Rod End Inserts instead of The whole?

[Necrobata]

Hey guys! ive been reading a little bit about what judges like and dislikes, and one of those things they dont like (that i have heard) is when a car has a double A arm suspension and the node that goes on the tire has a Rodend.

The explanation was (and here i come with my unborn language) that if you align the nodes, being nodes the holes of the RodEnds, some arm configuration has no tubing in that imaginary line between the rodend holes.

Maybe with some pictures it might be a better world ofr all of us:

We dont want this: http://tinyurl.com/454beb6

We want this: http://tinyurl.com/3dbmuau
And this: http://tinyurl.com/4ypuqo9

Now this is my first year in the team, and i wanted to know a few things before getting into designing.

I know tht Rodend are not used here, so ppl use Rod end inserts like this: http://secure.chassisshop.com/partdetail/COM10-T/
And my question is, how do you guys fit it in the hole of the node i want to make? is it welded? cuz ive seen several models like this and i see no weldment trace :S also, what if the construction of the base isnt well made and the insert doesnt fit or ends up hanging freeley inside of it?

Is this design advisable? works very well?

Plz advice! and thans for reading!

[PatClarke]

As a Design Judge who loathes 'Rod ends in bending', I can tell you there are many more very important reasons why you don't do that.

Your second example has some design issues too!

But, yes, encapsulated spherical bearings, used properly are a good solution.

Pat

PS, congratulations on doing some research before posting your request.

[Demon Of Speed]

Originally posted by Necrobata:
I know tht Rodend are not used here, so ppl use Rod end inserts like this: http://secure.chassisshop.com/partdetail/COM10-T/
And my question is, how do you guys fit it in the hole of the node i want to make? is it welded? cuz ive seen several models like this and i see no weldment trace :S also, what if the construction of the base isnt well made and the insert doesnt fit or ends up hanging freeley inside of it?

Is this design advisable? works very well?

Plz advice! and thans for reading!

Spherical joints are one of the major joints used for this application and they work well.

As for your question for how are they 'mounted'. They are not welded, would mess up the spherical bearing. There are two methods that I am aware of: pressed in (sometimes with a snap ring as well), and staked in. Aurora bearing had some god info on their website about this. Both ways require pretty close machining tolerances for the outside hole that the spherical bearing goes into.

[Necrobata]

Wait wait, theres an issue in those housings? my team wants to do it with chromomoly, but my question is, do you weld it? use epoxy? our housings will be made with Aluminum 6063 and the arms made of chromomoly, no faculty has given us advice in how to put them together because in past years we used the normal RodEnds.

And how can i set the inserts in the housings? what could stick them together?

Thanks for replying!

PS What considerations must be made in order to make a good encapsulated spherical bearings? can i have any link to that info?

[Gyro]

Necrobata,

It's my understanding that the spherical bearing in your last link is simply pressed into a hole of the correct size in the A-arm. I believe that's how my team did it on our previous car.

But press-fitting requires good machining tolerances, as Demon of Speed said. I think that's all there is to it...

[Ben K]

Our team made our inserts from 4130, left them .01" undersized, welded them in, stress relieved, then finally bored/reamed them out to the right size

We left a shoulder on one side and pressed them in. We oriented the shoulder in the direction of the worst case scenario (bump to stops putting a large amount of force into the bearing).

The biggest issue is the reaming/boring stage since you gotta pick up the center nearly dead on and have a good setup to hold it all down in a mill.

One tip for you--green bearing loctite (i forget the #) can be your friend if you screw up. The shear strength on that stuff is crazy high and it can work up to a .005" gap.

Ben

[Necrobata]

Ok guys, thanks to everyone for the replies, Ill take note, a friend of mine told me that freezing the insert and then putting it in the hole could work, so ill be using both methods, temperature and Loctite.

Maybe ill reply this with the final design, thanks guys!

[swong46]

Good to know on the green loctite, thanks!

[buggaero]

Simply make a cylindrical housing for your sphericals like everyone said.
Take good care of tolerances, also utilizing some common sense.
Once you realize it's a snap ring acting as the stopper on both sides, you just need to make few clicks on skf's or aurora's website for housing tolerances, snap ring tolerances, and bearing tolerances.
SKF lets you settle in the 3 of these as a combination and lets you aware of the final distances and spaces to be cut out and left on the housing.
take care of all the welding, and see how you going to work on it. That's something different in every design. The way you go around doing it.

We were a debut this year and i think nobody ever came around telling us what to use. let alone advising sphericals over rodends!
Research your way out.

[Mike Cook]

I use to do it like Ben said. After having varying success (very good if tolerances are held well, not so good if not), I think staking the bearings is a lot better. It requires making some staking tools but its way worth it.

Oh, and Pat, what do you see wrong with the second picture? The only thing I can really see is that the spherical bearing is slightly offset from the axis of the links. Not ideal, but may be certainly acceptable if taken into account.

[Necrobata]

Wait a second, Demon says that welding could mess up the spherical bearing, and Ben said to weld them then relieved.

Now let me get this straight (remember my difficulty with the language) when you relieve the stress, it means that you use a termical process on it? heat it up, let it cool off? that doesnt mess up the spherical bearing? i think the insert is made of steel and the housing is made of aluminum, loctite FTW?

And if i can weld, is reasonable to apply Loctite after? i would love to use both just in case, and well, guys a shoulder for me is a bodypart, whats a shoulder in the suspension?? is it the inserts housing?

Thanks for replying.

