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alvinlwh

Help needed to tame a M-05

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I doubt diff setups cause cars to randomly veer off to the side ;)

I do remember starting off with a beautiful 30$ trackstar servo that would act completely randomly if you were giving quick input left-right-left for instance. Not that it would be the same problem that you have of course. Did you check how the steering responds when you're static? Then with the car in your hand or on some support block, when adding power would the servo move on it's own? I would check that first. The best would be to make a simple video as others have suggested. Can you find a wide open space with nothing to crash into?

Also I'm assuming "crash" here doesn't mean traction rolling? Traction rolling is a different problem that you can sort out in due time when the car stops turning on it's one :)

Best of luck!

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1 hour ago, SupraChrgd82 said:

That’s a new 2.4gig radio, so I would rule out glitching from outside radio interference.  A loose connector may be a possible cause, in addition to the servo.  I’ve never seen a servo rotate due to malfunction, only stop rotating due to a malfunction. Damaged teeth on a servo gear can cause erratic behavior.  I presume your servo operates smoothly when turned by hand with the battery unplugged to confirm.

Yes, brand new with 4 other cars on it as well, without such a problem. All my cars seem to drift right somewhat when freshly built but can be sorted out by trim and finer adjustments. Definitely not a strong pull though! I had a servo that when I go from full lock to neutral, will go to the opposite lock before going to center, that servo is in the bin now obviously. 

1 hour ago, SupraChrgd82 said:

One of the first steps in setting up the car is setting the EPA by observing the left/right bump stops on the knuckles and backing down 1 click before max steer is achieved. A binding servo-saver in conjunction with excessive EPA can cause erratic handling.  Excessine EPA  can also allow dogbones to bind up in steering knuckles.

EPA is set up, 85% IIRC. However, this is happening not during any manoeuvre, but a straight line speed test with no steering input. 

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2 minutes ago, Pylon80 said:

I doubt diff setups cause cars to randomly veer off to the side ;)

I do remember starting off with a beautiful 30$ trackstar servo that would act completely randomly if you were giving quick input left-right-left for instance. Not that it would be the same problem that you have of course. Did you check how the steering responds when you're static? Then with the car in your hand or on some support block, when adding power would the servo move on it's own? I would check that first. The best would be to make a simple video as others have suggested. Can you find a wide open space with nothing to crash into?

Also I'm assuming "crash" here doesn't mean traction rolling? Traction rolling is a different problem that you can sort out in due time when the car stops turning on it's one :)

Best of luck!

It is not that random, bearing in mind, it is damp today, so poor traction may cause it NOT to veer off. On a good traction day (of the original crash) it happens almost all the time. I also suspect that the damp conditions actually makes the pulling more controllable today. 

I will try the static test when I wake up and report back (in bed now). Making a video will be difficult as I got no one to take the video for me and driving when using a phone is, well, difficult. 😉

Crashing as in it pull so hard and suddenly that I cannot brake in time (not that the brake on the 104 is that strong anyway) to stop the car from crashing into the bottom of a mash fence putting a hole in it (as shown in the photo). It was a solid crash at full (or nearly) speed. 

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12 minutes ago, alvinlwh said:

Yes, brand new with 4 other cars on it as well, without such a problem. All my cars seem to drift right somewhat when freshly built but can be sorted out by trim and finer adjustments. Definitely not a strong pull though! I had a servo that when I go from full lock to neutral, will go to the opposite lock before going to center, that servo is in the bin now obviously. 

EPA is set up, 85% IIRC. However, this is happening not during any manoeuvre, but a straight line speed test with no steering input. 

If the EPA's are setup correctly and a hard pull in a straight line from a dead stop it darts to one side or another is 95% of the time a diffirential problem>>> I would firsst yankout that diff flush out the ceramic grease and find a thick heavier grease... When the grease is too thin the grease can heatup and have a nasty effect of havin one wheel spin much faster then the other very smiliar to a limited slip in a car when you hit the gas and one wheel just spins like crazy.....

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lol...

I just noticed that the advices are all over the place, just like @alvinlwh's car.  

We all are trying to help, but I'm afraid we are not helping.  Sorry @alvinlwh!  

 

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14 minutes ago, Big Jon said:

I like the M-05 with a spool or putty, a smidge of toe-out, stock camber , and softer-than-stock springs/ somewhat soft dampening for driving around with touring car rally blocks. They "stall" in corners if you drive it too hard, terribly with an open diff. CV/DCJ axles are a necessity with a spool and a good idea with putty. The suspension must be free with no excessive friction - freedom of movement is more important than minimizing slop.

