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Front-end design: What does a strut rod do?

 
  #31  
Old 01-06-2003, 07:03 PM
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Front-end design: What does a strut rod do?

Based on the reactions I've read I'm not quite sure if I screwed up by submitting my last post. My goal was to give all of us some idea of the forces on the tire tread during the stop Paul outlined. All the math and physics junk in between the initial numbers Paul mentioned and the final loads isn't that important as long as it's done correctly. I'd certainly appreciate someone checking what I wrote.

The real result I was trying to present is that you get loads on the order of the following during a stop with Paul's numbers.

1. 1500 lbs toward the rear on each front tire tread
2. 1500 to 2500 lbs maximum upward on each front tire tread from the vehicle weight - the magnitude depends on the roughness of the road and/or potholes
3. No sideways forces on the front tire treads as long as you're stopping straight. I can do the cornering calculations if you give me some numbers.
4. No torques on the tread since the tire structure doesn't support significant applied torques.

Remember, these numbers are engineering estimates only. They are intended to tell you the forces are not around 10 lbs nor are they as big as 10,000 lbs. Despite their approximate nature, you can do quite a bit with these results and a little further analysis. I'll use these estimates every time over some of the "expert opinions" I've read on other message boards. From what I've seen on those boards someone's "expertise" is apparently proportional to the number of four letter words they can type. :-X23

George

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Old 01-06-2003, 07:41 PM
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Front-end design: What does a strut rod do?

George

You didn't screw up anything. You smoked my simple little mind but that's not your fault. We have to back up the truck here though. You got Paul and I headed for Barnes and Noble. And thats OK, we are interested in learning about suspensions. I was questioning Paul on one particular mount on his Gibbons. You need to see a PIC before we proceed. There are several ways to mount the Gibbons. Bolts, weld, or even rivets I suppose if you had the equipment. There will be other issues we want to discuss.

What we are looking for is a thoughtful and critical analysis of our IFS. (At least thats what I want). If someone sees a spot on my Volare that looks a bit weak and needs a gusset. I sure wish they would speak up now before I take the family for a ride. I have serious concern about my lower control arms. Should I box them?? Or does welding cuse more trouble than the box helps? My truck may weigh 500 pounds more than a Volare.

I would like to start from a simple generalization. "That part there looks too girly from a truck suspension" We can proceed to the physics as required but you need to understand the question before you invest so much time in the answer. I won't BS you and pretend to understand your last post. I have had some calculus and trig and that's it. Two decades ago!!!!

Hopefully there will be no thin skin here. Anyone who installs a custom IFS and is too proud to have it checked for weak spots is a fool in my opinion. All I have read on other forums and here is "your IFS sucks" but I don't have any solid evidence it is in fact dangerous, and worse, they have no solution. What good is that?

George, I thank you again for posting the info you did and hope you will continue to assist us when we get the PICs up.

'fenders
 
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Old 01-06-2003, 09:52 PM
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Front-end design: What does a strut rod do?


George, I've got a better question. Two actually.

Joe points out that the rivets on the frame that hold the crossmembers to the frame rails are pretty 'soft'. First question; did any of those rivets fall out of their holes after you ground their heads off or did you have to drive them out with a punch?

Second question; How thick are the frame rails on your F-250?

Thanks.

 
  #34  
Old 01-06-2003, 10:49 PM
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Front-end design: What does a strut rod do?

OK, here are a couple of pics of the infamous BatClip. Keep in mind that it is installed with the suspension compnents mocked up for fitment should a missing bushing or absent part look suspect.

This is a side view showing four of the five 3/8" mounting bolts per side. One was provided for alignment through an existing rivet hole and I drilled the other three. Not visible is the 1/2" bolt in the center which threads through the frame from the other side into a nut welded internally into the crossmember.

https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=11109&.jpg

This view is from the front corner and shows the strut rod and strut rod mount. Notice that it terminates in the same location as the original front spring perch. And yes, Paul, it is laterally in the same plane as the lower control arm pivot.

https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=12150&.jpg

This view is from directly above and shows the clearance that must be cut in the frame flange for the steering box. The clearance notch in the lower flange is not even half that size. The crossmember is attached directly opposite this notch, which I believe is plenty of support. No other modifications of the original frame are necessary.

https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=12151&.jpg
 
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Old 01-07-2003, 05:51 AM
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Front-end design: What does a strut rod do?

