Big Rock 3S BLX Motor and Motor Mount stabilization?

[Dre325]

Hi everyone,
2nd time running my Big Rock, I managed to run dead on into a concrete garbage can. User error. The car was amazingly fine, except the motor mount bent forward so far that the pinion was just barely contacting the spur and stripped it out. Also cracked a small portion of one half of the clutch housing where it interfaces with the rear diff. I flattened the motor mount out (a new one was not available anywhere I could find quickly), bought a new clutch housing which took a week to arrive, and put it back together and all is good. However, I'm gunshy to jump this thing now for fear of landing on the nose and bending the mount again. Wanted to see what you all thought of this idea.

The motor is heavy and sits suspended in the air from the motor mount by the two motor to motor mount bolts. In a hard front impact, I believe the motor just keeps moving forward and bends the mount since the motor isn't supported underneath or in front. I had the idea to wedge something under the motor to support it, but this wouldn't stop forward motion, had a 2nd idea to place something between the front of motor and back of ESC to prevent forward motion, but was afraid with body flex that this could actually be a bad idea and prevent some of the flex. My final idea, after recently changing the big batteries in my daughters' power scooters that use a glob of hot glue at the contacts to keep them from coming disconnected, is to put a glob of hot glue under the front of the motor. Not much, but enough to prevent it from moving up/down or forward as well in a front end collision. Hot glue is slightly flexible, and pretty easy to peel off if needed.

Any thoughts on this idea or any downside that anyone can think of? Has anyone tried something similar?

 

[*420+3RC*]

I use the high grade foam. Just cut to fit and e6000 to the chassis
https://www.arrmaforum.com/threads/ideas-for-a-motor-cushion.41678/

More ideas also

 

[Dre325]

I use the high grade foam. Just cut to fit and e6000 to the chassis
https://www.arrmaforum.com/threads/ideas-for-a-motor-cushion.41678/

More ideas also

So that seems like it would stop the up/down motor "slap" and protect the motor, but I don't see how that would help with the fore/aft motion which is ultimately what causes the mount to bend. Mine was bent like 30 degrees ! It's good to see that others are filling this gap, though, as that would give me a bit more confidence in my hotglue idea.

 

[*420+3RC*]

Good point my bad. The m2c mount also has a brace on it. Maybe that helps some atleast at the mount. But I'm not sure.

 

[Velodromed]

A month ago or so I put an o-ring (37mm I think) around the end of the motor can in each of my cars. someone recommended it here in the forum. I have not bent any motor mounts since. I don’t run head on into things very often but I do face plant and tail plant when I jump, which is similar. The o-ring does work.

 

[*420+3RC*]

Ive not seen anyone try to brace the motor from the front. I don't think the front force is what bends the mount. Straight ahead force lets the housing and screws and all take most of the force. Its the slamming down throwing that motor down which twists the motor mount. Even a head on hit isnt going to be straight ahead force due to the way the vehicle takes impacts. Imo now that im off work and could actually think about it. But im wrong....alot

 

[ThatDriverGuy]

After bending a couple stock motor mount plates I swapped it out with a Hot Racing one and a heatsink from Banggood. I just finished cleaning my rig and attached below is the heatsink I've been using for a few months.

As you can see, the bottom of the motor is covered compared to stock and I think the heatsink rests on the chassis once installed. It accepts a 50mm fan and if I had known this I would've gotten an aluminum frame one. Also, the way I have it installed in the truck makes removing the center driveshaft a pain at first as I have to remove the red plastic motor mount brace each time. Since I clean and look over the truck after each bashing session, I've gotten used to it.

I hope that helps!

 

[Kla912000]

After bending a couple stock motor mount plates I swapped it out with a Hot Racing one and a heatsink from Banggood. I just finished cleaning my rig and attached below is the heatsink I've been using for a few months.

View attachment 167310

As you can see, the bottom of the motor is covered compared to stock and I think the heatsink rests on the chassis once installed. It accepts a 50mm fan and if I had known this I would've gotten an aluminum frame one. Also, the way I have it installed in the truck makes removing the center driveshaft a pain at first as I have to remove the red plastic motor mount brace each time. Since I clean and look over the truck after each bashing session, I've gotten used to it.

