# Lapping



## stirlingmoss

Any hardcore racers here who regularly laps there chassis's?
I have a compound I would like for you to try. 
I get this paste from a medical device company i work for so you cannot buy it in stores, I think it would be far superior to what anyone is using for lapping t-jets.
Let me know.


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## Rich Dumas

I lap the gears, not the chassis itself. The brass gears used in many pancake cars usually have burrs or just fit too tightly and your car will run better if the gears are lapped. I lap gears with a mixture of automotive buffing compound and metal polish. The buffing compound has a more aggressive abrasive than other things that you might use and that reduces the lapping time. The buffing compound is too thick, that is why I mix it with metal polish. I use a special jig to lap gears, normally 15 minutes in each direction is enough. The exception to that are the early Dash gears, which are very difficult to lap, those take about an hour in each direction. That much lapping would remove the teeth from Aurora gears!


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## stirlingmoss

Are you interested in trying my compound free?
I cant tell you all of the ingredients of my paste but it does contains small amounts of very fine diamond dust.


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## slotking

I made a solution a while ago that worked pretty good.

I had small container (a car plastic case top)
I put some MMO, added lapping compound I got from home depot
I had a junk chassis I would put the gear plate on, place the car upside down in the mix and add power to the shoes.

that was it


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## alpink

stirlingmoss, I only drag race, but good gear mesh is just as important.
I would certainly like a small quantity of yout compound to try.
thnk you


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## yellerstang

*lapping*

Hey, sounds like fun. I have been using Novus plastic polish lately, it works great. I have used others, buffing compound for cars, car polish, headlight restorer polish, and some others. I like the Novus.


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## hartracerman

I have used wd-40 in a small container and it worked great and polished and cleaned at the same time.


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## Joe65SkylarkGS

Would some of you guys who do your own lapping please post a video of what you do??

We have a few new members here who can definitely benefit from watching some videos. 

???????

Me, I just kinda do my gears dry, no magnets or brushes, then I kinda just push em around with a stainless Dremel bit in every direction. Not a real "lapping" procedure, but I do get them to quiet down an awful lot!!!


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## Rich Dumas

I believe that the media in the automotive buffing compound is diatoms, which are composed of silica. That would be more aggressive than the calcium carbonate that is used in toothpaste and a lot of cleaning products. I would expect that diamond dust would be even more effective and might reduce lapping the time. I my case lapping time is not as critical because I use a jig, people that lap gears on the car would certainly want to reduce the time it takes to do difficult gears like the early Dash ones. I would like to try a sample of your lapping compound, I will send you a PM with my address. I still have one or two unused early Dash cars and those would be a good test. I could run a chassis as is, lap the gears for 15 minutes in each direction and run the chassis again. As I mentioned earlier it takes me an hour in each direction to lap those gears.


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## LDThomas

Always looking for a better mouse trap/lapping compound.


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## stirlingmoss

I hope to get those samples out Friday to those who already pm'd me, if I have extras I will get those out during the week.
Bare with me as these samples are gifts on me and I have to package them.
Hopefully this stuff will make your gears buttery smooth.


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## slotking

i have to do some digging

i thought i had a vid at ho vid library, but could not find it


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## Boosted-Z71

I use a thinned AT transmission fluid with some 1000 grit lapping compound mixed in, I lap using a .064 gauge pin shaft made up to mimic the armature & lap all gears at once with the axle installed. 

I have a battery Dremel tool that I use for power & a block setup to hold the chassis perpendicular to the dremel shaft to ensure it puts no pressure or bind on the arm gear.

I only lap 1 direction, and mark all gears prior for the best fit. I use a small paint brush to keep the compound in place and use very little of it. When finished lapping I clean & oil, then I test the bare chassis with axles, wheels, gears and arm installed, I use a roll test from an inclined block, you get them right they will almost roll like a hot wheels car. 

Stirlingmoss I would like to try some of your compound, will send you a PM.

Boosted


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## stirlingmoss

ok I have 6 samples ready to mail out tomorrow,its a small sample but should be enough to test.
this batch is very fine(wet) I would like feedback on this as I can change the formula.
if you guys like it ill send out more.


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## Boosted-Z71

Just wanted to say a Big Thank You to Stirlingmoss for the samples, I received mine today and plan on getting a chassis ready to lap sometime this week if work & life co-operates.

Initial thoughts on the compound, I like the consistency, not sure yet if its going to sling or travel much, seems clingy between the fingers. I am going to use a rough set of gears just to see how abrasive it is. 

Any idea on the grit grade of this compound, and is cleaning going to require a mineral based solvent? 

Again Thank You

Boosted


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## stirlingmoss

your very welcome 
this sample is a mild compound I cant reveal anything else

it will clean up with water..
also a 50/50 mix of Isopropyl alcohol and water will work even better.


