2-knowledge...

[cabbage]

Having taken a few days out to "pimp my lathe" I have spent most of the morning setting up a green grit wheel and trying my hand at sharpening Tungsten Carbide (or Wolframite as I was told to call it). I don't know if the angle etc is correct (Pop's note book said 7 °)... But the test tool has cut a wheel to a high gloss -so I can't be that far out. It looks a lot better than the furry mess that it was before.

Tomorrow the order from Technobots should arrive. Out of a bogie of four wheels I cut one with a 20mm dia hole to take the bull gear, two with bolt holes foe the sprockets and one normal one... The bull gear will sit in a 20mm dia hole and insulate the wheel from the axle. This will give me my gap detection sensor.

As the saying goes.... boring, boring, boring.

Regards

Ralph

[cabbage]

Parts have arrived from Technobots.  The shot below shows the bull gear with driver gear and the two sprockets next to the wheel blanks that they will engage with. I have a choice of a lot of tap and die work or welding things together...





Regards

Ralph

[cabbage]

Exploratory work with a file shows that the sprocket steel is not very weldable. The entire thing has a toughened skin and the teeth are probably more so! So it looks like roll pins for fixing the sprocket to the axle. (Ugh!).

More tea and gingernuts...

Regards

Ralph

[Peaky 556]

Ralph,if you prefer to weld them then why not give it a try?  The alternative to enable machining/drilling is to try and anneal the case hardening by heating to cherry-red then air cooling.
Have fun!
Tim

[cabbage]

I have an insane idea! If I machine a hole into the wheel that is "just" smaller than the sprocket, I heat the wheel, and then shrink the wheel onto the boss of the sprocket...

I would have to use loctite green to bond to the axle but there should be plenty of area for a good grip.

Something to think about over the weekend.

Regards

Ralph

[cabbage]

This may be classed as attempt one... It is not very successful...





Regards

Ralph

[IanT]

Forgive me if I'm teaching granny to suck eggs etc Ralph - but if you can hold that boring bar in the tool post then the set-up might be a bit more rigid/better supported than using that boring tool holder (which is mounted in the tailstock I assume?).

A piece of mild steel clamped in the toolpost and drilled at centre height (with a grub screw sideways into the bore) will do it - or clamp the boring tool tight in whatever QCTH you are using and set it to centre height....

Just a thought..

Regards,

IanT 

[cabbage]

Non of my "square" boring bars can be made to fit into the 12mm dia hole! I bought the boring head and cutters precisely to remove this problem!!! I am not very well at the moment and I admit that my mind is "out to lunch" on painkillers... The smallest bar I have will take an 8mm hole but there doesn't seem to be anyway to hold it in there other than upside down
(?)
Regards

Ralph

[John Candy]

Ralph,

I am sure Ian will provide a more detailed explanation but, since I happen to have my set to hand, a photo is attached.
The tool holder takes the bars as a close/tight  but sliding fit and the bar is anchored by simply tightening the toolpost screws which compresses the tool holder.

Mine are "Soba" brand and I bought them umpteen years ago from Chronos (the box describes them as "internal threading and boring tools set").

Regards,
John.

[cabbage]

After some "fun and games" we  have a 18mm hole in a wheel! I had to attack the boring bar with a green grit wheel and then be "artistic" with an angle grinder. The cutting part of the tool is now small enough the fit in an 8mm hole and thin enough to sit on a stack of steel plate offcuts...

Enough for today - we now know the process.

[IanT]

Sorry to hear you are not feeling so great Ralph.

It looks like you have solved the immediate problem & using the tool-post will be much better than using the tailstock.

John's clamping suggestion will certainly help steady round boring bars but you will still need some height adjustment method (such as packing or QCTH). If you have a set of carbide boring bars (that came with the boring head) - then they will most likely all have the same diameter round shank (mine certainly do). When you feel up to it - a good idea will be to clamp a piece of square mild steel on the top-slide (square to the lathes axis) and carefully stage drill it to the size of your boring bar shanks. A grub screw (or two) will hold the bars steady when mounted. I think you will find that you use them more in the tool post than in the boring head - as most of my boring is done to work mounted in the chuck.

Anyway, get better soon and good luck with your build.

Regards,

IanT   

[cabbage]

This is a "thought experiment" on how the motor will power the wheels. Inset to the tlhs is the 45T MOD1 bull gear. This is then driven by a 12T MOD 1 driver on the same shaft is a 40T MOD 1 reduction gear and finally the 12T MOD 1 spur gear from the motor shaft.

The red gears are nylon66 and the white gears are delrin.

The reduction is 12.5:1 this is adequate for and EMU or DMU.





Regards

Ralph

[John Candy]

Is there not a risk that the gears will strike wing/guide rails on crossings, etc. which may damage the gear teeth?

The clearances look to be VERY tight, especially if the wheel rims "dip" into the gaps in the crossings ("frog").
May be fine on your own track which (I believe) has "infilled" crossings to flange depth but other GTG circuits will probably not have infilling and guide rails may not be dead flush with running rails.

Regards,
John.

[cabbage]

Yes, there could be some problems running on foreign rails... I do use "flange runner" or "infilled" points on my track - along with frog rails silver soldered onto steel plate. Cliff Barker  states that his points are "infill" design. All my wheels are cut to a flange depth of 2.3mm regardless of suspension.

The delrin gears that I have ised over the years have had no problem ingesting anything and there is normally a base plate underneath. Delrin has the same strength as Aluminium and better wear characteristics than the nylon gears in my big lathe, soon to be replaced with metal ones! There may be some grumbling as the baseplate slides across wing rails etc.

The outer teeth of the bull gear is in line with the uncut coning. I don't think there will be any real problems as Tim and AndyB are likely to be the only tracks it will visit.

Regards

Ralph

[cabbage]

Dimensions strike again... The bogie side consists of an inner and outer plate bolted to a spacer at the ends. Ok no problem with that. But using the dimensions of one plate transferred to the other everything will fit. Use the dimensions for bogie plates as given and one is too large or the other too small...

So it is back to the graph paper to produce my own. The wheelbase will be 120mm as per the inner plate. Out with the tea and gingernuts.

Regards

Ralph