Lotus Elan and Lotus Elan Plus 2 Forums

I'm only playing at being an engineer but now I'm nearing turning the bore of my AKS pump module...the Lotus bearing is 24mm diameter and the housing is Aluminium ( or Aluminum..US ) can anyone advise what would be a nice snug press fit ?
Thanks



John

Google BS4500a limits and fits.

Well it's a start but am bogged down with charts and figures etc...am well out of my depth....just need to know how much smaller than 24mm the module needs to be for a good interference fit for a waterpump bearing..

http://www.mitcalc.com/doc/tolerances/h ... cestxt.htm


John

Hi John

Mark's Standard Handbook for Mechanical Engineers - 11th edition page 8-44
table 8.2.39

For nominal size 0.95 inch to 1.19 inch diameter
Class FN1 light drive fit interference 0.3 thou to 1.2 thou
Class FN2 medium drive fit interference 0.6 thou to 1.9 thou

Without doing the detailed press load calculations my guess would be to would aim for the top of the light drive interference and middle of the medium i.e. around 0.8 to 1.2 thou interference.

I have an original front cover and a similar module and modified cover somewhere around in boxes that I am still unpacking, I can measure them up in a couple of days if you want a cross check with actual practice.

cheers
Rohan

john.p.clegg wrote:Well it's a start but am bogged down with charts and figures etc...am well out of my depth....just need to know how much smaller than 24mm the module needs to be for a good interference fit for a waterpump bearing..

http://www.mitcalc.com/doc/tolerances/h ... cestxt.htm


John

I cannot give you the figures without knowing the limits to which the bearing has been machined to, 24mm is a nominal size. It seems rather small for a water pump bearing but its been years since I had one in my hands.

The Lotus standard waterpump bearing is 23.96 in the cold shed,23.96mm at room temperature (once the micrometer had warmed up )....so am looking at slightly less...23.9mm???

Anyone?

John

P.S.

Thanks Rohan (or anyone else with a bare front cover ),a true diameter would help...

Hi John
a couple of years ago I machined up a pump module the information from FAG bearings who make the water pump bearings for an Ali pump are bore tolerance is S6/S7 to X6/X7. with the bearing being the smallest dia bearing. I worked on a S7 tol. When pressing the bearing in heat the Ali to about 120 deg which expands the Ali enough so the bearing presses in easily. Instead of machining the circlip groove I used a M4 cone point grub screw.

You've been a long time waiting for your first post.....Congratulations...all I need to do now is equate that to mm's

Getting closer to 23.92mm ?

John

The od of the bearing should be 24/23.99mm so I would be tempted to check your mic, when I was an apprentice everything was left at least 24 hrs to stabilise before it went in the calibration lab, so I would leave it until tomorrow before measuring the size of the bearing. The housing size is 23.973/23.952mm. you will need to measure the bore with a bore gauge or internal micrometer, internal jaws on calipers have a small flat and off set which will not measure the true size but under size by an amount depending on the width of the jaw.

Once again,many thanks,just hope my old lathe is capable....

John

Measured up an original front cover - bearing bore worn / distorted to hour glass shape but centre area 23.96mm and outer ends around 23.98mm. So original interference was around 0.04 mm or 1.6 thou

Measured up a relatively new pump module made for the 30mm diameter bearing. Bore was 29.96mm. So interference was same at 0.04mm / 1.6 thou.

cheers
Rohan

Rohan (et Al)

Many thanks,will get on with it...

John

john
From the photo of your lathe I can't tell if it has a compound slide. if it has, turn it to 2 deg from the axis then for every inch on the slide the dia will only change by 70 thou giving you more control on the dia.

Iain

That is spooky!

I also have a shower pump kicking around on my workbench but at the end beside the lathe not the pillar drill.

Iain
Not being an engineer,hadn't a clue what you were talking about before I slept on it,but now it makes perfect sense (especially after doing the tracking on my pensioners shopping trolley and converting from degrees to mm's)

Thanks

John