Jump to content
Sign in to follow this  
The Twingo Lord

Help!!!!!

Recommended Posts

Looks like Lunchbox/Midnight Pumpkin?  I'm surprised that there was enough room for the motor to back out like that.  Even if I follow all the instruction, sometimes that happens. (to a lesser degree though)  

What happened was that your pinion gear wasn't mated properly with the spur gear.  Less than half of pinion met with spur gear.  That means the pinion had to endure twice the force.  That's like trying to catch a baseball with just two fingers.  That pinion gear wasn't designed for twice the force.  And a brushless motor probably made it worse too.  I would get a new pinion (and a new spur gear too, just to be on the safe side). 

Before you mount the motor, you should check to see if gears are mated well.  Without putting the cap (B2) just yet, push in the motor with the pinion.  Look through and see how the gears are meshed.  If the pinion is too shallow, raise it.  If your motor's shaft is too short, you might need to install a different motor. (though I doubt that such would be the case, because shafts are pretty standard)  Only when you see that the gears are meshed well, then install the motor using B2.  Good quality grease would help too.  

mslucE3.jpg

 

[Below is a photoshopped image of another car. But the point is that pinion and spur must line up]  

L5RYGUa.jpg

 

  • Like 5

Share this post


Link to post
Share on other sites

Is there only one screw holding the adapter to the motor?

If its a brushless motor, remove the adapter and use a bigger pinion?

Share this post


Link to post
Share on other sites

Maybe ditch the adapter and get hold of a 10T 0.8 Mod steel pinion.

And ensure it's aligned properly...

 

Share this post


Link to post
Share on other sites
13 hours ago, Juggular said:

Looks like Lunchbox/Midnight Pumpkin?  I'm surprised that there was enough room for the motor to back out like that.  Even if I follow all the instruction, sometimes that happens. (to a lesser degree though)  

What happened was that your pinion gear wasn't mated properly with the spur gear.  Less than half of pinion met with spur gear.  That means the pinion had to endure twice the force.  That's like trying to catch a baseball with just two fingers.  That pinion gear wasn't designed for twice the force.  And a brushless motor probably made it worse too.  I would get a new pinion (and a new spur gear too, just to be on the safe side). 

Before you mount the motor, you should check to see if gears are mated well.  Without putting the cap (B2) just yet, push in the motor with the pinion.  Look through and see how the gears are meshed.  If the pinion is too shallow, raise it.  If your motor's shaft is too short, you might need to install a different motor. (though I doubt that such would be the case, because shafts are pretty standard)  Only when you see that the gears are meshed well, then install the motor using B2.  Good quality grease would help too.  

mslucE3.jpg

 

[Below is a photoshopped image of another car. But the point is that pinion and spur must line up]  

L5RYGUa.jpg

 

I have a metal spur gear, so that’s good, but maybe I will get a bigger pinion gear, I think what happened is that it doesn’t have that little bump around the pinion, so it wasn’t lines up right. Also the pinion shaft is pretty long, so if I wanted I could do the same to the other side too!

Share this post


Link to post
Share on other sites

I'm beginning to wonder if maybe a different car might be a better fit for you than the Lunchbox. Something with proper adjustable gearing, and a slipper clutch to absorb driveline shocks. A Traxxas Stampede/Rustler/Slash comes to mind; the gearbox design is much more robust and able to handle high power than the poor Lunchie.

If you do stick with it, then I would suggest going back to the stock nylon spur gear. I'm highly suspect of the quality of a "metal" spur gear for this gearbox: what kind of metal? How well were the teeth machined? How true is it? Higher-quality (ie, Tamiya) gears will serve you better than poor-quality aftermarket pieces.

Also keep in mind that it doesn't matter how strong the gears are if the motor mount flexes (and it does). A tiny bit of flex in there makes a massive difference in gear mesh out at the end of that long pinion gear. You can eliminate that flex by removing the adapter and switching to an 18 tooth pinion (look at a Hornet instruction manual for details) but keep in mind that this will raise the gear ratio significantly, and make the motor work harder. You'll get more top speed, but more heat, slower acceleration, and shorter run times.