Is spool or putty an almost locked diff? Sorry, I have relatively little experience with RC so far. IIRC my toe out is as per the recommended in the guide 1.5mm on the turnbuckle. I don't think I can adjust my camber. IIRC I got stock springs (can double check) and soft CVA settings as it was originally meant for off/rough roading. I do have the 53597 Universal Shaft but not the newer (and more expensive) 42300. Suspension seems to be, far as I can tell, moving OK. 

24 minutes ago, Big Jon said:

As for the torque steer issue, the spool should take care of most of it, a digital servo should take care of the rest. Analog servos have very little holding power compared to digital servos, I think that the rotating forces might be overcoming the servo, if that makes sense. 

Sorry, beginner question again, what's a spool? I am thinking of getting a digital servo when I next do a parts order to see if it helps with the problem. Will update once I got it. 

26 minutes ago, Big Jon said:

M cars before the 7 and 8 are goofy little things that are really fun to tune and drive around in the street, sidewalk, yard, whatever. Too much power just spoils them. Really great drivers with touring car size tires, great shelters/light runners with M tires.

Someone suggested a gyro, I wonder if that will help? I tried a TT motor in it and find that it has plenty for the chassis, therefore I did not go crazy with the motor. It is still fun on wide open space, just if I can solve this veering problem, it will be even better. 

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6 minutes ago, Juggular said:

lol...

I just noticed that the advices are all over the place, just like @alvinlwh's car.  

We all are trying to help, but I'm afraid we are not helping.  Sorry @alvinlwh!  

 

Actually my replies are all over the place as well, the pain of typing on a phone, in bed. No worries, I often go back on the posts, to double check on things I may have missed the first time round. Tomorrow, I will start off with simple tests like static bench test first and get on from that. 

Any suggestions are, as always, much appreciated. 

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Sorry @alvinlwh! A spool is locked differential, with no way to compensate for different wheelspeed. The front wheels will be solidly locked together. Putty is very tight, provides for some shock absorption, but doesn't provide 100% solid locking.

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To me it sound like torque steer.

seting up the car geometry is badword of important.

Also balnce weight.

but probably torque steer and bad geometry with a loose diff (standard grease or too little)

 

if you just have build it… take you time to adjust and measure things.

 

if you dampers are soft that can also be a reason on smoothe surface I prefer harder springs.

 

and in general I like to gear high my cars since I run brushless. So with little throttle I can drive it easy bust fast.

 

I own a M05ver2.

also… remove slop on steering and lower arms

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3 hours ago, alvinlwh said:

If it is binding, will it not be difficult to return to neutral after a right move? This is when moving straight ahead with no right command from the tx. Meaning it goes right with no command input. 

I doubt that it is the steering binding. I had a car doing something very similar to that when one of the wheel bearings was on the way out and and was binding under load. At low throttle the effect was not particularly noticeable, and at full throttle there was enough power being put through to overcome the binding, but at medium throttle the one wheel would bind causing the car to veer off in that direction.

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Don't buy any new parts until you know what the problem is, especially a gyro which is surely unnecessary on a M chassis with a reasonable motor.

As somebody mentioned on the first page, put it on a work stand and eyeball it under various throttle conditions, if as you say it happens regularly you should be able to see it happen. Prop the suspension arms up to normal ride height. Set your phone up to video the front wheels (on the stand) at 60+ FPS so you can slow it down if necessary.

Swap everything left to right and try it again, does it veer left instead now? Everything that's not asymmetric e.g., shocks, links, bearings, wheels, tyres, everything. An unbalanced wheel might be impossible to diagnose unless you swap it to the other side and observe erratic behaviour following it (for example). That will eliminate said components which will allow you to narrow your focus.

What about slop? Is it the same on both sides? Can you add shims if you do have some slop (which is almost inevitable on an M05)?

Don't buy any new parts until you know what the problem is.

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If I where you I would look at the diff and rebuild it , I had that on a xv-01 that pulled always to one side rebuild the diff and the problem was gone, if thats not the problem then use another esc with an bec in it and if that does not work try another servo, yeh you have to try things to know what is wrong.

I don't believe it is torque steer because you running a mild brushed motor in it, I am running an 4300kv brushless motor in mine and it goes as straight as an arrow and is very easy to drive, the only thing is that I have to be gentle on the throttle on startup to avoid a lot of wheelspin, but even with a lot of wheelspin it goes straight.

