Big Rock Arrma Nero Diff Brain reversed?

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Big Rock Arrma Nero Diff Brain reversed?

DutchDriver

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Hey guys,

Yesterday I picked up a used Arrma Nero with Diff Brain for €250. It came with a Savöx servo and a Hobbywing 8BL-150A ESC. When I came home and drove it for the first time, there were some things that didn't seem right to me.
First of all, when I am in Blast mode, the centre and the rear differential are locked. When I go to Wheelie mode, they are still both locked. When I go to Drift mode, the centre diff is still locked, but the rear diff is unlocked! When I go to Climb mode, the front diff does lock. So what I am thinking here, my centre diff is permanently locked, and my rear diff works reversed. Will have a look today in my centre diff to see if something is stuck. I really wonder how I can fix the rear diff locking mechanism. I already attached and detached the Diff Brain wires and checked the colors on the Diff Brain when switching modes. Everything was okay.

Secondly, the car just doesn't make any wheelies. Even with my permanently locked centre diff, the front just never goes up. I am running on 6s, with the stock 15T pinion. Motor is really cool after a run, and ESC a bit warm, but not hot. The motor runs the stock ESC timing setting, which is 11,5 degrees. Is this ESC not strong enough for the car?

I am quite lost. If you guys can help me, I would be really happy.

Kind regards,

DutchDriver.
 

Ari33

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The blx 200 should be able to provide enough amperage for wheelies if the surface traction is there.
Are you using low or high C lipos?
Check that your esc's punch level is maxed out at level 5.

Edit- not sure how the diff brain is set up but it sounds like a servo somehow needs reversed.
 

DutchDriver

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The blx 200 should be able to provide enough amperage for wheelies if the surface traction is there.
Are you using low or high C lipos?
Check that your esc's punch level is maxed out at level 5.

Edit- not sure how the diff brain is set up but it sounds like a servo somehow needs reversed.
Thanks for your reaction. I am running a Hobbywing 8BL-150A. Running on 2x 5400mah 50C 3s batteries. Slipperclutch is already tightened. I will turn up my punch level a bit.

With the diffs: I think I am going to solder the plus to the minus on the microservo inside the rear diff. Do you think that will solve the problem?
 

Ari33

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If you cant do it on your radio I'd just buy a servo reverser.

https://uk-m.banggood.com/3_6V-24V-...5TMraKJP11zhrXS4DneAolkyaVtscxXQaAgQSEALw_wcB


But if you really want to go down that road
I think you need to also swap over 2 of the 3 wires going to the potentiometer inside the servo...might be quite tricky to do in a micro servo though.


See..



Edit- I. think that ESC is the same as the BLX185 and capable of aprox 90A continuous despite its 150A rating... while the standard esc for the Nero should be a BLX200 (aka Hobbywing Max8) which is a bit more capable.
See- https://www.arrmaforum.com/threads/max6-vs-max8-vs-hobbywing-quicrun-wp-150a-esc.10297/

I've just bought a Castle MM2 V2 v1.24sw with modified fw to remove the amp limiter for £105 posted. Using the 'Freeship' coupon code.
That would defo do the trick if your lipos are up to the job.

See- http://www.castlecreations.com/en/mamba-monster-2-2/monster-v2-retro-1-24sw-sold-as-is-010-0108-98
 
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DutchDriver

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If you cant do it on your radio I'd just buy a servo reverser.

https://uk-m.banggood.com/3_6V-24V-...5TMraKJP11zhrXS4DneAolkyaVtscxXQaAgQSEALw_wcB


But if you really want to go down that road
I think you need to also swap over 2 of the 3 wires going to the potentiometer inside the servo...might be quite tricky to do in a micro servo though.


See..



Edit- I. think that ESC is the same as the BLX185 and capable of aprox 90A continuous despite its 150A rating... while the standard esc for the Nero should be a BLX200 (aka Hobbywing Max8) which is a bit more capable.
See- https://www.arrmaforum.com/threads/max6-vs-max8-vs-hobbywing-quicrun-wp-150a-esc.10297/

I've just bought a Castle MM2 V2 v1.24sw with modified fw to remove the amp limiter for £105 posted. Using the 'Freeship' coupon code.
That would defo do the trick if your lipos are up to the job.

See- http://www.castlecreations.com/en/mamba-monster-2-2/monster-v2-retro-1-24sw-sold-as-is-010-0108-98
Thanks for the answer. I will try to reverse the servo. I will try to turn up the punch level first, see if that makes a difference. What do you think about the timing on the motor? It's on the stock ESC setting which is 11,5 degrees. The motor is really cool after a run.
 

Ari33

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Im no expert on the subject but it depends on if it is a wye or delta wound motor.

For a Delta wind 0 to 2 degrees Max. I'd try 1 degree should be just enough to stop cogging.

Timing advance on a "D" wind just causes heat, no change in RPM.

If Wye wind you could decrease it for more torque but lower rpms... or you could increase the timing a little for higher rpm at the cost of reduced torque... Iirc... just make sure you monitor the temps as you change things.
 

DutchDriver

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All right, so I did something else. As I already always wanted to drive with the centre diff locked, I decided to leave the centre diff as it is, and I put the rear diff servo in the centre diff connector in the Diff Brain. Now it works well, just the centre diff can't be locked or unlocked. When I put it in Blast mode, the centre diff is locked. When in Wheelie mode, centre and rear are locked. When in Drift mode, the centre and rear are still locked. When in Climb mode, everything is locked. I am happy with this setup now.
Something else, and this is a typical noob question, when I look at a Max8 ESC, I see that the motor wires go directly into the ESC. But the motor wires on the Nero motor are not long enough, so there are some extension cables needed right? On my current ESC there are already wires coming out of the ESC, so the cables are long enough to connect with the motor wires. How does this work with a Max8 or MMX?
Thanks in advance.
 

