Lapping TJet Gears - HobbyTalk
LinkBack Thread Tools Search this Thread
post #1 of 22 (permalink) Old 09-06-2013, 05:06 PM Thread Starter
Join Date: Mar 2005
Location: Clayton NJ
Posts: 236
Lapping TJet Gears

What does everone use to lapp the gear train on a Tjet? I use permatex lapping compound. I have seen some people use tooth paste etc.
dtomol is offline  
Sponsored Links
post #2 of 22 (permalink) Old 09-06-2013, 05:19 PM
Lifetime Member
beast1624's Avatar
Join Date: Mar 2009
Location: Irving, TX
Posts: 735
I have tried Novus #2 and a 50/50 mix of Brasso and Break Free gun oil. Both work pretty well.

Si vis pacem, para bellum
beast1624 is offline  
post #3 of 22 (permalink) Old 09-06-2013, 05:32 PM
alpink's Avatar
Join Date: Aug 2010
Location: uppaUS
Posts: 7,013
someone gave me valve lapping abrasive once (I'm not gonna mention Sgrig's name) without any advice.
I smoothed out a complete set of gears quickly. yes, no teeth left on any of them. so, you want something a tad LESS abrasive than THAT
alpink is offline  
post #4 of 22 (permalink) Old 09-06-2013, 05:39 PM
Elder Statesman
smalltime's Avatar
Join Date: Jun 2006
Posts: 602
smalltime is offline  
post #5 of 22 (permalink) Old 09-06-2013, 06:51 PM
Elder Statesman
Join Date: Nov 2007
Location: Greentown, Indiana
Posts: 1,370
SemiChrome & Transmission fluid, less of the 1st, more of the 2nd

Boosted-Z71 is offline  
post #6 of 22 (permalink) Old 09-06-2013, 07:34 PM
Model Murdering
Join Date: Jan 2007
Location: Western Wa
Posts: 7,331
They're really just an inefficient lil vacuum cleaner

Something around 400 and 800 grit and a lubricant that trips your trigger...give er take.

Everyones got their own voodoo formula. I prefer the the squeezens from a ripe banana and some comet; but the banana must be picked in Havana during the full moon or your results may vary.

400 to 800 is roughly around the size of all the crud and corruption the gear train normally eats over time. The idea is to simulate in short fashion, a gear set that has been well broken in over time. Under magnification, my observation has always been that T-jets are dirty nasting tar burning beasties. You can polish it to perfection but everything returns to it's naturally scuffed state after some use. I'm not trying to make light of a top five in the fundamental build process, but the idea is to hone in the optimum running clearance with a minimum amount of fan fare and call it good. Most especially after you've scrambled up gear sets. Extra drama time is better spent on selecting good gears in the first place or better yet, pick up shoe voodoo. Lapping should be a one and done process.

LOL @ Al...I'm sure Jim is just expiditing the process in his own way by using ashtray sand, obviously some stuff cuts quicker than others and for the inexperienced is best to sneak up on the process and learn the intricasys . It's been proven time and time again that there is more than one path. I just snip up some small squares of 600 wet and dry carefully polish the top and bottom gear sides on a running gear set with synthetic motor oil. The freed abrasive mixes with the oil and creates the exact slurry we require. I just use an old Aurora tranny and press the contacts against the screws with the chassis front tilted downwards so the spent slurry drools out neatly to the front of the gear plate. Once I hear that the "no go" point is achieved, I spritz the chassis with electrical parts cleaner, then blow it off, and re-lube.

In most cases there's no need for the insanity lappings. No sloppy prolonged immersions in tubs of secret potions, or slathering the contents tubes of high dollar goo and flinging it on yer shirt. Papering the gear set properly cures a multitude of ills. For the special builds, your chosen rouge goes any where 600 paper cant by applying it with the model murdering specialty application tool part # 0001 (aka der toothpick).

Enough lapping is just right, and too much is called excessive wear. Simply put it's and ear thing and the process itself must be developed to suit yourself and your own bench/needs.