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## Rich Dumas

*Test Results*

I got a sample of the lapping compound yesterday. I had an unused Dash chassis and I took the gear plate/armature assembly from that. The hole for the cluster gear shaft was a little loose, so I tightened that up and also swaged the idler gear to tighten it up. I put the assembly in a Dash chassis that was in Fray trim. Because I did not want to trim the gear plate rails I ran the car without a body. The best time with unlapped gears was 6.427 seconds. I lapped the gears for 15 minutes in each direction using the stirlingmoss compound. The compound was a good consistancy for lapping gears, the gears were really tight to start with. After I was finished with the lapping I flushed the gear plate with contact cleaner and then put it in an ultrasonic bath. After the gear plate was dried and oiled it went back in the car and that turned a best time of 6.063 seconds. I gave the gears another 15 minute pass in each direction but the lap times were about the same with a best lap of 6.042 seconds. It looks like the gears were about done with 15 minutes of lapping in each direction. If I had used toothpaste or regular metal polish the lapping would have taken hours.
Early Dash gears are very difficult to lap, the newer cars use a different alloy for the gears and those are supposed to be easier to lap.


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## vaBcHRog

I use Brasso. I epoxied two mounting posts to the bottom of a half a TJET box then I pour some Brasso and mount the chassis upside down and hook up two alligator clips to the pickups and run it. The old cans of Brasso were much thinner consistency than the new plastic bottles so I have to use a paint brush to spread it out.

Anyone know what would be good to thin it out with?


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## slotking

I am still waiting for mine

I have some good gears to test


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## stirlingmoss

slotking said:


> I am still waiting for mine
> 
> I have some good gears to test


I believe I sent yours out Friday.
I received lots of pm's /requests for samples but i was only able to send out 6 samples as they were all I had brought home at the time.


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## Rich Dumas

You could thin the Brasso with naphtha, kerosene or heating oil, but those are all moderatly flammable. Sparks from the car's brushes could possibly set fumes from many solvents on fire. The things that I mentioned have a higher flash point than most solvents. You could try vegetable oil. If you are a fan of Car Talk Felipe Berio Extra Virgin Olive Oil would be the thing to use.


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## slotking

> Sparks from the car's brushes could possibly set fumes from many solvents on fire.


COOL!!:dude::dude:

I got mine yesterday
testing will happen on friday

Thank you so much:thumbsup:


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## alpink

picked up my mail today and the lapping compound was waiting for me.
THANK YOU
I'll be trying it in the coming week and giving my evaluation.


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## stirlingmoss

any updates?


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## alpink

working on some bodies today. hope to get to some chassis tomorrow. I have a couple DASH I want to break in.


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## Boosted-Z71

I started building 2 fray type cars, 1 original Aurora & the other a Dash, I used the lapping compound on both chassis, Both lapped in, the gear sets are very smooth, quiet. I lapped all the gears, pinion to crown. It clings well, stays in place, I put it on with a cheap Testor's paint brush, slow speed on the Dremel and moved it around occasionally. 

All in all I think this mix is a winner, it did not break down during the lap, I scraped off the mix, prior to cleaning and put it into another jar to re-use it again. I like it better than the lapping compound mix I have used for years, its just a smoother and more consistent mix right out of the jar and throughout the process. 

Lapping took about 12 minutes on the Aurora and a little over 15 minutes on the Dash gears, they were both smooth and free and tested similar on the incline block test. 
I did not have to touch the gears afterwards, lap, clean and done!

As for cleaning, it was simple, I wiped the mix as best I could recycling as much as I could, then sprayed the parts with a mix of alcohol / water, then sent them to the ultra sonic cleaner for a 4 minute finish wash. I then inspected the gears under magnification to see what the wear/lapping pattern looked like, and I have to say is it was nice and even on both tooth & root on all gears. 

After cleaning / oiling / assembly I test on the incline block and they rolled really well & very quite

All and all this is a winner, really nice pattern on the gears without a ton of wear induced by the compound. 

The only negative I have to say about it is that for lapping the crown gear in it may be just a tad light on grit for the plastic gear, as these can be hard to cut, but if you have too much grit you will eat up the intermediate gear. So I still think it works well. 

But it is dead on for the top plate gears.

Thanks, I will be looking forward to more info on this 

Boosted


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## slotking

I used on some older noisy rtho gears,
It did help because the dyno showed better results.

