Scale Ultra 5k

[Fumey]

If the stars are in proper alignment and work allows, we should be able to attend Axialfest 2019. This has given me inspiration to get my fat ass in running condition. I’m gonna give the 5k a shot. I bought a used Bomber. It’s had some stuff done to it that I’ve undone. I’ve got it ready to go with a SCX 10 trans, 56t spur, Mamba X paired with a Holmes Hobbies 3500kv Puller Pro, Traxxas big bores, some aluminum beef tubes up front with some VP chubs and knuckles, ... I guess I want to know
A) what batteries you 5k guys are running
B) what gearing
C) what makes a 5k rig different than a rock racer?

[MAC FAB]

Certainly there is some sort of rules, otherwise get a 100c and 10,000~mah or better at whatever s count you run. Gonna be expensive, no stopping for fuel. Watch videos of the event and tune your rig accordingly. Being able to keep up with your rig with personal conditioning would be a close second, considering footwear as well.

[gottorque]

I run 5K 3s packs for Ultra events. There is some debate; or rather that some racers choose 2s and some chose 3s. High KV some would likely choose 2s and lower KV choose 3s. I guess my reasoning is that the higher voltage allows me to use less throttle to maintain a constant speed. The longer distances you start to go, the more you want to maximize mAh per mile (but that's getting beyond the subject of 5ks).


I am running a Tekin Roc412HD 3100kv/Mamba X geared rather steep at 54/12 or something like that with my Wraith trans equipped Bomber. However, my advice is to run whatever gearing is on it now and as you progress in training to experiment with rig setup. Majority of rigs competing at any given 5k are Bombers, but all have fairly unique setups.

5K rig verse rock racer- Well they are pretty close in nature in my opinion as guys frequently run both with the same rig. In my case, I only run Ultra with mine and was a little more weight conscious than I typically would with a rock racer. I have gotten away with not running beef tubes in my plastic housings and I run plastic/carbon beadlocks for lower rotating mass. Rock racing you tend to use brute strength to get through rocks quickly, where as 5k/ultra rigs...smooth is fast (line choice). The fast guys at AF this year were right around 1 hour to finish, vs rock racing you got heats and a mains of 3 to 5 laps of letting it all hang out. Not to mention the human endurance factor too, you cant drive your car faster than what you can run

[RockyMtn]

Interesting topic!
I am struggling to find the good combo/gearing (5k doesn't exist at all in France). I am living close to the mountains, so a very fast motor is not suited because I'll never follow it.
After an unsuccessful try with brushed system (550 motor), I'll give a try with a brushless Tekin RS GEN2 with a 21.5t with a 11t pinion in 3S. Goal for next year: The Fix 12h (yes it is a bit different than 5k)

[Chiphead]

One thing I found, I used more battery when I was actually racing (adrenaline was through the roof!) than during training.

I raced in the 2017 Axialfest Ultra5k. During training I would use three 3300 Mah 3s batteries and usually have some battery left. During Axialfest I ran out of battery on the last lap and that was starting with a battery in the car (duh) and two batteries in my pack.

I am running Holmes 3300kv Puller Pro, Mamba Monster X, 12/54 gearing with Bomber trans, aluminum beef tubes, VP knucks and c-hubs, Locked-up RC rear axle shafts, stock driveshafts and Chaotic Racing titanium links. During that race I killed a Holmes SHV500 servo. Now I have a Hitec D951.

After racing with Jake Wright (1st place) and seeing his rig back at camp, light weight is where it is at. He also does a lot with suspension design and tuning.

[RockyMtn]

Originally Posted by Chiphead

After racing with Jake Wright (1st place) and seeing his rig back at camp, light weight is where it is at. He also does a lot with suspension design and tuning.

That's the point: light weight.
My Bomber is almost stock (2 speed and SSD Racer wheels) and I can use 2x 2500mah 3S batteries on 6k. This was with the Quicrun 1080 and HH Torquemaster 550 21t with a 11t pinion.
Now I have to test that with the Tekin RS GEN2 / 21.5T.

[imthatguy]

In both years I only had to make one battery change. I run 3S, 3300mAh packs through an essentially stock drivetrain, stock gearing Bomber. Holmes 3300kv and BRXL. I tend to scope my lines a few metres ahead as I'm running and always take the path of least resistance. I run three to five times a week and spin on the stationary bike when I'm not doing that.

