Need help deciding...
 

Well, the time has come to commence my BL Savage procject...

Here are a few quick notes on the project:
-I plan to keep the 3 speed tranny
-Use a mechanical brake (untill I open up the tranny and figgure how to remove the one way)
-I plan to run 6S lipo or more (unless someone can convince me to run NiMh)

Basically I need help deciding on a motor/speed controler combo...

Now, I was always under the impression that the Bigmaxximum was a more powerfull and faster motor than the Feigao XLs... But is it worth the extra cost?

I currently have a few 1/18th scale trucks and cars running mambas and lipo... I absoloutly love the power my CRAY M18T with a compX motor and 3S has... I would like a similar (a bit slower obviously) power to weight ratio with the savage...

Now at the moment I am thinking about doing the following setup:
Feigao 7XL and a BK 9920.. Do you guys think that will be enough power, or can you recommend somthing else... I all honesty I would like to keep the motor/controller in around $4-500 tops.

With the Feigao XL, 15t pinion, 49t spur gear, 6S lipo with an estamated 20% driveline loss through the 2 speed tranny (I have yet to find the ratios for the 3 speed) the truck should go an estamated 46MPH with the motor at about 43000RPM.

Now, I read the BK with the new software is capable of up to 100000rpm and up to 20 cells (24v). Would I be ok running the 6XL motor, basically it will have the speed for sure, but will it have enough torque to wheelie and accelerate extremely quickly? Also, will the 9920 be able to handle the 6XL?

Now, I am open to ANY AND ALL suggestions, comments, recommendations. I am here to learn, so send them all my way :027:

This is the kind of performance I am looking for: http://www.rcpics.net/view_single.php?medid=70437

A bit more top speed would be nice too...
For run time I want 15-20 minutes... I would be EXTREMELY satisfied with 30 minutes.

6s on a 7xl will be pushing a lot of RPMs. I think I would go for a 8XL like in the video o even a 9XL.

That truck's owner is on this forum. I have seen the video before. I think he has a two speed in it. With a 8xl and the same gearing the 3 speed is 10% faster and has a 10% lower first gear as well. I think 6s on a 7xl well create heat problems. 8xl should put you at your runs time but it depends on the mah of the batteries.

One guy on the forums (can't remember his name) runs an 8XL on 20cells in his truck. He reckons the speeds are about 60mph. Personally I would reccomend the 9XL for this kind of voltage, as it will run a bit cooler and still push 50-55mph. With 4000mah lipos you should get 20-25minutes of runtime - maybe more/maybe less.

I've got an excell spreadsheat to calculate speed in first gear and 2nd gear using stock tires and stock gearing on the truck with 15:49 pinion:spur.
24V on the 9XL motor is only good for 39MPH in second gear with an assumed 20% speed loss due to aerodynamics and driveline friction .....

8XL on the same setup is good for about 44MPH with an assumed 20% loss as well...

I'd really like to be in the TURE 60MPH range, not the "I think it goes about 60".

To realistically do 60MPH in a savage with stock gearing your motor NEEDS to be turning just shy of 70000RPM.

Would an 8L have enough torque to move the truck well? An 8L at 22.2V is 68000RPM and would bring the truck to 60MPH with the assumed 20% loss.

The 8L can't even take 22.2 volts, let alone is has an rpm limit around 60,000 rpms. You have to realize, once you start dealing with high voltage and torque, you can gear higher than converntionally and mathematics won't always work out to the realistic in truck speed. An 8L, 6XL and 7XL would all be expensive toast on 22.2 volts with the warrior. Go with an 8 or 9XL. You'll be pleasently suprised when you see speeds higher than what you've calculated. Also, try controlling a 10lb beast moving that fast, good luck.

I know math will not get my an exact speed, but the motor and truck will never go faster than what I've calculated unless my calculations are wrong or the motor specs are wrong. Energy losses are always possible, energy gains are not.

With the 8XL geared to the sky with the fastest readily available pinion and spur combo (20t:47T) the truck will still only do 56MPH.

Can someone maybe recommend a different ESC/Motor combo that will be capable of higher RPM and still have torque or even handle higher voltage.. I've got nothing aginst going to 12s lipo if I can, actually it would be very nice...

Like I said, I'm aiming for the same or close to power to weight ratio that my 1/18 XRAY M18 and my RC18T have with a 2480MAH 3S lipo and Mamba CompX motors at 8000kv.

A guy named promod here has did an experiment. He took a little motor and a big motor and ran on same batteries to see the speed. It takes about 2000watts of power to reach like 60mph. You will need a big motor to handle that power consistantly. The name of that thread is david vs goliath. I think any way. look it up and read it. If you want all that I may suggest a 2240 or so. Use lipos for weight. About 8s should put you there. but you need to step the gearing up. If you run a 9xl or 8xl on a savage you need to run more gearing the 15 49. I would say 18 49 or so.That is just a guess.

Here it is: http://www.rc-monster.com/forum/show...=david+goliath

I'll start reading now :)

And, the plan was to go with lipos from the begining.. I've always run lipo in all my brushless cars.

Interesting read... So basically go with the bigger motor with lower Kv and gear it up...

Where can I get a Lehner 2240? I think he said the 2240 will work with the 9920 ESC, is that right?

But the 9920 will only do 24v. Can you recommend an ESC that can handle a 2240 and do higher voltage.. Just incase one day I want to go faster ;)

The 2240 can be got from mike. Just drop him an email. He will have to order it up. You can make the motor mount in the mean time. The 2240 has 4mm mounting screws and are farther apart.

Is the 2240 physically larger than the 8Xl? Can is still be fit low in the chassis like I was planning with the 8XL?

What's the price like on the 2240?