Vance, I already have a Ruby that runs. I have built three working simple
valved (one direction only) engines that run off compressed air. One of
them is made of LEGOs and is sitting beside me. It self-starts at ~20 PSI
and will run up to 40 PSI before the crankshaft frags.
I'm not worried about timing here, I'm worried about keeping the expansion
link straight.
Stephenson's link uses two eccentrics on one axle and therefore requires a
curved link to allow for the angular differences between full up and full
down while still being centered at 'neutral' (mid point.) The idea here is
to move one eccentric to one of the other axles so that the angular
differences cancel out from one axle to the other.
The valve linkage block shown in the .gif would be the part of the rocker
arm that is inside the frames. By moving the expansion link up or down you
change between the front or rear eccentric's movement, which are 180
degrees apart.
Now, can you think of a good reason why this setup wouldn't work?
If it weren't for my Lack of a lathe, and funding to buy one, I'd just mill
out curved links and give the loco a set of simplified Walscherts gear.
Trot, the fox who has some idea of what goes on in a steam engine...
At 08:15 PM 10/19/00 -0600, you wrote:
>Landon,
>
>I don't see why you need to have both axles coupled to the expansion link,
if
>they're also coupled by connecting rods on the wheels.
>
>What you show looks very much like Stephenson's link, though of course the
>omission of the cylinders and the valve rod make that conjectural. The main
>difference is that the slot in the expansion link is an arc in
Stephenson's gear,
>but you can show that the error is negligible in scale models. For
cylinders
>inside the frame, a direct valve rod should work, but for outside
cylinders, you
>have to have a rocker arm and time the eccentrics 180 degrees from a direct
>link.
>
>I suggest keeping an eye open for a copy of Martin Evans' "Model
>Locomotive Valve Gears". It's a bit hard to find (unless it's been
reprinted
>again recently) but well worth some effort to locate it.
>
>regards,
> -vance-
/\_/\ TrotFox \ Always remember,
( o o ) AKA Landon Solomon \ "There is a
>\_/< [EMAIL PROTECTED] \ third alternative."