I hope that helps!

I have the stock heat sink on the top of my motor as usual, and I also have a second smaller heat sink on the bottom of the motor resting on the chassis to support the motor. Very similar setup as yours. Supports the motor from bending the motor plate and allows the chassis to flex naturally.

 

[DRBNGR]

After bending a couple stock motor mount plates I swapped it out with a Hot Racing one and a heatsink from Banggood. I just finished cleaning my rig and attached below is the heatsink I've been using for a few months.

View attachment 167310

As you can see, the bottom of the motor is covered compared to stock and I think the heatsink rests on the chassis once installed. It accepts a 50mm fan and if I had known this I would've gotten an aluminum frame one. Also, the way I have it installed in the truck makes removing the center driveshaft a pain at first as I have to remove the red plastic motor mount brace each time. Since I clean and look over the truck after each bashing session, I've gotten used to it.

I hope that helps!

@ThatDriverGuy
Do you have link to that heatsink?

 

[Velodromed]

Ive not seen anyone try to brace the motor from the front. I don't think the front force is what bends the mount. Straight ahead force lets the housing and screws and all take most of the force. Its the slamming down throwing that motor down which twists the motor mount. Even a head on hit isnt going to be straight ahead force due to the way the vehicle takes impacts. Imo now that im off work and could actually think about it. But im wrong....alot

Actually, I think that head on hits including nose dives somehow do transfer into downward force on the back of the motor. I don’t have a technical proof… just all the times I’ve taken it apart and all the times I bent motor mounts (My hot racing motor mounts are pitted with hammer marks). That silly little o-ring on the back of the can really does help, Since I put one on all three of my cars I haven’t had a motor mount bend. And I’ve checked often over the last few weeks.

After bending a couple stock motor mount plates I swapped it out with a Hot Racing one and a heatsink from Banggood. I just finished cleaning my rig and attached below is the heatsink I've been using for a few months.

View attachment 167310

As you can see, the bottom of the motor is covered compared to stock and I think the heatsink rests on the chassis once installed. It accepts a 50mm fan and if I had known this I would've gotten an aluminum frame one. Also, the way I have it installed in the truck makes removing the center driveshaft a pain at first as I have to remove the red plastic motor mount brace each time. Since I clean and look over the truck after each bashing session, I've gotten used to it.

I hope that helps!

Nice!

I have the stock heat sink on the top of my motor as usual, and I also have a second smaller heat sink on the bottom of the motor resting on the chassis to support the motor. Very similar setup as yours. Supports the motor from bending the motor plate and allows the chassis to flex naturally. View attachment 167311View attachment 167312

Do you remember where you got that little heat sink? I’ve seen you show a picture of this before and I tried to fit one of my heat sinks simerally but they’re all too big. So I ended up going with an O ring. But I am always open to better methods.
I got the same fan on my granite and love it.

 

[Kla912000]

Actually, I think that head on hits including nose dives somehow do transfer into downward force on the back of the motor. I don’t have a technical proof… just all the times I’ve taken it apart and all the times I bent motor mounts (My hot racing motor mounts are pitted with hammer marks). That silly little o-ring on the back of the can really does help, Since I put one on all three of my cars I haven’t had a motor mount bend. And I’ve checked often over the last few weeks.

Nice!

Do you remember where you got that little heat sink? I’ve seen you show a picture of this before and I tried to fit one of my heat sinks simerally but they’re all too big. So I ended up going with an O ring. But I am always open to better methods.
I got the same fan on my granite and love it.

When I bought the Surpass 3670 motor the heat sink came with it. If I remember correctly I got it from Amazon.

Yes, those fans kick ass! They are better than the little Rocket aluminum fans. I have the same fan on my Typhon too.

 

[*420+3RC*]

Actually, I think that head on hits including nose dives somehow do transfer into downward force on the back of the motor. I don’t have a technical proof… just all the times I’ve taken it apart and all the times I bent motor mounts (My hot racing motor mounts are pitted with hammer marks). That silly little o-ring on the back of the can really does help, Since I put one on all three of my cars I haven’t had a motor mount bend. And I’ve checked often over the last few weeks.