Also, this may not be what you want to hear, but did you ever consider just maybe taking it a little easier? Driving fast and hard is cool and all, but if you're breaking things this often, the car is trying to tell you something...

  • Like 2

Share this post


Link to post
Share on other sites

Ah, metal spur gear could also harm the brass pinion. 

Generally Tamiya designs the pinion to be harder than the spur gear.  The pinion gear has 10 teeth but spur gear has like 50(?) teeth.  Each time one particular tooth of spur meets the pinion, the pinion has to turn 5 times.  That means pinion has to be 5 times as hard.  But if you had an aluminum spur gear, it's harder than plastic, so the poor pinion gets the short end of the stick. 

(On @markbt73's point : plastic gears give a little --the whole "trees break but reeds don't" seems to apply.  There was a Boeing engineer who faced a gear breakage problem on a very high RPM application.  Initially, he made it stronger and stronger but it always stripped. In the end, he made it out of nylon with lots of holes to keep it light. Going light and flexible solved it. Who knew weaker was stronger!)  

Anyway, the option is quite limited when it comes to Lunchbox.  As far as I know, the brass one is the only pinion for it.  Because of the tall neck, manufacturing cost is high, so 3rd parties don't seem to make it.  

[1]  But there is the Hornet's 18t pinion.  You can take off the motor collar/spacer, and install the 18t pinion for Hornet.  Don't get the aluminum pinion Tamiya sells, that's not harder than your spur gear.  There are steel pinions.  The gearing is too tall for regular motors, but brushless could handle it.  It reduces acceleration but increases top speed. Maximum speed would be higher. But it takes time to get to that speed.  You might find that it's slightly less willing to wheelie if you use an 18 teeth pinion.  It would be better if the gearbox allowed 13t or so, but the way it's designed, you can either fit the Lunchbox's long-neck pinion, or hornet's 18t.  If you tried to fit 13, 14, 15, 16, 17, 19 or 20 teeth pinion, that will destroy both gears.   

[2]  There are ebay sellers who makes adjustable motor mounts for $12 or so.  If you get one of those, you can use something like 13t.  3 more teeth is a lot.  But that would be suitable gearing for a brushless motor.  

 nRyDw8M.jpg

 

Share this post


Link to post
Share on other sites
1 hour ago, Juggular said:

[2]  There are ebay sellers who makes adjustable motor mounts for $12 or so.  If you get one of those, you can use something like 13t.  3 more teeth is a lot.  But that would be suitable gearing for a brushless motor.  

 nRyDw8M.jpg

 

On the lunchbox gearbox this can only go down to 17t and up to 21t. The adapter will hit the ridges on the outside of the gearbox when trying to go lower and anything larger than 21t will hit the motor mount screws "tunnel" on the inside. I tried to go lower on my Midnight Pumpkin and higher on my Grasshopper.

  • Thanks 1

Share this post


Link to post
Share on other sites

Also, the mesh on the 17t isn't very good so you may run into this same problem.

  • Thanks 1

Share this post


Link to post
Share on other sites
7 hours ago, Biz73 said:

Also, the mesh on the 17t isn't very good so you may run into this same problem.

Thank you for that input!  

So practically, it can only go taller. (That's a bummer, but I suppose that's the limit of the gearbox)

 

Share this post


Link to post
Share on other sites

Random tid-bit (and probably outside the scope of the question but...) Stormer made a small gear reduction unit that fit the Lunchie back in the day.

Share this post


Link to post
Share on other sites
16 hours ago, markbt73 said:

I'm beginning to wonder if maybe a different car might be a better fit for you than the Lunchbox. Something with proper adjustable gearing, and a slipper clutch to absorb driveline shocks. A Traxxas Stampede/Rustler/Slash comes to mind; the gearbox design is much more robust and able to handle high power than the poor Lunchie.

