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Post by wbj on Aug 22, 2020 17:41:59 GMT -7
I put this together hoping that it may be useful to those who are looking to tune a stock AW 4 gear chassis. It’s targeted at the beginner to intermediate builder of the 4 gear chassis. If this information is already covered here please let me know. Also I would like to see others on this site add their own insights to putting together a 4 Gear chassis.
Top plate – This is the first challenge to getting a 4 Gear to run… well. Before you do anything clean off all the grease on the top plate.
A) Armature gear – it seems that none are pressed on properly. They all have some type of wobble. Now there are two ways to handle this, first pull this gear and properly press on a new gear. Making sure that it is pressed on squared to the shaft. Second, you can try repressing on the original armature gear. Sometimes this works and sometimes it doesn’t… your mileage may vary. Most times when this gear has been removed and reused it will be lose on the armature shaft. If you can get it setup squared and not thingyed a little epoxy will help keep it in place.
B) Armature hole – needs to be peened, so that when the armature shaft is placed in the hole. The armature can be spun with your finger freely with no wobble. (.064” usually does for sizing the armature hole)
C) Large idler gear – This gear usually has too much play. When combined with a wobbly armature gear you have the beginning of a noisy drive train. This gear needs to be peened to take out any excessive movement. The gear doesn’t need to be tight on the gear post. But all wobble needs to be removed.
D) Small idler gear – same as Large idler gear. Peen the gear to eliminate wobble.
E) Cluster gear - this gear has been known to be the culprit causing some sweet gear noise. They all have way to much play in them. The challenge is to take the play out but not to a point where you are bring in any bind. What sets this gear apart from the other gears on the top plate is that it is held on by a rivet. You need to tighten this rivet… being very careful not to over tighten. As there is no way to “un-tighten” it other than drilling it out and replacing it with a screw. The best way to tighten this gear is to use a 1/8” drift. This can be set on top of the rivet, while the bottom of the rivet and be supported on a small anvil. (Remember just supporting the bottom of the rivet) Now just some light taps on the drift while it is placed on top of the cluster gear rivet. Easy does it and checking it after each time you tap the rivet. All you want to do is remove any excess play without introducing any bind. Patience is your best friend here. With the top plate assembled spin the armature with your finger. Everything should spin smoothly with no gear movement or any bind.
Chassis – remove the rear hubs and axle. Check the rear axle to see if it is straight. You can do this by rolling the axle on a perfectly flat surface. Most axles will not pass this test. What I recommend is to make up your own axle. I use .0625” drill blanks cut to size. Next the rear axle holes have to be tightened up. Peen so that the new axle when placed in the axle holes the shaft has no wobble and can be slid in and out easily. Now on to the rear hubs… like everything else they more than likely wobble. How I’ve been able to save and reuse these hubs is by reaming them. This works about 60 to 70 percent of the time. I take a .063” reamer and place the non cutting shaft in the hub hole. I then pull the reamer through the axle hole until the cutting edges hit the hub. From there l spin the reamer through the hub to cut and clean up the hole. When you are done here we need assemble the axle, gear and hubs back in the car. Let’s test what we have now. Take the top plate without the idler gears and just the arm installed. Take the chassis either with or without the rear end in place. Put the top plate on the chassis and use the chassis clip to hold everything in place. Take a finger and spin the armature gear. That arm should be free spinning with no wobble what so ever. Take the top plate with the idler gears and arm installed. Now take the chassis with the rear end all set with axle, hubs and gear. Put the top plate on the chassis and use the chassis clip to hold everything in place. Give the rear hubs a spin. What you should have now is a free spinning assembly. No gears wobbling or bouncing with everything meshing well. If not, go through the chassis and look for any binding points or any excessive gear tolerances. You can do this by holding a finger in the armature gear and moving the rear hubs. Then reverse this by holding the rear hubs while moving the armature gear. But if you took the time everything should be mesh well.
Next we will talk about completing the build. |
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Post by dynomike on Aug 22, 2020 18:09:24 GMT -7
Keep the info coming and thanx.
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Post by wbj on Aug 23, 2020 16:18:17 GMT -7
If you followed the steps above you should be on your way to having a pretty smooth running chassis. You should now have about two hours into this build if you are doing it right.
Let’s assemble the chassis so that we can put some power to it. Remember to give it a quick oil. Now place it on a powered piece of track and take listen. The sound should be much better if you followed the steps above. Sometimes there will still be some chatter coming from the crown gear. We will take care of this with the next step.
Now for the fun stuff… time to lap the gears. If you are not sure how to this there are a nice article on this site that will help you with this process.
Remember patience is paramount. These pancake cars are monuments to friction and vibration. Next time will go over setting up the armature and pickup shoes. |
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Post by ecbill on Aug 23, 2020 18:00:00 GMT -7
If you followed the steps above you should be on your way to having a pretty smooth running chassis. You should now have about two hours into this build if you are doing it right.
Let’s assemble the chassis so that we can put some power to it. Remember to give it a quick oil. Now place it on a powered piece of track and take listen. The sound should be much better if you followed the steps above. Sometimes there will still be some chatter coming from the crown gear. We will take care of this with the next step.
Now for the fun stuff… time to lap the gears. If you are not sure how to this there are a nice article on this site that will help you with this process.