>
>George, I've got a better question. Two actually.
>
>Joe points out that the rivets on the frame that hold the
>crossmembers to the frame rails are pretty 'soft'. First
>question; did any of those rivets fall out of their holes
>after you ground their heads off or did you have to drive
>them out with a punch?
>
>Second question; How thick are the frame rails on your
>F-250?
>
>Thanks.


1. Frame rails and crossmembers are all stamped or formed 3/16" thick sheet stock (although some of mine are now a bit thinner ).

2. NO rivets came out without at least some force. If you are asking about how well the rivets would transfer shear loads across the holes they filled, I would say the rivets completely filled the holes in virtually every case. That's what you would expect if they were installed using traditional "hot forge" technology.

Joe is correct WRT the rivet material. I would guess they are a 1008, 1010, or 1015 mild steel. They drilled very easily and almost certainly had a tensile strength less than 60,000 psi (415 MPa).

George

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See my 1956 F-250 in progress at www.clubfte.com/users/earl/index.html
 
  #36  
Old 01-07-2003, 06:26 AM
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Front-end design: What does a strut rod do?

[updated:LAST EDITED ON 07-Jan-03 AT 08:24 AM (EST)]Joe and Paul

I have a couple questions I need to ask before I ask any more questions.

This seems obvious but I better ask. Are these assumptions correct?

The torque strut mounts to the front bracket via rubber bushing? How about where it mounts to the lower control arm? Solid or bushed in some manner.

The torsion bar enters the lower control arm very close to where it bolts to the crossmember? The x-member sits tight to the frame on the sides and bottom? No shimming required?

What is frame thickness on an F-1, about 5/32-3/16???

I am still trying to get all the facts straight.

'fenders
 
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Old 01-07-2003, 07:52 AM
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Front-end design: What does a strut rod do?

The strut rod is mounted through a rubber biscuit bushing at the front mount and bolts solid to the lower control arm outboard directly behind the lower ball joint. No side shims were necessary - it is a snug fit to the rails. You actually have to pinch them a hair with a come-a-long to get the crossmember slid around them. The rail does not contact the crossmember at the bottom. It hovers slightly over it. This is due to the irregular shape of the rail in this location - there is a slight vertical curvature in this area. I've measured the frame thickness at approx. 1/8", but it may be 3/16". Eyeballed it with a tape, but never did put a micrometer on it.
 
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Old 01-07-2003, 08:48 AM
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Front-end design: What does a strut rod do?

Hopefully there will be no thin skin here. Anyone who installs a custom IFS and is too proud to have it checked for weak spots is a fool in my opinion. All I have read on other forums and here is "your IFS sucks" but I don't have any solid evidence it is in fact dangerous, and worse, they have no solution. What good is that?


Thats a very incorrect statement Dewayne.

ElPolacko (owner of Industrial Chassis) did a very detailed write up of how to build a proper M11 awhile before the STBXW thread. It went into the HAMB Techomatic but unfortunately all the diagrams are gone. Drop him an EMail.

On RRT, Phat had an extensive thread with photos of mods necessary to mail order kits. He is a pro rod builder. Search the archives.

And yes some IFS's that were shown over the past years do suck according to those qualified to say it.



 
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Old 01-07-2003, 10:41 AM
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Front-end design: What does a strut rod do?


George wrote;NO rivets came out without at least some force. If you are asking about how well the rivets would transfer shear loads across the holes they filled, I would say the rivets completely filled the holes in virtually every case. That's what you would expect if they were installed using traditional "hot forge" technology.

