Monogram McLaren M6A/M6B Upgrades

Monogram McLaren M6A/M6B Upgrades

Fixing some of the same mistakes on Monogram’s McLaren M6 that we fixed on their Lola T70

by Bob Ward (AKA Leighton Early)

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Where have we seen a photo like this before?  Oh, I remember…

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It was this one, in my article about fixing the designers’ mistakes on the Monogram Lola T70.

There is probably a good and sufficient reason why they jacked up the McLaren’s body into the stratosphere the same way they did with the Lola’s.  It may have something to do with having produced thousands of motors with those pesky European government-mandated electronic bits soldered to the top of the motor and needing to use them up.  I said in the Lola article I couldn’t see why they had to put them on top of the motor where there simply wasn’t room for them under the low contours of a CanAm car body, and I can’t possibly be the only one who pointed this out.   Perhaps we should try to add the design departments of all the slot car manufacturers to our newsletter mailing list.

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Don’t get me wrong.  The McLaren is a step forward from the Lola in several areas.  They fixed the problem with the spur gear dragging on the track by going to an anglewinder chassis layout, which allows a smaller-diameter driven gear.  This also lets them use smaller-diameter rear tires of equal width to the Lola’s under a narrower body.  The McLaren M6 was actually a smaller car than it looks like in photos and you don’t really appreciate that until you see one parked alongside any of a number of its contemporaries.  Monogram did a good job capturing the lines and proportions of the body, much better than on the Lola, which looks too fat in a few places where it should be a little more svelte.  The principal drawback to the anglewinder   arrangement is that it puts part of the motor where the traction magnet really should be, forcing the whole magnet installation too far forward.  Wood track and copper tape devotees will not be affected at all, but for others the magnet arrangement may be problematic.

So, the two goals for the M6 are to lower the body and to get some kind of useful magnet farther aft.  On the Lola I started by removing all the interference suppressors from the top of the motor.  This time I didn’t feel like doing that so I just replaced the motor.  I happened to have a brand-new Pioneer 21,000 rpm FC130 motor floating around the workshop (and now to be available on the VLH web site).  It’s a perfect snap-in replacement for the Monogram FC130 except for one thing.  It’s a double-ender, with the shaft coming out both ends.  I therefore had to cut it off at the endbell end so it would fit inside the body.  I used a Moto-tool with a carbide disc to do the job.  The Monogram anglewinder pinion gear easily comes off the original motor and installs on the Pioneer one.

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Next, I stripped the chassis down to its bare essentials.  I removed everything – motor, axle assemblies, guide, and magnet assembly.  Then I sanded the bottom 2/3 of the chassis completely smooth, removing the raised ring around the hole for the key that fastens the car in place inside its case.

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With the bottom of the chassis done I turned it over and began grinding away material from the top.  I removed 3/32″ of material from the areas highlighted in red below. The areas in yellow were cut down to the level of the chassis plate to give ample room for the lead wires.

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I mentioned above that one of the problems caused by the adoption of an anglewinder layout was that the entire magnet installation was moved too far forward. Compounding the problem is the magnet itself.  It doesn’t provide downforce over enough of the car’s width.  The fix for all this is shown in the photo below.  I CA glued a Professor Motor PMTR1030 1mm thick bar magnet in place as far aft as possible.  The 1mm magnet is strong enough to give adequate downforce and thin enough to allow proper clearance under the car.  On our Scalextric Sport test track it delivered good cornering grip without sticking the car down so much it bogged on the straights or didn’t need to be driven through the corners.  I can still drive the car tail-out but the bar magnet covers enough of the car’s width that it doesn’t lose magnetic grip at normal cornering angles.  The result is like a non-magnet car with higher limits.  The earlier step of sanding the bottom of the chassis smooth, removing the ring around the hole for the hold-down key makes this installation possible.  Before gluing on the magnet be sure to sand the face if the magnet to be glued to provide some “tooth” for the CA glue to adhere to.

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With the chassis done the next step was to do a little carving on the body.  That consisted of removing 3/32″ from each of the 4 body mounting posts (blue arrows) and also from the areas highlighted in red below.