[angrchair]

without beef patties, my bomber weighs 12 pounds! and it's not weighted :/
What is a light weight bomber considered to weigh?

[gottorque]

I'm 7.5lbs without battery. Its still a 'complete' bomber with spare and interior even but did not get drastic with weight savings. I could run smaller 3s packs but I train with 5000s so thats what I use lol.

Also note Scale Ultra specifies you need to use plastic housings for official races, and even outside of that most guys that I know run plastic (tubes ok of course). So for some, switching from metal to plastic could save you quite a bit of valuable ounces.

[Del Monte]

Originally Posted by Fumey

If the stars are in proper alignment and work allows, we should be able to attend Axialfest 2019. This has given me inspiration to get my fat ass in running condition. I’m gonna give the 5k a shot. I bought a used Bomber. It’s had some stuff done to it that I’ve undone. I’ve got it ready to go with a SCX 10 trans, 56t spur, Mamba X paired with a Holmes Hobbies 3500kv Puller Pro, Traxxas big bores, some aluminum beef tubes up front with some VP chubs and knuckles, ... I guess I want to know
A) what batteries you 5k guys are running
B) what gearing
C) what makes a 5k rig different than a rock racer?

I ran a Protek LiHV 3600 pack in this year's race. It's borderline but possible to do the whole thing on just one pack. I would definitely have a spare or two ready just in case.



I run a Mamba X with a 3500kv Puller Pro. SCX10 trans on a High Altitude Performance skid geared 14/54 with UD gears in both axles. Everything has to be SMOOTH to get good runtime and not have any issues. Driveshafts, gears, bearings, etc need to be fresh and smooth.



The biggest things I change between 5k and U4 setups is the stiffness of the suspension and the gearing. In a 5k, you really can't drive much faster than you can run. You don't need a truck that can go 30mph or land smoothly off a 15' double. I run softer springs and lighter oil on the 5k setup so that the suspension can cycle faster at slow speeds in the rocks and not bounce everywhere.

[RockyMtn]

Could be a silly question: tire recommandation!
I was wondering what would a good 5k tire. Because you don't need an agressive tire; it seems that the Axial BFG Baja are well suited for this application

[imthatguy]

Grip is definitely important. There's enough obstacles that you need to contend with, so I choose the ProLine Hyrax 2.2.

[RockyMtn]

Originally Posted by imthatguy

Grip is definitely important. There's enough obstacles that you need to contend with, so I choose the ProLine Hyrax 2.2.

Thanks for the feedback!

In fact I had in mind an event like The Fix. The tracks are "smoother" than a 5k event, so I imagine in this case you are more thinking about battery consumming.

[Fumey]

Just glued some Hyrax’ up last night! Those are some tall tires! I glued them to some Crawler Innovations 1” plastic wheels for a weight difference of about 5oz. less than the stock set. Trying to keep it light as possible. Which makes me question why I see so many spare tires in all the pictures I’ve searched. I can understand the need to balance it out for jumps, but that’d be more for rock racing?
Thank you guys, this has been a big help!

[Del Monte]

Originally Posted by Fumey

Just glued some Hyrax’ up last night! Those are some tall tires! I glued them to some Crawler Innovations 1” plastic wheels for a weight difference of about 5oz. less than the stock set. Trying to keep it light as possible. Which makes me question why I see so many spare tires in all the pictures I’ve searched. I can understand the need to balance it out for jumps, but that’d be more for rock racing?
Thank you guys, this has been a big help!

Big tires like Hyrax are nice in rock gardens I'm a big fan of KLR's too, they definitely hook up at speed.


Spare tires look right and help balance out most trucks at speed. A little bit of extra weight further back in the chassis helps get rid of some of the twitchy-ness of the stock setup.



Light wheels, tires, and axles are the name of the game for 5k's or long races like the Fix. Totally opposite of how we normally run crawler setups, but the idea is that a truck with less unsprung weight/more sprung weight will be smoother and bounce around less.

[RockyMtn]

Lots of good feedbacks for the Hyrax. With new batteries, this will be my next updgrade. I am more and more thinking giving a try to the Voodoo U4. Love the tread pattern