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Mikado


mjltuk
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Oh dear my Mikado is making nasty noises and jerks at start voltage.

Have read most everything about synchronising drivers, quartering and red loctite so now I've got a bit scared. Should I be with these pix?

post-973-0-64769000-1444578293_thumb.jpg

 

post-973-0-90886100-1444578560_thumb.jpg

Thought I would investigate further by removing the plastic valve gear to get a closer look and if necessary try Ray's fix of opening out the holes in the rods. Then I really messed up:

 

post-973-0-29805100-1444578694_thumb.jpg

 

I now realise I don't know how to disassemble/reinstall the plastic valve gear. I just can't find any good pictures of how it should look.

Any ideas please?

mike

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Can you post a video of it in operation and maybe include both sides so I can see what it's doing?  It looks like the right/engineer side eccentric rod is just loose or installed in a position too far away from the center axle.  Can you move it (rotate) by hand?  When reinstalling if there is ever any doubt as to where to position, default to positioning end of the arm closer to the center of the axle rather than further away to ensure you dont have binding problems.  Do be very careful if you need to tighten that eccentric arm screw it is very small and can snap if you put too much torque on it.

 

See this photo, reposition the eccentric arm (circled in Red) to a position more in line with the green line.  [uPDATED PHOTO]

 

post-16-0-82557200-1444587244_thumb.jpg

 

 

 

The arm on the other side of the engine looks like it's in the correct position so you can use that as your guide as well.  (This looks good - in green)

 

post-16-0-81751800-1444579686_thumb.jpg

 

 

Was the engine running ok then suddenly start doing this?  Did you do any work to the engine?

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Many Thanks Ray

 

Sorry no vid available.

 

Its new to me a couple of months ago, been run a few times and as is a good puller.

 

But the plastic valve gear has been flapping about intermittently and I've tried to fix it a couple of times before. This is the worst it has been, just like your video won't move off and then suddenly shoots off.

 

Can you please have another try with the red circle as I can/t see it.

 

mike

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Ok that helps.  If the plastic valve gear is flapping around then I'm pretty certain your issue is the eccentric rod being loose and is out of position.  Your problem is that with the eccentric this far out of position, when it goes around it's making a larger diameter circle as it goes around.  Which means that when the arm end gets to the extreme rear and forward positions it doesnt have enough linkage range to make it without pulling (in rear position) and too much linkage at the front.

 

Try this photo:

 

post-16-0-21724600-1444587217_thumb.jpg

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To explain another way, note the difference in the diameter of the circle on the left and right sides.  Green is the better smaller diameter path and the Red is the much larger diameter path of travel that it goes when going around.  By positioning the eccentric arm end in close to the center of the driver/axle it will travel in a smaller circle as it goes around which will eliminate the binding you are seeing.

 

post-16-0-24396200-1444587704_thumb.jpg

 

post-16-0-15517500-1444587705_thumb.jpg

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Many Thanks Sean that's also very helpful

 

Ray here is today's vid after trying to follow your advice.

 

My Movie.wmv

 

What do you think? Looks a bit better to me.

 

How would you think it got so far out of alignment? Should all the connections be tight? Is it right that there is no fixing where the plastic part enters the valve chest?

 

mike

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That looks good from a position perspective.  The only way it can get out of alignment is if it's not fully tightened down.  Must have been just a tad loose.  

 

It looks like it does have some pulsing (slows from binding a bit as it runs) and that is most likely due to driver quartering where the rods bind up just a bit at certain positions.  Easiest way to fix is to oval out the rod holes a bit (this assumes the drivers are tight on the axle end and aren't turning or can be turned by hand).  

 

This is how I address this problem:

http://www.rayman4449.com/Aristocraft_Mikado_Modifications_page.htm#Drivers_out_of_quarter_fix_rework_connecting_rod_holes

 

I think it's a good idea to try and eliminate any and all binding as it can for sure lead to a driver spinning on the axle over time. 

 

Not sure I see what you mean on the plastic part and the valve chest, can you explain or show photo?

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I maybe wrong about this one.....again. It appears that the crank shown should nearly point towards the nearest axle's center. I just looked at a couple of my steamers and that's what I see. I was looking at the crank's clock positions as the rods moved up and down. It seems like the easiest way to explain how it points. Maybe it is pointed differently on other models? They are slightly off center. They  have teeth on mine and will only point in certain directions.

 I need to figure this out on a O scale Texas type C&O that someone messed up the positions on. It even appears that they have two right hand assemblies on the engine?

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Your Fireman's side rear driver appears slightly out of quarter, based on the counter weight.  This is likely because that's the wheel that sees the most torquing when running (it is right next to the motor).  Check that.  If you do not want to remove the wheels, I'd suggest slotting the side rods with a dremel or router.