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2 hours ago, Fabia130vRS said:

Also you can use touring car wheels on that body and get a much greater grip and over all handling

As there are many suggestions, I will work through them to try and trace the problem. Thanks to you and many others for coming up with the suggestions. 

But this "greater grip" one, I just want to report back; today, I met up with a local fellow member of the forum. He had a test drive and the problem did not come up at all. There is a possibility (still got to test and trace) that it could be because it was very wet today and the car currently is on slicks, so virtually no grip. 

I will, in due course, ask about m-chassis tyres, as I am a little confused about them. But for the purposes of trying to sort out the veering issue, I will leave it first. 

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Also just in case it's not been mentioned, make sure the suspension is free in its travel, I had a lower spring cup on a buggy that was touching the wishbone and wouldn't allow the correct travel, and kept that side a bit lower so wouldn't centre itself. Make sure the mounting screws are not too tight, the top and bottom needs to pivot a bit.

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I did not read the thread in detail, but sudden and random hard pull to the right/left is usually caused by glitching from either RF interference or unstable BEC power.

I would replace the ESC first and if that does not help replace the receiver/transmitter.  

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I think I had found the problem. Thanks to the suggestion from first @Insane_jim_69 to set it on a stand and @TurnipJF about using a camera at high FPS, I had found the problem. The right wheel is not turning!

Now to trace if it is a binding of the drivetrain or diff problem. I will work my way inwards (to avoid taking the whole thing apart to get at the diff unless anyone can say it is definitely a diff problem). 

At this point, problems with the electronics can be discounted. 

Video is here, taken at 120fps, play back at normal speed, so it is long. This is actually the second video I had taken as I realised that marking a white line across the tyres actually makes the rotational speed easier to see. 

I can take more videos if necessary, just let me know which angle, and perhaps normal speed or high speed. 

Thanks again for all the suggestions so far. Time to get cracking. 

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Is that an open bevel diff?  If so, that could be an axle, bearing problem on the right side (?).   Anyway might be a good time to rebuild it...!

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Thats the diff for sure... Yank it and rebuild it a gear is prob binding check to make sure all flashing is totally removed its that or a chunk of somethin fell into the grease

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1 minute ago, Willy iine said:

Is that an open bevel diff?  If so, that could be an axle, bearing problem on the right side (?).   Anyway might be a good time to rebuild it...!

It is the stock diff (is that open or closed? Sorry still new at this) filled with "toothpaste like" ceramic grease (because I did not have AW grease when I built it). 

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Hard to say for certain without feeling how things are moving, but looking at how the wheel and CV appear to be moving slightly relative to the upright even when the wheel isn't rotating, I'd guess the diff itself is okay, but the bearing in which the right outdrive sits may be binding. That or the CV joint itself is stiff. Please let us know the outcome!

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5 minutes ago, Original Jardasius said:

Thats the diff for sure... Yank it and rebuild it a gear is prob binding check to make sure all flashing is totally removed its that or a chunk of somethin fell into the grease

Flashing? Wow! That is something I never thought of. Yes I do clean up flashing from plastic parts off a tree for static models but never thought of checking and cleaning for the gear parts from a bag. Thanks for the tip! 

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1 minute ago, TurnipJF said:

Hard to say for certain without feeling how things are moving, but looking at how the wheel and CV appear to be moving slightly relative to the upright even when the wheel isn't rotating, I'd guess the diff itself is okay, but the bearing in which the right outdrive sits may be binding. That or the CV joint itself is stiff. Please let us know the outcome!

One question about that CV joint, it came with AW grease, but most will say it is stupid to put that thick grease on the exposed drive train. Should I not grease it up then? 

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6 minutes ago, alvinlwh said:

It is the stock diff (is that open or closed? Sorry still new at this) filled with "toothpaste like" ceramic grease (because I did not have AW grease when I built it). 

Open diff is basically a non-limited-slip-like action diff.  But since you applied some grease to give the diff some resistance it's no longer an open diff.  It's functioning more like a ball diff with simulated limited slip action.   I don't know how much your grease is giving resistance, but there is definitely something odd going on outside the diff because that's quite a bit of resistance your right axle is giving.

 

 

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6 minutes ago, alvinlwh said:

One question about that CV joint, it came with AW grease, but most will say it is stupid to put that thick grease on the exposed drive train. Should I not grease it up then? 

Without grease it will seize and snap it in two... To properly grease it fully pull it out of the car and rotate it while you fold it to its max and slowly rotate it till you see the small gap and add a small dab into the gap, rotate it around a good bit then wipeoff the excess

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