Kronos XTR Horatio's XTR Build

[Horatio]

So finally, here they are:

Beautiful parts with a good finish. I noted with interest that Corally labelled their own parts incorrectly - so no wonder suppliers don't know what to do! Because the parts are handed - if you ever need just one side - order both, just Incase. You can't just flip them over because they're countersunk.

WCF parts need to be sealed. It's the law! So, Sharpie followed by Zap CA. I used thick this time, but usually I use thin.

Cotton buds (Q-tips) used to apply the CA. Be careful with plastic ones, CA can give off cyanide gas.

All the arm stiffeners can be fitted without removing anything - bar the shocks (at one end). On my rig, I needed to remove the rear mudguards.

Edit to add: The M2.5 screws are fairly tough to get started, so it's best to ream the holes slightly and then get them started with the screws before fitting the inserts.

Get screwed. Get screws!

Oh yes! The XTR is certainly a looker. I've always thought the XTR looks the most 'exotic' of all the basher Truggy platforms. These certainly add to that and make the arms less flexible. From a driving point of view, this should make the car feel more responsive.

The 21 XTR - a rare 'naked' shot - ready for more speed runs!

Whilst checking the suspension, I noticed that if the front suspension arm spacers (for changing caster) whilst in the rear position (for less caster) are allowed to swivel on the pivot pin - with the tab pointing downwards - these will 100% foul the steering/Ackerman plate.

I'm thinking of putting some fuel tubing between them - lug to lug - to mitigate the issue - keeping the lugs upwards at all times away from the steering.

 

[Horatio]

Took the XTR out today. It ran flawlessly and was very, very fast.

It did 0-60mph in a respectable time too.....

18/52 gearing. Gens 6S. Rocket 4292 1780kv Motor

And there's more to come.........

 

[Jeffwazz]

The carbon definitely makes it faster!

How stiff would the Kagama HD arms be compared to the original Kronos?

 

[Horatio]

The carbon definitely makes it faster!

How stiff would the Kagama HD arms be compared to the original Kronos?

The Kagama arms have been beefed up. Even compared to the V2 parts on the Kronos, the Kagama is beefy and has a more central driveline.

I could flex the arms whilst inserting the 3mm carbon stiffeners.

They don't flex any more. This ideal for tarmac use, perhaps not so ideal for rough use/bashing.

It drives really nice. Even with those big, heavy Jetkos.

 

[Horatio]

So my gearing and rollout calculator gave me a very accurate expectation of speed with both the T2E and the XTR. In fact, the calculation for the T2E on 15/48 and the sweep tyres was within 0.3mph. On the XTR, it came within 4mph. The real world differences were for some reason smaller with the Sworkz than with the XTR.

To calculate bottom line numbers, the process is:
1) Enter pinion & spur teeth value. 2) Enter transmission input & crown teeth values. 3) Enter tyre diameter/s in mm. 4) Enter battery voltage. 5) Enter Motor Kv. 6) Enter roll-out in MM/Rev.

The roll-out is calculated from the data entered from at stage 1, 2 & 3 and auto populates fields for 8 different pinion sizes, 2 different spur sizes and 2 different tyre sizes.

Optionally, battery voltage, motor KV and rollout can be entered in the data at stage 4, 5 & 6 which then accurately calculates top speed in MPH and KPH for 2 different setups so you can compare side by side.

Now I know the real world values for my XTR, I could easily enter an offset of 4mph and get even more accurate results. Based on this, I decided to go all out and fit the 19t Tekno pinion with the 52t spur, and relieved the motor mount to enable the mesh to be adjusted appropriately. According to the calculator, this should give a theoretical top speed of 76.70mph on the Jetko tyres and the 1780kv Rocket motor. If I offset the 4mph from the testing at the weekend, I can confidently expect 72mph in similar conditions.

On 19/46, would anyone like to guess?

The front upper suspension arms need to be slop free to track accurately.

4x6x0.2 and 0.1 stainless steel shims work perfectly to remove the slop on 4mm pivot pins.

Adjustments made to motor mount allow 19t pinion to mesh with 52t spur.

Motor temps stayed below 115°F after multiple passes last time. Let's see how it manages on 19t and a higher voltage battery.

Front driveshaft is due for replacement and will likely not survive more than a few more packs.

0-60mph times obviously get slower as the gearing gets taller, so the XTR will be the rig to pull higher gearing and get the top speeds.

The lighter, nimbler T2E will be geared for 0-60mph runs with smaller motors like the 1515.

 

[Horatio]

Hauling ass on big, sticky, belted road tyres takes its toll on driveline components. None more so than the centre front dogbone - because of the angle that it takes between the centre diff and front diff.

Note that there appears to be much confusion over part numbers and their descriptions:

This seems to be a recurring theme. Retailers/Distribution centres seem to list parts with the wrong description.

In other instances, with handed parts, in particular with CF arm stiffeners, the descriptions on the packet stated 'Left' when in fact it was a 'right' handed part. Thankfully, the right handed part was also incorrectly labelled as a 'left' - so provided you order both parts, you should end up with what you need.