Joe is correct WRT the rivet material. I would guess they are a 1008, 1010, or 1015 mild steel. They drilled very easily and almost certainly had a tensile strength less than 60,000 psi (415 MPa).


Thanks, George, this is what I expected. The rivets fit tight in all axes. As you point out, it would transfer shear loads well. I expect that even though it is soft material, it does its job perfectly.

When I recently learned that the function of the strut rods was to bear the load of braking forces, I started thinking about all the implications of those braking loads. Because the A-arms will likewise apply torque to the Gibbon's crossmember on the vertical plane of where it bolts to the frame I will try to install my crossmember with close fitting bolts or locating dowels. I will also weld some metal onto the inside of the frame to increase its cross section on that shear plane. I think these are small modifications that will add to my peace of mind.

The reason for the question about the thickness of the frame was just to find out if F-250 frames were thicker than F-100. I'm thinking about how I might box the frame. Because the frame is formed with a hump, a straight piece of C-channel won't fit well. If I find a donor frame and cut the front frame rails off, I could fit the left side of the donor metal to the right side of the frame to be boxed (and visa-versa). It should mate up with the hump pretty good. I was hoping that F-250 frames were slightly thicker than F-100 frames. I could box the frame up to the place where the strut rods are attached. I don't know how far back they might want to be boxed.

But the need to notch the frame for the steering box is a wrinkle. I'll have to mock things up and see what it looks like.

I did a little reading in the Physics book last night, getting my brain warmed up to the subject. Looks like this stuff falls under the category of 'Newtonian Physics'.

 
  #40  
Old 01-07-2003, 02:30 PM
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Front-end design: What does a strut rod do?

[updated:LAST EDITED ON 07-Jan-03 AT 03:31 PM (EST)]I've purposely kept quiet lately on this thread, cause I don't understand what the heck you guys are talking about.. I figure if I can't confuse the issue to shut up... I'm not even smart enough to confuse this topic...

As for the post on the HAMB... ElPolako did an excellent job explaining the install of a MII unit and also did a excellent critique on what's available on the market and what is junk... I havent seen the post on RRT but I'm gonna look for it...

Yall keep thrashing this... I get a sentence every now and then that I understand, but I trust Fenders will 'splain it to me in little words soon...


I appreciate all the good intelligent input here on this subject, you guys will make me smarter in spite of myself...

john ( just trying to maintain an acceptable level of cool )

BTW 286 merc... do you remember the thread title on the RRT thread that Phat did ???
 
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Old 01-07-2003, 04:27 PM
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Front-end design: What does a strut rod do?

I found these


http://www.roddingroundtable.com/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=2412&forum=DCForumID1

http://www.roddingroundtable.com/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=2421&forum=DCForumID1

http://www.roddingroundtable.com/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=2240&forum=DCForumID1

http://www.roddingroundtable.com/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=2595&forum=DCForumID1

Also found some of yours but I wont tell anyone


 
  #42  
Old 01-07-2003, 04:50 PM
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Front-end design: What does a strut rod do?

[updated:LAST EDITED ON 07-Jan-03 AT 06:28 PM (EST)]Here's one more of the inside of the rail showing all five of the attaching bolts.

https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=12273&.jpg
 
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Old 01-07-2003, 05:37 PM
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Front-end design: What does a strut rod do?

<<<I've purposely kept quiet lately on this thread, cause I don't understand what the heck you guys are talking about.>>>

John

Whats going on here is I hijacked Pauls thread. I apologize for that Paul. I am bad about doing that sometimes. I have been looking for an opening to discuss some of the various IFS systems for a LONG time. I know exactly zero guys with rodded F100s where I live. This is my only source of info others than magazines. I have been hoping for some time the Gibbons kit would get some prime time here. I like what I see so far and will post on that subject in a bit. It would have been easier if we had a thread on each system, one at a time, and gave them a critical look. Locate potential weakness and offer opinions on potential improvements. I have cause a confusing thread for sure. I am trolling for my next project and want to investigate my IFS options now.