I am looking for my dash gear plate to see how it works on new gears

more later


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## alpink

did up an early DASH for about ten minutes, very quiet now


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## stirlingmoss

Boosted-Z71 said:


> I started building 2 fray type cars, 1 original Aurora & the other a Dash, I used the lapping compound on both chassis, Both lapped in, the gear sets are very smooth, quiet. I lapped all the gears, pinion to crown. It clings well, stays in place, I put it on with a cheap Testor's paint brush, slow speed on the Dremel and moved it around occasionally.
> 
> All in all I think this mix is a winner, it did not break down during the lap, I scraped off the mix, prior to cleaning and put it into another jar to re-use it again. I like it better than the lapping compound mix I have used for years, its just a smoother and more consistent mix right out of the jar and throughout the process.
> 
> Lapping took about 12 minutes on the Aurora and a little over 15 minutes on the Dash gears, they were both smooth and free and tested similar on the incline block test.
> I did not have to touch the gears afterwards, lap, clean and done!
> 
> As for cleaning, it was simple, I wiped the mix as best I could recycling as much as I could, then sprayed the parts with a mix of alcohol / water, then sent them to the ultra sonic cleaner for a 4 minute finish wash. I then inspected the gears under magnification to see what the wear/lapping pattern looked like, and I have to say is it was nice and even on both tooth & root on all gears.
> 
> After cleaning / oiling / assembly I test on the incline block and they rolled really well & very quite
> 
> All and all this is a winner, really nice pattern on the gears without a ton of wear induced by the compound.
> 
> The only negative I have to say about it is that for lapping the crown gear in it may be just a tad light on grit for the plastic gear, as these can be hard to cut, but if you have too much grit you will eat up the intermediate gear. So I still think it works well.
> 
> But it is dead on for the top plate gears.
> 
> Thanks, I will be looking forward to more info on this
> 
> Boosted


thankyou for sharing! my "lapaste" sounds promising
just a note I can adjust the compound to your needs.


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## Boosted-Z71

I think your past the promising stage

Can you describe the adjustments you can make?

And any idea on how your going to sell this?

Boosted


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## stirlingmoss

Boosted-Z71 said:


> I think your past the promising stage
> 
> Can you describe the adjustments you can make?
> 
> And any idea on how your going to sell this?
> 
> Boosted


thankyou!
that's the problem I do not know how to market,sell or distribute it.
as far as adjusting the paste its just changing the amount of a certain component.


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## alpink

had a very stubborn older Aurora chassis .... even after thorough cleaning and carefull reassembly it was tight.
slathered a little compound on and ran it about 5 minutes each direction. smooth and quiet now.
this is not intended to be a race car, but I would like it to run well.
this concoction seems to work well.


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## brownie374

I need some!


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## wheelszk

Any chance of getting some?


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## Dyno Dom

Rich, can you explain the workings of your jig pictured in 2nd post??


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## Rich Dumas

When I powered up a car directly to do the lapping the lapping compound wanted to sling off unless I turned the voltage down, but then the motor wanted to stall. The answer to the problem was to turn the rear wheels with something that has a lot more power. I also race 1/32nd cars and I had spare parts from those hanging around. There is a Slot.it 21.5K RPM motor in a Slot.it sidewinder motor pod. The gears are 8/36. I use a spare crown gear to limit the side play and connected the end of the axle to the rear axle of a T-Jet chassis.


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## Bill Hall

Rich,

When using a mule, how do you know when you hit the sweet spot?


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## Rich Dumas

I put the car on the track and if it is quiet and it has a little coast I assume that the gears are good. With the lapping compound that I normally use 15 minutes of lapping in each direction is usually enough.


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## alpink

*kudos*



Rich Dumas said:


> I got a sample of the lapping compound yesterday. I had an unused Dash chassis and I took the gear plate/armature assembly from that. The hole for the cluster gear shaft was a little loose, so I tightened that up and also swaged the idler gear to tighten it up. I put the assembly in a Dash chassis that was in Fray trim. Because I did not want to trim the gear plate rails I ran the car without a body. The best time with unlapped gears was 6.427 seconds. I lapped the gears for 15 minutes in each direction using the stirlingmoss compound. The compound was a good consistancy for lapping gears, the gears were really tight to start with. After I was finished with the lapping I flushed the gear plate with contact cleaner and then put it in an ultrasonic bath. After the gear plate was dried and oiled it went back in the car and that turned a best time of 6.063 seconds. I gave the gears another 15 minute pass in each direction but the lap times were about the same with a best lap of 6.042 seconds. It looks like the gears were about done with 15 minutes of lapping in each direction. If I had used toothpaste or regular metal polish the lapping would have taken hours.
> Early Dash gears are very difficult to lap, the newer cars use a different alloy for the gears and those are supposed to be easier to lap.


your findings are very interesting and a good indicator of the value of this compound.
I like it. I hope that sterlingmoss finds a way to package it. :thumbsup:


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## Rich Dumas

Yesterday I picked up some Permatex valve grinding compound, it cost $4.50 for 1.5 oz. and is water soluable. I don't know if I have any Dash gears that have not been lapped, if I can find an untouched set I will try the Permatex stuff.


