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HopperLeo

A Frog (o)pinion

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Hi, back with another newbie question ;) 

So, I took my Frog out today for a spin with the 540 motor it comes with in the box. Fun! It's a little too 'sensible' at the moment though. I'd like to give it more 'guts' so to speak! 

With that in mind, I want to attach a GT Tuned motor and right now I'm searching for the right pinion to go with it...

As far as I understand the Frog uses the same 32 pitch pinion that the Grasshopper does. And the GT motor requires a 25t. 

Trouble is, I don't seem to be able to find 25t 32p pinions online? Can someone point me in the right direction please? 

Ta muchly :) 

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I think the 25T refers to the number of turns in the motor, not the pinion requirement.

Motor shafts are a standard size so why not just fit your existing motor pinion and see how that works out.

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Aha, got it! I shall definitely do that once the motor arrives, brilliant, thanks :)

Regarding pinion sizes, have I got it right then that... 

More teeth (higher gear) = lower acceleration and higher top speeds

Less teeth (lower gear) = higher acceleration and lower top speeds.

?

lol, I do have a real driving licence, honest :D

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20 minutes ago, HopperLeo said:

Aha, got it! I shall definitely do that once the motor arrives, brilliant, thanks :)

Regarding pinion sizes, have I got it right then that... 

More teeth (higher gear) = lower acceleration and higher top speeds

Less teeth (lower gear) = higher acceleration and lower top speeds.

?

lol, I do have a real driving licence, honest :D

Yes that's right.

Dont worry about asking questions... I've been on this site for over 3 years now and am still asking simple stuff too ;)

 

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Thanks Jason, comforting to hear :) 

So, how much difference does more / less teeth on a pinion really make to a set up like mine?

Is it marginal? Or substantial?  

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Marginally substantial, I'd say. You'll notice the difference, but it won't blow your mind. 

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5 hours ago, HopperLeo said:

Thanks Jason, comforting to hear :) 

So, how much difference does more / less teeth on a pinion really make to a set up like mine?

Is it marginal? Or substantial?  

The key is getting the motor running at its most efficient. While in theory a bigger pinion means more top speed, in reality it can make the car slower if the motor can't reach its max rpm. I don't know anything about brushed motors but assume that you could use heat as a guide like you would with brushless motors. Basically, set the gearing where you think it should be then check how hot the motor is getting, if too hot then drop a pinion or 2, if cool then you can go up a size or 2

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You shouldn't have to buy any gear. 

The frog (and the Brat) is very unique.  They gave you 3 pinions and 3 spur gears.  Which combination did you choose when you built your Frog?  

7BRjfP2.jpg

gZXrJU7.jpg

Since you are getting a faster motor, 6.7 gear ratio wouldn't be good. 

Brushed motor's torque is weak when compared to brushless motors.  The RPM they give you is the "bench RPM," without any load.  As Jonathon said, with load, the high RPM dies quickly.  Which is why a smaller pinion is recommended for a faster motor.  Theoratically, it will reduce the top speed. But in reality, high RPM will overcome the lowered gear ratio. 

I'd go with 8.5 gear ratio (Tamiya's general recommendation for buggies is 8 to 9 FDR).  Since the Frog is a light buggy, if you must, you could try 7.3 FDR (Final Drive Ratio, not Franklin Delano Roosevelt).  The lower ratio will give you more kick at the start, and also higher speed, because it won't kill the highend RPM like 6.7 gear ratio would.  (I hope you didn't toss the extra gears)  If it wasn't the Frog, as S-PCS said, changing 1 tooth size won't make an earth-shattering difference.  But FDR of 6.7 and 8.5 can be a substantial difference.  

On paper, the silver can has 14000 rpm, and the GT Tuned has 19000 rpm.  Pair the silver can with the fastest, 6.7 ratio, you get  2089 rpm at the wheels.  Pair the GT tuned with the slowest ratio of 8.5, you get 2235 rpm.  It's still 10% faster.  If you already had 8.5 ratio when you built your Frog, you are getting 1647 rpm, in which case, 2235 rpm would be 40% faster.  

You could ask, "what if I pair the GT with the fastest, 6.7 ratio? Wouldn't I get 2835 rpm at the wheels?"  Sadly, you simply can't get the bench RPM, if you give it more burden.  The maximum torque is somewhere in the lower-middle of the rpm band, not at the top.  The curve seems steeper with faster motors.  Which is why if you burden the faster motor, it may go no faster than the stock motor.  

FYI:   "Turn" means how many times the copper wire was wrapped around the core of the motor.  27 turns is the norm.  25 turn means having used thicker gauge wire, which allows more flow of electricity.  That makes the motor go faster.  It's confusing because people say "25t" motor and "19t" pinion.  It's the "teeth" when talking about a pinion.  

 

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To muddy the waters further, there's singles, doubles, triples and quad wound brushed motors too. For example, a 21T single would have a fat single gauge wire wound around the core 21 times. A 21T triple would have 3 smaller strands of wire wound around the core 21 times as well. IIRC, a single would have a nice meaty torque to it and a quad would be more for high rpms. The old Tamiya Technigold motors were 21T singles and had decent "grunt" for their era. 

