Large Scale Central

Accucraft C21 low power and short running and blow down valve

Electronics Live Steam
#1

I have recently got an Accucraft C21 from a friend who was selling all of his live steam stable of locos to fund a 1:1 scale loco rebuild.

It has not had many runs and is RC equipped.

Today I took it to my local meet (nice flat indoor track) to give it the first run since I got it.
It fired perfectly and the RC was impeccable in operation…BUT…

  1. it really had very little power (the regulator was tried at all positions and the reverser (Johnson bar) at all positions as well). In fact it would only pull a couple of Accucraft freight cars successfully around the track (10ft curves)

  2. Although it had been filled with water (to nearly top of sight-glass) and it had been fully filled up with gas (the gas tank in the tender is a huge one even for a dual burner like this loco has). The gas was at a warm room temperature as was the loco. The gas burners were working well… it steamed properly for less than 15 minutes before the gas ran out (the gas was not on a high setting at all!)

My friend says that is maybe still needing running in…

Also, although the Accucraft C21 instruction manual has a a photo (it is of a C16 not a C21) that shows that the loco has a blow down valve under the steam oil lubricator and it also states how to use it when firing the loco up …but there is no blow down valve on this loco.
All my other Accucraft locos (old or more recent) have a blow down valve but strangely this one does not… even if the instructions show it to have one! My friend says that he always used a syringe to suck out the gunk and water from the steam oil after a run.

Do you folk have any wisdom about the loco’s performance…and also as to why it does not have a blow down valve, given that Accucraft state that it does!

#2

Well,
I steamed her on rollers and she fired well.
She reached just under 60psi before the safety blew and then ran after quite a few back and forth with the Johnson bar.
When running slowly (whether controlled by the regulator or the Johnson bar) she definitely had a ‘sticky’ jerky motion. It was much like a ‘ker-chump’ ‘ker-chump’.
I sped her up and pressed down on the loco to the bottom of the springs and she soon registered the extra load and slowed down to the jerky movement.
I gripped the pilot beam and the cab and ‘twisted’ her one way and the other. She definitely did not like one of the twist directions and almost stopped.

After she cooled down I put her on her back in a cradle.
I have checked all steam piping and superheater and all is well with that.
I checked that the RC servo on the Johnson bar was doing a ‘full’ throw and it was.
I again checked the timing and reversing bar to central steam chest…all is spot on.
I then pushed the wheels manually.
There was a definite quite noticeable resistance as the pistons went in and out of the cylinders.
I undid the two main crank-rods.
I again pushed the wheels manually and thoroughly investigated the motion to see if there was any resistance… none was found even when pressing down on it heavily. All springs are fine too. No brake detail is fouling the wheels.
I reconnected the main crank-rod

I then ran the wheels and connecting rods manually again and checked the resistance… but something strange had happened…
There was now no ‘extra’ resistance during the cycle of motion.

I went though the investigation again but the ‘extra’ resistance did not return.

On righting the loco, I pushed it along on the surface and it moved smoothly with a constant small reistance.

There was a slight ‘squelching gurgling’ coming from one of the cylinders (it could be also clearly heard down the funnel).
This could be due to a little water left in the boiler or from the lubricator that had run into it as I turned the loco over and then circulating around the system ending up in the piston chest.

The next step will be to fire her up on the rollers again (when the weather allows me out) to see if her performance has improved (perhaps the ‘extra’ resistance blockage/friction may return under heat or steaming).

I do hope that this ‘cure’ is permanent!

#3

The C21 has piston valves vs slide valves. These often leak resulting in low power. I had the same problem. Dave Hottman fixed mine by putting O-rings on the piston valves. However he is through working on engines I think. I added a blow down valve that was made by David Bailey in the UK at DJB Engineering. He brought several to Diamondhead that year. I have no idea if he still has any. http://www.djbengineering.co.uk/index.shtml

They were very nice and well constructed and just bolted on. He sold them for $50 I think.