This page describes how I converted this engine from the American Flyer-compatible wheels and couplers to scale ones. The S-Helper Service box comes complete with both the scale couplers and the scale wheels. Nothing extra is needed. The tools required for this project are a set of small jewelers screwdrivers, curved tweezers, and perhaps a magnifying visor. As per Don Thompson (co-owner of the former S-Helper Service company), the method shown for gaining access to the wheelsets is the same for their F3 and F7 locomotives as shown on this page. The underside of the truck has four screws that need to be removed to remove the AF coupler.
The removed parts, including the screws, are no longer needed for this project (the manual suggests that the screws are needed later, but they are not).
The first step is to upgrade the wheels. From an e-mail reply from Don Thompson of S-Helper Service, this is the method I used to snap the plastic cover off of the metal gear box. I inserted a pair of curved tweezers in between the plastic cover and the wheels' axle. I then used the axle as leverage to push out the plastic cover.
At this point the wheels and gear box are fully exposed. The wheels come out easily just by lifting them up straight.
Before inserting the new wheels, I widened the wheel wipers. The old wheels are closer together than the new ones and so the wipers won't necessarily make contact (I found that out the hard way). I really bent them out a ways.
Inserting the new wheel set (on the left) isn't difficult, but it does require a bit of patience and persistence. The bronze bearings have to fall into their slots on the metal gear box. Do one at a time.
I used the curved tweezers to line one of them with the slot in the gear box and then pressed it partially into place. You must also pay attention to the wheel wiper.
I then lined up the other bronze bearing. When both were in position, I pressed the whole axle down. You can see the difference in the scale wheels (left) and the Hi-rail wheels (right) quite clearly in this photo.
Next, with one hand I grab the engine's body and with my other hand I pushed down on the plastic cover to get it into position. It requires a bit of force. I found that it doesn't snap fully in place. I then used a screwdriver to really snap the plastic under the tab.
To upgrade to the scale couplers, the instruction manual tells to you use the screws that held the AF couplers in place, but those turned out to be too short. When I looked around the SHS box I found a little bag with longer screws in it. I used those and they worked great.
Once the AF couplers are out of the way, you can clearly see the three mounting holes for the SHS (or Kadee) coupler.
It is then just a simple matter of installing three of the longer screws. Make sure to not tighten the center one too much or else the coupler will not return back to its normal, centered position.