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Morning all, what a lot of fantastic information to read through, thank you so much! I look forward to wrapping my head around it :) 

Just a quick reply to Juggular's question - curiously, I didn't get any spare pinions and gears as you mention. I bought it pre-built - Sacrilege, I know ;)  

All I got inside were the optional poles for the antennae, and a some small plastic parts to fit to the trigger of the controller. 

Odd that they didn't include those pinion / spur gears too...

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Do XBs come with ball bearings?  They probably come with white plastic bushings?  If so, you've got a good news.  (more upgradability = more fun!)  Ball bearings can boost speed and acceleration about 15-20% all by themselves.  And less load means you can squeeze out higher RPM from the motor too.  

Below cost only about $2 for ten bearings.  You'd need a dozen.  For less than $5, you can boost 15% already!  These are cheap bearings with inconsistent quality.  I would pick the most free-rotating 2 bearings for the spur gear.  After the motor, the spur gear has 6000 rpm when wheels turn only 2000 rpm.  You want the least resistance on the spur gear.  

https://www.ebay.com/itm/10pcs-685-5x11x4mm-Open-Miniature-Bearings-ball-Mini-Hand-Bearing-Spinner/162470235664?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I don't know what gears they put in the XB version.  My guess is that Tamiya doesn't like 6.7 ratio.  If you have 8.5 FDR with a 16 teeth pinion, you are good to go.  If you have 7.3, it might not be great for GT, but usable.  

If you want different gears, they are relatively easy to find.  Unlike 99% of other cars, you need one spur gear + one pinion to match it.  

https://www.ebay.com/itm/NEW-TAMIYA-BRAT-FROG-Pinion-Gears-HORNET-TBF11/142739002418?hash=item213be85432:g:9i0AAOSwYyRaE8BO:rk:2:pf:0

https://www.ebay.com/itm/NEW-TAMIYA-BRAT-FROG-Diff-Gears-Drive-Bevel-Spur-TBF6/312098645718?hash=item48aa8766d6:g:Zf4AAOSwYZ5aE8Aa:rk:1:pf:0

 

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Well, it seems as though I'd better get my tool box out then. And so beginneth the 'real' hobby ;) 

I've managed to get the wheel off (good start!), and it looks to me as though the bearings on the drive shaft are plastic... 

I need a stiff drink before opening up the gear box for the first time, haha, but if the drive shaft is anything to go on, I should probably go ahead and buy some shiny new ball bearings...yay :) 

Thanks for links, and poking me further down the proverbial rabbit hole. I shall be back with more up-dates as and when I pull this (beautiful) thing apart! 

Frog Drive shaft .jpg

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You will find your acceleration and top speed improve if you move to bearings at all points.

If you plan on running the stock Frog Tranny with a GT Tuned, use the 16t pinion supplied with the Frog.  It will be fine.  

Unless you're trying to break some speed record, I would go with the 16t pinion.  You might even try something like a CRP adustable motor mount and a Thorp 15t or 14t pinion???

You have to remember that the stock Frog Tranny is very temperamental, and will eventually spit at you...  If you really want to stress you Frog tranny, think about upgrading it...

Terry

 

 

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Just reporting back to say that today I got the metal bearings on the wheels and I just took it out the back for a spin. You were all right, it makes a massive difference! Debating whether I really need a tuned motor now. It's already pretty nippy :) 

And for those curious, I opened the gear box and they were metal bearings. They'd only used the plastic ones for the wheels. 

I think the next investment will be a bigger battery. 15 minutes with my 1300 mAH is a bit underwhelming right now. Any tips on how big I should go? Is there any disadvantage in choosing a 5000 mAH apart from it taking longer to charge? 

Cheers all :) 

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I love ball bearings.  

The improvement is broad in spectrum: in top speed, in acceleration, and in run time.  Top speed from 25km/h to 31km/h is over 20% improvement. 

The battery question depends on the chemistry.   

If you are getting a NiMH battery, I'd get something close to your need, not maximum mAh.  NiMH has some memory effect.  You'd want to fully charge, and almost fully drain.  The larger the capacity, the longer and harder that cycle would be.  

If it the battery is LiPo, then it's good to have larger capacity.  Because LiPo doesn't like to be fully drained nor does it like fully charged.  "Storage charge" is somewhere around 45% to 60%.  The larger mAh, the larger that gap is, so it would be more forgiving.  

 

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Fab advice as usual Juggular, thank you! And a great video. My Frog power slides now too. That's ball bearing power right there! ;) 

I would be using an NiMH battery, as I'm not far enough down the hobby rabbit hole just yet to be investing in the Lipo route. I'm savouring each little improvement bit by bit :) 

So, I reckon maybe an extra 3000 NiMH battery should fill my needs. I assume that will give me at least 30 minutes of racing time including the 1300 battery I have right now.

Cheers!

 

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Hey! Having just attached the GT Tuned motor, I just spotted that the pinion gear they fitted with the XB pre-built kit was the 18t.

So, it looks like the next investment might not be the battery after all, but a new 16t pinion gear and matching spur gear that wasn't supplied in the box.

Thanks a lot for those ebay links again Juggular!

EDIT: Actually, instead of ordering online, as I'm in Japan I might take a day trip to the Tamiya store in Tokyo soon...and I promise to only come home with gears...nothing else...promise ;) 

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