Finally ... Repairing a traction gearbox.

gerrypro said:
Did you test fit the bushes on the shaft before you pressed them into the gear?
Click to expand...

Of course not :) I'm not that smart. It didn't even occur to me to check. I'll try later and see if I can mount the gear into the lathe jaws.... if it's not possible I'll press the bushes out to measure and machine.

Imagine if you were in a hurry and thought this would only take a weekend to fix .........

seeya,
shane L.
 
You only have one true surface to work on, other than the bore of the bushes, in order to fit the gear into a lathe and that is the synchro cone! This is why the book says to rectify the OD of the gear teeth before removing the original bushings. It also says that if the wear is significant then the gear cannot be reclaimed! Not sure how they figure that as the bore where the bushes fit must be concentric with the pitch circle of the gears and the synchro cone?
I would try a rectification setting up on the bore with the bushes removed and then mount the gear with bushes fitted for a fine internal cut to bring the bore to size! Does this make sense?
 
It is pretty common for replacement bushings to be undersized. They will distort a bit when you press them in anyway, so to ensure a precise fit, you always ream after installation. I found this to be true recently when I replaced the small end bushes on my 1911cc engine. The wrist pins are 19.99 mm in diameter so finding a 20.000 reamer was not too difficult or expensive. Mic the shaft carefully. I suspect it will be something like 29.99mm in diameter so a common 30.00mm reamer can be used. The advantage of a reamer, of course, is it will follow the existing hole. If you decide to bore the bushings instead, be very careful to maintain concentricity....
 
citroenthusiast said:
It is pretty common for replacement bushings to be undersized. They will distort a bit when you press them in anyway, so to ensure a precise fit, you always ream after installation. I found this to be true recently when I replaced the small end bushes on my 1911cc engine. The wrist pins are 19.99 mm in diameter so finding a 20.000 reamer was not too difficult or expensive. Mic the shaft carefully. I suspect it will be something like 29.99mm in diameter so a common 30.00mm reamer can be used. The advantage of a reamer, of course, is it will follow the existing hole. If you decide to bore the bushings instead, be very careful to maintain concentricity....
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Hi :)
I agree with John and Gerry about this. All bushes 'close up' when you press them in. The general rule I was taught is they close up half of the interference fit. The old way was to press and ream bushes after fitting. Some were called 'prefitted' and were carefully sized and had to be pressed in with the shaft in the bush and 'tapped' a bit to flatten any high spots. (Mostly for king pins in my experience. But they do not rotate continuously like a gear.)
Yes you could carefully set up off the bore or the cone and skim the bush, noting the fact that the tool sharpening angle for brass is important so it does not dig in..Good luck.:)
Jaahn
 
Thanks all,

It looks like reamers start at about $100.... 30mm is quite a large size, so they are more expensive. It is possible the bushes are the perfect size, but they have "squeezed" down 0.2mm on installation!

oh, the adjustable ones are cheaper (which probably means there a fraction as good).

www.ebay.com.au

Reamers Blade Adjustable Hand Reamer 29.5-33.5mm Hole Expander Mill | eBay

Features:1.Every product has a unique Manufacturing Part Number label on the inner package that proves it has been qualified,which include Part Number,Model Number and inspection date information;2.If you have any questions about the item,please provide us the Manufacturing Part Number for...
www.ebay.com.au
 
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DoubleChevron said:
Thanks all,

It looks like reamers start at about $100.... 30mm is quite a large size, so they are more expensive. It is possible the bushes are the perfect size, but they have "squeezed" down 0.2mm on installation!

oh, the adjustable ones are cheaper (which probably means there a fraction as good).

[/URL]
Click to expand...
For what you need to skim out of the bore an adjustable reamer should be fine shane.

Ken
 
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well that works easier than I expected. The reamer was sent from Sydney (even though its location was china) so it turned up 4weeks earlier than expected.

20200912_112451.jpg


I'm guessing I'll need to adjust the reamer out about 10times and run it back through to gain 0.2mm.
 
View attachment 125345

well that works easier than I expected. The reamer was sent from Sydney (even though its location was china) so it turned up 4weeks earlier than expected.

