Fowler BB1 in 2"

[Jo]

  Problems 

The beam was too wide I needed to reduce it from 405mm wide to 370mm (-17.5mm) and the over flange width to 275mm from 304mm (-14.8mm). So I started by turning off the 14.8mm and my nice flanges 



Then I discovered I didn't have a fixed steady that went small enough on the Prazimat and the Myford was too short  :



So it ended up in the Colchester four jaw supported by a centre to take the 17.5mm off:



Having turned down the first end I realised  that if I put a 5mm flange on the end of the shaft the end was too short for my replacement flanges and the bearing and the required extra for the pinning  So I started toying with ideas of how to extend the shaft again 



I wandered round and round the workshop something (other than my  measurements) was not right.. 

Why had I taken 17.5mm off the ends and only 14.8mm off the main beam by the shaft  There was a slight possibility that I had got that 14.8mm measurement wrong and it actually should have been 19.05mm  There was an off chance.... best sleep on it 

Jo

[sco]

Bggr - I hate it when that kind of thing happens - you get a measurement in your head and are sure it's right.  Then after the material has been removed the doubt sets in...

Sure you will come up smelling of roses though!

Simon.

[Jo]

Thanks Simon  ,

So that was last night and as you might have noticed I did not post anything I didn't feel up to it   

Another day a fresh mind and I did my numbers again  the 19mm was the correct distance I should have taken down to allow separate flanges to be added  So back between centres remove the offending extra (allowing for a press fit for the flanges) measure and check yes 265mm between backs of flanges. Make up a couple of flanges and apply a bit of encouragement to fit them:

 

They are not going anywhere  So my corrected drawing has a lot of corrections:



But I still have a front axle beam and its bits are beginning to fit together



and I took a couple of bits of plate to size for the next little bit 

Jo

[Jasonb]

Are your new flanges a smaller dia? The old ones were larger than the across corners size, these look less

[Jo]

No they are also 25.4mm diameter, maybe the JB Weld forming the fillet is making it look smaller. I have a bit of fettling to do to knock the sharp corners off the beam and make it more like a forging so they might be slightly proud at the moment.

Hypotenuse on the beam measures = 27.319 

Jo

[Jasonb]

Ah, thats Hainings 7/8" beam rather than the 3/4" that the original 4.5" scales to making them look small.

J

[Jo]

The inside of the perch plates need to be cut out to go around the beam, so a quick bit of number crunching to find the centres of the curves and the correct profiles to let the DRO radius function take the strain  :



It won't fit just yet as I need to finish profiling the outside curves of the beam:



Another to go  .

Jo

[ths]

I like the look of what you're doing there, looking forward to seeing the fit, which will doubtlessly be impeccable.

Hugh.

[steamer]

That's a really nice feature on a DRO..  Parts look great!

We still need the popcorn eating emoticon.......

[Jo]

That's a really nice feature on a DRO..

It is Dave but the Chin-lese instructions do make a pig's ear out of explaining it to you. I think the one of the most confusing matters is what type of cut you are going to make, if you look at the illustration:



It is easy to confuse the top row and the bottom row, with cutting an internal or external curve  The curve type has nothing to do with that  You have to ignore the fact that they have swapped over the tool position and just look at the direction of the arc: the start and end position  If you are cutting from the inside or the outside of the curve is set later when you either add or subtract the cutter width from the diameter.

Each of those outside curves are made up of 45 separate hand entered coordinates, providing a 0.5mm increment between cuts. After 180 cuts it is easy to mix up your left hand and your right hand and cut into the metal for the first move rather than into the gash... so something you do in short bursts.

I will be graduating up to Z plane arcs shortly

Jo

[kvom]

Time for a CNC mill.   

[Jo]

Time for a CNC mill.   

 

I'm a hands on type of girl 

Jo

[Jo]

We still need the popcorn eating emoticon.......

Just for you Dave: 

Jo

[Jo]

When I chose the metal for the perch pad I used a piece of 10mm as I did not have a bit of 19mm big enough, so it was time to add a bit. A second piece was taken to size and two holes drilled through for locating the plates together:



Heat applied, gently tapped to make sure it went down firmly  then dipped in the pickle tank long enough for it to stop fizzing and rinsed in water, and this is what it looked like:



Then came problems  I could not get the DRO to start working  I programmed it and all it came up with was this:



The chin-lese did not explain that this screen is correct  and that it would not move until you started dropping the Z axis. Well it would have but the types of curves are swopped over so every time I dropped the head the display was the same  Finally I made the mistake of raising the head higher than the start point and the figures started moving. So finally I corrected the programmed type:



And spent what seemed a long time winding the table too and fro  which gave me the first side:



As I finished the second I realised that I didn't have a sharp 12.7mm slot drill and it was time to do something about it  no excuses I had to make the missing bits to enable me to sharpen end mills on the Union:



No  a job for tomorrow.

Jo

[Jasonb]

I thought a bit of that 20mm flat rust that you had in teh cabin would have done for those parts that are 3/4" thick, looking good though.

J