Rear Suspension Housings - Worn

[MRN I J]

I intend to bore for both bearings in one operation without removing the housing from the lathe.

My focus is on achieving a good fit and zero eccentricity for the 2 paired bearings; as you know, the 6206 is a single row deep grooved ball bearing and these will not be comfortable having to operate within an eccentric environment.   

Are you going machine the outside of the insert, then align & bore the housing then push the insert in using the lathe & loctite it in, then machine the internals of the insert.

[Dilkris]

I am first going to machine (line bore) the worn housings (which are not only butchered, worn oversize, oval and eccentric), to a maximum ID of 64.40mm in order to achieve a "circle". (This dimension has already been ascertained and shown to be varying from bearing housing to housing - 64.40mm proved to be the max ) 

I will then machine the sleeves to fit (size for size on the OD - 64.40mm ) with a wall thickness of 5/6mm (so as they are stable enough to be pressed into the housing), Loctite and pin with 3mm aluminum dowels.

Upon completion I will line bore again, reducing the ID of the sleeves to "size for size" for the 6302 bearings, - which will "drop in" - (I hope) - after sitting in the freezer overnight.

I will end up having sleeved the housings with aluminum sleeves having a wall thickness of a little over 2mm.

I will post pictures in a couple of days to close the thread.       

[jbcollier]

Steel doesn’t shrink much, or at all, when frozen or most ball bearings would seize at -40.

[EuropaTC]

Upon completion I will line bore again, reducing the ID of the sleeves to "size for size" for the 6302 bearings, - which will "drop in" - (I hope) - after sitting in the freezer overnight.

It's easy enough to calculate if that's going to work. (I know, that takes all the tension and drama from the occasion    )

To do the calcs properly you'd probably want the volume expansion but that would be messy to post here without math functions on my keyboard so I'm going for a very rough idea from linear expansion.

linear expansion = (coefficient of expansion) * Original Length * (Temperature change)

Coeff. for steel is roughly 11 x 10-6 (10 to the minus 6), Aluminium almost double that at 23. If your freezer is at -20C then the temp change will be between (minus) 30-40C. For ease of argument, let's take the diameter as 50mm and consider it as a simple 50mm rod that you want to slip into the housing.

contraction = 40 x 50 x 11 x 10-6 = 0.022mm (assuming I've got my decimal places right). 

Is that enough ? theory says yes but I don't know in practice with the round circle of a bearing and the depth it needs to drop in.

I would probably help things along by warming up the housing because Al has twice the thermal expansion of steel. The limiting factor will be which loctite you pick but I'd expect 100C should be do-able by most grades and the liners will be pinned as well. That should give you at least double the gap to work with ?

Brian

[Dilkris]

I have replied to the above Brian as a PM.

[rjbaren]

I met a guy on line in Michigan who is looking to "borrow" a pair of rear up rights so he can manufacture them.  I believe he wants to make them work with Knock off wheels.  If you have any interest I can forward he email.  I am planning to give him a front hub sometime this summer for his project. 

[Dilkris]

I met a guy on line in Michigan who is looking to "borrow" a pair of rear up rights so he can manufacture them.  I believe he wants to make them work with Knock off wheels.  If you have any interest I can forward he email.  I am planning to give him a front hub sometime this summer for his project.

I am the wrong side of the pond and the wrong type of owner to add value to this - but there are members that have spare rear uprights sitting on shelves - (and also are comfortable in modifying the original Chapman vision) - so I'm sure they will jump in and become involved in this opportunity.

[lotusfanatic]

 

I definitely spy a Zeus book! (under the Presto pocket book)
Mark

I pulled them all out..... and you are correct - you have eyes better than an eagle!!   

[TurboFource]

Any progress on housing repair?

[Dilkris]

Any progress on housing repair?

Hi TurboFource - "yes" indeed !! - what is remaining is to finish line boring the sleeves (which are now pressed and pinned in the housings) to 62mm c/w interference fit for the bearings. I will post pictures of all the stages of the operation before the end of the week.

In the interim - please see photo, (so you know I am really doing it...  ) - this was a picture I took of the items prior to "assembly" - you should be able to figure out what my thinking was - if not - it will become clear when I post in detail later as referred above. Chris 

[TurboFource]

Nice!

[Dilkris]

Every picture tells a story - so this in effect closes this thread - it has been quite a journey.

As can be seen I opted to sleeve the housings by making a purpose built jig and boring bar, (this being documented in earlier posts in this thread.) - this route was chosen more as a personal challenge - I just wanted to see if I could do it. 

Also - if you have worn housings there are now definitely 3 options:- Loctite 638, buy new ones, or sleeve them 

The finished sleeve wall thickness is just 1mm (aluminum) - I opted for this because A): my lathe would struggle turning this diameter in steel, B): it was not my intention to strengthen the housings, but to make good worn/oval bearing housings and C): I was mindful of comments made on the forum regarding the fragility of the original housings.

Couple of things I found to be of interest during the operation:-

1. The original housings appear very brittle, (they do not machine as you would expect aluminum to machine).
2. In setting up the housings prior to machining utilizing the 2 nylon alignment bushes I made for this purpose, (remember the housings  have to be aligned effectively on 3 axis...) - it was very clear that the journals were not only oversize (obviously) but oval AND eccentric in relation to each other... 
3. On one housing, the journal locating the outboard bearing was almost 17mm deep..... as you are all aware this is a critical dimension and should not exceed 16mm, (6206 bearing width). I am making good this dimension with 2 off 0.5mm shims during assembly.

The last photograph simply shows me drilling out all of the excessively worn 5/16 UNC tapped threads in the housings in readiness for tapping and fitting thread inserts, (Note: I am using 3 x D inserts to maximize on strength) 

 "yes" I read with great interest and respect all of your comments when I started this venture and I thankyou all for your input. If this was a commercial fix, then Loctite 638 it would have been.... 

Cost wise, it cost £80 (US$110) in materials and £24 (US$33) for the 3XD thread inserts and about £2000 (US$2,772) in labour at £30/hr ....

But if I had to do it again - with a bigger lathe and the sleeves pre machined for fitting, you could easily do the whole operation in a day.         


               

[GavinT]

You're obviously a genius, Dilkris. Well done, you.

Were the nylon alignment bushes in the original plan?
I presumed the boring bar heft was deemed sufficient for rigidity, no? . . or was this a belt & braces measure?
How big is your lathe?

Anyway, it's the end result that counts and it looks brilliant. 

[BDA]

Great work!! 

It's too bad you lathe couldn't handle steel for your sleeves but I think the aluminum will do what needs to be done.

Can you remind us what alloy you used for the sleeves?

[Dilkris]

Were the nylon alignment bushes in the original plan?
I presumed the boring bar heft was deemed sufficient for rigidity, no? . . or was this a belt & braces measure?
How big is your lathe?

Many thanks - I knew I was going to need alignment bushes to first set up the housing on the lathe - I considered making them from aluminum also, but in consideration of the worn surface finish on the housings I realized this was pretty pointless - I just needed bushes that would give me what I call "eyechrometer" measurements and decided Nylon would be fine - easy to machine and also "free" - I had a Nylon bread board in the garage....  (Note: Ideal for making bushes)

The size of the boring bar really was driven by the length of the square to round tool bit holder that I tracked down from Canada - (I could have machined this down - but didn't want to) - "yes" - end result was probably an overkill, but it proved very rigid.... 

Lathe is a bit of a toy - it is an EMCO Compact 8 (you can see it in the distance on the photo showing me pressing the sleeves in the housings - Image 09). Chris