14 replies to this topic

[GeezRX]

I'm working on retrofitting the Dodge Caravan rear sway bar onto my 3G and have decided that, for correct fitment, I need to fabricate some brackets to carry the upper end of the end links. I am trying to decide between two materials for the brackets, A36 mild steel channel or 6061 T6 aluminum channel. I've read up on it and think that either would be suitable for my situation (spirited daily driver...no auto-x or track use). Cost difference is negligible but weight and machining abilities favor aluminum. I'd appreciate input from any of the engineering types who still frequent the site. 

 

Thanks in advance to any who care to weigh in on this!

Edited by GeezRX, 21 October 2017 - 11:46 AM.

[gtpilot]

Why go through all that trouble?  Why not just make long end links instead?

[GeezRX]

Thanks for the response gtpilot...long end links are planned and of necessity. From my investigation, it appears that the correct way to set up the sway bar pieces is with the end links mounting 90* perpendicular to the sway bar ends when the bar is set level to a level car. With my exhaust configuration and the projection length of the Dodge bar arms, the sway bar eyelets are way past the existing tow hook mounting point and measure 11" +/- from the eyelets up to the underside of the frame rail when the sway bar is positioned level. See my documentation on the process so far at the link below, if interested.

 

http://www.redpepper...ods&mod_id=3055

 

As I see it, a new bracket is required to prevent the end links from having to project "back" to the existing bracket location(s) at an angle of 30-45* (?), hence the original question.

[gtpilot]

I guess I am still not seeing it clearly.  If you can drop a plumb bob directly down from the frame rail into the right location for the bottom end link to be positioned correctly (and @ 90 degrees by default) why not just make a simple mounting bracket at the top that will accept the top end of the end link...alleviating the LPDE bushings (which will cold flow over time and get loose) and the long open section of the C channel?  Everything would also be a lot stiffer.

 

Having an end link that is 12" long (or however long it would have to be) would also keep the angular offsets to a minimum as the car rolls.

[GeezRX]

OK, that's the knowledgeable info I was looking for...I assumed that "long" end links were not the acceptable way to go. Can you recommend a site that offers the pieces to DIY some links? McMaster-Carr only had coupling/sleeve nuts in 6" max lengths for 3/8-16 threads (my preferable size) and again, I assumed that using two coupling nuts together to achieve a desired length would likely not be suitable (?) I can now rethink using the Dodge end link brackets by moving them towards the rear enough to catch the links but would prefer to through bolt them on (they will not catch any of the 3 existing threaded fittings used by the OE tow hook bolts when placed in a position to catch the end links top mount in a perpendicular line up from the sway bar eyelets). Can I accomplish this without using any type of bushing between the frame rails or should I substitute some aluminum or steel ones? I'll just insert here that , unfortunately, I don't have the ability to weld items and although the fellow I use does top notch work, he rightfully commands a nice price...so I'm trying to accomplish this project without any "outside labor". Thanks for supplying valuable info towards this project sir!

[firstgencrx]

Maybe you could put something together that would work from some spherical rod ends and swedged tubing? The tubing comes in lengths from 4" long to 38.5" in what looks like 1/2" increments. From Speedway Motors anyway...

 

http://www.speedwaym...Male,29366.html

 

http://www.speedwaym...reads,5891.html

[gtpilot]

Maybe you could put something together that would work from some spherical rod ends and swedged tubing? The tubing comes in lengths from 4" long to 38.5" in what looks like 1/2" increments. From Speedway Motors anyway...

 

http://www.speedwaym...Male,29366.html

 

http://www.speedwaym...reads,5891.html

 

Yep - something like that for the rod and the top link (it looks like you need something else to attach to the sway bar?) and then use the c-channel with the opening facing down, bolted to the frame, and then use a bolt through both ears of the c-channel, through the rod end, so that the bolt is in double shear.  If you need to make spacers to center, or offset, the top end link that should be easy to do so you can make the c-channel wide enough to make it easier to catch the threaded holes in the frame.

 

Imagine the two plates (with the two red arrows by them) is your c-channel bolted to the frame...

 

https://www.google.c...iact=mrc&uact=8

[GeezRX]

Thank you gtpilot and firstgencrx for your knowledgeable input! Based on your suggestions I re-evaluated the project and made changes as shown in the new plan in my first post above. The table below reflects the material available for use in the end link brackets.

 

OK, I'll explain my reasoning on these and then will appreciate any input given back...3" or bigger stock gives me adjustment to move the brackets side to side as needed, still catches the existing threaded inserts and keeps the hardware to a minimum in size/quantity. Narrower is stiffer/stronger/cheaper. I am assuming again that, as the Dodge end link brackets are 0.200" thick, my best bet is to choose material of that thickness or above (?) for the replacements. I'll pick from the two iterations of the material in the list (size/wall) as I figure out exactly what is needed to catch the end link tops properly while still allowing use of the existing threaded inserts from the OE tow hooks.

The Speedway Motors items should work perfectly for DIY end links and I greatly appreciate the recommendation/links! I can use heim joints on both ends as the Dodge sway bar has a 10 mm hole on the leg ends.

