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Old 04-03-2017, 10:27 AM   #1
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Default Dealing with slop: Is this something that everyone does?

Howdy everyone,

I've recently been obsessing over slop in my cars setup. I have suspension guages, but there's always some play in the linkages, bearings, hinge pins...

So what do you do? How do you handle it?

I've seen the foam spacers on associated cars, around ball cups, but I suspect those are for dirt infiltration, rather than sucking the play out of the ball cups.

Tamiya people have huge selections of shims, and shim kits to chose from.

I've heard of people using reamers.. but I'm not sure how they're applying them.

Now.. is it even important? What do you do?

I've gone over my M05, with some shims, and I've pulled the swingarm pivot fore and aft slop out, and I've taken what I could out of the knuckles. More importantly, I put shims in the hubs to remove as much axle play as I could.

Between those changes the car hunts less, and does what I tell it to, more often.

Tell me about your cars! And your tricks, and what you use.
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Old 04-03-2017, 10:43 AM   #2
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All my R/C vehicles have some slop, some more than others. The Tamiya minis seem to have the most from my experiences and it takes a lot of time and effort to reduce it as much as possible. The M05 is very sloppy out of the box but can me made better with various shims.
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Old 04-03-2017, 11:40 AM   #3
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Every car is going to be different but a little slop is normal and won't affect handling. Most cars today are designed to have a certain amount of flex built into the chassis and suspension arms so making tolerances too tight can cause binding and actually make handling worse. If the car drives straight and is consistent when cornering, I wouldn't worry about it.
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Old 04-03-2017, 12:08 PM   #4
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There are ways of removing slop, that don't involve making tolerances so tight that they bind up.

There are backlash compensating gears. There are nuts that have preload built into them. As we've covered, shims can suck up most of the play in parts. "preloading" a joint does the same thing. In the case of touring cars, droop screws make sure the shocks aren't sloppy. (That reminds me, I need to do something about droop screws on my TT02b)

I'm still interested in what people use reamers for, do they also get precision ground rods to remove swingarm slop?

"Wouldn't worry about it" doesn't seem to be the rule in r/c. There are tweak tables, precision wheels, all sorts of gauges, to do chassis setup. There are special lubes to reduce shock shaft stiction.

If there's less slop in the suspension for setup.. you're going to spend a lot less time at that setup jig to make sure everything is ok.
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Old 04-03-2017, 02:00 PM   #5
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While slop is unwanted for onroad rc cars it is overrated in its negative effect.
It will not hurt to reduce it, but having it to a certain amount like up to two or more millimeters won't hurt performance also. For example I have a TT02. You can move the suspensions around 5 mm (box stock) and the car runs very well. My old TC6 had a lot of slop also and it was always one of the fastest cars indoor and outdoor.
Why is that slop does not hurt up to a certain amount? Well look at your suspension geometry. While having slop in a standing position it will pre load while the tires move and thus "taking out" the slop.
Nevertheless buy some shims (for example from Yokomo) to reduce it and or control it. Where you never want slop is the steering. Just make sure it still moves freely after shimming
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Old 04-03-2017, 02:04 PM   #6
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Just be careful that you don't put axial preload on bearings as this can cause extremely rapid wear.
I've found with the M-Chassis cars that they actually handle better with no shims at all, at least with the stock setups. Sometimes compliance is your friend.
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Old 04-03-2017, 02:27 PM   #7
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Quote:
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Why is that slop does not hurt up to a certain amount? Well look at your suspension geometry. While having slop in a standing position it will pre load while the tires move and thus "taking out" the slop.
Putting a load on, sure. That's why I mentioned the shocks and droop on touring cars. Where I seem to see.. what I think.. is slop, is during transitions, or on bumpy surfaces.

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Nevertheless buy some shims (for example from Yokomo) to reduce it and or control it. Where you never want slop is the steering. Just make sure it still moves freely after shimming
To let you in on the secret... I spent a few dollars at mcmaster, and bought a whole bunch of shims. My M05 had some unpredictable behaviors when transitioning, and those were mostly cured by the application of shims. Those were mostly placed on the axles, reducing uncontrolled wheel movement from 5-6 degrees down to 1-2 degrees. I also took something like 1mm out of knuckle movement within the front uprights.

Sadly, I did not do any direct a-b testing on that.

On my DT02, I had a similar experience. Which lead to discovering some.. other problems.. with that chassis. Before I even gave it a good run, my TT02b got more than 1mm of end play, and 5-6-7 degrees of wheel free movement sucked out with shims as well. They both track straighter than they did before.

I even used a few on my TC4, sucking up some of the slop in the axles there, reducing their wiggle. I can't say I saw much improvement there, at least that I can necessarily blame on that, but I was turning much better laps saturday. I'm willing to say that might have been psychosomatic.

What made me start this thread, was looking at ball ends. Ball ends have slop. If you put the lightest bit of preload on them, the slop all goes away. I think that might be something worth pursuing.

All of this was done, with checking to make sure I didn't add any friction anywhere. :-) Free movment trumps controlled movement, IIRC.
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Old 04-03-2017, 03:20 PM   #8
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Good points and well explained.
Those where called foam things, they were used indeed to keep dirt out of the ball stud and ball cup surfaces. Would use them again if I could make myself ones in other material.