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## Bill Hall

Rich, 

I think the Napa house brand is private labled by Permatex. It worked quite well for the T-Dash, but the disclaimer is that it will never change the sound of the harder gears for the fussy types.

I dont do much automotive head work anymore, but still use a fair amount of compound for honing my vintage reel lawnmower. I adopted push mowing as one of my cardio exercises. Night crawler, bird and squirrel activity brings up little stones or gravel from the sod, that nick up the knives. Although the compound is water base, I found it breaks quickly and gets sloppy fast when diluted with water. I use ATF as a dispersant instead. As you would expect the mower's knives and anvil are quite hard, but it doesnt take long to bed the barrel once or twice a year.

I had always used Clover brand oil base compound in the past, because it stays put when your doing valve work. Slurry work is an entirely different matter. I find that the water base product is easier to get into suspension, and cleans up much easier for slot car work (read, "small"). Hot soapy water (New Dawn) gets it clean on the first pass, when the TM isnt looking. A short blast of air, then a squirt of contact cleaner while holding the chassis vertical to flush any residual particles, and finish with compressed air; or your hairdryer if you dont have the luxury of compressed air. 

I've tried most everything in the way of abrasive slurries for lapping T-jets. The softer original alloy (s) respond nicely to coarse and medium rubbing compounds for autobody. I especially prefer the autobody compounds for plastic gears. The rubbing compounds are slightly less aggressive and dont rag up the gear's smooth factory finish by cutting too aggressively. 

For T-jets, I eventually cut out the middleman; and just began using 600 wet dry paper with oil, to lightly dress the gears while running. This way the tooth edges get deburred, and the tooth mating surfaces get lapped, all in one simple step. The gear teeth carve the grit off off the paper and instantly whip it into suspension with the oil. It makes it's own slurry, the particle migration is good, and I find it to be a less messy lapping method overall. 

While running, I lightly dress the underside of the driven gear, idler gear and the arm gear by carefully slipping the paper under the edge keeping the direction of rotation in mind. Then just kiss the top edges of the gears. Then I repeat with 1200, just because I'm a nut. Like any other slurry mixture, add more oil if things start to get dry or gummy, and bog down excessively.

I usually position the chassis nose down, and add the oil at the driven gear; so the by product drools down front onto the long portion of the gear plate. You can just swab it off as you go or wash it off later. After the first pass at 600 you'll hear power train pipe up and hit the sweet spot quickly. All in all, it goes quickly. A mere matter of two maybe three minutes total. A thorough clean up takes me way longer.

Arguably not the same thing as dis-assembling the gear plate, flat lapping the gear surfaces; then re-assembling and then lapping the teeth. Thats not something I want to do for every T-jet style metal geared chassis; but it's proven to be a very effective way for people without presses and pullers to quickly get almost instant horsepower for cheap.

For the T-Dash, I just went straight back to the traditional compounding method for something a little more aggressive simply based on the knowledge that the chosen alloy was harder, and they were really singing from the get go. 

There is no one right way, I use whatever method applies, based on the mistakes of the past.


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## Boosted-Z71

Bill Hall said:


> I dont do much automotive head work anymore, but still use a fair amount of compound for honing my vintage reel lawnmower.


Bill I worked on a golf course for many years in my younger days as a mechanic and I have ground, sharpened & lapped more bedknives & reels than I want to remember, We always used Clover oil based brand compounds, I happen to have some Napa brand water base compound that actually states it is made for Napa by Permatex.

I had to chuckle on your cardio comments on the reel type push mower, it was a flashback to my golf course days, many hours spent grinding reels and bedknives, when sharp they cut really nice, that rear roller also gives you a nice stripe. We always used folded newspaper strips to check the cut, get it to cut one of the 2 strips all the way across and you had a mower that would run all day long. 

As a kid I had a Craftsman reel type mower with a Brigss & Stratton 3.5 hp engine on it, it was also self propelled, a real mechanical nightmare with the self propel / clutch mechanism and engage drive system for the reel, I think it weighed nearly 70 pounds. I cut a ton of yards around our neighbor hood, everyone liked that I could stripe their yard, it was a real mowing machine.:wave:

Boosted


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## slotking

> Any hardcore racers here who regularly laps there chassis's?
> I have a compound I would like for you to try.


Finally got to do a real test today

I chucked the arm up to a dremel, and let run.
I did not even think about which way the arm was turning, but the dash gears did quiet down a good bit more. I like the compound


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## alpink

it worked well for me


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