Bushing cups

[Belgian1979vette]

Is there any reason why a designer would not use a split housing for the bushings for instance on the bushings in the A-arms of our vettes. This would prevent a whole lot of issues related to assembly and disassembly.

Maybe it's not strong enough, although, with enough hard bolts ...

Anyway, does anyone know ?

 

[Twin_Turbo]

What do you mean by split housing? Do you mean, why is the rubber vulcanized to the iner and outer sleeve???

 

[Belgian1979vette]

What do you mean by split housing? Do you mean, why is the rubber vulcanized to the iner and outer sleeve???

No, I'm not asking specifically with the rubbers in mind. As you know i'm trying to mount the solids or a combination of solid with nylon (i'm trying to get someone to machine specific bushings for a steel/nylon right now). Anyway, normally on the C3 A-arms we burn out or drill out the rubber or whatever and then we disassemble. With solids it is not possible and can only be done with a press. Lengthy process and if one tries to press out bushings there is a lot of risk in bending the arms etc.

Since i need to have the eyes in the arms align bored and having it brought back to size with a metal ring after aligning the bushings, i was thinking of maybe cutting half of the eye off and welding in a split sleeve in which the bushing is placed. This sleeve could then be closed with bolts.

Its kind of hard to explain without a drawing (have not yet found out how to publish my cad drawings here) but if you take a look at my pictures in the bushing thread i have, you'll see the eyes of the vbp arms (round steel shells). When you cut these exactly in half and weld a flat piece of metal with bolt holes on the ends of each halve, you could just as easy bolt the halve of these together and place the bushing in there with ease.

Anyway this is a hand drawing of it

 

[BBShark]

That design would put a lot of force on the sleeve retaining bolts. It might work if the split was horizontal (rather than vertical). Sort of like how a U-joint strap works.

 

[Belgian1979vette]

I was thinking of that. The problem is that is impractical to put the flanges horizontal.

What one could do, is make a recess in the flange in which the other one sits. That could take up some of the vertical forces.

 

[BBShark]

Why is it impractical?

 

[Grampy]

You can press solid bushings in stock arms. I have solid sleeves in my A-arms. I turned/milled new upper and lower cross shafts from 17-4 PH to get the correct diameter and surface finish for the bushings. The solid bushing sleeves are turned from from 416 St Stl that are a light press fit in the stock arms. The OD is stepped to press in both bore sizes in the arms. The bushing sleeves are lined with a commercial bushing made with a TFE liner and a FRP body. We use the bushings in our products and they are bullet proof. The bushing sleeves have o-ring seals to keep junk out of the bushing. There are reinforced TFE thrust washers between arms and bushings to take axial loads.

Grampy

 

[Belgian1979vette]

You can press solid bushings in stock arms. I have solid sleeves in my A-arms. I turned/milled new upper and lower cross shafts from 17-4 PH to get the correct diameter and surface finish for the bushings. The solid bushing sleeves are turned from from 416 St Stl that are a light press fit in the stock arms. The OD is stepped to press in both bore sizes in the arms. The bushing sleeves are lined with a commercial bushing made with a TFE liner and a FRP body. We use the bushings in our products and they are bullet proof. The bushing sleeves have o-ring seals to keep junk out of the bushing. There are reinforced TFE thrust washers between arms and bushings to take axial loads.

Grampy

Looks quite promising, you have a picture of those ?. But what did you do to align the bushings. With bushings that have no 'give' they need to perfectly aligned,otherwise the shaft will bind and the bushings will wear prematurely.

 

[Grampy]

I took a few pictures for you of the lower are bushing - front and rear. Hope this helps.

I didn't have any alignment issues. I did not do anything to the std factory a-arms so either all the holes are nicely aligned or the arms have enough compliance that they self align. This mod is about 30 years old and has never given me any problems. (Other than the missing bolt I just found).

Grampy

 

[Belgian1979vette]

Grampy,

I think they actually aligned themselfves. In your pictures you can see the edge of the outer hole is not totally aligned with the edge on the bushing.

I just sent in my drawings of the lower shaft and am still awaiting a price offer for having them machined.

How thick was the ptfe liner that you used in there ?

The loosening bolt seems to be an issue with all bushings that turn, likewise with poly's. I made the shaft so that there is a threaded end on them. I will use a castle nut on there to secure them.

 

[Grampy]

I don't remember any problems pressing the bushings into the arms so they were probably pretty close to start.

The PTFE liner is a commercial non-lubricated bearing. The brearing shell is an FRP epoxy tube about 1.5mm wall thickness. The reinforcing fibers are spiral wound. The PTFE liner in the shell is very thin. Probably about 0.1 mm.

The bolt I lost was one of the two front lower cross-shaft mounting bolts, not one of the axial retention bolts but I absolutely agree with your design idea. I like the idea of integrated fastener with castle nut. I'm not sure if I tried that but found it too long to insert in the arm. Check your dimensions.

I think when I finsh ( if I live that long) converting the Rochester FI to EFI I need to make some A-arms to go with the bushings and cross shafts.

 

[mrvette]

I don't remember any problems pressing the bushings into the arms so they were probably pretty close to start.