View attachment 125346

I'm guessing I'll need to adjust the reamer out about 10times and run it back through to gain 0.2mm.
Armidillo said:
My guess is you've already overshot...
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Close... The highest point on the reemer was 29.95 when measured before use.... but the bush was 30.05 when I checked. Which makes it perfect on the splines and they don't chop it up getting it on .... and slightly sloppy on the shaft (which is probably the best you can hope for). Getting it perfect would be simple if you didn't need to slide the gear down an unworn splined shaft to get it into position.

Now ..... I spend weeks/months trying to find where the spring and retainer ball/rod is that I put away safely ..... It sure isn't there among all the bits.... sigh ..... Who's for hours and hours and hours of turning the shed upside down and searching ... arrrrhhhhh....
 
Yay! Work is progressing again!
The manual state that the running clearances as stated may seem excessive but are actually necessary. Very close tolerances will result in the gear seizing on the shaft!
 
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Well I've just wasted a couple of hours searching everywhere I could think of in the shed ...... I was so careful with these gearbox bits .... how have I lost the spring and bearing. I've just gone back through all of the photos in this thread hoping to see exactly what it looks like ..... and spotted this .....

attachment.php


That's the old rolltop desk that was out in the shed/office .... back before we were flooded and out of the house for months (and everything got frantically shoved around into storage)......

Hmmmmmm


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That desk went over into a shipping container so we could use the office/shed as a rest area while the house couldn't be entered.



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that's the spring right ?

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It must be, I'll see if it fits.
 

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gerrypro said:
Yes that is the dowel and spring from the back of the second cluster on the primary shaft!
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Yes! It did fit. I'm not sure where the celeron washer was from that I fitted.... but it seems perfect.

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I couldn't see an easy way of fitting a feeler gauge in there (a 0.05mm feeler gauge would just bent or tear either way).... It looks to be about 0.07 -> 0.12 if measured and rotated. which makes sense as the celeron washers change in thickness by that much (where they are pressed to make the oil guide they are thinner).
 
Handy to have a workshop set of slip gauges, they help with setting up gearboxes and differentials, you don't use them often but over the years my set have been invaluable. That reminds me I must give them another spray of preservative oil in their fitted box as any surface rust ends their ability to stick together, and they have been stored away for years in a cupboard at the back of the workshop. Yes slip gauges and a few dial gauges make life easy.

I got mine 50 years ago and a stickybase (magnetic) dial indicator holder also makes life easier. The on off slide on the stickly base is hard to push, but I guess that was why I was able to buy it cheaply secondhand.

Nice to see how you are progressing with this repair and of course the help of Gerry to guide you Shane.

Nice post.

Ken
 
gerrypro said:
By 'slip' gauges I presume you are talking about 'feeler' gauges?? Or is it something else?
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Slip gauges are lapped and finished on the surface so that each distance piece is rotated onto the other, the surface tolerance is such that each piece will hold to each other until you twist them apart, very expensive piece of kit, but often mentioned when setting the pretension tolerance of a differential and bluing in a helix gear. Anyway that is a rough description, they were a common aid to setting machinery in the Ordnance Factory where I was an apprentice.

I acquired mine when a small set was pawned (perhaps by a thief?) at the Central Loan pawnshop for the princely sum of $10 loaned - after three months and not redeemed they could be put in the shop window, sold without auction and I was happy to give them a small profit as they really didn't know what they were, I am only assuming that the set was stolen as they were never reported as stolen (verified by a police records property tracing check Australia wide).

It was an absolute rule to ensure extensive checks were made before articles were purchased or sold at auction if over the $10 minor loan price. And no insider favour price allowed, the dealer set the price to profit.

This is a description of the use of slip gauges, and the grades.

https://www.yourarticlelibrary.com/metrology/slip-gauges-need-accuracy-and-uses/95276

Ken
 
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Thank you for that information.
Strange, Dad was apprenticed as a Fitter and Turner with the Victorian Railways and worked his way up to the rank of 'Inspector of Tests' in the Metalurgical Laboratory of the North Williamstown workshops. He never once talked to me about slip gauges. Neither are they mentioned in his bible that I still possess, 'The Machineries Handbook' ( 11th Edition Industrial Press Lafayette Street New York 1942 ).
 
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