Gravity class insights

Talk forum for HO scale slot cars. 1/87 and 1/64 scale.

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Re: Gravity class insights

Postby jpennington » Thu Jan 02, 2014 3:00 pm

John great to hear about the progress on the Parma track. Hopefully it can lead to a race event there. There will be a gravity exhibition race at the national this year. Mo and I have had some early talks about it being during the first part of the race weekend.

On another note I would like to share some pictures and information on a very innovative and impressive build by Trevor Machuga, on of our Michigan racers. Trevor has taken quickly to this class and as you see his talents are quite apparent. Here is what Trevor has to say about his three gear sidewinder build:

This car started out with the idea of how could I create a sidewinder using a "traditionally sized" HO armature, like the kind found in Tyco or Super G+/G3. The motor can and magnets came out of a toy building that was used to ring a bell. The can is identical to those found in Bachmann Tracksters HO scale jeep and van that are made to run on railroad track, only the magnets are stronger than Bachmann. This motor is much narrower than the usual TycoPro HT50 motor or the 440X2 becuase the magnets are 1/2 the thickness of Tyco 440 magnets but of similar strength. The narrower motor allowed for great sidewinder placement with the use of a t-jet 9 tooth pinion as an idler gear. The endbell is a combination of two Bachmann trackster endbells. One was turned 90°, the open brush ends filled with "A+B" epoxy, and 00-90 holes drilled and tapped to mount G+ brushes. You will notice that one of the brushes is very close to the rear tire. This was the limiting factor for how far back the motor could be placed in the chassis and still have brushes on the sides, and that is why the idler gear was necessary.
The most challenging piece was the idler gear bracket which supports one end of the idler gear. About 10 hours went into the construction of this bracket, all done by hand and "eyeballed" into position. Care had to be taken to bend it to the right thickness to go over the idler. Lining up the holes was also tricky, because this was done visually without measurements by placing the bent bracket over the can and idler shaft and drilling small holes - progressively enlarging them to size and position until everyting was lining up correctly.
The front half of the chassis is from a Landshark kit where I flattened the sides, trimmed off the body mounts, recessed the pickup wipers, and cut out extra-long notches for the 0.32' single main rails. The distance along the main rails from the motor to the front pan is the same as on the inline mini-motor Landshark. I "borrowed" this feature because I am assuming that the amount of chassis flex will be similar and I do not own a track for extensive testing.
Rear axle is titanium from JW's so that it is not attracted to motor magnet. Gearing is 9th pinion, 9th idler, and 24th driven gear. The floppy body mount is similar to that found on other sidewinders but is also removable to allow access for gear and tire pullers.
I have driven this car with a 3-ohm and a 7.5-ohm armature. Despite the wide resistance range, the car was very stable during hard acceleration out of the corner with either arm, producing surprisingly low tail wagging even with the 3-ohm arm. I think that a mid-range arm will yeild a very drivable, competitive car.
This car started out with the idea of how could I create a sidewinder using a "traditionally sized" HO armature, like the kind found in Tyco or Super G+/G3. The motor can and magnets came out of a toy building that was used to ring a bell. The can is identical to those found in Bachmann Tracksters HO scale jeep and van that are made to run on railroad track, only the magnets are stronger than Bachmann. This motor is much narrower than the usual TycoPro HT50 motor or the 440X2 becuase the magnets are 1/2 the thickness of Tyco 440 magnets but of similar strength. The narrower motor allowed for great sidewinder placement with the use of a t-jet 9 tooth pinion as an idler gear. The endbell is a combination of two Bachmann trackster endbells. One was turned 90°, the open brush ends filled with "A+B" epoxy, and 00-90 holes drilled and tapped to mount G+ brushes. You will notice that one of the brushes is very close to the rear tire. This was the limiting factor for how far back the motor could be placed in the chassis and still have brushes on the sides, and that is why the idler gear was necessary.
The most challenging piece was the idler gear bracket which supports one end of the idler gear. About 10 hours went into the construction of this bracket, all done by hand and "eyeballed" into position. Care had to be taken to bend it to the right thickness to go over the idler. Lining up the holes was also tricky, because this was done visually without measurements by placing the bent bracket over the can and idler shaft and drilling small holes - progressively enlarging them to size and position until everyting was lining up correctly.
The front half of the chassis is from a Landshark kit where I flattened the sides, trimmed off the body mounts, recessed the pickup wipers, and cut out extra-long notches for the 0.32' single main rails. The distance along the main rails from the motor to the front pan is the same as on the inline mini-motor Landshark. I "borrowed" this feature because I am assuming that the amount of chassis flex will be similar and I do not own a track for extensive testing.
Rear axle is titanium from JW's so that it is not attracted to motor magnet. Gearing is 9th pinion, 9th idler, and 24th driven gear. The floppy body mount is similar to that found on other sidewinders but is also removable to allow access for gear and tire pullers.
I have driven this car with a 3-ohm and a 7.5-ohm armature. Despite the wide resistance range, the car was very stable during hard acceleration out of the corner with either arm, producing surprisingly low tail wagging even with the 3-ohm arm. I think that a mid-range arm will yeild a very drivable, competitive car.

