Making a new suspension linkage?

deesta · Oct 31, 2014

The top link on my Intense 6.6 needs replacing due to a badly fitted bearing (by the previous owner) which has pushed some of the bearing seat out meaning the bearing will not seat flat anymore.
Intense do not make them any more and cannot find any available anywhere so I'm looking to make my own.
I'm a CNC machinist so have all the skills necessary but was wondering a couple of things:

What is the best grade of aluminium to use?
How could the design be improved?

I believe Intense used 6061 for their linkages. 6082 is a newer, better grade but would something like 7075 be even better?
Here's a pic showing the existing linkage:

I can feel some flex in this so would like to stiffen it up if possible. Thoughts?
Cheers
Steve

Walt · Oct 31, 2014

It's pretty unlikely that the rocker is flexing significantly, so you're not going to be able to fix that with more material. I'd just use 6061.

-Walt

deesta · Oct 31, 2014

Walt said:
It's pretty unlikely that the rocker is flexing significantly
-Walt

I can see some flex at the linkage when trying to twist the rear triangle. I was thinking of making the internal web with larger rads to improve the rigidity at that point as it appears to flex either side of the central web.

Walt · Oct 31, 2014

I don't think you see the *linkage itself* flexing, though. You might be seeing flex where it attaches to various pivot points on the frame, but that's a big hunk of aluminum. I would be pretty shocked if there was any significant flex that you could fix by adding material.

But hey, go for it. A few extra grams of aluminum isn't going to hurt anything.

-Walt

ktm520 · Oct 31, 2014

What Walt said. Stiffness is equal across alloys. The only way to increase stiffness is adding material. 6061-T6 and copy the design.

-Todd- · Oct 31, 2014

How bad is the bearing fit issue? If it's just a loose slip fit now, you can fix that stuff with the right kind of adhesive and some know how...

Shoot me a PM if you want some ideas.

deesta · Oct 31, 2014

Walt said:
I don't think you see the *linkage itself* flexing, though. You might be seeing flex where it attaches to various pivot points on the frame, but that's a big hunk of aluminum. I would be pretty shocked if there was any significant flex that you could fix by adding material.

-Walt

You might be right and it might be an optical illusion, will have another look later

ktm520 said:
What Walt said. Stiffness is equal across alloys. The only way to increase stiffness is adding material. 6061-T6 and copy the design.

That's the main idea, to increase the blend rad's between the side plates and the centre web.

-Todd- said:
How bad is the bearing fit issue? If it's just a loose slip fit now, you can fix that stuff with the right kind of adhesive and some know how...

Shoot me a PM if you want some ideas.

The bearing is still a good fit but the seating face isn't square to the opposite side as it's been swagged out due to the bearing not being fitted properly and tightened off square.

TigWorld · Oct 31, 2014

deesta said:
I believe Intense used 6061 for their linkages. 6082 is a newer, better grade but would something like 7075 be even better?

I'm surprised its not made from some sort of 2xxx series aluminium. Typically, for a full CNC machined part something out of 2011 or 2024 will machine better and not have a significant disadvantage in strength. The connecting tube isn't welded is it? Then 6061 would make sense.

Montanadan · Nov 2, 2014

Are you sure it isn't fractured, allowing some flex?

WaveDude · Nov 3, 2014

If the seating face is the only issue, can you just run a boring bar in there and face it flat again?

Lic-Niner · Nov 3, 2014

I would try machining the bore out and making a sleeve to press into the rocker link with the correct ID for the bearing. Something around .020 wall thickness to leave as much material on the original part as possible while being thick enough to survive bearing installation. A stepped sleeve that is thicker at the top would work even better. You can pick up the location of the undamaged side of the link when you machine the bad side out to regain bearing alignment. That would be far less work than reverse engineering the entire rocker link

deesta · Nov 3, 2014

Can't see any cracks. Looks like it's just a little flexy which may go towards the general flex the 6.6 is infamous for.
Can't rebore the seating face asAthens mmisaligned bearing has pushed some of the seating face through so it won't sit flat at all..

deesta · Nov 14, 2014

Managed to get some machining done today. Just got one more side to go. Looks like it will be a fair bit more rigid than the stock one.

adarn · Nov 15, 2014

Nice!!

TigWorld · Nov 15, 2014

Looking good. What grade alu did you end up going with?

deesta · Nov 15, 2014

Thanks guys. Went with 6082 T6 in the end. It's a slightly better grade than the 6061 originally used.

Guest · Nov 15, 2014

deesta said:
Thanks guys. Went with 6082 T6 in the end. It's a slightly better grade than the 6061 originally used.

sweet lookin piece. Since intense no longer produces them perhaps an opportunity for you :ihih:

ithacking · Nov 15, 2014

Just curios why didn't you use steel? Besides the weight, steel would finish all flex - correct me if i'm wrong? And i remembered that it would be tougher to make that from steel.

deesta · Nov 16, 2014

ithacking said:
Just curios why didn't you use steel? Besides the weight, steel would finish all flex - correct me if i'm wrong? And i remembered that it would be tougher to make that from steel.

Steel would be stiffer but would weigh an awful lot more than aluminum.

deesta · Nov 18, 2014

Thanks for the kind words.
Had a chance to get the opposite side done so linkage is finished. Just in the process of making new shoulder bolts then off to the anodiser..

Making a new suspension linkage?

deesta

Walt

deesta

Walt

ktm520

-Todd-

deesta

TigWorld

Montanadan

WaveDude

Lic-Niner

deesta

deesta

adarn

TigWorld

deesta

Guest

ithacking

deesta

deesta

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