Ari33

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Nice workaround!

Regarding the esc wires.. You would typically connect the motor wires by soldering on the appropriate sized male and female bullet type connectors of your choice.. bought seperately.

See

Before you go buy a new esc I'd definately try a known quantity high C lipos in it first... just to rule out the possibility that your lipos C rating is not true (not uncommon) or that they are old and deteriorating in performance.

Turnigy HD, Nanotechs and Graphenes with a C rating >50C are typically very good
 

DutchDriver

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Nice workaround!

Regarding the esc wires.. You would typically connect the motor wires by soldering on the appropriate sized male and female bullet type connectors of your choice.. bought seperately.

See

Before you go buy a new esc I'd definately try a known quantity high C lipos in it first... just to rule out the possibility that your lipos C rating is not true (not uncommon) or that they are old and deteriorating in performance.

Turnigy HD, Nanotechs and Graphenes with a C rating >50C are typically very good
Thanks.
Will soon go to my local hobbystore to see what they recommend for an ESC. About the batteries, in my country, those brands are really hard to find. What do you think about the gensacearespammers Bashing Series? 3s 5000mAh 50C. They are not expensive in my country.
 

Ari33

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I have no experience with gensacearespammers but online reviews are generally positive from what I can see.

Did your lipos come with the truck? If they did they may be a bit worn out, lacking in punch and its defo worth ensuring that is not the main problem before you invest in a new esc.

What are the ESC space max dimensions for the Nero?
 

DutchDriver

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I have no experience with gensacearespammers but online reviews are generally positive from what I can see.

Did your lipos come with the truck? If they did they may be a bit worn out, lacking in punch and its defo worth ensuring that is not the main problem before you invest in a new esc.

What are the ESC space max dimensions for the Nero?
Yes, the lipos came with the truck. I think they are good tho. The acceleration is quite good, so is the top speed. It just doesn't make wheelies. I can't afford new batteries and a new ESC unfortunately.
 

RoxioRU

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Hey guys,

Yesterday I picked up a used Arrma Nero with Diff Brain for €250. It came with a Savöx servo and a Hobbywing 8BL-150A ESC. When I came home and drove it for the first time, there were some things that didn't seem right to me.
First of all, when I am in Blast mode, the centre and the rear differential are locked. When I go to Wheelie mode, they are still both locked. When I go to Drift mode, the centre diff is still locked, but the rear diff is unlocked! When I go to Climb mode, the front diff does lock. So what I am thinking here, my centre diff is permanently locked, and my rear diff works reversed. Will have a look today in my centre diff to see if something is stuck. I really wonder how I can fix the rear diff locking mechanism. I already attached and detached the Diff Brain wires and checked the colors on the Diff Brain when switching modes. Everything was okay.

Secondly, the car just doesn't make any wheelies. Even with my permanently locked centre diff, the front just never goes up. I am running on 6s, with the stock 15T pinion. Motor is really cool after a run, and ESC a bit warm, but not hot. The motor runs the stock ESC timing setting, which is 11,5 degrees. Is this ESC not strong enough for the car?

I am quite lost. If you guys can help me, I would be really happy.

Kind regards,

DutchDriver.
If I were you, I would first check the slipper clutch, maybe it’s worn out, it just slips
 

DutchDriver

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If I were you, I would first check the slipper clutch, maybe it’s worn out, it just slips
Thanks for your reaction. I already thought of that as well. I tightened the slipper already, but it didn't seem to make a big difference. When I give full throttle, the car makes a high buzzing/screaming sound. Only with full throttle tho. You think that is from the slipper? I already tried to get the centre diff out of the car, but there is just one screw whose input for the hex key is totally worn out :(
 

DutchDriver

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Thanks for your reaction. I already thought of that as well. I tightened the slipper already, but it didn't seem to make a big difference. When I give full throttle, the car makes a high buzzing/screaming sound. Only with full throttle tho. You think that is from the slipper? I already tried to get the centre diff out of the car, but there is just one screw whose input for the hex key is totally worn out :(
Quick update: I ran the car today with maximum punch level. Still no wheelies. Also I had a problem again with the diff lock mechanism in the rear diff. You could hear the servo, but nothing changed. I could turn the knob on my transmitter, but the rear diff kept being locked. Is the microservo not strong enough?
I also used my grinder to sharpen a line in the worn out hex screw, and after that I could easily unscrew it. That means that tomorrow I will look in the centre diff and will check if the slipper clutch is worn out.
 

DutchDriver

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Quick update: I ran the car today with maximum punch level. Still no wheelies. Also I had a problem again with the diff lock mechanism in the rear diff. You could hear the servo, but nothing changed. I could turn the knob on my transmitter, but the rear diff kept being locked. Is the microservo not strong enough?
I also used my grinder to sharpen a line in the worn out hex screw, and after that I could easily unscrew it. That means that tomorrow I will look in the centre diff and will check if the slipper clutch is worn out.
This is what my slipper clutch looks like. It looks like it is from Hot Racing. Is it worn out? I don't know what to look for really...
Thanks.
 

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RoxioRU

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This is what my slipper clutch looks like. It looks like it is from Hot Racing. Is it worn out? I don't know what to look for really...
Thanks.
Yes, this is a hot race, you have a large and uneven wear, I recommend replacing the entire unit.
 

SthlmM

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Hi!

Regarding your diff servos i would reccomend you to redo The end points for them.
Its easiest done with all diffs outside and open bit with all parts in oke of The halfs of The casing.
It is tricky and can take some time and a couple of tries but Its worth it!

Edit! Always engage/dissengage The diffs when Rolling in low speed with out load.
 

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