The PTFE liner is a commercial non-lubricated bearing. The brearing shell is an FRP epoxy tube about 1.5mm wall thickness. The reinforcing fibers are spiral wound. The PTFE liner in the shell is very thin. Probably about 0.1 mm.

The bolt I lost was one of the two front lower cross-shaft mounting bolts, not one of the axial retention bolts but I absolutely agree with your design idea. I like the idea of integrated fastener with castle nut. I'm not sure if I tried that but found it too long to insert in the arm. Check your dimensions.

I think when I finsh ( if I live that long) converting the Rochester FI to EFI I need to make some A-arms to go with the bushings and cross shafts.

HUMM??? please start a thread, curious about that thought....

:friends::suspicious:

 

[Belgian1979vette]

I don't remember any problems pressing the bushings into the arms so they were probably pretty close to start.

The PTFE liner is a commercial non-lubricated bearing. The brearing shell is an FRP epoxy tube about 1.5mm wall thickness. The reinforcing fibers are spiral wound. The PTFE liner in the shell is very thin. Probably about 0.1 mm.

The bolt I lost was one of the two front lower cross-shaft mounting bolts, not one of the axial retention bolts but I absolutely agree with your design idea. I like the idea of integrated fastener with castle nut. I'm not sure if I tried that but found it too long to insert in the arm. Check your dimensions.

I think when I finsh ( if I live that long) converting the Rochester FI to EFI I need to make some A-arms to go with the bushings and cross shafts.

I thought about that. The threaded part doesn't need to be that long. So i hope it will go in. I remember that 1 end of the shafts can go through the hole intirely, so it should go.

Being an engineer grampy, any idea's in using a split shell to retain the bushing in place. I was thinking of making a step in the shell to take up any forces it may experience.

BTW : who did you buy the liners from ?

Thanks

 

[BBShark]

I was thinking of that. The problem is that is impractical to put the flanges horizontal.

What one could do, is make a recess in the flange in which the other one sits. That could take up some of the vertical forces.

Being an engineer grampy, any idea's in using a split shell to retain the bushing in place. I was thinking of making a step in the shell to take up any forces it may experience.

Still waiting to find out why a horizontal split is "impractical".

 

[Belgian1979vette]

I was thinking of that. The problem is that is impractical to put the flanges horizontal.

What one could do, is make a recess in the flange in which the other one sits. That could take up some of the vertical forces.

Being an engineer grampy, any idea's in using a split shell to retain the bushing in place. I was thinking of making a step in the shell to take up any forces it may experience.

Still waiting to find out why a horizontal split is "impractical".

To make full use of a split housing for mounting of bushings, you would have to cut the eye in the arms in half (cut the outer half off). If you put the flanges horizontal, one of them will end up in the arm...I fail to see how that could work out in practice. Besides being very difficult to arrange it would also weaken the arm substantially i would think. It would not bring anything additional in strenght. The shell would have to take both horizontal and vertical forces (although i think that the horizontal ones are stronger, which is another reason i would put it vertically, the bolts body will take the force, whereas in a horizontal position the bolts will experience shear).

 

[BBShark]

To make full use of a split housing for mounting of bushings, you would have to cut the eye in the arms in half (cut the outer half off). If you put the flanges horizontal, one of them will end up in the arm...I fail to see how that could work out in practice. Besides being very difficult to arrange it would also weaken the arm substantially i would think. It would not bring anything additional in strenght. The shell would have to take both horizontal and vertical forces (although i think that the horizontal ones are stronger, which is another reason i would put it vertically, the bolts body will take the force, whereas in a horizontal position the bolts will experience shear).

The arm does not have to attach in the middle of the eye. In fact the arm could be the lower half of the eye and the top half a strap. That certainly could be made stronger than your present arms and I have not heard of any failures of them to date.

So, I obviously disagree that this arrangement would be weaker. Also, do you believe that U-joint bolts "will experience shear" (as a primary component of force)? How is this different?

 

[Belgian1979vette]

I'm not to sure what you're trying to discribe here.

 

[Grampy]

Happy New Year Yves,

The PTFE insert I used are the GAR-FIL type made by GGB bearings. They are available in Europe. I used a bespoke 1.5mm wall insert. You can get commercial 2.5mm wall (or 1/8 inch wall if you prefer imperial units parts). make many types of PTFE liner bearing shells.

As to housing design, you can certainly make a split housing. It can be split either vertically or horizontally and you can step the split to react loads across the split ( like a main bearing cap). Of course a split housing will inevitably be bigger and heavier than a closed one piece design. The split must be able to carry the applied loads. Your limit loads are those that the ball joint stud will take. The ball joint releases all rotational degrees of freedom so you only react tension and compression forces at the cross shaft.

I don't understand how split housings will solve the alignment issue. The split housings must be aligned with the same precision as one piece ends unless you are relying on the compliance of the part to compensate.

From my own experience I recommend you just press the solid bushings into the stock a-arm and see if the cross shafts rotate reasonably freely. If so you have saved yourself a lot of work. Pressing the bits in is no big deal and you don't need a big press.

Grampy.