Slater's Crank Axle

Susie

Western Thunderer
Hi All,

I have started to make a crank axle for a GNR C2, and want to use a Slaters axle as the foundation: the webs and eccentrics to be silver soldered on.

Now, does anyone know what grade of steel Slater's use? If it is a leaded free-cutting steel then the silver solder won't take, and I'd rather know this before I attempt the silver soldering, otherwise I'll use soft solder or Loctite and pin it.

Of sourse, if anyone has successfully silver solded a Slater's axle then please let me know.

Thanks in advance,

Susie
 

AndyB

Western Thunderer
Why not email Slaters?
David White explained (during a talk a few years back) that they have problems with the quality of the steel they buy - sudden hard spots that don't do their CNC machines any favours.

Andy
 

Ian@StEnochs

Western Thunderer
Hi.
I have made a few crank axles based on Slaters S7 axles and just assemble them with soft solder and a .7mm brass pin through the web. I use 188 solder and powerflo flux. To ensure full solder penetration I file a groove in the hole in the crank web before forcing them onto the axle. Heat the assembly with a flame and touch the solder onto the web where it meets the axle and watch the solder flow through all the gaps. Allow to cool naturally and then wash and dry before removing the axle between the webs. None of my axles have failed in service.
Remember to slip the excentrics on before the cranks as they are imposible to to fit afterwards. Been there made the boob!
Ian.
 

oldravendale

Western Thunderer
I've done it with success the same way as Ian describes. In fact, although he didn't say so in his posting, I believe Steph now uses one of the Loctite adhesives.

Brian
 

Susie

Western Thunderer
Hi Guys,

Thanks for your suggestions. Andy, I emailed David White; here is his reply:

Dear Susie.
The axles are leaded m/steel. I think silver solder is a bit overkill, the ones we make for our G1 Kirtley and the 16mm De-winton are ordinary soft soldered and we have never had a failure, if you use best electrical 60% tin 40% lead you will not have a problem.
Kind regards
David

So all is solved! This means that the other components can also be FCMS, which makes things easier. I'll post a pic of the completed crank when it is done.

Susie
 

Susie

Western Thunderer
Hi All,

Well the crank is made! I decided to make it in just two pieces: the Slater's axle as one piece, with everything else as a single lump, machined from the solid.

First a two inch length of 1" FCMS was faced off, and then the various centres pilot drilled using the milling machine, working to coordinates.

This was then mounted in a four jaw chuck and the left hand crank pin machined:

L1000118c.jpg

Then succesive eccentric sheaves were machined, and lastly the right hand crank pin, everything being done with a parting tool.

L1000127c.jpg

Then the hole for the axle was drilled and reamed 3/16"

L1000129c.jpg

The axle was then soft soldered in, and the webs machined to size. Lastly the bit of axle between the webs was cut away and then all cleaned up with files and emery cloth.

L1000133c.jpg

Here is the finished item attached to the driving wheels:


L1000137c.jpg

The wheels have been recessed on the rear face and shaped.

Hope this is of interest,

Susie
 

adrian

Flying Squad
Hope this is of interest,
Definitely - just curious how you worked out the offsets for cutting the eccentrics. I presume it's an independent 4-jaw but how do you mark out or set the offset on the jaws to machine the eccentrics in the right place?
 

AndyB

Western Thunderer
Definitely - just curious how you worked out the offsets for cutting the eccentrics. I presume it's an independent 4-jaw but how do you mark out or set the offset on the jaws to machine the eccentrics in the right place?
Adrian,

I'm not sure if your question is how does one know where the centres should be, or how they are set in the machine. If the latter then Susie's second paragraph: "...and then the various centres pilot drilled using the milling machine, working to coordinates" tells the first step
Using a 'wiggler' in those centres, each is successively centred by adjusting the 4 independent jaws.

Andy
 

adrian

Flying Squad
I'm not sure if your question is how does one know where the centres should be, or how they are set in the machine.
Both actually now that I think about it - so thanks for highlighting that, I always like to understand how things are made and I can follow the process now.
 

Overseer

Western Thunderer
Thanks Susie for posting this. I hadn't considered machining the cranks and eccentrics in one piece. It looks like could be easier and stronger than assembling individual pieces. The marking and drilling of pilot holes makes setting it up in the four jaw chuck simple. I have everything needed including drawings of some crank axles I want to make so will have to try your method out. What grade is the FCMS you used? I have 1214 in stock but it is quite a bit tougher to turn than the leaded 12L14.
 

Susie

Western Thunderer
I kept the initial description brief as I wasn't sure about posting, but here are some more notes.

The steel is some that I've had in stock for a while, and is probably EN1A (1213) although it turned so nicely that it might be leaded. I have quite a stock of 7/8" ENIA Leaded (12L14) which I will use another time though. The 7/8" is just large enough to accept the crank and eccentrics.

I drew out the whole assembly to a scale of 1mm to 10 thou (seems odd but is easy to work to) and then made a chart showing all the coordinates: the axle centre, the crank pin centres, and the four eccentric centres, the latter are not square to the crank pins but are in advance by 22 thou, remembering that one of each pair is for forward gear, the other backwards. These were all drilled with a 1mm stub drill using the mill as a jig borer.

As Andy B has suggested, they were set up using a wobbler and a clock. It was surprisingly easy to set up, with less than a thou run-out on all settings. All turning done with a 3/32" parting tool in a rear tool holder, at 54 rpm for the interrupted cuts and 300 rpm for the continuous cuts, which seemed happy enough with no dig-ins, and the occasional dollop of Rocol to keep it sweet! When turning the eccentrics it is only necessary to loosen two jaws of the chuck and turn the blank round to get an approximate setting, as they are all on a common pcd.

Although the hole for the axle was reamed 3/16, the hole needs opening up by a few thou ( to 4.9mm) through the webs to give the solder some space; 188 degree solder and Baker's fluid. The center section where the eccentrics are remains at 3/16 to keep the axle on line. I put a centre-pop in the middle of the axle to give some interference to stop it dropping through the hole while it was heated up.

The whole thing took about four hours to make. It might seem a lot of work, but I think it is easier than trying to fit loads of little bits together, keeping them in the right place. The assembly is 24mm wide - okay for S7. I would certainly use this method again.

Susie
 

OzzyO

Western Thunderer
Small point Susie, but could you put the photos up at full size in your post as it makes reading the post and photos easer.

All you have to do is say insert photo at full size.

Nice work by the way, did you pin them as well?


OzzyO.
 
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