# Aristo Mikado Driver Slipping....a simple sollution



## Tom Parkins (Jan 2, 2008)

The drivers on Aristocraft Mikado slipping and losing quartering has been well discussed on this forum and the Aristocraft forum. I believe Greg has it pretty well documented on his web page. But I did the Loctite thing, several times. Each time it would be okay a little while then.......something would slip. Two things I came across for your consideration. 

1. One particular driver (L4) would sometimes be okay then just be totally loose. No matter how much I tightened the screw, the driver still turned, but I also noticed that the screw turned too. FINALLY..... It was inside the gear box where the axle attaches to the gear with 3 little screws. Two of them completely out and the 3rd was very loose. Tighten up all three and now no problems. 

2. The 3mm screws that hold the driver to the axle. I replaced the Aristo screws with some stainless screws. I stripped too many phillips heads on Aristo screws. Some how these stainless screws just seem tighter. Even without the Loctite they seem to do a solid job. Is it possible that the Aristo screws are just tiny tiny bit undersized and don't hold the threads tightly???? Just a thought. But that just seems like way too simple of a solution. 

She runs fine now. 

Tom


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## Greg Elmassian (Jan 3, 2008)

If the screws that attach the axle to the gear are loose, it won't make the wheel slip on the axle, it will leave the axle loose on the gear, and eventually pull apart and strip the threads in the gear. 

Another thing that is often overlooked is when the axle fits "into" the wheel too deeply... now the screw is supposed to bear on a lock washer, and the lockwasher bears on the wheel. 

If the axle goes into the wheel too deeply, it will project past the lip where the lock washer fits. Now the screw bears on the lock washer, and the lock washer bears on the axle tip... no clamping force on the wheel. 

Yes, the metal in the Aristo screws is junk, the philips slots wear out easily... the stainless screws are a great idea. Someone mentioned thy are available at Ace Hardware. 

A warning, often if the screws are loose that hold the axle to the wheel, this may be from improper back to back spacing, and having turnouts try to spread the wheels. 

In the picture below, improper back to back causes the wing and guard rails to try to rip the wheels apart. When you have a heavy loco banging into a situation like this, the result is usually the 3 small screws loosen or rip out of the main gear.










Greg


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## TonyWalsham (Jan 2, 2008)

Be careful about tightening the three small screws in either side of the gear. 
Given the shoddy quality of the screws they can vary slightly in length. As they use the same holes to mount the axles to the gear for either side, if the screws are tightened too much, they can actually touch the screw on the other side causing an intermittent and *"mysterious"*short.


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## Greg Elmassian (Jan 3, 2008)

Recently, the screws are trimmed on the ends so they cannot short, if you pull them out, you can see that the ends are normally "nipped".... 

But of course, that makes them even shorter, with less purchase in the gear. 

The fix is to drill a second set of 3 holes, use longer screws and offset the screws between sides so no chance of shorts. 

Greg


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## Tom Parkins (Jan 2, 2008)

I tightened down pretty good on those screws, never even gave it a thought regarding shorts. I did ponder using Loctite on the gear screws but then thought I might be screwed (ooooh) if the gear stripped. I'm battery power so shorting is not an issue to me, but that is some great advice for our track power friends who might read this forum. I will keep that piece of info tucked away when I help trouble shoot somebody else. Thanks for the explanation. 

Tom


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## Greg Elmassian (Jan 3, 2008)

The concerning part is the screws being loose. If they tightened down well, that is great, means no stripped threads. Often the threads are stripped, and you wind up getting a new gearbox. 

Have not seen the shorting issue in a long time, but can happen in early locos. You will sure know when it happens! Melted gear and the gearbox locks up. 

Loctite might be fine on the threads, but because the gear appears to be nylon, it might not adhere very well. 

Keep an eye on them and see if they loosen again. I'd also check your back to back and see if you have any turnouts that have the situation illustrated by the picture above (that's an SD45 block I believe). 

Regards, Greg


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## Ted Doskaris (Oct 7, 2008)

The motor block in the picture of a prior post is the first generation 3 axle version for the Aristo SD-45. You can tell from its tilt to one side. SD45s with these will more or less upright themselves when going down the track.

As to the 3 mm stainless steel screw, I had purchased them sometime ago from Digikey and use them as needed. 

Two possible Phillips pan head SS screw lengths offered: *M3 x 6 mm*, *M3 x 12 mm*.

When the screw head of the original Aristo one would be ruined trying to get it out, I use a drill bit made with a reverse twist to drill it out in the CCW reverse direction - often not having to drill down so much but to get a good "catch" on what's left of the head and the old screw comes right out.

This technique also works great when trying to remove the car body shell from the chassis of an Aristo (and likely other brands) diesel when there is typically a screw that is in too tight. The reverse drill bit in a drill motor operating in the reverse rotational direction takes it out immediately.

-Ted


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## TonyWalsham (Jan 2, 2008)

Posted By Greg Elmassian on 25 Aug 2011 10:48 PM 
Recently, the screws are trimmed on the ends so they cannot short, if you pull them out, you can see that the ends are normally "nipped".... 

But of course, that makes them even shorter, with less purchase in the gear. 

The fix is to drill a second set of 3 holes, use longer screws and offset the screws between sides so no chance of shorts. 

Greg 

Hi Greg,
Simple fixes do not appear to be the forte of AristoCraft.
Just as well they didn't do that though, because if they had designed the axles correctly and had proper quatering of the wheels, drilling different holes would put the quartering out.


