Nothing to lose really.

Ok, so today I played "Bob-the-bodger who cannot weld". For the life of me I could not lay a decent weld-bead.
I have no idea why things were so poor, but I have finally managed to get the parts to stick together.

I did all but 2 bodges welds before the rain started and then I tried the "fat-boy-bouncing" test. By standing with both feet on the centre-joint and pogo-ing while one end was on the floor and the ends of the axle-tube were on axle-stands.
Nothing snapped or gave way (yet).

I suspect that I will have to re-do the welds, but at least the parts are now firmly attached to one another. :)

I was also please to find that the absolute ends of each side of the axle tube was 1,000 mm equidistant when measured from the same spot on the main keel.
So its pretty much square and may not be "crabbing" down the road when finished.


IMG-20230511-144345-924.jpg
 
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The first cut was the deepest. Cut on the right side went off-true and will need some tidying up with a file.
not sure how "out-of-line" the 2 sides are and I won't really know until I put the inside bearing stops in place and pop a bearing in each side.
It may be that they are so misaligned that it will be impossible to insert the axle-ends into the 2WD unit. We shall see. :)

IMG-20230517-152147-689.jpg
 
Today I struggled with the bearing and bearing stop placements on the inner ends of each side of the rear axle.
No room for any power tools to access inside the outer axle tube to gently open out the bore to allow easy bearing placement.
So it was all by hand :(
I got both inner bearings installed as a temporary fit in order to see if the removal of the centre section of the axle-tube had allowed the escape of "forces" to drive the two sides out of alignment.
Here is a very short video where one of the half-shafts has been inserted all the way through from its own side across the gap and straight into and through the inner bearing on the other side. 🆒
 
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....and Oh dear, that's torn it. :(
I had a sudden revelation in the middle of the night.
I cannot install keys into keyways without at least 2 key-lengths of free space in the gap between the inner axle bearings and the ends of the 2WD unit.
Why?
Because you need to ensure the key is sitting in the keyway on the shaft, so it has to be placed in the keyway as the keyway begins to enter the keyed 2WD unit part; and you can only do that if there is a keys length of free space to pop the key into the slot just as the keyed axle begins to enter the 2WD unit's keyed adapter.
I have no space. :( I can't get the space either by making the removed centre section larger, or by making the 2WD unit narrower.
So it looks like it will have to be roll-pins after all.
 
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A shame. Still it'll be interesting to see if roll pins will do. What size pin are you thinking of? Whilst a bigger pin equalls a bigger hole, the bigger pin will be more resiliant and probably less likely to oval the hole.
 
Popshot said:
A shame. Still it'll be interesting to see if roll pins will do. What size pin are you thinking of? Whilst a bigger pin equalls a bigger hole, the bigger pin will be more resiliant and probably less likely to oval the hole.
Click to expand...
I was thinking a 3 or 4mm pin.
 
Iirc your shafts are 15mm. I was thinking 4mm. The force on the pin will want to oval the hole. A bigger pin will spread that force better but me saying 4mm is 100% a guess. I suppose if you start at 3mm and watch it for some time you can easily go bigger. Harder to go smaller.
 
Popshot said:
Iirc your shafts are 15mm. I was thinking 4mm. The force on the pin will want to oval the hole. A bigger pin will spread that force better but me saying 4mm is 100% a guess. I suppose if you start at 3mm and watch it for some time you can easily go bigger. Harder to go smaller.
Click to expand...
No, the shafts are 12mm Silver steel. So 4mm is about the biggest I dare go. :(
 
Further problems.... Oh dear. :(

I am seeing bearing alignment issues in each "half" of the axle.
If I insert a half-shaft in the outer bearing pair all is good and rotation is pretty easy.
Once the half-shaft goes through the single inner bearing things get "sticky" and rotation is affected and the half-shaft seems to "bind" and does not want to be inserted any further.:eek:
Not sure what I shall/can do about it at this point. ... but only since the inner bearing stops were welded in place. :( Thinking cap on.
 
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Fine adjustment hammer.

OR

Insert a longer shaft into the bearings and lever it into place. 12mm might not give you enough leverage before it bends though.
 
Ok, with the use of some "Tap-True" fettling sauce applied with a large hammer we seem to have a better bearing alignment. 🆒
I have a feeling that free-running is never going to match that of a wheel with just a stationary stub-axle and a drum-brake hub.
Having to move 3 bearings and the axle itself means coasting distances may be shorter than otherwise.
It is a "Trade-off" of course, just like everything else in life.
So now I can worry think about end float across both half-shafts instead. ;-)
 
I spent some time on the lathe trimming down one of the 2WD units screw-in adapters.
This has allowed me to insert the 2WD unit into the rear axle assembly and push the half-shafts in.
If you look closely, you can see that a washer has been inserted in the LH side and sits between the adapter and the inner bearing race.
There was not quite enough clearance to slip a similar washer on the RH side and I will make the washers thinner so that both can be inserted during assembly.

Even without keyways or roll-pins, turning the 2WD sprocket(s) makes both half-shafts turn (purely through friction fit).