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Mike,

I was working on my mallet's lead drive train last night (same drive train as the mikado), and after I was done, I ran the locomotive on rollers to double check my work.  I found a new problem in the rear drivers.  What I noticed was the rear set started later than the front.  Letting the drivers rotate slowly, I found one point where there was a tiny, almost imperceptible bind in the drive train between the #2 and #3 driver linkage. I removed the links using the 4 and 5 mm socket head drivers and opened up the linkage hole.  I replaced and everything rolls really smoothly and at the same time. 

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Hello again, just back from a week away

 

Many Thanks to Joe Jerry and Mark, they're all very helpful contributions.

 

Yes it seems that on mine the front three drivers are firmly fixed, but that the #4 has a bit of slop in it - I'd guess a few mm. Do I need to measure it accurately or is that enough info to mean that its worth trying Ray's solution of opening up the holes?

 

Otherwise apart from taking lots of photos are there any tips on how to disassemble the drive train?

 

Thanks again

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Hello again, just back from a week away

 

Many Thanks to Joe Jerry and Mark, they're all very helpful contributions.

 

Yes it seems that on mine the front three drivers are firmly fixed, but that the #4 has a bit of slop in it - I'd guess a few mm. Do I need to measure it accurately or is that enough info to mean that its worth trying Ray's solution of opening up the holes?

 

Otherwise apart from taking lots of photos are there any tips on how to disassemble the drive train?

 

Thanks again

 

When you say the front three drivers are firmly fixed, do you mean that the connecting rods have no slop and seem to be tight with no play?  Or do you mean that the drivers won't spin on the axle end and #4 is showing some signs of being loose?

 

It sounds like what you are describing is there is some binding in the connecting rods which is pretty common.  First thing I would do is see if you can make each driver spin on the axle end by hand.  If you have any that turn then let us know and will need to address that issue first.  If all drivers are secure on the axle end then I would run the engine very slowly and note the slack in the rods between #1 & #2 drivers, then #2 and #3, etc as the driver goes around.  You should be able to wiggle and have slack in all positions as it goes around.  if it bind ups and gets tight in one or two positions around then you have some binding from a driver or two being out of quarter a bit and will want to look at ovaling out the holes on the connecting rods.  If you go to oval out the holes you need to make sure you note where the contact points are on the rods, it's not just the holes that can need to be reworked as some parts of the rods make contact where they fit together so watch closely.  But you can start with the holes and see how well it works and if you still have issues you can rework some of the other less obvious contact points.

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Many Thanks Ray

 

There is movement/play on all the connecting rods OK, so I guess that I mean that driver #s 1-3 don't spin. Moving the driver #s 1-3 from side to side the movement is about 1mm only. Today there seems hardly any difference on #4, perhaps 2mm of movement.

 

In order to see if they spin at all I presume I need to remove the drive train, yes? That's where I am stuck, can I just remove the con-rod between #3 an #4, and again I am presuming on both sides.

 

Best wishes

 

mike

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If there is in fact pulsing as it runs (ie not running perfectly smooth) then there is some binding in the drive train.  This means the rods are binding up due to the drivers being out of quarter.  I'm assuming this is what is making you continue to even want to further inspect the engine.  When the driver is spinning on the axle end you will know because of how far it slides/spins side to side.  I've always been able to determine this without removing the drive train from the engine.  If it helps, hold the driver on the other side and see if you can spin the driver.  Holding the driver on the other side will prevent any movement at all.  You can remove the rod screw/pin from that particular driver and that will allow the driver full movement if it is loose.  

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Many Thanks again Ray

 

Have now had another look. There is virtually no spin on the axles of any of drivers #1 - #4. But the connecting rods are very tight - should the hex screws that connect the parts of the connecting rods together be tightened?

 

I have now taken off the conn. rods to driver #4 on both sides and the motion is then virtually perfect (i.e. no surging/binding) at the lowest voltage I can deliver. When I try to put them back the alignment is clearly off and is very tight fit and the surging returns. Can you confirm that this is a case where opening out the holes in the connecting rods to an oval would likely be a solution?

 

Thank you for your patience.

 

mike

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If the rods are getting tight that means they are binding.  That wont be because the hex screws are loose.  You will want to remove the drive train completely from the engine and do a careful analysis of what is binding where.  I would not assume that ovaling out just one rod hole will fix it.  It's best to oval out a more than one and spread the amount of material taken out over more or all of the holes.  So yes what you are describing sounds like all you need to do is oval out the holes and possibly some of the other contact points between the rods(latter may not be necessary).

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