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## Tom Parkins (Jan 2, 2008)

Quartering Question?

I always understood that quartering was where the left side and right side were 90 degrees out of phase. Is that really important on an Aristocraft Steam engine? Quartering would be strictly ornamental the way I see it on the valve gear. What is truly important is the alignment of all of the drivers on the same side. That is to say the counter balance is at 12 o clock on each and every driver on the right side. Left side could be in any position, but all the drivers on that side must be exactly the same position. Am I correct on that? 


Tom


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## Totalwrecker (Feb 26, 2009)

It was important in steam chests, so that at least one side had power to start turning the drivers. 
On your model they can be at other degrees (all same) but that coulds affect (look off) your chuffs in your sound... 

John


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## Greg Elmassian (Jan 3, 2008)

As Lewis Polk said himself: "the side rods are purely ornamental", but it is definitely important to have the drivers on each side synchronized with each other, agreed. 

Regards, Greg


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## TonyWalsham (Jan 2, 2008)

If AristoCraft had built models that had something other than 90 degrees quartering they would (rightly) have been pilloried for that. 
So, if AristoCraft had decided to fix the screws into nylon gear problem it would not matter, as, given their existing wheel mounting system, the wheels can be set anywhere. *SET* being a somewhat fluid word in the case of the past, and possibly current, crop of AristoCraft locos.


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## Torby (Jan 2, 2008)

Never had trouble with the axle coming loose from the gear, but often have the wheel come loose from the axle. I'll get some new 3mm screws from ACE. Thanks for the tip. Never had trouble with Madam Mallet on a turnout, except now and then on a 10ft diameter turnout with an immediate 10ft the other way. Of course, if something derails the pilot truck, she'll try to go the wrong way on a turnout every time. 

I just watch mine careful when I'm starting it. If it doesn't start smoothly, inspect for a loose wheel. 

I'm told that inside the gear box, there's an idler gear between the worm gear and the axle. I thought there was just the worm and gear. Anyhow, I'm told sometimes this gear slides to the side on its axle and disengages. Never had one of those gear boxes apart myself.


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## Therios (Sep 28, 2008)

I might be WAY out of line here as I have no knowledge of these "screws" or where they are on the block. But attempting to picture them in my head and when I hear that you can actually short them by getting them nose to nose, I was thinking and that is always a problem. But seriously, If they can touch end to end this sounds like a through hole to me. Would nylon be strong enough to use and bolt and nut? Just go all the way through with them? 

Just asking.


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## Greg Elmassian (Jan 3, 2008)

There are two metal half axles that bolt to a nylon gear. ANY connection between these two axles and you have a dead short. There are 3 holes drilled through the gear to attach the axles, 3 screws from each side. if they are too long, they touch each other and short. If you put a single screw through, you make a really high quality dead short between the wheels. 

I'll get a picture sometime to show you... 

Greg


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## Therios (Sep 28, 2008)

So a nylon bolt and nut would not work? It would definitely NOT be a short.


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## Greg Elmassian (Jan 3, 2008)

Probably not strong enough, and there's very little room for the head of a large enough bolt or nut... it's very tight clearances in there... 

In the picture below, the ball bearing for the axle has been removed... you can peer inside and see that where the metal axle is attached to the plastic worm, well, it's pretty tight in there...

I don't have a picture handy showing the gear out of the gearbox with the half axles attached...

Greg


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## Ward H (Jan 5, 2008)

Timely thread for me. I bought two used Mikados earlier this year. Run I ran once. The other I ran quite a bit. This one locked up last week. Looks like at least one gear box is damaged. ( Wheels spin freely on one axle) Put my other Mikado on the bench to install a Revo and that one slipped a driver and locked. After reading this thread I worked on it last night. None of the wheel screws were more than hand snug so several wheels were slightly out of quarter. I replaced all with the SS screws as recomended and successfully set the quartering on all drivers so the motor block runs real smooth. 

Now I am ready to tackle the first one. 

Question 1. Do you have to unsolder the motor to allow enough tilt to slide out the gear boxes? 
Question 2. Do you have to take apart the metal strip, bearing and BB/Spring to open up the gear box?


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## Tom Parkins (Jan 2, 2008)

Here are a few pictures of the gear box. I believe that this particular gear box is from an Aristo SD45 but it is the same gear box as in the Pacific, Miikado and Mallet and other prime mover engines. 




The Gear box is now open. Notice the 3 screws that hold the axle to the gear. 



The gear and axle combination. 



The axle is separated from the gear. If that axle looks a little bent or skewed it is. That is why the axle is on the workbench and not in the locomotive.


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## Therios (Sep 28, 2008)

Awesome... sorry if I was out of line, but pictures make it so clear. Thanks for doing those for me.


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## Ward H (Jan 5, 2008)

Tom, Thanks for the photos. Helps me to know what I am getting into. 

Did you have to unsolder the motor to get the gearboxes out?


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## Tom Parkins (Jan 2, 2008)

IF I recall the motor has a plug on it and it just clipped out. I don't recall unsoldering on anything. 

Tom


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## Greg Elmassian (Jan 3, 2008)

Motor soldered in normally, also there are 2 wires that carry the track pickup that are also soldered the same circuit board. 

Sometimes you can lift stuff up and get the gearboxes out. 

Greg


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