IMG-20230525-131120-792.jpg
 
Today we got some "key learnings" handed to us by life and "Mr. Short-cut". :mad::eek:
  1. It is much harder to cut threads in Silver Steel than Mild Steel.
  2. If you use a die-holder and a "die" you are therefore cutting "full-depth" threads in 1 pass.
  3. The resistance in the thread cutting operation can easily overcome the clamping force of a 4-jaw chuck or even a record #3 bench vise on smooth, round stock.
  4. The marks left on the material by the chuck/vise when it loses its grip can mean it will no longer pass through the bearings and you need to burnish the stock down again.
  5. Hand cutting the threads with a die & holder can sometimes result in a distorted "wobbly" section of thread at the start which eventually straightens itself out, so make sure your stock is over length and can accommodate any need for any wobbly-thread" to be trimmed off.

On reflection it clearly would have been better to cut these M12 Fine threads (LH & RH) in the lathe in multiple shallow-cut passes.
Setting up my little chinesium non-rigid lathe for thread cutting is a real PITA, which is why I tried to avoid it.
No-one has died and all the mistakes are non-fatal. 🙃
 
Danny, are you using a circular split die?
They can be opened up a tad to allow accurate thread sizing and ease thread cutting, but they can break if over done. [1 & 2]

On cutting, go quarter turn forward cut, then back half a turn relieve swarf, quarter forward to engage & quarter cut. Repeat to thread depth. This can be even less than or more than a quarter turn depending on thread pitch size. Use the resistance as a guide and feel your way. [2-3-4]

Wobbly threads can be controlled by using your tailstock with a suitable 'backing piece'. A short bar that has faced squared off ends with a hole to allow the threaded bar to pass through and can be 'trapped lightly' against the tailstock quill or use a centre (for so far) to get started, and follow as close as you skills allow as it's a 2 or 3 hand operation, don't ask me how I cope but you do get big biceps for free. You need to follow what you do with the back and forth thread cutting.
This stops the wobble to a good degree depending on your dexterity. Becomes natural after a while. The short bar can come from those little left over pieces or scrapped work (2~3" long) that would be binned (in my case). [5]

I shan't mention coventry dies, I find them useful, it just throws mud in this situ. (Good for staight threads, can't be back and forthed, but can be 2 or 3 cuts to depth. There done it now!).

Oh, and I would grip the mother hugger tight with a 4J even if marking OD. A file and flat stone will dress it good enough if no one sees it. You won't squish in to silver steel if it's good quality, ie not Asian stuff.

GL
Martin
 
Dale Rider said:
Danny, are you using a circular split die?
They can be opened up a tad to allow accurate thread sizing and ease thread cutting, but they can break if over done. [1 & 2]

On cutting, go quarter turn forward cut, then back half a turn relieve swarf, quarter forward to engage & quarter cut. Repeat to thread depth. This can be even less than or more than a quarter turn depending on thread pitch size. Use the resistance as a guide and feel your way. [2-3-4]

Wobbly threads can be controlled by using your tailstock with a suitable 'backing piece'. A short bar that has faced squared off ends with a hole to allow the threaded bar to pass through and can be 'trapped lightly' against the tailstock quill or use a centre (for so far) to get started, and follow as close as you skills allow as it's a 2 or 3 hand operation, don't ask me how I cope but you do get big biceps for free. You need to follow what you do with the back and forth thread cutting.
This stops the wobble to a good degree depending on your dexterity. Becomes natural after a while. The short bar can come from those little left over pieces or scrapped work (2~3" long) that would be binned (in my case). [5]

I shan't mention coventry dies, I find them useful, it just throws mud in this situ. (Good for staight threads, can't be back and forthed, but can be 2 or 3 cuts to depth. There done it now!).

Oh, and I would grip the mother hugger tight with a 4J even if marking OD. A file and flat stone will dress it good enough if no one sees it. You won't squish in to silver steel if it's good quality, ie not Asian stuff.

GL
Martin
Click to expand...
Hi Martin,
These were solid "un-split" dies (LH & RH).
I tried to start them off in the lathe with my MT2 tailstock die-holder etc. to ensure a square-on thread but it wasn't liking it after a few turns (chuck began to slip) in each case.
The LH thread I did manage to get started for a couple of threads at least; and it was square & straight, so moving to a vise and doing the 1/8th/1/4 fwd and 3/4 back jig-dance worked fine.
The RH thread just did not really want to start in the lathe chuck at all (even with a decent chamfered end on it). The switch to the vise and a manual holder is what gave me the "wobbly" off axis start section, but it straightened itself out. I just noticed it when I centred the piece in the lathe chuck (<1-thou) and saw the thread showing a wobble/bent section of threading at the live-centre end in the tailstock.
I have 3" of spare length on the shaft so I will just thread a bit more and cut off the wobbly bit and re-face and chamfer. :)

Thanks for all the advice and tips. Biceps-R-Us. ;)
 
You could have reduced the thread diameter to 3/4 thread depth safely, to remove some metal. (even more in bad cases).
I always use a die stock, with the machine spindle locked (or lowest gear).

No machine cutting possible?
I tried die cutting 1" x 24tpi a few months ago and that wasn't fun.
Ended up screw cutting it when the tips arrived.

The die was a 'bad thread' dresser really, but I had to have a go. Got it cutting but not well.
We learn every day.


Martin.
 
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