Go Back  R/C Tech Forums > General Forums > Electric On-Road
Slowing Down the Front Diff >

Slowing Down the Front Diff

Slowing Down the Front Diff

Old 11-23-2011, 09:20 AM
  #1  
Tech Elite
Thread Starter
iTrader: (2)
 
DesertRat's Avatar
 
Join Date: Mar 2011
Location: Sniffin the 'Sauce Fumes
Posts: 3,693
Trader Rating: 2 (100%+)
Default Slowing Down the Front Diff

I have a JRXS-R that I intend to run rubber tire on carpet with, my problem is that I have tried a front spool but the feel of the car with a diff in the front is more in-tune with my style, but only when its tight instead of a more open diff. In running the diff as tight as it needed to be to limit the slip it wore out very quickly, becoming gritty in the course of a few runs and ruining the thrust bearing. I have tried using thick black grease in the diff but it was only marginally better than the standard white diff grease. Ideally I could replace this with a gear diff with thick fluid but no such thing exists for this older car, so what do you think my best course of action is to slow the diff down without destroying it? Any help is good help.
DesertRat is online now  
Old 11-23-2011, 09:24 AM
  #2  
Tech Champion
iTrader: (73)
 
MikeXray's Avatar
 
Join Date: Oct 2006
Location: New York
Posts: 5,755
Trader Rating: 73 (100%+)
Default

Originally Posted by DesertRat View Post
I have a JRXS-R that I intend to run rubber tire on carpet with, my problem is that I have tried a front spool but the feel of the car with a diff in the front is more in-tune with my style, but only when its tight instead of a more open diff. In running the diff as tight as it needed to be to limit the slip it wore out very quickly, becoming gritty in the course of a few runs and ruining the thrust bearing. I have tried using thick black grease in the diff but it was only marginally better than the standard white diff grease. Ideally I could replace this with a gear diff with thick fluid but no such thing exists for this older car, so what do you think my best course of action is to slow the diff down without destroying it? Any help is good help.
That's a tough one, especially with the R's plastic outdrive, when you try and tighten the diff to the point it should be the threads will strip. We used to be able to run a oneway in that car and it wasn't terribly loose off power, might be worth trying. If not, keep working on the setup until a spool is comfortable, look at mike haynes old posts, I know he ended up with a setup on old JRX springs I think in the 8lb range in the rear.
MikeXray is offline  
Old 11-23-2011, 09:32 AM
  #3  
Tech Elite
Thread Starter
iTrader: (2)
 
DesertRat's Avatar
 
Join Date: Mar 2011
Location: Sniffin the 'Sauce Fumes
Posts: 3,693
Trader Rating: 2 (100%+)
Default

Originally Posted by MikeXray View Post
That's a tough one, especially with the R's plastic outdrive, when you try and tighten the diff to the point it should be the threads will strip. We used to be able to run a oneway in that car and it wasn't terribly loose off power, might be worth trying. If not, keep working on the setup until a spool is comfortable, look at mike haynes old posts, I know he ended up with a setup on old JRX springs I think in the 8lb range in the rear.
Thanks, the spool will probably be my final outcome anyway, but on a spur-of-the-moment deal I bought one of Stormer's last one-way bearings for the car, so I'll have to give that a try especially as I am a roll-through-the-corner and let-the-setup-scrub-speed racer as opposed to always being on the brakes. I am currently running the softest JRXS spring in the rear, i think its 10.5 pounds, and a 15 pound in the front, and it works well to get the dive and squat that the car seems to need in rubber tire, and the swaybars keep it from cornering like a short course truck. I'll give the one-way and spool option a go, its free so I might as well.
DesertRat is online now  
Old 11-23-2011, 09:52 AM
  #4  
Tech Master
iTrader: (5)
 
Chaz955i's Avatar
 
Join Date: May 2009
Location: NE Ohio
Posts: 1,108
Trader Rating: 5 (100%+)
Default

Originally Posted by DesertRat View Post
Thanks, the spool will probably be my final outcome anyway, but on a spur-of-the-moment deal I bought one of Stormer's last one-way bearings for the car, so I'll have to give that a try especially as I am a roll-through-the-corner and let-the-setup-scrub-speed racer as opposed to always being on the brakes. I am currently running the softest JRXS spring in the rear, i think its 10.5 pounds, and a 15 pound in the front, and it works well to get the dive and squat that the car seems to need in rubber tire, and the swaybars keep it from cornering like a short course truck. I'll give the one-way and spool option a go, its free so I might as well.
For rubber tire on carpet IMO you will be at a major disadvantage running a front diff. Just too much lost drive off the corners. Perhaps try an automotive grease like a wheel bearing grease to try to slow down the action? Messy but may get your diff to where you need it.

