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View Full Version : How would you do this? (Stevo would do it in 5 mins)



Timleech
06-23-2009, 02:58 PM
Fuel pump camshaft from 1930s diesel engine.

http://i559.photobucket.com/albums/ss38/Timleech_2009/DSCF2423.jpg

http://i559.photobucket.com/albums/ss38/Timleech_2009/DSCF2421.jpg

It's driven by the skew gear at the left. The left hand end drives the cooling water pump, the cams in the centre drive the fuel injection pump elements, the lump on the right is the governor bob weight assembly. The rather inadequate (IMO, though it has lasted 70 years!) drive for the governor has worn slack and needs dealing with.
A lot of work was done to the engine about 8 years ago, much of it good work but unfortunately they didn't finish the job! The bearing surfaces at either end of the shaft look to have been resurfaced in some way, haven't yet decided how but I want to avoid doing anything which will disturb them.
I'm inclined to set the shaft up with chuck and steady, cut off the worn stub, then bore the shaft end and maybe screw and loctite a new piece, then turn slightly oversize & cut new keyway, bore out bobweight holder to suit.
Any better ideas, or reasons why not to do it that way?

A bit of a rant now. The engine was built with Whitworth threads, with just a few BSF. Whoever did the overhaul work replaced every single nut and bolt, apart from the 1/2", with UNC :rolleyes:
Nothing against UNC in it's place, I'm sure most of us in the UK have interchanged Whit and UNC on odd occasions when it's been expedient, but to make a point of doing it on a whole engine when all the tappings and studs are still whit..............
Apart from being WRONG, I have Whit spanners for every occasion but just the bare basics in AF sizes.


Tim

Circlip
06-23-2009, 03:07 PM
Bearing surfaces could have been Hard Chromed, would have brought them back to size. Is it possible to take the lightest skim off the smaller dia. to make it true and remake the bit on the bob weight carrier.?? Or bore and sleeve (Shim) the carrier??

Regards Ian.

macona
06-23-2009, 04:40 PM
You could turn the stub down a bit and press fit a new sleeve over it. Loctite it in place.

John Stevenson
06-23-2009, 05:06 PM
Chances are the surfaces could have been metal sprayed so you don't want to go anywhere near this with a welding torch of any description.

What you suggest it doable but a simpler way is forget the screwing, you get more shop time for a start, as it's just too much hassle making sure everything is square on.

Support on a steady drill and ream or drill and bore oversize, go deep enough so you can get a cross pin / roll pin behind the flange in the bit that doesn't matter.

Turn an oversize stub up so it's a nice sliding fit polish to get this. Roll a bit of straight knurl on the stub close to the business end, loctite, whack in and cross drill and pin, then turn to fit the cleaned up bob weights.

The idea of the sliding fit is so you have no surprises as it's going in.

Many times I have seen stubs belted in and stopped dead too short, knowing it fits is half the battle, the knurl gives you the tightness and grip you need together with the gorilla snot and roll pin.

As you say 5 minutes to do it, 10 minutes to write it up.

.

Timleech
06-23-2009, 05:13 PM
Yes I think hard chrome is most likely what's been done.

Suggestions are probably viable, I'm a bit concerned, gut feeling, about weakening the stub any further. It really needs a new keyway in the shaft. Ideally in the bore also, but that one might have to stay as it is so long as I can make the two parts a good push fit together.

Thanks
Tim

edit - written before seeing John's post, thanks John.

John Stevenson
06-23-2009, 05:53 PM
If the keyway is a bit sloppy in the bore and it's not easy to repair being infernal a good dodge is to machine the new keyway in the shaft on the piss by about a couple of degrees.
This makes the key bear on one side at one end and opposite side at tother end.

Sounds a bodge and it is, but it's got me out the sh´te before now.

gambler
06-25-2009, 01:55 AM
If the keyway is a bit sloppy in the bore and it's not easy to repair being infernal a good dodge is to machine the new keyway in the shaft on the piss by about a couple of degrees.
This makes the key bear on one side at one end and opposite side at tother end.

Sounds a bodge and it is, but it's got me out the sh´te before now.

could someone translate this to english?

wtrueman
06-25-2009, 02:19 AM
OH gambler; you are so not with it!! Don't you know, he said: if it don't fit, hit it with a bigger hammer!! Wayne.

Circlip
06-25-2009, 03:59 AM
Dunt tha understand inglish Gambler mi ducks??

Wot tha's ter doo is cut't kayslot on a bit of a slant allreyt? Is that berra fo thi ??

Regards Ian.

gambler
06-25-2009, 04:02 AM
Dunt tha understand inglish Gambler mi ducks??

