of strap welded together. Maybe some reinforcement on the area. Hard to tell from a picture though :).

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mustang3550

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looking good so far. I question your spindle side bushing. Would be better if that was 1 piece bent to a C, as it appears to be three pieces of strap welded together. Maybe some reinforcement on the area. Hard to tell from a picture though :).

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Yes it is 3 pieces I dont have access to a brake to make a "C" it measures 1.990. Wish I did have that option... a 1/2 inch piece is about all I can use to "box" it on top and bottom..
enurydeg.jpg


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eqmdef8

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I was thinking about recommending boxing it, but I'm not all that familiar with the IRS range of movement and didn't know if it would limit travel. If you could box it without contact that would definitly secure it up.

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