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Need help with AMT hardbody chassis


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#1 sportblazer350

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Posted 01 July 2019 - 09:31 AM

i built an AMt hardbody car using a repop AMT brass chassis and a 36D motor. Problem i am having is that these chassis only have one hole in the motor bracket so can only use one screw to hold down the motor. Issue i am having is that no matter how tight i get the motor screw, it eventually comes loose after a few laps and i get gear chatter. So what is the method to keep the motor tightly in place?

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#2 MattD

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Posted 01 July 2019 - 09:58 AM

hot glue fixes many problems, so does  thread lock


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#3 Rotorranch

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Posted 01 July 2019 - 10:18 AM

Do you mean the screw in the endbell? Or the bracket on the can side?

 

If it's the endbell, you can take a bit of super glue on a toothpick, and dab it in the screw hole. Let it set up before reinstalling the screw.

 

Rotor


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#4 Martin

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Posted 01 July 2019 - 10:25 AM

There are 2 slots cut into the chassis. If you make a thin strap that clips in there then goes over the motor to the slot on the other side of the motor. If fit tight it will prevent the motor from its twisting torque

reaction. 

Similar to a Cox motor clip.

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#5 Pappy

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Posted 01 July 2019 - 10:32 AM

I'd use Shoe Goo to hold it in place. It will hold it but when you need to remove it you can cut it loose with an Xacto knife. We use Shoe Goo on all our 1/32 scale cars to hold in lead, lead wires, lighting kits and motors.


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#6 Martin

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Posted 01 July 2019 - 11:09 AM

The important thing here is to arrest the torque reaction of the motor. So there are many ways to do this, not to mention you could solder it in place. 

I was thinking of a clean way to fix this or how the factory should/would have done it. 


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#7 sportblazer350

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Posted 01 July 2019 - 09:57 PM

thanks for the ideas guys. I was thinking of making a brass piece that would make for a second endbell screw to help hold the motor in place. The steel holder on the can side does nothing to keep the motor in place, at least for my issue. Since these cars were raced back in the 60's, there must have been a solution to this problem?  I'll try the Shoe Go as I have a new tube, and it is easy enough to remove. 


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#8 Ramcatlarry

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Posted 01 July 2019 - 10:04 PM

Obviously AMT had no clue that nylon cannot keep a motor in place beyond display.  Creative alterations (hotroding) is always in order with factory kits.


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#9 Gary Bluestone

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Posted 03 July 2019 - 03:57 AM

To start with, the screw that is typically used, is too big and ends up cracking the endbell. Use the other side and start with a smaller diameter screw. The other issue on all AMT chassis, is the brass under the drive side of the motor tends to bend from torque. We usually solder a bit of brass rod on either side, over the cutaway in the chassis , which is it's weakest point.



#10 sportblazer350

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Posted 04 July 2019 - 07:00 PM

Gary- not sure what you mean by the other side? The motor attaches with only one screw hole on the endbell side, which is the issue.

 

I tried some ShooGoo along the bottom of the motor on both sides and it seams to be a solid fit, so i will track test it next time i am at the raceway and report my findings.


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#11 MSwiss

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Posted 05 July 2019 - 09:14 AM

He meant rotate the motor 180 degrees, so you had a fresh hole, to put in a new screw.
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#12 sportblazer350

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Posted 06 July 2019 - 07:31 PM

Mike Swiss: Oh, i get it now! lol!!   But anyway, one screw is not enough. I did not want to solder in the motor, and i think that the Shoo Goo idea will work best, as it has a bit of cushion, maybe that will help with vibrations from motor to chassis: We'll see, next time on the track, which will be next Thursday night. I wanna race this baby in our Vintage Racing 36D class. 


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#13 Dave Crevie

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Posted 07 July 2019 - 08:50 AM

A little late getting in on this since I was away. On my AMT chassis I made a brass plate to solder to the end bell bracket with a large

hole for the bushing boss and that extended up to catch the upper screw hole in the endbell. Much as Glenn was thinking.  



#14 sportblazer350

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Posted 07 July 2019 - 03:20 PM

Hi Dave, yes that would have been my next step- to make that brass motor mount adapter to use two screws. Let's see how the Shoo Goo works first. I built this to race, and hopefully entice others to build AMT cars for racing. Hardbodys rule!!  :)


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#15 Dave Crevie

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Posted 08 July 2019 - 11:32 AM

I had a lot of success with these chassis back in the day. Once a few pecadilloes were assessed they worked quite

well. Obviously the a addition of the motor bracket was first. Second was to tack solder the front section to the rear

after the wheelbase was set. And check that it is straight before doing so. The fit is sloppy enough that the joint could

slip in a wreck and the wheelbase could shorten up, or the front could cock to one side allowing the front/rear alignment

to go out. I would also epoxy the motor bracket in. 



#16 Gary Bluestone

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Posted 09 July 2019 - 03:17 AM

I have heard that the whole rear section of the chassis behind the rear body mount strip, will flex from pressure caused by the crown and pinion gear side thrust. That is why you lose gear alignment and why the motor comes away from the bracket.The cure is to strengthen the chassis with 2 small tubes soldered just below the screws that hold the motor bracket. I don't suggest soldering the motor .



#17 Dave Crevie

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Posted 09 July 2019 - 11:23 AM

The best fix would be to solder the rear bracket to the chassis pan, but it is aluminum. What is needed is to

lock the bracket in so it can't shift in relation to the axle. Building up epoxy around the inside of the bracket

worked pretty well. The screws alone, even with lock washers, just didn't work.



#18 sportblazer350

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Posted 11 July 2019 - 11:12 AM

thanks again felllas for the additional tips. Yes, I already soldered the two chassis halves together. Next I will epoxy the rear section nuts and bolts. Will track test her out tonight at the C.A.R.S. Vintage Slot Car Club meeting and report my findings. 


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#19 sportblazer350

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Posted 12 July 2019 - 02:15 PM

track test update: so the Shoo Goo worked, not more loose motor and gear chattering issues. Next: how to make this car race worthy. I was recommended to shorten the front wheel width, but i will try maximum width again. I have tried both silicone coated rears and foam rears, but those are wide and this chassis is narrow, so i need to find a proper narrow rear tire......H&R Racing maybe? I need a 1-1/8" od. Maybe a narrow vintage set of Candies, if they made such a tire? Any suggestions would help, as i think that i have too much rear end traction. For any out there with AMT original or repops like mine, please lmk what tires you use in the rear.  I really want to enter this car in one of my Vintage Slot Car races, and hopefully some others will build a hardbody 36D car. I have a Cox Cheetah that i may also try to set up for racing, it was painted a bright metalflake green, so why not? 


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#20 Jay Guard

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Posted 12 July 2019 - 03:43 PM

Glenn:

You might want to check out Pro-Track's tires on Professor Motor's website.  They have a lot of tires in both wide and thin widths as well as many diameters, not to mention that their wheels are probably the most beautiful in the industry.  I used them for my jail door sports car and they worked perfectly.  I believe that they have silicone coated foam tires too.


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#21 Dave Crevie

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Posted 12 July 2019 - 04:30 PM

At the filming of the Vintage Tech Hunters episode I ran Pro-Track rears as I didn't have the right type of wheels and tires

ready. The natural rubber 241Ns worked great. 1 1/16th o.d., .700 wide. The original fronts are hard molded rubber, and

are fine as is.







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