<<<Thats a very incorrect statement Dewayne.
ElPolacko (owner of Industrial Chassis) did a very detailed write up of how to build a proper M11 awhile before the STBXW thread. It went into the HAMB Techomatic but unfortunately all the diagrams are gone. Drop him an EMail.>>>

Carl

I am sure you are right about El Polackos expertise. I canít get past his foul mouth. I don't associate it with intelligence. My loss.

Ďfenders

 
  #44  
Old 01-07-2003, 06:39 PM
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Front-end design: What does a strut rod do?

[updated:LAST EDITED ON 07-Jan-03 AT 07:44&nbsp;PM (EST)]WARNING, Every bit of the following is opinion and nothing more.

I can't get 'rages link to work but I found the PICs in his gallery. Want my initial gut reaction? I'll put it in little words so Niolon can follow along. I don't know any big words John so you are catching a break here.

I like the Gibbon's x-member a lot. It looks like it fits very well. A good fit is important for something bearing this kind of load. I like the way the upper control arm shaft bolts are horizontal and bear the load on the vertical portion of the x-member where it appears very strong. This is an advantage over a Volare clip where the load is bore in a shear situation by two bolts standing straight up.

The torsion bar design looks sound. I don't see where any advantage exists over my crooked T-bar Volare but I think they are both good designs. It is so hard to get the ride height correct with some of the other systems. At least on the first attempt. This has got to be the biggest advantage of any T-bar IFS. Adjust the ride height a bit, get another alignment and youíre set.

Torque rod, strut, whatever you want to call it. I think this innocent looking bar is the key to running a car suspension on something heavier. I think almost all potential IFS problems would immediately go away with something to keep the control arm from ripping the ears off the x-member. You can reinforce the x-member all you want and youíll always have a questionable situation. The leverage created by a control arm in an emergency stop has got to be tremendous. Wish I could put a number on it but I canít. It just seems obvious to me.

Control arms. I am probably paranoid because I can't cite any Chrylser failures on stock rides. I remain unimpressed with Chrysler lower control arms. I think it is a weakness of the Gibbons and the Volare. Probably not a danger due to the fact that lower arm movement is controlled by the torque strut.

If I was installing the Gibbons kit, I might consider bolting it in as Joe did. I would probably use 7/16 bolts with very thick and high quality hardened washers. 3/8 bolts might work fine but I see no reason not to upgrade to 7/16 for the added strength. The upgrade is practically free. Paulís mention of some backup material in the inside of the frame is another potential improvement. Of course, precisely drilled holes lessen the possibility of x-member movement. I donít see any risk of danger with the way you have it now but I see some added assurance for a five dolar investment. Regarding boxing of the frame. I would probably box it with 5/32 plate. Only because I assume you pulled the x-member by the firewall like almost everyone does. I realize you will increase the danger of frame cracks where the boxing ends. I am non-committal on the boxing issue. I could be talked out of it for this IFS.

Thanks for posting the PICs Joe, I have a better idea of what the Gibbonís kit is about now.

Getting long here but I have one question. I wonder if its addressed in your instructions. Chrysler IFS is very sensitive to caster adjustment. Many Chryslers and specifically Volares require some negative caster for good handling characteristics. (Some Mopars feel like they are on ice with positive camber. I have read about trucks having the same problem if you screw up the install of Volare. Opinions vary but you need to get a couple degrees negative with a Volare. Do you know if its an important consideration with your setup. If so, how do you account for it. Or at least make sure your alignment man can get it in the correct range?

Take it or leave it, every bit of it is my opinion and dissenting thoughts are welcome.

'fenders
 
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Old 01-07-2003, 06:39 PM
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Front-end design: What does a strut rod do?


Joe,

Excellent photo.

Do I see a Grade 5 bolt in the middle? I think that's a good idea, it's less notch sensitive than a Grade 8 bolt (less sensitive to getting nicked and forming a crack on the nick). I'm sure you will torque those bolts during final assembly.

 

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