Wot tha's ter doo is cut't kayslot on a bit of a slant allreyt? Is that berra fo thi ??

Regards Ian.

well that clears it up nicely:eek: :)

John Stevenson
06-25-2009, 04:23 AM
Sorry,
American translation.

Eff'n th' keyway is a bit sloppy in th' bo'e an' it's not easy t'repair bein' infernal a fine dodge is t'machine th' noo keyway in th' shaf' on th' piss by about a couple of degrees. This hyar makes th' key bar on one side at one ind an' opposite side at tother ind, cuss it all t' tarnation. Soun's a bodge an' it is, but it's got me out th' sh´te befo'e now.

.

Timleech
06-27-2009, 06:59 AM
Bit of an update -

That spigot wasn't 70 years old, it had already been renewed - not sure how it was held in, but it was fairly tough stuff relative to the shaft & I hit a void about 1" in from the end.
Shaft is waiting for the keyway, been sorting out other turning jobs & other peoples' c*ck-ups on the same engine.

Next problem....
Look at the pic again, the bearing at the RH end is 1.25" dia & about 2.5" long. The LH one is 1.125" dia, 3.5" long.

http://i559.photobucket.com/albums/ss38/Timleech_2009/DSCF2423.jpg

The RH bearing bush is 'old', there's about 5 thou clearance, I was debating whether to make a new bush. Then I checked the LH bearing, which was obviously renewed when the other work was done, no evident damage or major wear to shaft or bush, 10 to 11 thou clearance!! Bear in mind that the LH bearing keeps the skew gears in engagement, and there was excessive backlash there before I started.
These are bronze bushes with a token bit of pressure oil feed, maximum 500 rpm. What would be a 'good' clearance? Keeping the length of bearings in mind my guess would be 2 to 2.5 thou on each, though of course that assumes the original borings in the end castings were done properly in line. I can always ream a bit out if the shaft is tight when assembled.

Thanks
Tim

John Stevenson
06-27-2009, 07:22 AM
Sounds about right to me Tim at 2.5, I think at these revs and scant oiling I'd prefer a bit of bag to getting something relating to ZF specs that seized up first time you let the bath water out.

Thought you'd have done this last week ?

BTW what happened to the old Dean Smitt and Grace? Does the Trent and Mersey now have a new island ?

Timleech
06-27-2009, 07:42 AM
Sounds about right to me Tim at 2.5, I think at these revs and scant oiling I'd prefer a bit of bag to getting something relating to ZF specs that seized up first time you let the bath water out.

Thought you'd have done this last week ?

BTW what happened to the old Dean Smitt and Grace? Does the Trent and Mersey now have a new island ?

Thanks John.

It's an ongoing saga. the camshafts (yes, it's a twin cam engine!) had had the bearing surfaces skimmed & new bushes made, trouble was the skimming was tapered and eccentric. etc etc. Oh, and the odd dry-docking to sort out, as well as dealing with some minor issues with the new lathe and working out how to use it (needs a degree to understand the gearbox!).

The old DSG is still on dry land, plonked outside the gate waiting for someone to say they want it ;)

Tim

Peter S
06-27-2009, 09:03 AM
Tim,

Any chance of some info on the engine, e.g. what make it is, size etc?

Thanks!

Timleech
06-27-2009, 10:25 AM
Tim,

Any chance of some info on the engine, e.g. what make it is, size etc?

Thanks!


It's a National DM2, built by the National Gas & Oil Engine Co., Ashton-under-Lyne. They were a licensed version of the Russell Newbery design, which is still being built in ones & twos

http://www.russellnewbery.co.uk/engines.html

Two cylinders, 18bhp @ 1000 rpm, from memory about 4.25" bore x 6" stroke, horizontally opposed valves in a clerestory combustion chamber (conical piston crown).

Some RN parts can be used, directly or adapted, but there are too many differences in the timing and governor gear for RN spares to be much help.

Tim

ligito
06-27-2009, 05:02 PM
Sorry,
American translation.

Eff'n th' keyway is a bit sloppy in th' bo'e an' it's not easy t'repair bein' infernal a fine dodge is t'machine th' noo keyway in th' shaf' on th' piss by about a couple of degrees. This hyar makes th' key bar on one side at one ind an' opposite side at tother ind, cuss it all t' tarnation. Soun's a bodge an' it is, but it's got me out th' sh´te befo'e now.

.

That's for Dave Cofer, isn't it?:D

gnm109
06-27-2009, 05:04 PM
I thought he was suggesting a larger spanner for more purchase to gain access to the gudgeon pin. Once finished, clean everything with parrafin. ;)

.