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# Bearing assembly inside circular tube, need some help.

## Bearing assembly inside circular tube, need some help.

(OP)
Hello people!

In the last few days it has emerged a problem with my design regarding bearing solution. Take a look at the picture I have attached. I have a circular tube (I.D. 112mm and O.D. 120mm) that is 6 meters long. Inside this tube there is a axle, 35mm in diameter. My problem is how I get bearing assemblies inside the tube. I want a bearing solution 2 meters from each end of the tube, like on the picture. But I dont have the possibility to drill or cut the steel tube, so I cant use set screws or something similar to hold the bearing in place. Do anyone of you have a good solution to how I can install a bearing inside this tube?

The tube will be filled with oil, so the bearings will get good lubrication. The rpm of the shaft will be maximum 800-900.

(OP)

### RE: Bearing assembly inside circular tube, need some help.

First, you use epoxy or Loctite to lock the inner races to the axle.
Let that cure thoroughly.

Then, apply epoxy or Loctite to the OD of the bearings (or OD bushings if they are required to get the right OD to slide in the pipe), slide the pipe over the bearings, position the pipe relative to the axle,

When you need to service a bearing, you build a new assembly.

OR,
You could use thin tubes to space out the inner races, and tolerance rings on the OD, but you may need special assembly tools to keep the tolerance rings in the right axial position while assembling the pipe over them. The advantage is that you can make the assembly serviceable, so you don't necessarily have to stock an entire assembly as a spare.

Mike Halloran
Pembroke Pines, FL, USA

### RE: Bearing assembly inside circular tube, need some help.

(OP)
Tanks for the respond Mike!

I have been thinking on the loctite solution, that seems like a quite easy and cheap way to install the bearings in the tube. But there is one thing that might be a problem. When I have putted Loctite on the O.D. of the bearing (or bushing), and try to slide the bearing inside the tube, I think all the Loctite will be wiped of the O.D. of the bearing because of the friction to the wall. And since its 2 meters (6 feet) of tube to get past, I think all of the Loctite is wiped away. What do you think about that problem?

The option with tolerance ring seemed interesting. I have no experience in using these rings. I guess I need a bushing between the bearing and the tolerance ring to get the right O.D.? I found a bearing assembly that are used in a Porsche that uses this principle, take a look:

http://forums.rennlist.com/rennforums/attachments/...

http://forums.rennlist.com/rennforums/928-forum/60...

I want to explore the possibility to use tolerance ring in my assembly. Do you know any companies that have a large amount of different tolerance rings and bushings?

### RE: Bearing assembly inside circular tube, need some help.

Vertical or horizontal ?

I don't picture you having good control over the diameter and roundness of the ID of the pipe 2m in from the enda.

Vertical pumps use a few bearings to stabilize the long thin shaft. Some are rubber and use the water as the bearing.
Items 9 and 26 here -
http://www.pumpfundamentals.com/images/BOWL.jpg

Back in the 1960s Pontiac used small diameter driveshaft running between the front engine and a transaxle in the back of the car, and forced the driveshaft into a curve to allow a flatter floor.
http://www.pontiacsonline.com/Delorean%20tempest%2...

Shown schematically in the Second image down here -
http://www.sportscardesigner.com/corvair2.jpg

I believe the shaft had ball bearings pressed onto it, and it was assembled by sliding it into the large curved housing.

In literature the support bearings' function strictly as dampers for certain modes of vibration.
I did not know that John Z Delorean had come up with the concept.

### RE: Bearing assembly inside circular tube, need some help.

(OP)
This pipe is horizontal.

The drive shaft of the 60s Pontiac looked very interesting, it would be of interest how the bearing are mounted in the tube. To mount/press ball bearings on the axle would not be a big problem. But its how to get it inside the tube, and make the O.D. of the bearing stable so it doesn`t move later.

### RE: Bearing assembly inside circular tube, need some help.

Mount the bearings in a tube that's a bit smaller then your existing tube. Slide that tube into the existing tube.

### RE: Bearing assembly inside circular tube, need some help.

Okay, CNC or mold some nylon bulkheads into which the bearing outer races will snap or can be bonded or otherwise retained.
The bulkheads can have quasi-radial fingers, or a generally conical shape, or pretty much any elastically deformable geometry that will allow the bearings and bulkheads to pushed into the outer tube with the assembled shaft.

Mike Halloran
Pembroke Pines, FL, USA

### RE: Bearing assembly inside circular tube, need some help.

Looks like the Tempest housing was NOT a tube.
"The shaft was housed in a upside down, U-shaped channel joining the front and rear
ends."
http://www.kscpoci.org/1961_1963_Pontiac_Tempest.p...

That sounds like a much more manufacturable, maintainable design than what I assumed to be the case. I should have known the Estes/Delorean/Knudsen team would do it right.

### RE: Bearing assembly inside circular tube, need some help.

If the pipe is stationary and the shaft rotates, you need a tight fit on the shaft.
What are the tolerances of the shaft, will they give a tight fit if you were to use a bearing?
Since 112 mm is not a standard OD size for a bearing, you might have to place another pipe into the 112x120 pipe.

The insert pipe would have an ID of 80 mm and an OD of 112 mm. Then, you could use a deep groove ball bearing such as the 6307, which as dimensions of 35 x 80 x 21 mm. The machining tolerance of the OD of the insert pipe would be a transition fit which would let you gently press the insert pipe into your existing one.

You could machine some small grooves in the insert pipe on each side of where one of the 6307 bearings would sit so that you can place snap rings (circlips) to hold one of the the bearings axially.

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