Locomobile Cylinder Drains July 2009
For those builders who are steaming; I'm sure that by now you have figured out that the engine fills
with quite a bit of water and will create a hydraulic lock, which will cause the cylinder not to continue
its stroke and/or difficult valve function. Thus causing undo stress on the crank, web, connecting rod,
connecting rod shank and the valve train, such as roll pins shearing or breaking. The original cars did
have some sort of cylinder drain to drain the condensed water out so as not to cause the stress it
I have installed cylinder drains in my cylinders and after about 2 months of testing I have not broken
a roll pin or had the undo amount of water stress in the cylinders; I have pictures and designed a
template tool that can be copied to install the drains without dismantling or removing the engine. The
following is instructions to add this modification to your Locomobile as well.
I used all brass 1/8" pipe fittings and valves, (no nylon or plastic balls or seats) readily available
at your local plumbing supply, these fitting are standard rated at 250-300psi. As per the pictures you
can see I used a 90' degree block and short nipples to the valves and then just bent some copper tubing
from the valve to the ground. Some of the pictures are of Doug Tombs engine; which I modified for him
during assembly. I performed this modification on my assembled/ running car.
1. Make the drill angle guide as shown in the pictures, remove the exhaust pipes and
the long valve control link. Make a protective cover out of cardboard or paper to prevent the metal chips
from getting into the linkage when drilling.
2. Measure from the cylinder edge down .250 inch; measure .300 inch from the side of the steam chest; mark
this location with a center punch; rotate the crankshaft so the piston is below this position. Tape the
drill guide you just made to the steam chest. Using an 1/8th inch drill bit; measure from the tip of the
drill bit down the shank 1.1inch and place a flag (masking tape works best) at this point on the drill
3. Place the drill/bit on the center punched mark and align to the same angle as the guide,
drill in the cylinder down to the flag, at this pint you are close to braking through into the cylinder.
Vacuum out all the chips/ filings( I used a plastic straw I taped to my vacuum end); magnetize the bit
and fill the flutes with grease, the grease will hold the filings, continue drilling, do not force the
bit, let it drill go naturally, upon your first feeling of the bit breaking through, STOP, withdraw
the bit clean it and regrease and continue drilling slowly until the bit passes through, withdraw
again and clean the bit, Vacuum out the hole. This is the pilot hole for the rest of the drilling
4. Fill the hole with grease to at least ½ in depth; I am using 1/8 inch pipe brass fittings, so I
need to drill and tap this hole with an 1/8" tapered pipe tap, this required a drill bit in the letter
series R; measure from the drill bit tip down ½" and mark using the flag method, fill the flutes with
grease and following the drill guide angle drill down to the flag, constantly cleaning and regreasing
the drill bit flutes. Don't forget to clean out the hole of grease and filings when done.
5. Using a #6 drill bit, and the grease and clean method described, redrill the pilot hole; this is the
same size bore as the steam access ports in the cylinder under the valve/ steam chest. Remember to clean
and regrease the bit before final break through into the cylinder; use your angle guide to keep the
correct angle. Clean out hole with vacuum and a magnetized rod or other drill bit.
6. Fill the center hole with grease; tap the hole with the 1/8" tapered pipe tap to the bottom on the
hole. Clean out the grease/ filings, I used a piece of welding rod with a magnet on it to protrude into
the cylinder in order to remove any stray filings.
7. Repeat this procedure with the 3 other holes. Take your time, I spent about an hour per drain.
8. Reassemble, open valves, steam up and blow steam through the drains to help clear out possible
When first firing for a run, open the valves, build up steam, with valve lever in the neutral position push
the throttle, put the car in forward or reverse and then move the car for about 25 feet and then reverse
direction, when all you get is steam coming out of the drains close them and then have a nice cruise.
This method has worked flawlessly for me for 2 months now, especially since I was breaking roll pins and
you could feel the cylinders hydro lock and bind.
I went to a show this past weekend and had a crowd all day, I won the Best Vintage Car trophy, over 5 foot
tall. Unfortunatly; on the way home, one of the connecting rod shanks snapped at the valve arm. After
dismantling I could see that the arm square alignment was being forced to round out. I am convinced that
this is due to the stress put on that shank from previous hydro locking. I have been reading about some
of the ideas everyone has for the valve linkage and all are quite sound in my opinion, but the cylinder
drains will alleviate any future stress along with stronger and tighter valve linkage, and make our cars
even more reliable. I'll report on my repair as soon as I finish.
Click here for almost complete picture
Update 2010: Modelworks are now Steam Traction World their website can be found HERE
Go to page:
Kit One and Two.
Kit Three and Four.
Kit Four B and Five.
Kit Six and Eight.
Addendum Kit Ten.
Kit Seventeen and Eighteen.
Leaf Spring Modification.
Brake Pedal, Brake Line, and Throttle Pedal Installation
Fuel Line Pickup Modification.
Super Heater, Hand Pump, and Plumbing.
Some Final Assembly and First Time Steam Up.
Road Test and a few Modifications.
Locomobile Cylinder Drains July 2009.