Savage 2 speed tranny gearing? - RC-Monster Forums

jhautz · **Savage 2 speed tranny gearing? -** 04.08.2007, 02:56 AM

Just doing some quick math on gearing for a savage. I know what kind of gear ratios I can run on mt maxx and revo, so I'm assuming I can run similar overall gear ratios on the Savage I going to start. One thing I'm not sure about is the 2 speed tranny. I'm planning on keeping the 2 speed...at least to start.

If I set up the over all gear ratio in frst gear to be slightly lower than I would normally run in my maxx, that would set the second gear ratio to be slightly higher than I would normally run in my maxx. I'm thinking that this should allow me to run with overall higher top speeds but still draw lower amp loads in low end acceleration. This is the upside of the 2 speed tranny.

What are the downsides of keeping the 2 speed tranny? I have read in a few threads that some have locked it in 2nd gear. Is the only benenfit of this less moving parts to break? Just trying to understand why some would do that since there doesnt seem to be a benefit to eliminating it.

Serum · 04.08.2007, 03:02 AM

only downside is that you need to use an extra servo, Y cable and the mechanical brake.

another thing that was rather annoying to me; with a 'direct drive' you have got better air control when jumping than with a mechanical brake. Especially when you are using the HPI dual disc brake. Which is not a brake, but just a way to immediately stop the wheels from turning.. (metal to metal is a big nogo in braking) this lame design is the result of the cheap servo's HPI is using. By only looking at the brake lever the truck will flip over. (worthless IMO)

with a good brake and a fast servo on it, the aircontrol will be perfect.

jhautz · 04.08.2007, 04:08 AM

What kind pinion/spur gear ratio do you run with the 2 speed? I'm guessing I'll be starting with the 49/20, but think I could easily fo 49/24 without any issue. Again... This is based on known overall gear ratios that work for me on my maxx and revo.

Serum · 04.08.2007, 04:10 AM

what motor?

jhautz · 04.08.2007, 04:16 AM

For now a 9XL on 5s or 14 cells depending on what I'm doing with it at the time.

Serum · 04.08.2007, 04:31 AM

Here, i always find this handy to calculate it and save to your puter..

http://rc.stuurmijmail.nl/calculators/speedsavage.xls

jhautz · 04.09.2007, 06:27 PM

Thanks Serum.

I have a similar sheet that I use for calculating gear ratio and speeds.

I was actually wondering if you had any real world input from one of your setups.
It probably doesn't matter though. Every truck is different depending on the motor, batteries, tires, weight, etc... I should be able to get a decent base line from the overall gearing I run in the Maxx and Revo.

Just wasn't exactly sure how much the 2 speed would effect the motor and ESC temps. Was thinking that running an overall gear ratio for the Savage 2nd gear that I normally would run in a single speed setup might undergear the it for first gear and cause the motor to run hotter. Then on the flip side, gearing it up to get similar overall gear ratio in first gear would overgear 2nd gear and cause ESC temp issues.

I'm sure it won't take me long to figure out, just looking for a base line to work from is all.

pb4ugo · 04.10.2007, 12:33 AM

Where can you get a pinion larger than 15 tooth? I see you saying you will use a 20t, and I've never seen those.

jhautz · 04.10.2007, 01:02 AM

Quote:

Originally Posted by pb4ugo

Where can you get a pinion larger than 15 tooth? I see you saying you will use a 20t, and I've never seen those.

Right here in the rc-monster store. Page down to the mod1 5mm bore pinions. After 15T they only have even numbers, but they go up to 24T

http://www.rc-monster.com/gears.php

pb4ugo · 04.10.2007, 01:07 AM

Wow, don't I feel silly, I only saw the hardened ones that go up to 15t. Thanks.