Savage Flux Conversion to 1717, Center Diff, XL Length, Mech Brakes

[rcs2022]

Have been enjoying the RC for less than a year now, this forum has provided a lot of insight to the hobby through its members and their great conversions, tips and experience. I feel I need to return something back by posting my humble conversion. Please remember this is my first Conversion with minimal tools; In fact my first RC truck, not counting my sons MLST.

Lots of ideas have come from different conversions and forum members, a thanks to all.

It started with the need for more power and a center diff. I enjoyed my standard Flux a lot, but wanted to lessen the wheelies and of course more power. I pefered to do it the custom way as much as possible. And obviously with the recent Castle Creations sale; got my self a 1717.

Design Considerations:
To limit Wheelies, i thought of 2 things; Motor Forward as much as possible, and a center diff.
Moving the motor forward and reversing it, the steering servo had to be relocated.
Batteries for now will remain in the side trays.
I got the HPI Racing Wheelbase Conversion Set Savage Flux; # 102404, I am aware of the many aftermarket TVP's available and motor mounts, but decided on a bit of challenge and decrease the cost. Another thing for the price of HPI # 102404 it includes the 4x widened axles also, i happened to have them on my Flux and broke one of them; now i have 3 spares ;)

I used a hot bodies diff which I got cheap on ebay, hope it holds; may upgrade later after everything works out fine.
Obviously I will be using the monster mamba ESC of my stock Flux
Intention of using mechanical brakes to lessen the load on the ESC, this will come later.

For starters here is the general idea:



Another view:




Comments, Feedback and Ideas Most Welcome!

[rcs2022]

I am a bit ahead in status, but want to go through the steps.

Here is a blowup of the parts for the center diff and motor support:



I'll be using 3mm Alum plates attached to the TVP's; 6mm top and bottom alum plates for supporting the center diff; and 6mm motor mounting plate. the motor will be supported on the back plate using 4 screws; 3 screws going through the 3mm plates will be used for mesh adjustment.



Mechanical brakes will come later, but here is the general idea. Will have to mount the springs on the other side; and probably gotta notch the back 6mm motor plate. Haven't tried mech brakes on a brushless setup before, i dunno if while ESC is in forward does the servo rotate as if applying throttle in a nitro?

[rcs2022]

Well on with the build.

Here are the first cut plates:



First test assembly, to check alignment.



I offset the Motor and Diff as much as possible to lower the motor as much as i can, to achieve a lower CG.

[rcs2022]

Now with the first test fit, I used the XL rear dogbone in the front and found a 109mm dog bone at my LHS fit perfectly, even with the offset motor and diff. Servo already relocated as shown.

[rcs2022]

I supported the whole mount with motor and diff using 6 screws going through some holes in the TVP's and even used the rollbar screw as a support also, I tapped the 3mm plates for easy installation and dismantling. I like how low the motor is. The mesh adjustment moves the motor up and down, so as i gear up the motor has to be raised, buts its minimal. now installed with a 15mm pinion and 50 spur.



View of the rear, hoped by lipos would fit there. actually they don't.



View of the Front. The Motor actually clears the TVP's by a mm.



And please excuse the cleaning of the truck and the crude cuts in alum Was anxious getting everything together and testing. Will grind and file the pieces later on.

Also to mention the servo arm clears the motor; here the servo is at full swing. hoped i could swap the dogbones to move the motor more forward but they would get in the way of the servo arm.

[coolhandcountry]

Why is your plans to keep the Mechanical brakes?
They wouldn't be needed really.
Oops missed that one piece.

[rcs2022]

Originally Posted by coolhandcountry

Why is your plans to keep the Mechanical brakes?
They wouldn't be needed really.
Oops missed that one piece.

As my current plan to run the 1717 on the MMM 5S at first and then 6S, heard a lot of mixed opinions about the 1717 and MMM, thought to go safe, and plus i liked the challenge. Wouldn't you think it relieves the ESC of additional stresses.

