MMP timing problems. How do I offset mechanical timing?

[Olle P]

UPDATE: I've posted a complete re-cap of this thread in post #28.

Due to an insufficient product description I ordered a TrackStar 17.5T sensored motor for my crawler.

As I got it home today and opened the box I found out that it has a mechanical timing adjustable only between 15 and 45 degrees (where 30 degrees is default).
What might be a good thing is that I'll have to set it for running in "reverse", which means the timing is negative.

Question is how to program my MMP to make the motor run the best (ESC using the sensor and adjusting to 0 degrees actual timing) at low revs.

The different manuals from CC only says:
- Set the mechanical timing to a minimum.
- C.H.E.A.T. will add the selected timing at higher revs. (Zero electrical timing at revs <1,900 rpm?)
- S.M.A.R.T. will use sensor (how?) at low revs and then add timing while running in sensorless mode at higher revs.
- A specific electrical timing for all speeds is available only in sensorless mode.

I think it all boils down to if C.H.E.A.T. and/or S.M.A.R.T. will automatically compensate for negative mechanical timing at low revs?

 

[Twisted Nuts]

The Novak ballistics are the same way.
On the 5 MMP combos I own I leave the 10* of timing in the esc, and leave the motor alone at 15*. Never had any heat issues running any of my setups with 20/87 gearing.
My fastest one being an 7.5T. And all of them are silky smooth.

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[Olle P]

Do you leave it in SMART mode (the default)?
Do you run the motor in its normal direction or in reverse?

 

[Twisted Nuts]

Yes leave it in smartsense, I run normal direction

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[DickyT]

It is a brushless motor, you will be fine at 15*.

The big issue with advanced timing and reverse is with brushed motors. It eats comms and brushes very rapidly and generates a ton of heat when you reverse an advanced timing (more that 7* or so) brushed motor

 

[Olle P]

So running a BL motor at -15* is no sweat?

What puzzles me more is that this motor comes with a default 30* timing, yet the MMP thinks that for BL (sensorless) motors in general 15* is a "High" setting...

 

[Twisted Nuts]

That's electronic timing, the motor is mechanical timing. Leave the esc at10* and the motor at 15*.

Gear accordingly

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[Olle P]

... Leave the esc at10* ...

That's just my concern:
The 10* setting is for sensorless mode.
At the low motor speeds that worry me it will run in sensored mode, and there's no ESC setting to adjust the sensored timing below 1,900 rpm (the minimum speed to activate the CHEAT timing boost).

There are no timing adjustments available at all with the ESC in "sensored only" mode and CHEAT inactive.

 

[Twisted Nuts]

Why are you wanting to change timing running a sensored motor?
I'm running 5 sensored MMP combos and I have not touched the timing settings on any of them.
I may be misunderstanding you though

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[Olle P]

Why are you wanting to change timing running a sensored motor?

Possibly because I don't know how it works.

The perceived problem is that the motor (sensors) has a mechanical timing of -15 degrees (can be adjusted up to -45) and running with negative timing is, AFAIK, not the best option for torque and efficiency at very low speed.

The MMP has no adjustment for the sensored timing, at least not at very low speed.

I've asked Castle about this, and got a reply that they haven't done much testing of low speed handling, since they opt for the high speed market.

To get rid of the problem I have a few ads out to see if anybody wants to buy the motor in its pristine condition (me losing some $15 on the deal). If I don't get a buyer in a week I'll test it to see how bad it is. I may or may not have to flip the tranny back into its original direction to get the motor running properly.

 

[Twisted Nuts]

Put it in exactly how it is, these aren't brushed motors! Lol
that motor will have enough torque at low speeds to break anything you want it to.
Set the motor at 15* and the esc at 10*.
No cheat mode and set it to smartsense brushless. Put a 86t spur and start with a 18t pinion if your running axial.


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[JohnRobHolmes]

You will be fine with timing in the negative, if you have programmed the MMP for reverse rotation. It compensates and knows what to do.


I like running cheat mode to get tons of speed and power from sensored motors. For more efficient running the smart mode is a much better choice, and realistically a superior method of motor control. Run it in smart mode first, and if you don't like the speed then use Cheat mode at 35 degrees of advance since you can't adjust mechanical timing to zero. If your motor heat is OK then start adding more cheat a few degrees at a time. When you hit the threshold of poor commutation efficiency the heat will skyrocket, then back it off 3 degrees or so in cheat mode.


Using timing instead of gearing for wheelspeed allows for better stall torque and low speed control. Volt up, gear gown! Or in this case- Cheat Up, Gear down!

 

[Olle P]

Thanks Nuts and John!

Finally these two last replies get me the info I want! "thumbsup"

 

[JohnRobHolmes]

No problem! I should clarify that using electrical timing in the MMP is better than using mechanical timing on the motor. You will lose stall torque with advanced mechanical timing. You do not lose stall torque using the Cheat or Smart sense modes, thus my recommendation to set mechanical timing as low as possible and use ESC programming for the power and speed you want.

 

[Olle P]

Installed it (with a 16T pinion for good measure) and had a quick indoor test drive now. (The battery starting out at "storage" level.)
First impression is that with negative timing the start gets a bit jumpy, and only when the sensorless mode (and +10* timing) kicks in does it behave well.
Backing up, with the motor running in its intended direction, is much smoother, quicker and also more responsive.

I'll do some more testing, but as of now it seems like I will turn the tranny around again to get the motor running forward.

 

[Olle P]

I have run into a strange and totally unexpected problem:

On a level floor I do a slow start of the motor, slowly increasing throttle until the motor starts spinning (at around 15% of max throttle) and keep the throttle there. The green LED flashes as it should.
Then, when the crawler hits an obstacle that requires a little more torque to negotiate, the yellow LED on the MMP comes on with a constant light (in addition to the flashing green). (According to Castle's FAQ a constant yellow light is something that isn't supposed to happen at all while driving.)
When the yellow light comes on the maximum throttle/voltage available is frozen at that level. Pulling the throttle trigger harder doesn't add any power to the motor.
When I release the trigger it's all reset back to normal.

- This happens with the motor running in either direction, but of course with the red LED flashing while reversing.
- The battery (2S LiPo) voltage stays above 7.5V (measured with a logger hooked to the battery during the run).
- Cutoff is set to 3.0V/cell, auto LiPo mode.
- Punch control is disabled.
- The problem is there no matter if the "Start Power" parameter is set to Medium or High.
- There seems to be no problem at all when I accelerate quickly from standstill to >50% throttle.

Any Idea what causes this problem, and how to negotiate it?

 

[Twisted Nuts]

When you let off the trigger does the esc go through the arming sequence again?
Does the light on the rx go off for a moment?

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[Olle P]

When you let off the trigger does the esc go through the arming sequence again?

No, it just goes back to idle, with the yellow LED flashing as it should.

 

[OhioSuperSport]

not to take away from your thread but what does it mean if it does reset the arming sequence?

 

[Twisted Nuts]

You need a BEC.

By the way olle do you have a bec on your rig?

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