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With the body done it was time to reassemble the car.  All the mechanical components snap back into place.  I had to put some lead wires on the Pioneer motor.  Any of the various brands of silicone-insulated lead wire and brass end connectors will do the trick.  If you find that you don’t get a good tight fit between the lead wire connectors and the guide you can double over the ends of the braid to tighten things up.  You can also replace the stock guide with an aftermarket one from Slot It, NSR, or another manufacturer of your choice if you wish.  When you put the body on be sure the lead wires pass through the two areas that were cut down to the chassis plate.  This is to keep them from being pinched between the chassis and the interior tub.  One caution:  the two front body mounting screws need to be shortened because of the reduced length of the front mounting posts.  If they are left at stock length they will try to poke through the surface of the body when tightened down.

Before track testing I sanded the rear tires to make sure they were making full contact with the track surface for best traction.  With that done I broke in the motor a bit and then explored the modified car’s performance capabilities.  The Pioneer motor is very quick on the straights and the new magnet installation gives good but not excessive grip, making the car fast and fun to drive.  There is plenty of scope for tuning the car further to equalize it with other cars or to obtain a desired performance level.  And, of course, the car now sits down low over the wheels like a proper McLaren M6A should.

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Here’s the modified M6 next to a similarly modified T70.  Perhaps the third try will be the charm for Monogram and their next CanAm car won’t need modifying.

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And here, just for fun, is a shot showing the relative sizes of the M6, the T70, and a Carrera M20.  This shows what a compact car the M6 really is.

 

 

Monogram McLaren M6A project, part 2

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A while back I wrote an article on how to modify a Monogram McLaren M6 CanAm car to get the body down lower over the chassis and enhance the cars performance. Since then I’ve decided that there is room for more improvement, so I built a second car to try more ideas.  One feature of the car I found annoying the first time around was the motor brush housing that sticks up from the top of the FC130′s endbell.  This made it more difficult to get the rear of the body down where it belongs.  However, the FK130 motor doesn’t have that problem.  As you can see in the photo below, the FK130 is completely flat on top. That will allow the body to be lowered more easily.  The FK130 fits into the same length and width as the FC130 but requires modifications to the mount.  I had some Falcon motors floating around, so I decided to see what it would take to fit one into the McLaren chassis.

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The can end of the motor mount would be unchanged, while the endbell end would need considerable modification to fit the FK’s smaller bushing housing and make room for its lead wire tabs, which come straight out of the end of the motor instead of on top as on the FC.

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This photo shows the original FC130 installation (l.) and the new FK130 installation.  To get from one to the other I needed to fabricate a sleeve for the motor mount.  I CA glued a length of Evergreen Styrene 5/16″ O.D. plastic tube inside a length of 3/8″ O.D. tube.  When the glue set I cut a slice off the end, made a small flat spot in one side, and had a perfect adapter to allow the FK130 shaft bushing to fit snugly in the mount.  I discovered, however, that the mount for that end of the motor was thin enough that it didn’t really offer enough surface to glue the adapter to.  I could foresee the adapter  coming unglued from of the mount under the stress of snapping the motor in or out.  So, I dug through the junk box until I found an old broken chassis with an intact FC130 mount built into it. (This, friends, is why you should always save your broken chassis.  You never know when you may need part of one for a kitbash project.)  I cut out the FC130 endbell mount portion of the chassis and trimmed it so it could be CA glued in place outboard of the original endbell mount, effectively doubling its thickness and providing lots of gluing surface for the adapter.  With everything glued in place I cut the notches for the FK130 lead wire tabs and still had a more than adequately strong snap-in mounting for the FK130.

The car’s original anglewinder pinion easily transferred over to the shaft of the FK130.  A little adjustment of its position on the shaft gave a smooth, quiet gear mesh.  I installed a Slot It guide up front, and replaced the original lead wires with Professor Motor lead wire and eyelet connectors, which fit easily but snugly into the guide.  With the axle assemblies snapped back in place the car was ready for body installation and track testing.  I used on-track testing to determine the optimum magnet installation for the more powerful FK130.  After trying a number of combinations I settled on two Professor Motor PMTR1030 1mm bar magnets CA glued to the bottom of the chassis as shown below.

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This magnet arrangement looks a little odd, but it works well, and only delivers a reading of 310 grams on our Magnet Marshal, a quite moderate figure. With the Falcon motor, Maxxtrac M28 tires, and this magnet fit the car is fast, highly drivable, and runs just fine on a single Scalextric standard power pack per lane.  Of course, you can modify the magnet arrangement to deliver more or less downforce, but the very low clearance under the chassis doesn’t leave enough room for thicker magnets unless you recess them into the chassis, which will not be easy to do.

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Here’s the completed chassis from both left and right sides.  And if you are racing against other owners of Monogram McLarens…

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THIS is the view of it they will most likely get.

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