Diff oil for fun and profit!

[Mrowka 496]

Getting ready to build a re re Kyosho Javelin. 

Against my better judgment, I will probably use gear drives in front and rear differentials. Motor will be a 17.5T HW, ESC also by HW. Battery is a 2S, I may go for a 3S in the future. I will build the belt drive version, FWIW.

What weight differential oil should I use? I was planning to use a fairly heavy oil, something 10,000 or higher, but I am open to suggestions.

[ACCEL 2014]

long runs or short?

try 5K- 7K first, 10K's a lil' too thick,

but what do i know ? i'm just Slick

[Mrowka 496]

Probably fairly long runs - it's a basher and not a racer.

[Mrowka 496]

Also, to overthink this further, maybe I should use a heavier oil in the rear differential and lighter weight oil in the front?

[Carmine A 2046]

4 hours ago, Mrowka said:

Also, to overthink this further, maybe I should use a heavier oil in the rear differential and lighter weight oil in the front?

For Competition.... It's usually the other way around. However, if you're after a Basher that you can kick the Rear out when you want to.... 

5K Front, 10-15K Rear.  But I didn't give that advice!! 😜

[Mrowka 496]

4 hours ago, Carmine A said:

For Competition.... It's usually the other way around. However, if you're after a Basher that you can kick the Rear out when you want to.... 

5K Front, 10-15K Rear.  But I didn't give that advice!! 😜

Explain the first paragraph further, please.

[Carmine A 2046]

14 minutes ago, Mrowka said:

Explain the first paragraph further, please.

For most AWD Racing, having a tighter Diff in Front is, most of the time, better for high speed cornering.

If you were asking about "Kicking the Rear out" -  Power Sliding, Drifting, Fish Tailing.... 

Tighter Rear Diff causes Oversteer. 😉

[Mrowka 496]

Also, while we're on topic, how does run time affect the choice of diff oil?

[TwistedxSlayer 1290]

5 hours ago, Mrowka said:

Also, while we're on topic, how does run time affect the choice of diff oil?

Not enough you'll notice.

[Re-Bugged 10156]

I built my Javelin with what was in the box diff oil wise and with the belt. I've never raced so I am definatly no expert on different oil weights. But out the box is my most used car for sure.

I did however start of with a Hobbywing 17.5t Justock brushless motor with a Xerun XR10 Justock ESC, acceleration was good but top end was a bit underwhelming so put a 13.5t of the same type motor in and a 26 tooth pinion in on 2s and that livened things up. Its never thermaled on me which is great as there isn't any room for a fan on the ESC.

 

Just a couple of things that I also did was to make a gasket out of an old servo box between the motor and mount as I found dirt was getting through the motors vent slots into the Spur and Pinion gears.

I also put a dap of Threadlock on the steering linkages as one came loose and locked up the steering when it jammed against the chassis.

I really enjoy the Javelin, they are great buggies.

 

 

[Mrowka 496]

I built mine with 15K diff fluid in the rear and 10K in the front. My kit didn't come with diff fluid, so I got to get creative and stuff.

Build was straightforward, as I said, like a fairly intricate Lego set. The directions are detailed and diagrams plentiful. Follow them to the letter and you will end up with a car.

I used a HW 17.5T motor of some kind and the same ESC you did. I used Fast Eddy bearings all around and also Turbo Optima wheels and tires. The original wheels were too nice to trash. Steering servo is a very fast, powerful titanium gear Hitec, and almost certainly overkill.

Stock 25T gear for now, which is way undergeared, but I didn't want to cook the motor or ESC and I can always add more gear.

Took it out last night for a shakedown run in my rather rough backyard. Car drove nicely, low speed handling was better than I expected. Shocks soaked up bumps well. As you said, acceleration was good but not dangerously fast on the top end. Motor and ESC stayed icy cold.

Managed to lose a screw in the steering knuckle in fairly short order. Replaced it, but I started having problems with steering constantly wanting to pull to the left, no matter what I did with trim. I couldn't find a mechanical problem; eventually the issue seemed to go away after I turned everything off, recentered, and turned it back on.

The transmitter was an eBay special (USD 4.99 used) so that may be the culprit.