 

 

Lastly (for now), I want to inquire about the Spacers that I spec'd in my original plan, and have tentatively left in the new plan, for use inside the frame rails. I felt that these would prevent compression of the upper/lower sections of the frame rail box when the through bolts were tightened down and likely add stiffness too. The rear most through bolts surely need something as the holes will be drilled directly below and centered in the existing 1"(+/-) OE holes that lie under the rubber drain plugs on each side of the package area. I obviously wasn't aware, previously, of the cold flow issue with the LDPE material and could readily substitute aluminum or steel spacers in their place? I'll also assume that any spacers used on the upper end link cross bolts should be steel or aluminum also?

I'm old, but this dog continues to love learning new tricks, so thanks greatly for sharing your knowledge and opinions, previously and in the future!

Edited by GeezRX, 26 September 2017 - 12:50 PM.

[gtpilot]

You need to try and simplify it to this - go download a Solidworks eDrawing viewer and take a look.  You can zoom in/out, rotate the assembly, etc.

 

https://www.dropbox....ssem1.EASM?dl=0

[GeezRX]

You need to try and simplify it to this - go download a Solidworks eDrawing viewer and take a look.  You can zoom in/out, rotate the assembly, etc.

 

https://www.dropbox....ssem1.EASM?dl=0

I got the viewer and yeah, we're on the same page. I think my original pictures with the plumb bob may have not been clear enough. The "bobs" hung from the existing tow brackets merely to make it easy to attach them hands free and merely to help with the side to side setting of the sway bar. The actual point where the end link brackets need to reside is reflected in the (very crude, sorry...wish I could afford something like SolidWorks!) picture below, with hopefully a clear enough explanation of the situation. I feel like it will be very difficult to make (or attach) just a short end link bracket where needed. Any narrower than the 3" and I'd have to use square tube and make it into channel and then I'm concerned it wouldn't give me enough room side to side to catch the existing inserts and the rod end. I just have to decide on the actual material to use, as per the original question, and I can move forward.

 

The help/ideas are greatly appreciated!

Edited by GeezRX, 20 September 2017 - 01:23 PM.

[gtpilot]

OK - now I get all of the constraints...great job of explaining it!  If it were me, I would use steel in this application and make it like this - you could make it stiffer by capping off the ends (would require welding though).  I suppose that you could make it out of aluminum and give it a go?  I would just check it periodically for fatigue cracks.

 

I am lucky - I work for a contract Design and Manufacturing company, they provide the Solidworks license...all told, that is about an hour of sketching between the two assemblies.

[GeezRX]

I'm glad I got it explained clear enough. Those Solidworks drawings are awesome, thanks so much for expending the time on them! I won't say how long I spend in "Paint" to accomplish the crude stuff I put out. I need to check and see if there is a "freeware" program similar to SW that I could get. It would certainly make the design phase of my projects much more enjoyable, quicker and easier on an old man's eyes among other benefits! 

Based on your second representation, I'll look closer at using some square or rectangular steel stock for the brackets. I'll definitely post up the finished product. Thanks again for all the input you've given me!

Edited by GeezRX, 14 September 2017 - 01:50 PM.

[gtpilot]

Happy to help with anything like this that anyone wants to try and accomplish.  Modding cars is fun stuff!  

 

I seriously think that the three existing threaded inserts are more than enough to keep that bracket from moving (I did not run a stress analysis on it but from experience with doing similar things they have worked) and the square tubing will help immensely to keep the deflection of that tube down when the end link is under tension...under compression it is just getting forced into the frame rail.  Steel will also have a much better fatigue life as opposed to aluminum.

 

One other thing to do is put a chamfer on the end of the spacers where they meet the spherical joint so the joint can't bind.  Since you have different lateral offsets for the driver vs. passenger side it will be easy to make the spacers the right size to center the end links so they are vertical...all in all a win-win (the 3" channel helps too!).

[GeezRX]

I was investigating CAD "freeware...

I'll have to say that after looking at that frame rail and the inserts in it, I was really concerned about how much tension would be put on it/them from the bar's force. Tightening the bolts on the OE tow hooks when they were holding the "bobs" felt like the inserts would break free with very little effort. I guess the compression also concerned me and that's why I thought large outside diameter spacers over through bolts would be advantageous...none of which is based on engineering data, just simply my seat of the pants feeling. Care to stipulate a material for the spherical joint spacers? I'll put your suggestions into play when I get to the assembly stage. Need to wait for the next SSI check to purchase necessary materials!

 

After further layout work, it will be necessary for me to use 3" x 2" rectangular tubing on the passenger side and 4" x 2" rectangular tubing on the driver side to get it to work. I'll use .188 wall stock to keep the weight down to a minimum in the A36 steel.

Edited by GeezRX, 20 September 2017 - 12:00 PM.

[gtpilot]

I would make the spacers out of steel, which is what I did on my racecar.  

 

I would definitely use as large a diameter Grade 8 washer (or similar material quality) underneath all of the bolt heads to spread the clamping load of the bolts...if it makes you feel better put a through bolt in?  Alternatively, weld the tubing to the frame rail?