New C cordless drill

[mastercabman]

I was at my local Woodcraft store today,pick up a new sanding pad for my Rotex and checked out the new drills from Festool.
They felt pretty good in my hand.I like the light,the weight and the fuel gauge.
One thing i noticed on the C drill is that the torque control wheel when turn to a lower number,the speed also decrease.(in the driving mode)  At first i was thinking that it was a speed control but the guy there told me it was the torque selecting wheel.
Why is the speed slower as you select a lower torque?

Also, i am thinking of either buy a new drill or get new batteries for my 6 years old C12's.The first drill,i got the 3.0 ah battery kit then i got the 2.4 ah kit.2 years ago i replaced 2 of the batteries and now it seems that the batteries are not holding the power that it used to be.My drills are doing ok for now.My question is,how good are Li Ion batteries?Are they really worth it?
I am thinking that maybe it is time for me to get a new drill with the new technology.
Any input would be great.

 

[Brice Burrell]

The logic must be if you need a low torque setting you're working with something delicate and a reduced speed would help control the results.

You'll also need a new battery charger if you decide to upgrade to lithium batteries.  A new charger and a couple of batteries might be costly enough to make it worth considering a new drill.  My T15 drills are about two and half years old now and the batteries are doing very well.  There is of course a small degradation in their performance over that time.  So far so good but time will tell. 

 

[AlexThePalex]

Why is the speed slower as you select a lower torque?

The speed is slower with a higher torque because speed and torque are related to each other, inversely. The force of the motor is transferred to the bits by gears. Look at the picture below.

[attachimg=1]

If you look at the gears on the left you can see they are the same size. Since one tooth of the top gear moves one tooth of the bottom gear they both move at the same speed and with the same torque. One turn of the top gear means one turn for the bottom gear.

But with the gears on the right, the bottom is double the size of the top gear and also has double the teeth. Since one tooth of the top gear moves one tooth on the bottom gear the top gear now needs to make two turns before the bottom gear is fully turned. As a result the bottom gear runs at half speed compared to the top gear. But it has double the torque because the difference in size between the two gears works as a lever.

[attachimg=2]

The point where the two gears touch their teeth is the point where the man in the picture above pushes, and the axle of the big gear is the pivot point (fulcrum). By applying a small force on the long end of the lever you create a bigger force on the short end of the lever, while it turns around the pivot point. See pic below.

[attachimg=3]

 

[mastercabman]

Why is the speed slower as you select a lower torque?

The speed is slower with a higher torque because speed and torque are related to each other, inversely. The force of the motor is transferred to the bits by gears. Look at the picture below.

[attachimg=1]

If you look at the gears on the left you can see they are the same size. Since one tooth of the top gear moves one tooth of the bottom gear they both move at the same speed and with the same torque. One turn of the top gear means one turn for the bottom gear.

But with the gears on the right, the bottom is double the size of the top gear and also has double the teeth. Since one tooth of the top gear moves one tooth on the bottom gear the top gear now needs to make two turns before the bottom gear is fully turned. As a result the bottom gear runs at half speed compared to the top gear. But it has double the torque because the difference in size between the two gears works as a lever.

[attachimg=2]

The point where the two gears touch their teeth is the point where the man in the picture above pushes, and the axle of the big gear is the pivot point (fulcrum). By applying a small force on the long end of the lever you create a bigger force on the short end of the lever, while it turns around the pivot point.

Alex,thanks for the drawing but i'm not talking about changing gears.
On the drill there is a torque stop control selector wheel.You adjust the torque and the drill will stop at that setting.When i set the wheel on a lower # the speed was decreased.Not happening on my C12.
Also,when i tried the new T18 i don't recalled if it did the same thing.

 

[mastercabman]

The logic must be if you need a low torque setting you're working with something delicate and a reduced speed would help control the results.

You'll also need a new battery charger if you decide to upgrade to lithium batteries.  A new charger and a couple of batteries might be costly enough to make it worth considering a new drill.  My T15 drills are about two and half years old now and the batteries are doing very well.  There is of course a small degradation in their performance over that time.  So far so good but time will tell.   

Brice,thanks.I already have a charger that will charge the new battery(I had to buy one when one of my charger died after been pluged to a bad generator)
As far as using Li-ion batteries,you have not see any major draw back?

 

[AlexThePalex]

Ahhh, duh, was thinking you were talking about the switch. [doh]  [embarassed]

Must be done for better control then, as Brice said.

Btw, the old C12 can't take Lithium batteries, if you want to get Lithium batteries you'll have to get a new drill.

 

[mastercabman]

Btw, the old C12 can't take Lithium batteries, if you want to get Lithium batteries you'll have to get a new drill.

That is what i'm trying to decide.New drill or buy 2 new batteries for my old C12.

 

[Brice Burrell]

Ahhh, duh, was thinking you were talking about the switch. [doh]  [embarassed]

Must be done for better control then, as Brice said.

Btw, the old C12 can't take Lithium batteries, if you want to get Lithium batteries you'll have to get a new drill.

[doh] [embarassed] Alex is right, I forgot the old drills can't use the new lithium batteries.

......As far as using Li-ion batteries,you have not see any major draw back?

Well, they don't preform well when cold.  That's not really a big problem for me since I share their aversion to working in the cold.  If you do leave them in the truck overnight in the winter throw them on the charger to warm them up.  Using them in the cold isn't a problem as long as they don't sit idle for too long. 

Other than the issue of the cold I haven't found any shortcomings.