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-As in "quick to build" - on the track? TBD
Some time ago I described the building of the BRM V-16 using Mac Pinches excellent body shell and laser cut chassis. At the time, I said that I wanted to use a high revving motor and short gearing to emulate the prototype but, alas, I could not fit my motor of choice and ended up with an SCX motor with which I have never been totally happy.
When I devised a scheme to fit the new Scalex style mini-motor to a standard drilled mount, I decided to re-fit the car with one of these and ordered one of the black 30,000 RPM variants.
I put the car on the track to make a few laps for a "before and after" comparison and decided that it was running so smoothly (perhaps benefitting from some running-in over the past several years) that I didn't want to take it apart.
I wanted to try both the mounting scheme and the motor and do it in time for the Slot Car Convention this week but with only a weeks building (and paint drying) time left, it had to be quick.
I have a box with almost all of the bodies that Mac has made and a few of the chassis as well so - let's have a look. BRM - done, Talbot Lago - done, Auto Union - did one recently, W-125 - in process with a different chassis/motor combination - I've always liked the Alfetta and 4CLT (and have Merit-bodied 1/24 versions) so.....
The Alfetta is the bigger car but has a "pinched-in" shape just aft of the front wheels and the chassis fit looks problematical so - the 4CLT it is.
Cut apart the chassis parts with an abrasive disc and solder up the rear end with standard 3/32 bronze bushings fitted - now let's look to the 6 possible positions for the front axle. The wheelbase of the 4CLT is 2500mm (exactly matching the cut-outs on the body) but the closest two positions are either 1.75 mm to long or 1.82 mm too short for the scale 78.125 mm model wheelbase. Solution: I used the "longer" set-up and ground (the chassis material laughs at files!) 1.75 mm off the rear of the tabs that slot into the base plate. This meant using a chassis jig to solder up the front because the precision of the original tab and slot fit was lost. At the same time I soldered in the guide tab in reverse with the smaller hole over the base plate hole - the larger hole is exactly the right size for the sleeve of the TSRF guide that I planned to use.
The motor adaptor plate was made from a bit of 0.0625" brass the width of the chassis and the height of the motor. A clearance hole for the bearing was drilled in the center, two more holes, drilled and tapped 2-56 on the horizontal center 12.4 mm apart and two holes, on a 5 mm radius 30 degrees from the horizontal were drilled for clearance for the 2mm motor mounting screws and countersunk.
The adaptor plate was mounted to the motor with 2mm FH machine screws.
end of the first evening
The gear collection yielded a 46 tooth aluminum "drag" gear and a 10 tooth Wizzard brass pinion (HO stuff so it has the needed 1.5 mm bore). The big gear just clears the gear cut out in the chassis and the pinion is soldered to the shortened motor shaft.
Now about wheels, tires and weight - The 4CLT mounted 5.25 X 17 tires in front and 6.50 X 16 tires at the rear. These scale to 0.8750" (F) and 0.903" ® with section widths of 0.21" and 0.26" respectively. These are relatively small tires for the era and may reflect the fact that the design of the 4CLT has more in common (except wheelbase) with the "voiturette" class of the 30's than with its 8CTF forebear and the Talbots and Alfettas of the day. In any event, this wheel and tire size means that using a typical "rattle pan" slung under the chassis would reduce the ground clearance below the 2 mm often stipulated in vintage races. The solution I came up with was this: A piece of 0.0625" brass was cut to fit the chassis cut-out with 0.010" clearance all around. This was sweat soldered to a piece of 0.016" brass the same length but the full width of the chassis. The chassis material is about 0.040" thick so, with a pair of wire "L's" soldered to the rear and cross member of 0.016 brass screwed to the front from the top, it "hangs" in place with 0.010" movement in all 3 directions. (There is adequate clearance under the motor to allow this movement)
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The wheels are BWA and the tires are Ortmanns - rear and Scalex Maserati 250F front (the rib on the BWA wheels was narrowed to accomodate the front tires and then the outer edge of the rim turned down as well.
While this was going on, body mount post were fitted and the body primed. Before I primed the body, I used an idea I gleaned from another thread (MAF's Mercedes collection?) and ground out the dash and thinned the edge of the cockpit. This would also allow me to fit the curious "half-dash" that these cars carried:
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end of the second evening
Today I painted the body (Dupli-Color red lacquer - great stuff - 5 coats in less than an hour, painted the (already primed) metal bits, reshaped the driver under hot water and primed him and made up the wheel inserts. The BWA 0.45" inserts will fit right in but the cupboard was bare so I made some up from Ninco "Classic" wheels. These require that the wheel be bored out slightly to fit so, making advantage from neccessity, I bored the fronts to 0.500" and the rears to 0.480" to give the impression of the two different size wheels.
Will he make it for the 0:400 departure Thursday? - to be continued.
