bambuko loco works 0-6-2 (Fowler)

[bambuko]

It's really freelance, Fowler inspired
Using Fusion 360 for CAD modelling.
Imported manufacturer's drawing on page 136 in Brian Wilson's book into CAD:



Two front (coupled) axles are to be equalised and rear (driven) axle is to be sprung (giving in effect four point suspension):



We shall see... how it comes out The idea is that with three axles without suspension of some kind, only two axles at best give you some traction. It's probably un-necessary complication (as proven by countless 16mm locos) but it is my railway, so whatever rocks my boat goes

I did some analysis of valve gear and changed it slightly, to get valve events slightly better (I know it is presumptious of me )
Using W. B. Hall's "An approximate, but logical, method of designing valve gear", followed by D. L. Ashton's "Design Procedures for Valve Gear" I have come up with a design for Walschaerts gear:



TBC

[bambuko]

That's how far the CAD design got, before I have decided to start cutting metal:



Drilling 10BA holes using Bridgeport
Sensitive drilling chuck helps...
Marking out is there just a sanity check



Here, frames and drilling atatchment next to them.
It fits in 1/2" collet and allows me to use milling machine's digital readout.

[bambuko]

I plan to braze frames together (as recommended by LBSC), using assembly/brazing fixture:



and from another angle:



Of course, it wouldn't make sense to produce this jig just for one loco, so it is made adjustable, can be used (with other parts) for inside as well as outside frames and different locos etc, etc.

[IanC]

That's very impressive.

I wish I had the skill and tools to scratch build.

I shall follow this with interest.

Ian

[Hydrostatic Dazza]

Sweet, there are some sweet features in your build.
I will enjoy following this build, Please keep us fed with pics and commentary.

[tom_tom_go]

Equally impressed, looking forward to future updates.

[daan]

And another metalworking wizard.. Very nice! I love the CAD drawings, they give a nice idea of how the loco will look like and help as guidance to match the work with the drawing from about every angle possible. Aonther thread to follow.

[bambuko]

Thank you for your encouragement guys
Will try not to dissapoint with updates, but they are likely to be less frequent than some here...
It is not ready made design, so I am sure there will issues that will hamper the progress, plus I am very slow worker
Next will be the hornblocks. They are very simplied and purely functional, but not really visible from outside so I am OK with it.



These are front hornblocks for the two equalised axles.
As you will see, most of the time I do not bother creating drawings

I am planning to use 10BA hex bolts to secure hornblocks to frames (all secured with Loctite), but regular 10BA hexagon looks huge, so I have ordered 10 BA bolts with one size smaller (12BA) heads.
These come from:
https://www.ekpsupplies.com/steel-one-s ... crews.html

[daan]

Just a little thing to add to the CAD drawings. I came across this on the web, where the CAD drawings are used as a base for 3d printing the difficult parts. It is used where normally one would use castings.. May be it's an idea for anyone homebuilding locomotives?

[bambuko]

Yes indeed - this is one way, particularly where appearance of finished part matters and one off castings are not available or not economical.
Some parts are easy to fabricate, others not so...

[bambuko]

Bolts from EKP arrived next day - happy customer.
They are 2.5mm AF instead of the standard 10BA being 3mm AF.
Not much, but to me - worth it (I know emphasis here is on having fun rather than rivet counting or hex sizing . but I like it, so...)

Here the comparison:



I took two middle screws from another (G1) model and replaced 10BA with 12BA hex (both are 10BA thread).
Close ups like this are brutal - need to do more finishing

[tom_tom_go]

I can appreciate this as I am anti-CSK screws where they are not needed!

[Hydrostatic Dazza]

On the Subject of BA screws, the quality varies a lot, which is very annoying. I have various 10BA screws that measure from 1.62mm to 1.68 over the crests which presents problems of loose fits and possible stripped/damaged female threads. I seek the answer for a consistent quality supply.

[bambuko]

As far as I know BS93 tolerance for 10BA is 1.675 max and 1.605 min.
So the numbers you quote are within tolerance.
My 10BA (both old stock from un-known source and latest from EKP) measure 1.65
I haven't checked them all, just a few.

[FWLR]

Great thread, impressed with your work. there was a quote I read only this morning from a site ( just can’t remember which one) But this is what I read.

Rule 1. Keep the gauge alive. (I think)

Rule 2. There are no rules.

You are so right, it’s your build…..

[bambuko]

Thank you @ FWLR
Managed to get some work done... front hornblocks temporarily secured to frames for drilling (and later tapping 10 BA)
At this stage axlebox opening in the hornblocks are undersize (metal on), with final machining to size to be done after the frames are brazed and hornblocks are bolted and Loctited to the frames (we shall see how this theory works in practice... )

[bambuko]

Today, spent a lot of time tapping the holes in hornblocks:



An exercise in patience , with occasional clenched buttocks
32 holes tapped, 16 more to do on rear hornblocks, plus 12 for keeps...
I reckon I will be sick of small thread tapping for a while

Here the results:



BTW next to the tap holder is homemade 12 BA socket (better than commercially available ones afaiac)

[tom_tom_go]

Excellent work, I can only marvel at your skills.

[FWLR]

I agree, that’s some very nice skill being shown.

[bambuko]

You are far too generous guys
Glad you enjoy it! - thank you for your kind comments.