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Allen Mogul Timing

Posted: Mon Apr 16, 2018 9:13 am
by Dale_F
I am still helping my friend with his Allen Mogul. Last problem was the sticky throttle, which was fixed thanks to this group. Now the timing...

It was not running "true", so I found by backing the rod into the slide valve on the left side one and a half turns, I got it to run even and true and sound perfect, but only when running forward. If run in reverse, it "lopes" terribly. Since I only changed one side, I know it is on the left. If I screw the rod back into the valve, it will run acceptably in both forward and back, but is not perfect.

So my questions are....
1. Do I leave the rod in the perfect position and push the locomotive when I need to go backwards (just kidding on this one but was considered!)
2. Do I leave it in the "best of both" position.
3. Is there something else I can adjust. If you use the names of the linkage pieces I am supposed to adjust, please also include the description so I can find it. I do not know each pieces name without having to try and look it up!


Re: Allen Mogul Timing

Posted: Mon Apr 16, 2018 9:24 am
by cbrew
morning Dale.
the adjustment you need is on the rod from the reverse eccentric strap to link clevis on this side.
you should see these jam nuts. i would loosen the one on the clevis end, turn it a half turn and test again.

Re: Allen Mogul Timing

Posted: Mon Apr 16, 2018 9:30 am
by Dale_F
Thanks Chris! I will try it after work this afternoon.

Re: Allen Mogul Timing

Posted: Mon Apr 16, 2018 9:35 am
by cbrew
you may not be able to get reverse dialed in perfectly do to he limits on thread pitch. but you should be its with in reason.

Re: Allen Mogul Timing

Posted: Mon Apr 16, 2018 10:33 am
by NP317
If you want to do this the Absolutely Correct way, as in timing a new locomotive, you will need to:

1) Perform any required rebuilding to eliminate all slop in the valve train;
2) Verify the eccentrics are set correctly (that procedure should be in the original Allen drawings);
3) Then go through the valve setting procedures for the valve rod you tried adjusting, plus the link lengths that CBrew suggested.

Non-trivial, but it works.

Re: Allen Mogul Timing

Posted: Tue Apr 17, 2018 7:54 am
by Fred_V
Here is a video I did on timing an Allen. May help.

Re: Allen Mogul Timing

Posted: Thu Apr 19, 2018 3:45 pm
by Steve Alley
Allen Models has the instructions sheet for setting timing of engines. Call me 775-782-3800 or best to e-mail me at . Most important is the slop and check the rocker arms. This is were most slop is. Then make sure you find neutral on the Johnson bar and linkage. Next if you fine this two things to be off. Then go though the timing of engine. If you don't you put the horse in front of the cart and need to start over. Also if there is slop in the drive train or rods, check this first. Finding top dead center of piston clearance is important and need to be corrected before timing. The instructions are for a new build and things are tight and correct clearances. Yours is not!! Important to make sure that anything out of order is corrected before timing. This is the foundation of your house. You don't add a room to your house before you address the foundation. I am here to answer questions if you call or wright to me. More than welcome to ask to help you out. Like most I have my way. but some miss steps and you are the one that is working on this and my eyes or there's are not there to point out problems that need to be address before timing is adjusted. Example I have a RRSC American that loosens up the set screw on the rocker arms. Its out of time and will not back up. Only needs to be tighten once and a while. Novice would have you rebuild the engine and finally fine it was just a loose rocker arm that was making all the problem. Simple fix and running again for three meets then it happens again. So see valve timing was correct on all but on thing and you chase all over the engine. Hope this helps and give me a call. But remember I am helping you with your eyes and there is a disadvantage of this.

Steve Alley

Re: Allen Mogul Timing

Posted: Sun Apr 22, 2018 2:23 pm
by John_S
Are your outside rocker arms silver soldered onto the shaft, or still only held in by the roll pins (as called for on the drawings)? This was a design flaw that is known and almost everyone goes back and silver solders the arms to the shaft. The pins would wear the bronze arm casting and introduce a lot of slop in the valve motion resulting in timing issues. I think I ran my mogul for about a year before going back and brazing them together.

I have also since replaced my original die blocks and all pins with hardened 1045 material. The clevis pins were originally made from plain old hot rolled material (I didn't know at the time as I was about 17 years old!). Eliminating as much slop from the eccentrics to the valve stem should be your first step.

Re: Allen Mogul Timing

Posted: Thu Apr 26, 2018 9:04 pm
by johnpenn74
I will 2nd John S comment about the rocker arm. Set screws don't work. On my 4-4-0 I drilled and reamed for a taper pin.

I will also suggest NOT adjust the excentric strap lengths as a means to adjust your timing.
There is a design length from the clevis to the eccentric centers. Take the whole thing (clevis, links, straps) off and measure the length from clevis to theoretical center of the excentrics (the dimension is on you drawings). Get this set for all 4 eccentrics THEN trim the rocker arm.

A lot of people work it the other way starting at the cylinders and working towards the eccentrics. I think it is backwards.

The angle of throw in the eccentric is what is throwing the timing off. I will argue you set your timing by starting at the eccentrics and working your way forward. When I calculate the numbers based on the J bar in the corner and the valve theoretically cracking at top dead, I cam up with 23.5 degrees. You can set the excentric throw by using a protractor between your allen wrench in the set screw and the frame of the engine.


Re: Allen Mogul Timing

Posted: Mon Apr 30, 2018 10:28 am
by Boiler Builder
For simplicity, Mr. Allen put the link lifter saddle pin on the link arc centerline.
Because of this, the valve gear CAN NOT be adjusted for very short cut-offs.
I spent 3 full days trying to time an ALLEN Ten Wheeler. Even notched the quadrant for short cut-offs, but anything shorter than about 50% and the engine started to choke. The link lifter saddle pin has to be offset behind the link arc centerline to work properly at short cut-offs. See the photo of a real Stephenson link.
Stephenson valve gear link lifter pin offset on a real locomotive
Mr. Allen was a very smart man. Had he put the offset in the blue prints, can you imagine the results of saddles being installed backwards, problems fabricating the saddles, etc, etc...... He kept it simple for the 95% of his product that would only be run in full gear forward 95% of the time.