Grasshopper Killed

[ChrisRx718]

Lockdown death count: 3

I've managed to destroy my counter gear in my Grasshopper.

Bodyshell is looking a bit rough too, spends a lot of its time on its roof 

Frank looks a little concerned about why his car now sounds like a Nitro fuel car at full throttle; but doesn't move? 

Pop that gearbox off:

In-keeping with the Grasshopper ethos of a small motor, I had fitted a Hobbywing 2435 brushless motor (same size as a 380) and associated 40A ESC (Sensorless).

This setup works really well with the exception that you have to run a pinion shaft spacer and an odd-size pinion. This might be the source of my issues.

I've ran 5 packs through it, then 2 3S packs finally resulted in failure!

You can see the pinion / spacer sleeve here:

On closer inspection:

Oh dear 

So not as 'indestructible' as people make out. Or perhaps that's because I wasn't using it correctly. What's 50,000 RPM between friends?!

Question is, do I rebuild it with the same setup or acknowledge that I was wrong and just put a Hornet / 540 setup in there?

 

[Wetman]

Poor Frank looks terrified 

[ruebiracer]

3s in a Grasshopper with Brushless? Did it ever have contact to the surface, or just flying after launch?

The pinion doesn´t look a too good fit to the spur, so I´d say this in combination with the power chosen wore out the counter gear. If you rebuild it that way, you can Count the minutes it will last again… 

You could try to use a bigger pinion, though. every teeth more in this Rough module should improve contact area for the counter gear...

[dannymulder]

I think the gear mesh was not right, normal the gearbox is very strong, I have run it for years with a normal 540  can, 3800kv brushless motor.

[DeadMeat666]

I'm sure the alloy wheels didn't help either, adding a significant amount to the rotational mass, making it harder for the transmission to spin.

Edit: That's if they are alloy wheels; on closer inspection I'm not quite sure.

[Ferruz]

I would go to 540 motor specs, should be more than enough power for you to enjoy the Grasshopper realistically, without Frank having to consider upping his life insurance every time you run it.

Nice experiment fitting the smaller BL though!

[TurnipJF]

There is something about the tooth profile on that pinion that doesn't look quite right. I would go for a 540 size motor and a proper steel 0.8 module 18 tooth pinion.

[Carmine A]

You COULD keep that Motor (RECOMMEND staying with 2S though)... 

I agree with @TurnipJF in that the Pinion looks "off". Is that a 32 pitch gear? You wouldn't be the first! 😜 

Get an 0.8 Mod, 18t Pinion Gear, and consider getting an Aluminum Spur Gear. (A couple of Aftermarket companies sell them, like Yeah Racing, GPM...)

IF you're staying Brushless. If you go with a 540 Brushed, a standard Spur Gear will do. 😉

[SupraChrgd82]

In my Hornet experience, the stock drivetrain is best.  At one point I put a 15t motor in mine.  I was only able to crash faster. After rebuilding to the 27t and new gearbox case, it became fun and reliable again.  Much like motorcycles, I beleive it's more rewarding to drive a slow car fast than drive a fast car slow.

[Carmine A]

55 minutes ago, SupraChrgd82 said:

.....I beleive it's more rewarding to drive a slow car fast than drive a fast car slow.

VERY profound!! 👍👍

[Juggular]

5 hours ago, TurnipJF said:

There is something about the tooth profile on that pinion that doesn't look quite right.

Grasshopper is very hard to kill.  I'd say that's an achievement!  (RIP for the gear, though)

Looking at the photo, I thought the teeth looked small too.  

Aluminum gear is worse than nylon.  I once thought, "aluminum is metal! it's got to be stronger than plastic!"  No, not on gears.  Some Boeing engineer tried to make gears stronger with aluminum, steel, and titanium. All stripped. In the end, nylon gear solved the problem.

Gears don't just turn. Teeth rub on each other.   

Nylon gear giving a little + some good grease, it's very strong against wear.  Sadly, aluminum doesn't give. And because of the rubbing, the surface is easier to grind away than nylon.  I think we had a member whose aluminum gear got ground to a pulp few months ago?  

I'd use the correct pinion you got, and get another nylon gear from Tamiya. 

What grease did you use? 

 

[Raman36]

Drop a 3.5 turn brushless motor in there with 3S and watch it hit 88 mph before it goes back to the future 😂

[Killajb]

While I'm not quite sure what the intent is here, I still find it interesting nonetheless.  If you want to resolve the gear issue, as others have noted the proper pinion gear and motor spacing would help.  I used a Tamiya motor adapter to mount a 380 motor in my grasshopper, along with the same brass pinion adapter you are using, but with a blackfoot/monster beetle/lunchbox pinion.  Should be able to run 3s and your brushless motor without chewing any of the gears at least.

[ChrisRx718]

Great service from Time Tunnel Models, new spur gear ordered Sunday, delivered today.

A quick rummage around my spares I found an 18T pinion (ribbed, for her  ) which I can only assume came from my DT02 kit. 

The mesh seems right anyway.

Out with the old:

Insides of the gearbox were littered with plastic shavings stuck in grease:

And there it is, all fixed and ready for some more gentle running. I switched the radio gear with the intention of perhaps letting my daughters have a go (5 & 7). Could I simply install the original 380 motor and run it off the same ESC? ESC is an old trusty TEU101BK I found in my spares.

[nowinaminute]

You could try a 2838 or 28 45 motor? They are the same dimensions as a 380 and 390 respectively, will fit the 380 Motor mount but have a 3.175mm shaft like a 540 motor. Then it should just be a case of finding a 0.8m/32dp 10t pinion.

 

[skinned]

2s.....and either a 17.5 or a 13.5 will be plenty..