Oil grooves for bushings?

[keith hodgsonParticipant @keithhodgson40059]

Hi all,

Tried a search, but couldn’t see that this topic had come up before.

I’m restoring an early 30s 2 stroke motorcycle engine which still has phosphor bronze bushes for the main bearings. It also has a Villiers flywheel magneto clamped to an extension of the rhs main bush, meaning that for a 3/4″ dia shaft, the bush is just shy of 2″ long. I’ve made the lhs bush (shorter, in 2 pieces), and am now about to start on the rhs, but this one has figure of eight oil grooves for lubrication.

Can’t think of a way to machine these, my leadscrew is 4 tpi, so pitch of grooves is way too coarse. Been on internet/youtube, and seen a home made lathe accessory that involves bevel gears driven from chuck, priced up same, about 300 quid from HPC – for one bush this seems a bit OTT.

Has anyone made one of these/could offer a service for my bush (willing to pay), or has another solution?

Maybe a set of 2:1 bevel gears, largest 3-4″ second hand (long shot) for 50 quid?

[DiogenesParticipant @diogenes]

A topslide set parallel with the mandrel axis (with the screw disconnected) will traverse the tool in & out if you can figure how to drive it -there are any number of ways of achieving a reciprocating motion from a rotary drive.

Depending on your lathe, it may also be possible to utilise the RH end of the leadscrew as a ‘power take-off’.

https://507movements.com/toc.html

 

[Peter Cook 6Participant @petercook6]

There is a suggestion here that people have used a swash plate approach to driving the tool in and out.

[Michael GilliganParticipant @michaelgilligan61133]

Lovely animation here:

https://youtu.be/KE4o8WometM?feature=shared

MichaelG.

.

[rjenkinsgbParticipant @rjenkinsgb]

You can use timing pulleys with a long belt running over a couple of idlers to move from a vertical belt off the chuck to a larger horizontal one, rather than bevel gears.

All the parts are quite cheap on ebay, amazon, aliexpress etc.

Example images here:

https://media.springernature.com/lw685/springer-static/image/chp%3A10.1007%2F978-3-642-17755-2_3/MediaObjects/193019_1_En_3_Fig18_HTML.gif

[noel shelleyParticipant @noelshelley55608]

A diamond point chisel and some careful work will do it . Noel.

[Howard LewisParticipant @howardlewis46836]

You could use a Mandrel handle to drive the chuck.

Set up the changewheels to give the required pitch for the oil grooves.

The Leadscrew will need to revolve faster than the chuck, maybe 2 or 3 times, to give a coarse helix.

Put a boring tool into the bore of the bush,(But not yet touching) Ideally, set the Tumbler Reverse to move the Saddle AWAY from the chuck.

Decide where you want the oil groove to start (I would recommend having it start and end within the bush)

The bring the boring tool to touch the bore, and then further to produce the depth of groove needed, probably only 0.005″ or so. That will be more than quite sufficient to spread the oil.

Then rotate the chuck, with the mandrel handle to cut the groove, stopping before the tool comes out of the bush.

Probably 1/4″ from each end will be enough.

Take the tool away from the bore, and the job is done, apart from any removal of burring with a small scraper.  Do NOT use any abrasives!

There will be a clearance of of the order of 0.002″ to 0.004″ between shaft and bush, so you don’t want to provide a passage to drain the oil out of the ends of the bush.

(Far less than that will cause bearing failure in pressure fed white metal bearing at less than 2500 rpm!)

HTH

Howard

[noel shelleyParticipant @noelshelley55608]

VERY loosely in the same vein Rover back in the 50/60s used a reverse running oil groove to prevent oil leaking down the first motion shaft of their gearboxes – no oil seal. Noel.

[bernard towersParticipant @bernardtowers37738]

The gearbox in the HA vivas did the  same just dont jack the rear up too high!!!. Dont ask me how I know!!!

[duncan webster 1Participant @duncanwebster1]

Prop shaft seal on HB viva was very easy to change, good job as they didn’t last very long

[keith hodgson]

On 28 February 2025 at 11:24 keith hodgson Said:

Hi all,

 

I’m restoring an early 30s 2 stroke.. …

..I’ve made the lhs bush (shorter, in 2 pieces)..

I have seen elderly 2-stroke engines where the bushes were also expected to seal the crankcase – if this is the case here and there are no other seals you should probably stick as close to the original dimensions/format as possible.

 

[rjenkinsgb]

On rjenkinsgb Said:

You can use timing pulleys with a long belt running over a couple of idlers to move from a vertical belt off the chuck to a larger horizontal one, rather than bevel gears.

All the parts are quite cheap on ebay, amazon, aliexpress etc.

Example images here:

https://media.springernature.com/lw685/springer-static/image/chp%3A10.1007%2F978-3-642-17755-2_3/MediaObjects/193019_1_En_3_Fig18_HTML.gif

Maybe the bevel gets out of an angle grinder would have suitable ratio. Quite inexpensive new in FE import form or even cheaper from a dead angle grinder intercepted on its way to the bin! (I kept a dead one lying around for over 12 years in case I had use for the gears before finally weakening on Wednesdays tip run.)

Clive

[keith hodgsonParticipant @keithhodgson40059]

Thanks for your thoughts guys, did think the manual chisel method might be a bit awkward, what with the bore/length ratio, but maybe not?

Will look into angle grinder bevel gears, but can’t see my luck holding that they equate to 2:1………

Came across the swash plate after posting, could get my welder son on that one…….

Lots to think about.

Cheers

[JasonBModerator @jasonb]

Find a friend to 3D print a couple of plastic gears

[NimbleParticipant @nimble]

Hi Keith,

2:1 Bevel gears,  various mods and no of teeth are listed on Ali Express at very reasonable cost.

I am in the process making one of these devices, and will attempt to post pics later.

Nimble Neil.

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