boBQuincy
<font color=green>I am not carrying three pods<br>
- Joined
- Nov 26, 2002
- Messages
- 5,077
Disney's model monorails are getting poor reviews on the Disney Store website and deservedly so, they do not run well. However, the monorails are not available now and I would much rather have one that does not run well than none at all, we can always fix the poor running.
Which leads into this analysis:
I recently converted a Mark VII to WhisperJet for a fellow modeler. He reported that it had trouble pulling the full train so I asked him to send me the cars and rear cab to see why they added so much drag. We don't see the problem with the stock monorail because it has more pulling power but the extra drag still causes slower operation, more noise, and faster battery drain.
Here are the numbers:
Pulling power - stock monorail - 100 grams
Pulling power - WhisperJet - 70 grams
Rolling resistance - a good WDW train (3 cars and rear cab) - 20 grams
Rolling resistance - Mark VII train out of the box - 50 grams
and... Rolling resistance - Mark VII train reworked - 20 grams!
Here is how I did it:
The cars:
all the top rollers are out-of-round with molding flash that makes them hang up on the sides of the cutout. After truing and rounding the edges one roller on each car still did not roll easily. The recess for the roller is not deep enough (or the recess for the shaft is too deep) so the roller scrapes on the rounded recessed area. I added some 0.25 mm shims under the shaft to raise the roller and that corrected the problem.
The rear cab:
the top rollers didn't roll well so I trued them but one was so out of round that it became too small before it was round. I made a new one from 1/4" ABS rod. Replacing the rollers with new 3D printed ones will be my standard method now.
The top roller cutouts had molding flash that interfered with the rollers, I filed them a little larger.
The side rollers at the cab end are a strange design. The shafts are 2 mm, the rollers are bored for 2.4 mm, the lower pockets that hold the shafts are 3 mm. The side rollers lift the rear cab enough so the top roller does not touch the beam and does not roll. I don't see how this can work well, and it doesn't. The WDW model has similar wheels but they fit the shaft and do not move up and down, they work Who knows why the designers changed this?
To make it more like the WDW model I trued the rollers (to 10.5 mm diameter), sleeved the lower pocket with 3 mm OD brass tubing, and raised the rollers to allow the top roller to actually touch the beam and roll.
The between car diaphragms:
these add a lot of drag in a curve. The plastic diaphragms effect can be reduced by trimming off one fold, they still add to the look without adding so much drag.
Which leads into this analysis:
I recently converted a Mark VII to WhisperJet for a fellow modeler. He reported that it had trouble pulling the full train so I asked him to send me the cars and rear cab to see why they added so much drag. We don't see the problem with the stock monorail because it has more pulling power but the extra drag still causes slower operation, more noise, and faster battery drain.
Here are the numbers:
Pulling power - stock monorail - 100 grams
Pulling power - WhisperJet - 70 grams
Rolling resistance - a good WDW train (3 cars and rear cab) - 20 grams
Rolling resistance - Mark VII train out of the box - 50 grams
and... Rolling resistance - Mark VII train reworked - 20 grams!
Here is how I did it:
The cars:
all the top rollers are out-of-round with molding flash that makes them hang up on the sides of the cutout. After truing and rounding the edges one roller on each car still did not roll easily. The recess for the roller is not deep enough (or the recess for the shaft is too deep) so the roller scrapes on the rounded recessed area. I added some 0.25 mm shims under the shaft to raise the roller and that corrected the problem.
The rear cab:
the top rollers didn't roll well so I trued them but one was so out of round that it became too small before it was round. I made a new one from 1/4" ABS rod. Replacing the rollers with new 3D printed ones will be my standard method now.
The top roller cutouts had molding flash that interfered with the rollers, I filed them a little larger.
The side rollers at the cab end are a strange design. The shafts are 2 mm, the rollers are bored for 2.4 mm, the lower pockets that hold the shafts are 3 mm. The side rollers lift the rear cab enough so the top roller does not touch the beam and does not roll. I don't see how this can work well, and it doesn't. The WDW model has similar wheels but they fit the shaft and do not move up and down, they work Who knows why the designers changed this?
To make it more like the WDW model I trued the rollers (to 10.5 mm diameter), sleeved the lower pocket with 3 mm OD brass tubing, and raised the rollers to allow the top roller to actually touch the beam and roll.
The between car diaphragms:
these add a lot of drag in a curve. The plastic diaphragms effect can be reduced by trimming off one fold, they still add to the look without adding so much drag.