[moose]

I think just some translation loss here -

One way of doing it is:
1. turn steel insert, leave undersized for bearing
2. Weld steel insert to A-Arm
3. Stress relieve
4. Bore steel insert to size
5. install bearing & retaining ring

You're not welding/heating the bearing at all this way.

There are some other possibly shadier ways of doing it, getting the bore damn close, using some sort of insert to keep the bore true, making it a bit oversize and filling with green loctite, etc. Use these all at your own risk. Sometimes making a couple of extra a shady way and going with the best ones can be faster than doing it the best way if you don't have the right tools.

[Mike Cook]

Necro,

Ben said, weld up the a-arm with the spherical bearing sleeve (the sleeve is the part that the bearing will be pressed into later on) undersized by about .005-.01". After it is welded up he suggested stress relieving it. I have never practiced this. A-arms will almost always fail in buckling. I have failed probably 6 or 7 that way, and about 4 more pushrods. No welds have ever failed. So make your choice, stress relieve it or not. THEN, buy your self a reamer (like a drill bit, but designed for removing very little material and making a very precise bore). The reamer should be about .0005" smaller than your spherical bearing. For instance, if running a com-5 spherical bearing (http://aurora.thomasnet.com/viewitems/commercial-industrial-units-spherical-bearings/ries-spherical-bearings-ptfe-liners-available-demo?&bc=100|1050|1054), which has an outside diameter of .750", ream the bore of your spherical bearing to .7495".

In this simple design there are two ways to hold in the spherical bearing. You can put snap rings on both sides of the bearing. Or you can put a snap ring on one side (the side you push the bearing in from) and a shoulder on the other. The shoulder is just a basically like a seat for the bearing to sit on.

If the bore is loose (i.e. oversized) you can use locktite to help the bearing from moving around, but in reality you should re-make the arm.


Alternatively, you can stake the bearing in the arm. Staking a bearing is basically rolling the edges of both sides of the spherical bearing over the edge of the sleeve holding it. This locks the bearing into place axially. I found this a much more secure way to mount bearings. See all the tech documents on auroras website here:

http://www.aurorabearing.com/t...rticles/default.html (http://www.aurorabearing.com/technical-resources/articles/default.html)

and here:

http://www.aurorabearing.com/t...al-data/default.html (http://www.aurorabearing.com/technical-resources/technical-data/default.html)

Bye,

[Necrobata]

mister Cook i apreciate the reply, and im sorry to bring this topic from the graveyard once again but i have other doubts.

I may speak nonsense from now on due to language issues and i apologyze if so.

The bearings have shoulders, wich are like a seat for the bearings,

1- Shoulders should be welded right? but th ehousings are made of aluminum and the inserts and shoulders of alloyed steel, non soluble metals cant be welded together right?

2- Ans well, we spoked about the housings-inserts methods but how about the chromoly from the A-arms and the aluminum from the housing?

3- Last one, i spoke to my Materials teacher about the aluminum that i should use for this, he told me to aim the aluminum from the 2xxx, 5xxx and 7xxx series, anyone has an advice about this? a specifical alloy or something? im going to investigate anyways.

thanks for the replies http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Goost]

If I'm in a hurry I usually tell newbies that 7075 is the only aluminum that belongs on a race car http://fsae.com/groupee_common/emoticons/icon_wink.gif (unless being welded of course - 6061). In my experience outside of FSAE really 7075 (usually -T6 or -T651), 2024, and 6061 are the most common structural and machinable alloys. As far as chromally tubes, take a look at 4130 or 4140. I'm sure you know this but w w w . matweb . c o m can give you the properties of just about any material. If you don't know at all where to start sometimes wikipedia can get you on the right track.

[Mike Cook]

mr. necro

I know that you may not be an expert at the English language and I'm really not very good with it, but it may help if you try to be consistent with your grammar. For instance, capitalize the first letter of a sentence. Also, 'I' should be capitalized.

Anyways, I will try to answer your questions, but the best way would to be draw a picture. Unfortunately, I'm lazy and uploading a picture is a pain in the ass.

1) Usually the shoulders are machined into the housing you are pressing the bearing in to. So no, they would not be welded. Also, for the most part, only like materials can be welded.

2) I'm not sure what you are asking, but I would recommend that you either use an all steel arm, or an all aluminum arm. Steel is easy to weld and readily available to, so I would use that.

7000 and 2000 series can't be welded.
5000 series resists corrosion very well and is almost always used for gas tanks. It is also very ductile so it can be bent with out cracking, and is easy to weld.
6000 series is very common, and I would recommend using this for most parts. 7000 series is very strong, but is also a lot harder and more brittle than 6061. It is very sensitive to scratches and nicks and will crack so it is important to have a good surface finish.



Originally posted by Necrobata:
mister Cook i apreciate the reply, and im sorry to bring this topic from the graveyard once again but i have other doubts.

I may speak nonsense from now on due to language issues and i apologyze if so.

The bearings have shoulders, wich are like a seat for the bearings,

1- Shoulders should be welded right? but th ehousings are made of aluminum and the inserts and shoulders of alloyed steel, non soluble metals cant be welded together right?

2- Ans well, we spoked about the housings-inserts methods but how about the chromoly from the A-arms and the aluminum from the housing?

3- Last one, i spoke to my Materials teacher about the aluminum that i should use for this, he told me to aim the aluminum from the 2xxx, 5xxx and 7xxx series, anyone has an advice about this? a specifical alloy or something? im going to investigate anyways.

thanks for the replies http://fsae.com/groupee_common/emoticons/icon_smile.gif