I shim arms, hubs and axles to have minimal play and try to keep camber/toe slop maximum 0.5*, more than that and I can't seem to be satisfied when the car is on the set up station.

Also, I want less wheel wobble as I was surprised at how much my AE cars had and how good it felt afterwards. For me, less wheel motion in flex felt so solid I pursued those foam things and lubing the ball studs to have solid consistent handling (lubing was sort of a mistake with foam material, it turns quickly into sandpaper).
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Last edited by 30Tooth; 04-03-2017 at 03:36 PM.
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Old 04-03-2017, 04:44 PM   #9
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slop isn't always bad. Depends on the car.
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Old 04-03-2017, 10:54 PM   #10
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I'd love an explanation on how that could be? Any time you don't have control over a tire, you're looking at random tire behavior.

Tell me about your examples.

Now, I've also been bad, and tighened up things to the point they had binding. That is probally more detrimental than having slop. It at least makes servo behavior funny....
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Old 04-03-2017, 11:05 PM   #11
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Quote:
Originally Posted by Nerobro View Post
I'd love an explanation on how that could be? Any time you don't have control over a tire, you're looking at random tire behavior.

Tell me about your examples.

Now, I've also been bad, and tighened up things to the point they had binding. That is probally more detrimental than having slop. It at least makes servo behavior funny....
Read through the Tamiya Mini Cooper thread and you'll see many discussions about how the M-Chassis cars tend to work better with a bit of slop. Shimming it can often make it handle unpredictably, even if it isn't binding.
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Old 04-04-2017, 01:21 AM   #12
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I appreciate the reply. But saying "go read a 29,000 post thread" is bordering on rude. At the rate of 1 post every 5 seconds, we're talking 40 hours of reading.

Add into that the time it takes to digest and decide if a post is coherent, useful, and worth cross checking... well I do have a day job, and these are toy cars. :-)

This is assuming you're not trying to be sly about saying "take a long walk off a short pier."

I've done both from time to time depending on my mood that day...

Anecdotally, shimming my front and rear hubs, and my front knuckles removed some of the unpredictability I was having, and lead to having more control when things did start to get squirrelly. I suspect the shims on the knuckles had little to do with it, but the better wheel control did.

If shimming is causing unpredictability, that makes things sound like binding to me, I wonder if under load things are flexing enough to make things bind up when they're shimmed up on the bench. I've seen many projects where people with my obsessive slant take things a step to far, and things go very crosswise. eg: Projects never get finished, because they're not perfect. Things get tuned to the edge, so close, that they spend most of their time ~over~ said edge. Or the best example, the triumph motor, built to all of the "good side" of factory tolerances, ending up so tight that it can't be turned over. :-)
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Old 04-04-2017, 01:48 AM   #13
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Quote:
Originally Posted by Nerobro View Post
I appreciate the reply. But saying "go read a 29,000 post thread" is bordering on rude. At the rate of 1 post every 5 seconds, we're talking 40 hours of reading.

Add into that the time it takes to digest and decide if a post is coherent, useful, and worth cross checking... well I do have a day job, and these are toy cars. :-)

This is assuming you're not trying to be sly about saying "take a long walk off a short pier."

I've done both from time to time depending on my mood that day...

Anecdotally, shimming my front and rear hubs, and my front knuckles removed some of the unpredictability I was having, and lead to having more control when things did start to get squirrelly. I suspect the shims on the knuckles had little to do with it, but the better wheel control did.

If shimming is causing unpredictability, that makes things sound like binding to me, I wonder if under load things are flexing enough to make things bind up when they're shimmed up on the bench. I've seen many projects where people with my obsessive slant take things a step to far, and things go very crosswise. eg: Projects never get finished, because they're not perfect. Things get tuned to the edge, so close, that they spend most of their time ~over~ said edge. Or the best example, the triumph motor, built to all of the "good side" of factory tolerances, ending up so tight that it can't be turned over. :-)
I did read through that whole thread, took me a few months, so I'm not expecting you to read through the whole lot in one go. But there is a search function. Keyword slop, you'll find a bunch of posts from tony gray and a few other knowledgeable mini guys. They've driven a lot of minis, both shimmed and unshimmed, so their experience is worth listening to even if they can't provide a technical explanation. The short version is that it's fine to remove some of the axle play with shims, and maybe a little bit in the steering rack, but it's generally counter productive to worry about the rest of it.
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Old 04-04-2017, 07:37 AM   #14
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That's something I can get behind. (The take some play out..) The axle play my M05 had was... hilarious.

The steering rack, I have some tricks I want to try. And the steering linkages. I'll report back on those.

Something that's always stuck in my craw, is "this just works". Not knowing why make me batty.
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Old 04-04-2017, 07:53 AM   #15
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Quote:
Originally Posted by Nerobro View Post
That's something I can get behind. (The take some play out..) The axle play my M05 had was... hilarious.

The steering rack, I have some tricks I want to try. And the steering linkages. I'll report back on those.

Something that's always stuck in my craw, is "this just works". Not knowing why make me batty.
There's no money behind efforts to scientifically prove why m-chassis cars behave the way they do, so unfortunately "this just works" is probably the best you're going to get for a while from certain aspects of this hobby.
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