# Performance problems: Quartering



## Charles (Jan 2, 2008)

A while ago we sent to a fellow steamer a kit for an Accucraft GS-4 including combination levers and ball bearing rods for DIY install. Recently the engine was sent to us due to performance issues: wheels would not rotate. We found two issues: 
1) #3 driving wheel out of quarter (one side of the wheel could be turned by hand around the axle) Note that the counterweight is not parallel with the one on the other driver.











The wheel to the right with smaller counterweight is the one in question. 

In order to fit the wheel into the quartering jig, the axle ends needed to be center drilled and cored. This was accomplished on the lathe with the standard 3 Jaw chuck and a #1 center drill. Be sure to use generous amounts of cutting oil to keep the stainless cutting smoothly. 

Most newer Accucraft (and all Aster) engines come with the axle ends hollowed out for use in a taper point quartering jig. These are easy enough to make, and for those wanting a simplier solution, there are commercially available ones such as the kit available from Metalsmith in the UK. This one can be setup for either right or left hand lead by simply flipping and swapping the endplates.


2) The OEM rod bearings had been rat-tail filed out to compensate for quartering issue at the factory, evident in the 1st and 3rd set of rods, look at the smaller bearing. Roller (ball) bearing rods shown for reference of the proper diameters.











Having completed the quartering of the one wheel the new update rod with roller bearing installed rolled freely and smoothly. Now it will run and can be timed correctly with the additional of the combination lever kit











The thing to remember when updating/upgrading an engine; make sure to check all related parts to ensure smooth operation with little drag or binding.


Next is the combination levers and suspension work to ensure weight evenly is distributed over the drivers (#2 and #3 carry less than 15% of the total weight as delivered).


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## SalM (Jan 2, 2008)

Thanks for sharing that issue with the GS4........I love mine but a trip to the gararge was in order to do some checking out.........everything seems in order EXCEPT my second driver is not doing its share of carrying the weight of the engine...............I will look closer after it warms up down here later today...........A trip to N.J. may be in it's future. Thanks again for posting.


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## Greg Elmassian (Jan 3, 2008)

Charles, please excuse the dumb questions, but: 

1. Just to verify, the bearing holes were "elongated" at the factory in an attempt to compensate for the problem? 
2. Can it be determined what caused this? Like the "stud" to mount the con rod was in the wrong place on the driver? 
3. Am I crazy, it seems that elongating the hole just adds too much play in the side rod and still allows "lockup"? i.e. does not solve the problem. 

Just trying to learn here. 

Regards, Greg


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## rkapuaala (Jan 3, 2008)

Quartering has always been a dark art to me thanks for shedding a little light on it. Maybe someday you could find the time to devote a whole thread to this.


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## rbednarik (Jan 2, 2008)

Greg, 

If the drivers are not exactly 90* apart, a close tolerance bearing will not allow full rotation of the drivers. To compensate the bearings are indexed (ovaled or drilled off center) to allow the chassis to roll freely. The crank pins are the correct distance across all 4 drivers, so the quartering was the only item in question here. These wheels are on round axles, with no quartering marks, so unless you can visually see it, the wheel must be pulled and placed in a quartering jig. 

The ovaled hole does not eliminate the lockup that a tight tolerance bearing will have, since it only allows the wheel to be free to move when it reached the point of binding.


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## xo18thfa (Jan 2, 2008)

Charles: Wheels coming out of quarter raises my eyebrows a bit. How are these wheels attached to the axle? 

The key thing to quartering is that all the axles are exactly the same. The angle could be 89 or 91 degrees, but they have to be exactly the same. That's the reason for the quartering jig. It positivley sets each axle. Quartering is a somewhat "sloppy" art. Axle boxes on the bigger engines float around in the frame as they bump over the track. If everything where machined to extreme tolerance, the wheels could bind on every little bump. That's why these engines "wear in", not "wear not"

I've elongated some siderod holes on my scratchbuilds. Just the ones that need it to get it rolling smoothly. Sometimes eccentric bearings work too. The frames on one of my scratchbuilts ended up with slightly different, so the side rods are different lengths. Runs fine. These things need "tweeking"


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## David Leech (Dec 9, 2008)

Charles, and I guess Ryan, 
You say "#3 driving wheel out of quarter (one side of the wheel could be turned by hand around the axle) Note that the counterweight is not parallel with the one on the other driver." 
Since it was loose enough to be turned by hand, I am surprised that it was a problem. 
I would have thought that the axle friction, and the coupling rod would have kept it in position as it can't really do anything else. 
Or am I wrong here. 
All the best, 
David Leech, Delta, Canada


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## Steam Paul 1 (Jun 18, 2010)

Thanks for the excellent information, photos, and reference to Metalsmith. We appreciate the time that you've taken to share this with all of us.