EM
Some time ago I described the building of the BRM V-16 using Mac Pinches excellent body shell and laser cut chassis. At the time, I said that I wanted to use a high revving motor and short gearing to emulate the prototype but, alas, I could not fit my motor of choice and ended up with an SCX motor with which I have never been totally happy.
When I devised a scheme to fit the new Scalex style mini-motor to a standard drilled mount, I decided to re-fit the car with one of these and ordered one of the black 30,000 RPM variants.
I put the car on the track to make a few laps for a "before and after" comparison and decided that it was running so smoothly (perhaps benefitting from some running-in over the past several years) that I didn't want to take it apart.
I wanted to try both the mounting scheme and the motor and do it in time for the Slot Car Convention this week but with only a weeks building (and paint drying) time left, it had to be quick.
I have a box with almost all of the bodies that Mac has made and a few of the chassis as well so - let's have a look. BRM - done, Talbot Lago - done, Auto Union - did one recently, W-125 - in process with a different chassis/motor combination - I've always liked the Alfetta and 4CLT (and have Merit-bodied 1/24 versions) so.....
The Alfetta is the bigger car but has a "pinched-in" shape just aft of the front wheels and the chassis fit looks problematical so - the 4CLT it is.
Cut apart the chassis parts with an abrasive disc and solder up the rear end with standard 3/32 bronze bushings fitted - now let's look to the 6 possible positions for the front axle. The wheelbase of the 4CLT is 2500mm (exactly matching the cut-outs on the body) but the closest two positions are either 1.75 mm to long or 1.82 mm too short for the scale 78.125 mm model wheelbase. Solution: I used the "longer" set-up and ground (the chassis material laughs at files!) 1.75 mm off the rear of the tabs that slot into the base plate. This meant using a chassis jig to solder up the front because the precision of the original tab and slot fit was lost. At the same time I soldered in the guide tab in reverse with the smaller hole over the base plate hole - the larger hole is exactly the right size for the sleeve of the TSRF guide that I planned to use.
The motor adaptor plate was made from a bit of 0.0625" brass the width of the chassis and the height of the motor. A clearance hole for the bearing was drilled in the center, two more holes, drilled and tapped 2-56 on the horizontal center 12.4 mm apart and two holes, on a 5 mm radius 30 degrees from the horizontal were drilled for clearance for the 2mm motor mounting screws and countersunk.
The adaptor plate was mounted to the motor with 2mm FH machine screws.
end of the first evening
The gear collection yielded a 46 tooth aluminum "drag" gear and a 10 tooth Wizzard brass pinion (HO stuff so it has the needed 1.5 mm bore). The big gear just clears the gear cut out in the chassis and the pinion is soldered to the shortened motor shaft.
Now about wheels, tires and weight - The 4CLT mounted 5.25 X 17 tires in front and 6.50 X 16 tires at the rear. These scale to 0.8750" (F) and 0.903" ® with section widths of 0.21" and 0.26" respectively. These are relatively small tires for the era and may reflect the fact that the design of the 4CLT has more in common (except wheelbase) with the "voiturette" class of the 30's than with its 8CTF forebear and the Talbots and Alfettas of the day. In any event, this wheel and tire size means that using a typical "rattle pan" slung under the chassis would reduce the ground clearance below the 2 mm often stipulated in vintage races. The solution I came up with was this: A piece of 0.0625" brass was cut to fit the chassis cut-out with 0.010" clearance all around. This was sweat soldered to a piece of 0.016" brass the same length but the full width of the chassis. The chassis material is about 0.040" thick so, with a pair of wire "L's" soldered to the rear and cross member of 0.016 brass screwed to the front from the top, it "hangs" in place with 0.010" movement in all 3 directions. (There is adequate clearance under the motor to allow this movement)
The wheels are BWA and the tires are Ortmanns - rear and Scalex Maserati 250F front (the rib on the BWA wheels was narrowed to accomodate the front tires and then the outer edge of the rim turned down as well.
While this was going on, body mount post were fitted and the body primed. Before I primed the body, I used an idea I gleaned from another thread (MAF's Mercedes collection?) and ground out the dash and thinned the edge of the cockpit. This would also allow me to fit the curious "half-dash" that these cars carried:
end of the second evening
Today I painted the body (Dupli-Color red lacquer - great stuff - 5 coats in less than an hour, painted the (already primed) metal bits, reshaped the driver under hot water and primed him and made up the wheel inserts. The BWA 0.45" inserts will fit right in but the cupboard was bare so I made some up from Ninco "Classic" wheels. These require that the wheel be bored out slightly to fit so, making advantage from neccessity, I bored the fronts to 0.500" and the rears to 0.480" to give the impression of the two different size wheels.
Will he make it for the 0:400 departure Thursday? - to be continued.
EM
