I have had a question poised by a member regarding the full forward and reverse gear of Tich and the related movement of the die block in the expansion link. Following our chat I have had a look at my Solidworks model and found a similar concern.

See below:

I have had a look at my CAD drawings and the originals in the book and I have kept the dimensions of the reach rod the same. So between centres the holes are 160.337mm apart (6 5/16&quot. I have taken some screen shots to show you. It seems that I have the same problem…

Here is the model in mid-gear, middle of expansion link.

Here is 15 degrees backwards (limit of sector plate)

Here is the die block at the bottom of the expansion link (20 degrees).

Full forward gear (limit of sector plate)

Die block at top of expansion link

The amount of overrun on the sector plate seems like a lot but the difference between the obtainable full gear and the movement of the die block in the expansion link does not. I am almost sure that LBSC just made the expansion over-sized.

I think that it would make sense for the full forward and reverse gear to have correlated movements of the die block to the extremes of the expansion link, but it does not seem so here.

Can anyone shed some light on the above?

Regards

Ryan

Hi Julian

You are right, I never thought of it that way, after all, correct valve events are what count ultimately.

I have dabbled with some simulation software in the past but never really got it working properly, I suppose now Ill have to…

I do however think that the Tich valve gear is fine for normal operation as there have not been many complaints. Maybe if one were to optimise it further, there may be some changes to be made.

Thanks again Julian

Now for the valve spindle forks.

These are machined from 6 mm steel plate.

Test fitting the combination levers.

Above, the levers are tested in the forks with some 3 mm dowel pins.

Next, file the radii on the fork ends and turn the spigot on the front of the fork and thread M3 for the valve spindle.

"a pin through the side of the return crank through the centre of the end of the crankpin is i think preferable to LBSC's arrangement. if you add a split and a locking bolt as well (as per the above pic) then this might help set the return crank and eccentric rod lengths but personally i would add a pin as well after this has been done.

it is probably obvious but a crankpin that has a return crank fitted should always be pinned to the wheel from behind (just in case!)"

Julian

I refer to the text above regarding the the crankpin that has a return crank fitted. Only now have I realised what you were getting at. At the time of writing, my wheels were already pressed onto the axles and the crank pins pressed into the wheels.

Is there any way to fix the crank pins to the wheels now? I would have liked to scotch key these pins if I had known earlier. The crank pins are pressed into the wheels pretty tight and I doubt they would move but I suppose there is always a chance.

Any thoughts?

Regards,

Ryan

Hi Julian

My tight fit is as you describe it above, hopefully it will be sufficient.

I have now completed the pivot pins for the combination lever-radius rod interface. These are 2 mm with 1.2 mm e-clips, tiny turning I tell you!

Thanks Dave!

Happy New Year people!

Here are some photos of some of my productivity towards the end of last year.

Embryo Union links

Almost finished union links

My TICH

Thanks guys.

Neil, with the current exchange rate and the shipping charges Reeves add to their South African packages, I could buy enough music wire to make all the springs I could ever want… so that was never an option unfortunately!

Anyway, here are some photos of Tich with a new "spring in her step", as it were, as well as some others.

I have done a quick design of a manual drain cock, based on some research and along the lines of what I like.

I have come up with the following, keeping in mind I do not want something bulky:

The threaded parts are M2 and the steam hole is 1mm. There are minimal moving parts and only the need for one washer and nut. The cocks will be lever operated from the cab by means of levers or bicycle cable in a brass tube. Does anyone have any better ideas before I go ahead? I do not want auto drain cocks as I feel the manual ones are more "Romantic" if that makes sense…?