Paul
SA #480


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## Charles (Jan 2, 2008)

Posted By David Leech on 06 Dec 2010 11:11 AM 
Charles, and I guess Ryan, 
You say "#3 driving wheel out of quarter (one side of the wheel could be turned by hand around the axle) Note that the counterweight is not parallel with the one on the other driver." 
Since it was loose enough to be turned by hand, I am surprised that it was a problem. 
I would have thought that the axle friction, and the coupling rod would have kept it in position as it can't really do anything else. 
Or am I wrong here. 
All the best, 
David Leech, Delta, Canada David
The wheel being loose on the axle is the problem when dealing with tight tolerance bearings. A degree or three out of quarter can cause quite a headache and make for some serious binding. To an extent the slight amount of float allowed between the axle boxes and the frame will take up a little bit of intolerance in the quartering of the wheels, PCD of the wheel on the axle, or even the location of the crank pin, but the amount that this wheel was able to move was too much. 


As we were placing the wheel in the quartering Jig, I was able to get the 90* desired, however, with the wheel loose on the axle, the quartering would not stay true and caused the spacing of the crankpin centerlines to become out of spec. To remedy this, I gave a tooth to each face (the bore in the hub of the wheel and the axle end, and applied a specialty grade loctite that not only fills gaps, but also is rated for high stress and heat applications. The quartering was set while the loctite was still solvent, then left to dry (in the jig) on the furnace while the loctite was setting up.


The rest of the axles are such a tight fit in to the axle (having to be pressed in via vise and parallel bars) that the quartering is easily held. This one wheel was the culprit as the chassis is now smooth as can be and has no binds or hesitation regardless of the rotation of the drivers.




Bob
Axles are pressed on to the wheels. Axle is stainless and the wheel center (hub) is brass. Usually there is enough of a friction fit to ensure a long lasting hold in the quartering, but it is subjective to the QC at the factory. You are correct in the asymmetry of some engines, but as these are mostly machined to close tolerance, when fitting retrofitted roller bearings or tight tolerance friction bearings, the engine needs to be as symmetric as possible.


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## xo18thfa (Jan 2, 2008)

Pressed. I hope it's not a recurring problem.


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## rbednarik (Jan 2, 2008)

Bob, 

This is only the second engine I have had where the press fit has failed on a driving wheel. It has happened on the pilot.trailing wheels of other Accucraft engines, but this is mostly due to using a plastic insulator between the hub and axle, which often becomes impregnated with oil or deforms from heat, causing the wheel to slip on the axle. 

I have done many Accucraft drivers in the quartering jig and most all of them are well quartered. 

The RMC AC-6 conversions we do require a driver to be pressed off the axle in order to swap the axle boxes, these are a cast steel driver center and stainless axle, pressfitted with loctite, these are such a tolerance fit that they are pressed together in a specially adapted machinists vise with parallel bars and a wheel gauge jig. The quartering jig allows enough room to start the wheel on the axle (and still be able to move it for adjustment) before doing the final press with the bearing grade loctite. 

Unless the quartering is set wrong from the factory, most of the engines out there will be fine as they tend to be "adjusted" to run satisfactorily. I do not necessarily agree with adjusting a bearing versus re-quartering the driver in question, but to each his own on how to get the engine to preform.


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## xo18thfa (Jan 2, 2008)

That's right, the wheels are insulated. I did metal on metal press fit one time. That was a fiddle job. I'll key and loctite next time.


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## rbednarik (Jan 2, 2008)

Bob, 

Only the pilot and trailing wheels are insulated axle-hub. The driving wheels are insulated between the tyre and the wheel center, so the axle-hub press fit is metal-metal. As you know, it is quite the chore to get right and a real pain when something is just a fraction off!


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## xo18thfa (Jan 2, 2008)

Posted By rbednarik on 06 Dec 2010 04:13 PM 
Bob, 

Only the pilot and trailing wheels are insulated axle-hub. The driving wheels are insulated between the tyre and the wheel center, so the axle-hub press fit is metal-metal. As you know, it is quite the chore to get right and a real pain when something is just a fraction off! 




It took me hours to do 4.


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## RimfireJim (Mar 25, 2009)

The tolerances for a press fit in this size range are in the tenths of thousandths on each part, not an easy thing to create or even measure. A slightly loose fit augmented with one of the Loctite retaining compounds is one solution. Another is using a straight knurl on the shaft (not sure if that is practical on this small of a shaft - would need a fine knurling tool).


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## Mike O (Jan 2, 2008)

Charles, Ryan, 

Thanks for taking the time to post this information. The post and subsequent discussion is a great primer for us still learning. 

Mike


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## TrotFox (Feb 15, 2008)

Posted By Mike O on 07 Dec 2010 06:16 AM 
Charles, Ryan, 

Thanks for taking the time to post this information. The post and subsequent discussion is a great primer for us still learning. 

Mike 
And there are none of us still breathing who are not "still learning". 

Trot, the steamable, fox...


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