Nice!

Do you remember where you got that little heat sink? I’ve seen you show a picture of this before and I tried to fit one of my heat sinks simerally but they’re all too big. So I ended up going with an O ring. But I am always open to better methods.
I got the same fan on my granite and love it.

My bad I was tired. I was just meaning I never seen some one put a "brace" at end of the can. All under or around. Im terrible esp thru typing getting across what I wanna say

 

[SrC]

If I owned a 4x4, I guess my first upgrade aside from a servo would be the M2C motor plate /chassis brace. Bent motor mounts are primarily what keeps me from getting a 4x4. And the BRCC interests me if any. There is so much chatter about this OE Motor mount being a major issue. $72. seems high for a 4x4 M2C upgrade out the box, but there is no better option?

https://m2cracing.net/arrma-vorteks/583-m2c-3160-arrma-17mm-hub-extenders.html
\
(This link appears to be for the hub extenders, but it links to the motor plate/mount)

 

[ThatDriverGuy]

@ThatDriverGuy
Do you have link to that heatsink?

[CA$19.25 17% OFF]DHK Hobby 8381-9M1 3670 Motor Upper Lower Mount 1/8 8381 8382 8384 RC Car Part RC Parts from Toys Hobbies and Robot on banggood
https://banggood.app.link/N6pMvn0Pgjb

 

[theekorr]

M2c mount is the answer imo. I have been considering an “L” bracket screwed to the chassis on the front of the motor for support because I have seen sooo many stock ones bend from front impacts. Two days ago I hit a curb head on at full bore with my M2C mount and all is well. This even with a larger 3670 surpass can.

 

[1.21 Gigawatts]

There is a hole in the chassis just in front of the motor mount on the motor end. A simple interference fit wedge that has a protrusion that snaps into to the hole could be 3d printed. Or you could just screw it in through the hole.

This would prevent the bending of the mount if caused by the forward movement.

 

[milehighspeed]

1.21gigawatts is on the right track. This has worked for me. hopefully works for you.

https://www.arrmaforum.com/threads/tired-of-bent-motor-mounts-on-3s-try-this.45620/#post-635852

 

[Tim Holbrook]

Hi everyone,
2nd time running my Big Rock, I managed to run dead on into a concrete garbage can. User error. The car was amazingly fine, except the motor mount bent forward so far that the pinion was just barely contacting the spur and stripped it out. Also cracked a small portion of one half of the clutch housing where it interfaces with the rear diff. I flattened the motor mount out (a new one was not available anywhere I could find quickly), bought a new clutch housing which took a week to arrive, and put it back together and all is good. However, I'm gunshy to jump this thing now for fear of landing on the nose and bending the mount again. Wanted to see what you all thought of this idea.

The motor is heavy and sits suspended in the air from the motor mount by the two motor to motor mount bolts. In a hard front impact, I believe the motor just keeps moving forward and bends the mount since the motor isn't supported underneath or in front. I had the idea to wedge something under the motor to support it, but this wouldn't stop forward motion, had a 2nd idea to place something between the front of motor and back of ESC to prevent forward motion, but was afraid with body flex that this could actually be a bad idea and prevent some of the flex. My final idea, after recently changing the big batteries in my daughters' power scooters that use a glob of hot glue at the contacts to keep them from coming disconnected, is to put a glob of hot glue under the front of the motor. Not much, but enough to prevent it from moving up/down or forward as well in a front end collision. Hot glue is slightly flexible, and pretty easy to peel off if needed.

Any thoughts on this idea or any downside that anyone can think of? Has anyone tried something similar?

Looking for a 3s BLX Big Rock FIXED motor mount, Arrma quit making it. FIXED is 100% better than adjustable and will eliminate most of the problems I see on this page

 

[BigP]

Fix is easy: Just one 3M Bumpon under the end of the motorcan. Costs: 50 Cent.

No more problems for me on my Arrma 3s/4s.

In the Picture is my 4s V2, here is just 2 bumpons for some reason.
Normally just 1 directly under the motor.

And then its time to send it: