Jump to content
Sign in to follow this  
Gazzalene

Lower turn motor,do i need to alter gearing?

Recommended Posts

I am ordering a lancia delta XV01 kit tomorrow, it has no motor inc so I asked here about what I should go for to get a perterformance,only fun running on 7.2v nimh

Was recommended a 15t will be good compromise. I have since read that changing motor will need the gearing to be changed also to suit.

What can I run Turn wise with the supplied kit pinion and gearing? or if a 15/17t is a good way to go what pinion and main gear will I need to order?

Share this post


Link to post
Share on other sites

Lucky you!  XV01 is still on my wish list.  

Going with a pinion with 1-2 less teeth would be good.  While 15t has more torque and more rpm, they come to play only at higher rpm.  If you lower the gear ratio, you can make better use of the high RPM.  Looking up the manual, it comes with 22t pinion with 8 FDR?  The lowest is 21t with the ratio of 8.4:1?  While 8 is already low, if I were to use a fast motor like 15t, I think I'll go with 21t.   

 

Here are the bell curves (I hope I'm reading this right).  Compare the torque difference between 27t and Sport tuned (only 23t).  Yellow line is at 10,000 RPM.  Silver can (dotted curve) has more torque.  Sport Tuned has less torque at this point.  Orange line is at around 15,000 RPM.  Silver can still has like 25% more torque at this point also.  At about 18,000 rpm, the silver can has 1000 g/cm of torque.  Sport Tuned has maybe 600 g/cm.  40% less torque than the silver can.   

But at 20,000 RPM, Sport Tuned does have more torque, only because silver can dropped out of race.

I6Qj1IV.jpg

[Note: A silver can cannot really go as fast as 18,000 RPM. This was a lab test at constant voltage.  In real life, NiMH's voltage drops down to 5v when accelerating--LiPo drops down to 6v]  

Lowering the ratio allows the hot motor to spool-up faster, and allows higher RPM.  If you are using 15t, the difference could be even more pronounced.  This is why dropping a tooth would be better.  But don't buy 20t or 19t pinion. The motor may not have room to get closer than with a 21t pinion.  If the spacing isn't right, you can destroy gears.

IF there is a room for the motor to move closer to the spur gear, you can make the slots longer and use smaller pinions.  Instead of gong through all that trouble, however, it'd be easier to get a cheap TBLE02S ESC and a 13.5t motor.  And use a 23t pinion. Brushless motors have more torque, so you can go a tooth up.  

 

Share this post


Link to post
Share on other sites

Thanks for the really detailed and clear info,i appreciate that.

I thought about going Brushless but have the Batts and esc already.

Can I ask what you would fit brushed wise for "sprited" running,using the supplied parts then?

Share this post


Link to post
Share on other sites

You only 'need' to change gearing if the motor or ESC runs too hot. Otherwise, if you aren't racing it's a matter of preference. Less teeth will give more acceleration, more teeth will give higher top speed. If you labour the motor by gearing it for high speed and then running at low speed most of the time it will just run inefficiently, resulting in the electronics getting hot and the battery getting drained faster.

A 15t brushed should turn about 30,000-35,000rpm if i'm not wrong. If the XV-01 standard final drive ratio is 8:1, at 100% rpm tamiya rally block tyres will be going about 59kmh. In reality, when actually under load you will probably only reach about 70-75% of maximum rpm so about 42km/h or so. If you put a 15t pinion in then you'd have a top speed of 30km/h and the car would accelerate faster and run cooler.

I would order some other pinions to try anyway just in case it does run too hot on the standard pinion. There are cheap sets of 13t-17t 0.6 module pinions on ebay
https://www.ebay.com.au/itm/M0-6-3-175mm-13T-33T-0-6-Module-Pinion-Motor-Set-Gear-For-1-10-RC-Car-Truck/333281900182?hash=item4d99263696:m:mzyWDetdZanYSm0Eigv8uHw&frcectupt=true

Installing a 30mm motor fan will also definitely help keep the motor cool. Again, hit up ebay for "30mm rc motor fan" to find a cheap one.

Share this post


Link to post
Share on other sites

Just for comparison I recently popped a 15t double running off a Lipo into a TT-02B. It had the 68t speed gear spur and a 19t pinion... It properly cooked the motor running on cut grass! Have since put a 17t pinion and the original 70t spur with a twenty odd year old 19t double with a heatsink and had no more issues. So I would definitely follow the advise above and go down a tooth or so or use a slightly higher turn motor. I realise the buggy's bigger wheels alter things somewhat but thought it might be helpful. The speedo is a Hobbywing 1060 for reference. 

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...