[image]Image[/img]

[image]Image[/img]

[image]Image[/img]

[image]Image[/img]

Joel
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Re: Gravity class insights

Postby LDThomas » Fri Jan 03, 2014 3:26 pm

Very nice!
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Re: Gravity class insights

Postby slotking » Sat Jan 04, 2014 11:49 am

very nice
impressive

:nos:
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Re: Gravity class insights

Postby K.L. VanAtta » Thu Jan 23, 2014 9:15 pm

Joel,

Thanks for the information on the Gravity Class cars and components, a needed refresher for me. On my second read of all the posts and taking the time to ponder what was written. Gravity Class/Brascar type cars are still a major interest, as is slot car racing is in general.

Hope to speak/write more to everyone soon,

KLV
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Re: Gravity class insights

Postby stez1970 » Thu Jan 30, 2014 2:20 pm

The Parma Brass Wars 1972 National Championship track surface has been repainted and the track is already half non magnetic braided. So far the cars that have been tested on the partially braided track works with contemporary copper pick up shoes. If many of you recall who had raced on the track way back when, the pick shoes required using fuzzies. This track is going to be a blast for the Gravity and Brass cars.
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Re: Gravity class insights

Postby jpennington » Mon Feb 03, 2014 8:01 pm

John,
Any insights as to when a big race might be on the Parma track?
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Re: Gravity class insights

Postby stez1970 » Mon Feb 03, 2014 8:35 pm

Joel,

As of Saturday the track was 50% braided. The braid is super smooth and silky. John Reimels, Paul Ryer, Dave Muse and Don Hall as well as myself were checking it out. Peter powered a few lanes and we tried T-Jets and G-Jets. All went real well. Maybe John Reimels will bring some of his Brass War cars to Lenjet this Wednesday night for testing. We are hoping that the track will be completed very soon. I know Peter has some nice photos of the progress. I'm hoping that he posts some of them.

Many drivers have asked Peter what the surface track color would be. Peter has kept the original olive green color for the surface. Track section numbers will also be the same as the original which were yellow. It appears that the exterior walls and track infield will not retain the original pinkish orange color.

When the track is completed, we'll need to test it. I'm pretty confident that it will pass with flying colors. Once that is done, Peter will probably put together an experienced Brass Wars and Gravity Class race committee. I'm hoping that you will be on it. The committee will draw up the rules and pick the race date. Maybe we can have two races on the same weekend. One Brass car race using 1970 type rules and one using contemporary gravity class rules. We won't have to worry about magnetic down force issues since there is no magnetic down force. It will be very interesting what the committee will come up for rules. Thank You.
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Re: Gravity class insights

Postby slotking » Mon Feb 03, 2014 11:11 pm

FYI

I am now selling MAGNOTs
they stick to anything non-ferrous :lol:

good luck with this class

seeing what people are building is really awesome!
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Re: Gravity class insights

Postby LDThomas » Tue Feb 04, 2014 10:53 am

MAGNOTS - sounds like a fancy name for glue... :lol:
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Re: Gravity class insights

Postby stez1970 » Tue Feb 11, 2014 9:51 pm

The 1972 Parma Brass Wars track is now 99% completed for the track braiding. The only thing left is the dead strip. The track is looking fantastic. Most of the MARC guys had a good look at it during last Saturday's MARC event at Lenjet.

Were expecting a winter snow blast this week so I'm guessing that the dead strip won't be done till next week.

Peter and I are looking at color schemes for the exterior walls and infield. The origianl walls and infield were a pinkish orange. As I mentioned earlier Peter kept the original track surface color which is a olive green. Looks cool. Were looking at maybe yellow walls with a black infield. Any ideas out there? Thanks,
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Re: Gravity class insights

Postby jpennington » Wed Feb 12, 2014 5:00 pm

Avocado green and almond were 1970s colors! Perfect for that "70s track". :D
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Re: Gravity class insights

Postby stez1970 » Wed Feb 12, 2014 5:23 pm

Thanks Joel,
We'll put that combination in the pool. Maybe an almond infield.
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Re: Gravity class insights

Postby jpennington » Mon Mar 10, 2014 1:19 pm

Two updates:
1. There will be a support race for gravity cars at this year's HOPRA Nations. It will be on Wednesday June 25th in the evening, see the HOPRA website for details.
2. There is a proposal with the HOPRA Senate to recognize the Gravity class. Please be in contact with your representive. I feel this will be highly valued sanctioning for these cars and serve some important future with our hobby.

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Re: Gravity class insights

Postby gregw » Mon Mar 10, 2014 1:29 pm

Stez, pics of the Parma track? I remember you and Peter showing me the track before the restore started and can't wait to see it done!
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Re: Gravity class insights

Postby jpennington » Mon Mar 10, 2014 4:32 pm

Here is a picture of the Parma track work in progress that John shared. Quite awesome!
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