Last edited by Bill Hall; 09-06-2013 at 10:17 PM.
Bill Hall is offline  
post #7 of 22 (permalink) Old 09-06-2013, 09:17 PM
Lifetime Member
Illinislotfan's Avatar
Join Date: Mar 2009
Posts: 133
While we're on the subject of reducing friction, has anybody tried filing down the gears? See idler gear in photo below. I saw this idea in an old issue of Model Car Science, the theory being the less gear there is to mesh, the less the friction produced, so I tried it. All I did was lay a file on the workbench, and slide the gear back and forth until it was about half the thickness. I wish I could say it allowed me to run amazingly faster, or the motor ran way cooler, but I don't have any way to objectively test, and didn't see any obvious differences. Has anyone else tried this?

No retreat, no surrender
Illinislotfan is online now  
post #8 of 22 (permalink) Old 09-06-2013, 09:45 PM
Elder Statesman
ajd350's Avatar
Join Date: Sep 2005
Location: Beecher, IL
Posts: 1,272
From the standpoint of less tooth contact friction, your idea is sound. It will, however, make the idler gear less stable due to reducing the contact area at the post. The net effect will at best cancel out. A wobbling or loose idler is a huge power drain. Most rules (if you race under them) do not allow that kind of treatment anyway.

+1 on Simichrome
ajd350 is offline  
post #9 of 22 (permalink) Old 09-06-2013, 09:49 PM
Elder Statesman
old blue's Avatar
Join Date: May 2007
Location: St. Louis, Missouri
Posts: 998
I have not tried that, but I did try beveling the teeth of the gear to reduce the friction against the other two gears. I would love to say that it worked great, but in the process I opened up the center hole so badly that now all I have is sloppy beveled gears! Live and learn.

Old Blue
old blue is offline  
post #10 of 22 (permalink) Old 09-06-2013, 10:02 PM
Join Date: Feb 2012
Location: Plainfield IL.
Posts: 314
I do it the easy way RT-HO gears, just put them in. No lapping needed.

Slow Ed
Steelix_70 is offline  
post #11 of 22 (permalink) Old 09-06-2013, 10:16 PM
Elder Statesman
slotking's Avatar
Join Date: May 2008
Location: fairport
Posts: 1,999
I started off using crest tarter control toothpaste
hook a dremel to the axle and spin backwards.

I then decided to make my own cutting oil.
I ground polishing compound (polishing sticks from lowes) into marvel mystery oil. I have a chassis that i put the gear plate on flip it upside down into the mix and lap the gears in.

works very well

what surprise me was the 1st time i did it, the mix was to high and it came shooting up though the brush holes and did not miss a beat
slotking is offline  
post #12 of 22 (permalink) Old 09-06-2013, 10:23 PM Thread Starter
Join Date: Mar 2005
Location: Clayton NJ
Posts: 236
Laping T-jet gears

I use an ameter in series and measure the current, that way you can see when the load meaning the amps decrease you are reducing the friction.
dtomol is offline  
post #13 of 22 (permalink) Old 09-07-2013, 02:04 PM
Lifetime Member
Join Date: Nov 2007
Location: portage,in
Posts: 2,164
I have to agree with Ed,rtho and go!
brownie374 is offline  
post #14 of 22 (permalink) Old 09-07-2013, 02:28 PM
Elder Statesman
ajd350's Avatar
Join Date: Sep 2005
Location: Beecher, IL
Posts: 1,272
I like those too, but for those on a budget lapping may be worth a shot.
ajd350 is offline  
post #15 of 22 (permalink) Old 09-07-2013, 10:00 PM
Elder Statesman
slotking's Avatar
Join Date: May 2008
Location: fairport
Posts: 1,999
the rtho gears are great.

but knowing how to lap gears can not hurt
slotking is offline  


Quick Reply

Register Now

In order to be able to post messages on the HobbyTalk forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome