Re: Getting my SB 9C working


eddie.draper@btinternet.com
 

It wasn't confined to entry level lathes. Our 14.5" toolroom from 1943 has C/I bearings.


It would certainly have saved a lot of cost, production time, and possibly scarce copper, lead & tin based alloys. And time has proved that it is satisfactory for the purpose, so long as it is well looked after, which is possible in a static application. It even helps to give it a spin by hand with the belt tension off prior to first switch on, just to prop the shaft up on an oil film. There is a further possible benefit: Because the copper, lead & tin alloys have thermal coefficients of expansion much greater than most ferrous materials, it is possible to run smaller clearances / higher speeds with a given oil viscosity and flow rate before differential thermal expansion takes up all the clearance and leads to a thermal runaway causing seizure and damage. Don't know if that was considered as part of the design concept, and don't know whether anyone has ever done the sums / experimental work, but could be worth a look see. The down side, of course, is that if you do get wear or a seizure, the repair is a much more serious job. The shaft on our 14.5" toolroom appears to have been metal sprayed as part of a previous owner's repair.


Cast iron isn't suitable for every application. During W W 2, The British built a large (for us) fleet of 0-6-0 industrial shunting saddle tank locomotives referred to as the "Austerity" class. They were intended as upgrades over smaller factory locos, a standard armaments depot loco, and some were sent into Europe to move military supplies. There's info on Wickipedia for anyone interested. The point of this ramble is that in order to save bronze and whitemetal normally used in the coupling rod bushes, a batch were built with cast iron bushes instead. They didn't last terribly long and all were replaced with the normal materials. Even bronze and whitemetal don't have a hugely long life on locomotives, as the bearings are subjected to misalignment as the loco negotiates twisted track and the axles tilt relative to each other, impact as the thrusts reverse, and LOTS of grit, much environmental, but some applied deliberately to the wheels as sand to provide adhesion to the rails, not to mention water from rain and what gets spilled when topping up the tank. I gather the army's standard remedy for a hot bearing was to stand it under the water filler bag and turn on the valve.


In short, cast iron bearings have their places, but locomotives ain't one of them.


Eddie




------ Original Message ------
From: "john kling via groups.io" <jkling222@...>
To: "SouthBendLathe@groups.io" <SouthBendLathe@groups.io>
Sent: Friday, 18 Dec, 20 At 22:19
Subject: Re: [SouthBendLathe] Getting my SB 9C working

Was the simple use of headstock iron by South Bend on there entry level lathes such as the workshop lathes simply a cost cutting measure. This approach has been used Goodelll
Pratt and other low cost manufactures but not all (such as Atlas).
On Friday, December 18, 2020, 3:17:00 PM EST, eddie.draper@... via groups.io <eddie.draper@...> wrote:


A number of points have been made in various posts on this topic, and I will now chuck in my five pennorth.


1. Anyone acquiring a lathe with a plain bearing headstock, particularly one that depends upon wick (felt) feeds, is strongly recommended to strip out the applicable bearings, muck out the oil containers and renew, or if only lightly soiled, clean, the wicks, felts, whatever BEFORE applying power for the first time, regardless of whether it is seized or not. If it is seized, I would regard it as absolutely mandatory, as there's no knowing what you might find that could cause immediate further damage. It might be "only" varnish, which is bad enough in itself, or it might be much worse. This also allows an opportunity for bearing inspection.


2. Applying a torque to a threaded fastener is only an approximate way of achieving bolt tension and stretch. The results are heavily dependant upon thread and under head friction, which can vary quite considerably. If you have an assembly that you want to put back together exactly as it came apart, forget about torque, and mark the rotational positions of each fastener in relation to fixed surfaces, ensure that each goes back in the same hole (and with the same nut & bolt pair where applicable) and retighten to the same position. You will have the same stretch as before, regardless of torque. You might want to record the torques as you tighten, but I suspect you will be amazed by the wide disparity.


3. Once you have cleaned all out, provided operating wicks / felts, and reassembled everything, set the endfloat, then perform a shaft lift and lateral displacement test. If you got there in time, they won't need adjusting. If they do need adjustment, follow the instructions.


MX & HNY to all,


Eddie

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