If you do stick with it, then I would suggest going back to the stock nylon spur gear. I'm highly suspect of the quality of a "metal" spur gear for this gearbox: what kind of metal? How well were the teeth machined? How true is it? Higher-quality (ie, Tamiya) gears will serve you better than poor-quality aftermarket pieces.

Also keep in mind that it doesn't matter how strong the gears are if the motor mount flexes (and it does). A tiny bit of flex in there makes a massive difference in gear mesh out at the end of that long pinion gear. You can eliminate that flex by removing the adapter and switching to an 18 tooth pinion (look at a Hornet instruction manual for details) but keep in mind that this will raise the gear ratio significantly, and make the motor work harder. You'll get more top speed, but more heat, slower acceleration, and shorter run times.

Also, this may not be what you want to hear, but did you ever consider just maybe taking it a little easier? Driving fast and hard is cool and all, but if you're breaking things this often, the car is trying to tell you something...

Ok, I like the stupidity of it though. I’ll get some more gears, and fix the mesh, and try it again, if I break it again, I think I’ll put in a sport tuned and stop the stupidity lol!

Share this post


Link to post
Share on other sites

 

15 hours ago, Juggular said:

Ah, metal spur gear could also harm the brass pinion. 

Generally Tamiya designs the pinion to be harder than the spur gear.  The pinion gear has 10 teeth but spur gear has like 50(?) teeth.  Each time one particular tooth of spur meets the pinion, the pinion has to turn 5 times.  That means pinion has to be 5 times as hard.  But if you had an aluminum spur gear, it's harder than plastic, so the poor pinion gets the short end of the stick. 

(On @markbt73's point : plastic gears give a little --the whole "trees break but reeds don't" seems to apply.  There was a Boeing engineer who faced a gear breakage problem on a very high RPM application.  Initially, he made it stronger and stronger but it always stripped. In the end, he made it out of nylon with lots of holes to keep it light. Going light and flexible solved it. Who knew weaker was stronger!)  

Anyway, the option is quite limited when it comes to Lunchbox.  As far as I know, the brass one is the only pinion for it.  Because of the tall neck, manufacturing cost is high, so 3rd parties don't seem to make it.  

[1]  But there is the Hornet's 18t pinion.  You can take off the motor collar/spacer, and install the 18t pinion for Hornet.  Don't get the aluminum pinion Tamiya sells, that's not harder than your spur gear.  There are steel pinions.  The gearing is too tall for regular motors, but brushless could handle it.  It reduces acceleration but increases top speed. Maximum speed would be higher. But it takes time to get to that speed.  You might find that it's slightly less willing to wheelie if you use an 18 teeth pinion.  It would be better if the gearbox allowed 13t or so, but the way it's designed, you can either fit the Lunchbox's long-neck pinion, or hornet's 18t.  If you tried to fit 13, 14, 15, 16, 17, 19 or 20 teeth pinion, that will destroy both gears.   

[2]  There are ebay sellers who makes adjustable motor mounts for $12 or so.  If you get one of those, you can use something like 13t.  3 more teeth is a lot.  But that would be suitable gearing for a brushless motor.  

 nRyDw8M.jpg

 

What pitch I are the gears in the lunchbox? I might do that.

Share this post


Link to post
Share on other sites
8 hours ago, Juggular said:

Thank you for that input!  

So practically, it can only go taller. (That's a bummer, but I suppose that's the limit of the gearbox)

 

Yes, I was bummed it wouldn't go down for my Pumkin and up further for my Grasshopper. It is also for the ORV chassis, so I'm guessing that's where the pinion numbers in the Ebay ad come from.

  • Like 1

Share this post


Link to post
Share on other sites

Maybe a stupid question but that pinion looks very clean. Did you use grease on the gears?

  • Like 1

Share this post


Link to post
Share on other sites
2 minutes ago, Ray_ve said:

Maybe a stupid question but that pinion looks very clean. Did you use grease on the gears?

The same question came to my mind too.  

And I think the pinion is 32 pitch?  0.8 is compatible.  Even though they are not exactly the same, the difference is small that most people use them interchangeably.  

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×
×
  • Create New...