[rcs2022]

Now on with the electrics, installed the MMM,



Took it for a test run, with the following setup:
5S 2S + 3S Turnigy 5000 mah 40C Lipos
15t Pinion
50t Spur
GS Wheels and tires, close to mashers 3.2 in size and weight (150mm dia)
put the lowest settings on the MMM especially brakes
Punch 100%
motor timing lowest
Brakes 30%

Well everything was fine in the first couple minutes, still not going full WOT. And all of a sudden the MMM smoked!

According to my calculations the gearing is close to a standard Savage Flux. Gearing was for around 96 Km/h around 59 mph. Anyway long story short, got the courage and hooked up my other MMM, and guess what, it was great. got more courage and went WOT, this 1717 is really impressive! cool temps, plenty of torque, and with this setup wheelies were minimal.
Seems will have to send my new smoked ESC to Castle.

EDIT: gearing is for 96 km/hr on 6S, assuming 3.7 Volt per cell, with the 5S run gearing is for around 79 km/hr

here are the eagletree graphs of my run:



same graph but zoomed:



What impressed me was the temps of the ESC, (hadn't hooked up the motor temp sensor yet )



Here is where i need some opinions and comments!

Should i gather more courage and try 6S?
I like speed, so how high can i gear up safely? this motor should have plenty of reserve torque.

The controversial part, will the Mamba Monster (MMM) extract all the power of the 1717, i know its rated for 120 Amps, and more for short bursts, but the 1717 also if i recall correctly is rated for 2000W (4000w surge) or should i invest in a bigger ESC?

Mamba XL, Phoenix ICE 200, or a Hydra Ice?!

Given the 45,000 rpm limit of the 1717 can it be run on 7S or maybe 8S?

[coolhandcountry]

It could have been a bad part in the esc.
Good to see you got it going though.
Why did you change the timing before testing?

I had the same experience with 1717 and mm, its extremely important to use high discharge batteries and good connectors, like the castles 6.5mm. i also recommend a cap bank and gear it closer to 70kmh.. the 1717 is just brutal power wise.


btw nice project, fun to see custom builds.

[fastbaja5b]

...this is why I abandoned the MMM (Which I am very cautious on at the best of times) and went the MMXL, and I'm only intending to gear for 40mph on 6s (granted at 5b length)

[rcs2022]

Originally Posted by coolhandcountry

It could have been a bad part in the esc.
Good to see you got it going though.
Why did you change the timing before testing?

Its just that i was fiddling a lot with the settings when it was still stock with the 1515 2200kv motor, and thought as a start to get everything back to normal settings while trying the 1717. Is there a recommended timing for the 1717 with MMM, i went with the lowest for my first test runs.

[rcs2022]

Originally Posted by freddy

I had the same experience with 1717 and mm, its extremely important to use high discharge batteries and good connectors, like the castles 6.5mm. i also recommend a cap bank and gear it closer to 70kmh.. the 1717 is just brutal power wise.


btw nice project, fun to see custom builds.

Honestly, got the Cap Pack, just need to install it. my batts are Turnigy 5000mah 40C should be able to give 200 amps continuous, or close. Well given the graphs posted earlier, I think i will keep it there, i mean my temps are fine till now. Will have to do more rigorous testing, WOT back to back continuously, and I'll report them back.

And THANKS for the encouragement

[rcs2022]

Originally Posted by fastbaja5b

...this is why I abandoned the MMM (Which I am very cautious on at the best of times) and went the MMXL, and I'm only intending to gear for 40mph on 6s (granted at 5b length)

I understand, how much does your truck weigh?
just weighed mine:
truck with body; no wheels and no batteries 4436 grams
tires and wheels 1163 grams
Batteries (5S) 770 grams
so all in all 6369 grams = 14.63 lbs full load, including eagletree and gps module (i know they are negligible but just for accuracy)

[rcs2022]

Edited Post #8
EDIT: gearing is for 96 km/hr on 6S, assuming 3.7 Volt per cell, with the 5S run gearing is for around 79 km/hr.