I fought for a long time trying to make a diff work and once I went to a spool and got used to it I was really kicking myself. They are better.
Chaz955i is offline  
Old 11-23-2011, 10:10 AM
  #5  
Tech Elite
iTrader: (9)
 
seaball's Avatar
 
Join Date: Sep 2001
Posts: 4,304
Trader Rating: 9 (100%+)
Default

Originally Posted by DesertRat View Post
so what do you think my best course of action is to slow the diff down without destroying it?
i have had good success by sandwiching in an o-ring on one/both sides of the pulley. sounds goofy, but throwing one in just inside of the balls on each side will do the trick. you can play with the number (one side or two), durometer rating, and thickness (to a degree) in order to vary the resistance. as you build the diff, the orings will hit first. then, they'll compress until the diff rings finally hit the balls. it's actually pretty sweet.

looking at the losi pulleys, there's little space between the balls and the center bore. however, that should suffice as you're likely looking at 1mm thick o-rings on each side to start. i don't know what that center bore is, but you're looking at something like this:

ringers

ringers-2



if you really want to get scientific with the o-rings, go here: www.mcmaster.com

Last edited by seaball; 11-23-2011 at 10:23 AM.
seaball is offline  
Old 11-23-2011, 10:26 AM
  #6  
Tech Master
iTrader: (3)
 
Xpress's Avatar
 
Join Date: Nov 2001
Location: Onroad Bermuda Triangle...
Posts: 1,742
Trader Rating: 3 (100%+)
Default

Have you tried the "brown" diff grease that Losi sells? We used to use it in the front diff when running foam tires. It is way thicker than reg diff lube.
Xpress is offline  
Old 11-23-2011, 10:29 AM
  #7  
Tech Champion
iTrader: (73)
 
MikeXray's Avatar
 
Join Date: Oct 2006
Location: New York
Posts: 5,755
Trader Rating: 73 (100%+)
Default

Originally Posted by seaball View Post
i have had good success by sandwiching in an o-ring on one/both sides of the pulley. sounds goofy, but throwing one in just inside of the balls on each side will do the trick. you can play with the number (one side or two), durometer rating, and thickness (to a degree) in order to vary the resistance. as you build the diff, the orings will hit first. then, they'll compress until the diff rings finally hit the balls. it's actually pretty sweet.

looking at the losi pulleys, there's little space between the balls and the center bore. however, that should suffice as you're likely looking at 1mm thick o-rings on each side to start. i don't know what that center bore is, but you're looking at something like this:

ringers

ringers-2



if you really want to get scientific with the o-rings, go here: www.mcmaster.com
I never tried that, but the oring that holds the diff in the eccentric should be the right size to try that out.
MikeXray is offline  
Old 11-23-2011, 10:33 AM
  #8  
Tech Elite
Thread Starter
iTrader: (2)
 
DesertRat's Avatar
 
Join Date: Mar 2011
Location: Sniffin the 'Sauce Fumes
Posts: 3,693
Trader Rating: 2 (100%+)
Default

Originally Posted by seaball View Post
i have had good success by sandwiching in an o-ring on one/both sides of the pulley. sounds goofy, but throwing one in just inside of the balls on each side will do the trick. you can play with the number (one side or two), durometer rating, and thickness (to a degree) in order to vary the resistance. as you build the diff, the orings will hit first. then, they'll compress until the diff rings finally hit the balls. it's actually pretty sweet.

looking at the losi pulleys, there's little space between the balls and the center bore. however, that should suffice as you're likely looking at 1mm thick o-rings on each side to start. i don't know what that center bore is, but you're looking at something like this:

ringers

ringers-2



if you really want to get scientific with the o-rings, go here: www.mcmaster.com
I tried that, for some reason it felt kinda jerky for me, instead of being fluid it would hold on to a certain point and then let go, and that didn't feel like a viable diff action for touring car.

Originally Posted by Xpress View Post
Have you tried the "brown" diff grease that Losi sells? We used to use it in the front diff when running foam tires. It is way thicker than reg diff lube.
I have heard of brown Losi grease, never seen a tube of it in person. I doubt it would be much thicker than the black stuff I tried, but I will keep an eye out.

In summary, I'm going for the spool and then maybe trying the front one-way, keeping the diff fresh for the once in a blue moon we may run foamies or as a backup for the rear diff.
DesertRat is online now  
Old 11-23-2011, 10:51 AM
  #9  
Tech Elite
iTrader: (9)
 
seaball's Avatar
 
Join Date: Sep 2001
Posts: 4,304
Trader Rating: 9 (100%+)
Default

Originally Posted by DesertRat View Post
I tried that, for some reason it felt kinda jerky for me, instead of being fluid it would hold on to a certain point and then let go, and that didn't feel like a viable diff action for touring car.
yep, that's the drawback is that the force/torque curve peaks at the 'break' point and settles in to some dynamic constant (or close). friction, in short. you can minimize this by lubing up.

the above won't be as soft on center as a viscous gear diff, but if built correctly, will allow for some off-power diff action, if that's what you're after. plus, it's fairly easy on the drivetrain.
seaball is offline  
Old 11-23-2011, 10:52 AM
  #10  
Tech Master
iTrader: (3)
 
Xpress's Avatar
 
Join Date: Nov 2001
Location: Onroad Bermuda Triangle...
Posts: 1,742
Trader Rating: 3 (100%+)
Default

If you are pretty good at fabricating things you can also try this:

Find some of the old Traxxas rulon pegs that they used to use in their slipper clutches. Take the diff pulley and drill out two (opposite each other) of the diff ball holes to the same dia as the rulon peg. Take two of the pegs and cut the length down to just a little thicker than the diff balls. Insert the pegs into the holes you drilled out and then build the rest of the diff like normal. The diff balls keep the pegs from getting totally smashed, but they provide much more friction against the rings and the diff is really difficult to turn over.....kind of like a g diff w/putty.
Xpress is offline  
Old 11-23-2011, 11:12 AM
  #11  
Tech Master
iTrader: (5)
 
Chaz955i's Avatar
 
Join Date: May 2009
Location: NE Ohio
Posts: 1,108
Trader Rating: 5 (100%+)
Default

Originally Posted by seaball View Post
hit the balls. it's actually pretty sweet.
Only you Seaball. Only you.
Chaz955i is offline  

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not 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 Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.