Remember patience is paramount. These pancake cars are monuments to friction and vibration. Next time will go over setting up the armature and pickup shoes. Any difference in the lapping technique between brass gears and plastic? |
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Post by wbj on Aug 24, 2020 15:31:48 GMT -7
ecbill, No difference that I am aware of... what I did find is that rubbing compound works well on the plastic gears. A little Dupont #7 mixed with some oil to a pancake batter consistency works well for me. One thing to remember when using the rubbing compound it has to be cleaned off quickly. As it a pain to clean up when it dries. I finish it off with a high speed spin using Brasso. I hope this helps?
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Post by wbj on Aug 24, 2020 15:40:06 GMT -7
After we’ve lapped the gears we should have a smooth running gear train. If you are still getting some noise it usually is from the cluster and crown gear. Hit it one more time with you lapping compound. Just the cluster and crown while paying some attention to the area between the crown and chassis. This should take care of that noise. Up next is setting up the armature and brushes. If we have done everything right the arm should be spinning free with no wobble. If it wobbles at all, time to fix it.
Now the 4 Gear armature spins counter clockwise. I’ve seen it mentioned that you should press the brush “fingers” from under the chassis to get more brush tension. Do not do that! The reason why is that this sets the brush where the leading edge is high in the brush pocket. This will cause the brush to rock in that pocket and not make good contact with the commutator. (You can get away with this in a magna traction as that arm spins clockwise.) You want those fingers to be parallel to the bottom of the chassis. If the fingers are bent use caution and make them parallel. Make sure that you support the fingers from the bottom of the chassis while you are repositioning them. Again, proceed with caution… just a little pressure applied from the brush pocket side with a toothpick. Next we need to take the brushes and give them a good polish on some 4000 grit paper. Just clean them up and make sure you knock down any hard edges that would come in contact with the commutator. Once this is done we are going to stretch the brush springs. I typically set the brushes so that they are just barely in the brush pocket. (This is just as a starting point as we look to see what the armature wants.) Stock springs will usually give you this look. If not take a toothpick and place the brush spring on it. With your finger nails holding the spring from both sides just slightly stretch it. Remember just a little as we want to sneak up on it. This may have to be done several times to hit the sweet spot. Assemble the chassis and put some power to it. If the car is not spinning up either you have too much or too little brush tension. It’s time to either put a little more stretch or take a little out. To take some out take the spring between your fingers and give it a good squeeze. What you are looking for is enough brush pressure to make power but not too much to reduce that power. Be prepared to spend some time looking for the right combination. |
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Post by Deleted on Aug 24, 2020 16:19:49 GMT -7
very, very interesting  |
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Post by ecbill on Aug 24, 2020 17:40:32 GMT -7
ecbill, No difference that I am aware of... what I did find is that rubbing compound works well on the plastic gears. A little Dupont #7 mixed with some oil to a pancake batter consistency works well for me. One thing to remember when using the rubbing compound it has to be cleaned off quickly. As it a pain to clean up when it dries. I finish it off with a high speed spin using Brasso. I hope this helps? Asked about that because the plastic 4G gears I lapped with semi chrome polish seem to deform the teeth. |
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Post by wbj on Aug 24, 2020 18:00:39 GMT -7
That's interesting... could you give some detail on how they were deformed? How long did you lapped them and at what voltage? I'm curious.
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Post by ecbill on Aug 25, 2020 4:44:39 GMT -7
That's interesting... could you give some detail on how they were deformed? How long did you lapped them and at what voltage? I'm curious. You're asking me to dig back in to the foggy part of my memory. It seems like about 10 minutes and probably 9 volts. |
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Post by dave632 on Aug 25, 2020 8:12:43 GMT -7
I have always used Simichrome for this process. For me it has worked but it might take several 5-10 minute runs on
the chassis running at a low voltage of about 6 volts, then cleaning it all off.
The cluster gear rivet on the afx 3 and 4 gear is the other problem as mentioned previously.
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Post by GTS on Aug 25, 2020 19:22:26 GMT -7
Thanks Wally, for posting this 4 gear build info, great stuff! At my age, I tend to forget more than I ever thought I knew and this is a great review for me.
Very much appreciated!!!
Hope it turns into a 'sticky'.
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Post by AJR on Aug 26, 2020 13:56:46 GMT -7
Great information WBJ!! Thank you for taking the time to compile and post all of that. A very good road map for anyone to have a competitive car. I'm posting a link to the cluster gear modification that I have been doing for awhile now. This eliminates "peening" of the rivet and actually allows for adjustment in the cluster gear. A definite upgrade. Screw size is 0-80 3/16" Washer M1.6 x 4mm x 0.3mmand can be found on Ebay. Link is below. nitroslots.com/thread/4246/4g-cluster-kitOne other suggestion is to always glue the armature gear, crown gear, and rear wheels. I glue every one of them in all classes. I have had too many come loose during a race....I do not trust press fit on anything. I use regular gel super glue for this. On anything Comp Class and up I solder the armature gear. Just a couple of things I do.... |
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Post by dynomike on Aug 26, 2020 15:09:02 GMT -7
Is any particular brand better for this application?
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Post by Deleted on Aug 26, 2020 16:06:22 GMT -7
Mike, I prefer original Aurora plastic
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