Anyway, this got me thinking. Whilst the Kronos XTR is a fine rig, what it really needs is a revised chassis. One might argue - Corally have already done this with the Kagama. True enough. But what I'd like to do is get a precision chassis fabricated out of quasi lay-up woven Carbon fibre, with 100% straight driveline. Then bolt the ends back on. If the chassis has to be a bit wider to accommodate stuff, so be it.

 

[Horatio]

New driveshaft is 1-2mm shorter than the original item.

Dogbones with replaceable pins might be a cool idea - especially for the centre front. I'm happy to replace the dogbone or dogbone pins, rather than drive outputs/inputs. The harder HD outputs wear the dogbone quicker than the original black items.

Before:

After:

This angle might be the reason why the Kronos is 4mph away from the calculated speeds, Vs the same calculations with the T2E which are only 0.3mph away.

Either way, improving driveline angles should really help with the wear that's generated and I think a sexy, woven carbon fibre chassis would elegantly solve the issue, improve weight distribution and provide some more space for.....going faster.

 

[AngrySection8]

Took the XTR out today. It ran flawlessly and was very, very fast.

View attachment 6103
View attachment 6104

View attachment 6105
It did 0-60mph in a respectable time too.....
View attachment 6106
18/52 gearing. Gens 6S. Rocket 4292 1780kv Motor

And there's more to come.........

Looking to do some 0-60 this weekend, I'll post my times when I do it, got the asuga ready so hopefully I'll find time today as they're talking yet another round of severe weather for my area tomorrow, getting ridiculous, been non stop tornadoes in my area for about a month

 

[Horatio]

Looking to do some 0-60 this weekend, I'll post my times when I do it, got the asuga ready so hopefully I'll find time today as they're talking yet another round of severe weather for my area tomorrow, getting ridiculous, been non stop tornadoes in my area for about a month

Good grief - sorry to hear about your extreme weather events.

I'm really looking forward to seeing your 0-60 times. IMO, it's just as challenging - if not harder - than getting good top speeds.

Good luck & keep us posted!

 

[AngrySection8]

Good grief - sorry to hear about your extreme weather events.

I'm really looking forward to seeing your 0-60 times. IMO, it's just as challenging - if not harder - than getting good top speeds.

Good luck & keep us posted!

Yeah it's getting old, lost roofs on 3 of my hog confinement buildings, which I'm not complaining considering some of the devastation I've seen elsewhere.
I'm definitely interested to see the 0-60's, never messed with that feature on the gnss so it'll be interesting to see, currently got the asuga set for 66mph per the calculator but with voltage sag and some tire expansion it's hard to say, it should hit the 60mph every pass at least to get some times

 

[Horatio]

Yeah it's getting old, lost roofs on 3 of my hog confinement buildings, which I'm not complaining considering some of the devastation I've seen elsewhere.
I'm definitely interested to see the 0-60's, never messed with that feature on the gnss so it'll be interesting to see, currently got the asuga set for 66mph per the calculator but with voltage sag and some tire expansion it's hard to say, it should hit the 60mph every pass at least to get some times

View attachment 6173

Crikey! Scary stuff.

Were your pigs alright?

With 66mph on your calculator, you should hit around 62mph I reckon. That's got to be spot on.

 

[AngrySection8]

Crikey! Scary stuff.

Were your pigs alright?

With 66mph on your calculator, you should hit around 62mph I reckon. That's got to be spot on.

Yeah, they all survived.
And I'm guessing you're probably pretty spot on, previous gearing claimed 63 and gps put it right at 60, I added 1 tooth just to make sure it would hit the 60 pass after pass

 

[Horatio]

@AngrySection8 - Well - I did 11 0-60mph runs today with the T2E.

See what you can do with those times.

 

[AngrySection8]

@AngrySection8 - Well - I did 11 0-60mph runs today with the T2E.

See what you can do with those times.

Here ya go, power wise it's got a lot more left in it, I only charged the batteries to 3.9v/cell and I've got the esc turned down pretty good to attempt to grab traction but traction is definitely my biggest issue

 

[Horatio]

Here ya go, power wise it's got a lot more left in it, I only charged the batteries to 3.9v/cell and I've got the esc turned down pretty good to attempt to grab traction but traction is definitely my biggest issue

View attachment 6194

View attachment 6195

Crikey moses! That's insanely fast. What ESC and Motor are you using?

 

[Horatio]

I was a lot less conservative. All my batteries were charged to 4.2v, running 6S, and my punch setting on the Castle MMX for the 1515 was at the default setting.

Every run was purely manual control, no stability aids. My tyres can light up easily, especially if their temps are under 80°F.

I'm very impressed with your times.

 

[AngrySection8]

Crikey moses! That's insanely fast. What ESC and Motor are you using?

Castle mmx8s and the same motor you're running in your xtr just the 1500kv variant. Those runs were on the stock knobby tires, didn't want to risk blowing a method pushing it like that, on that car the esc is set to low take off, 60% punch, and I have a small curve in the throttle, it's capable of so much more if a guy could plant the power, 8s is no joke, she's a violent car

 

[Horatio]

Castle mmx8s and the same motor you're running in your xtr just the 1500kv variant. Those runs were on the stock knobby tires, didn't want to risk blowing a method pushing it like that, on that car the esc is set to low take off, 60% punch, and I have a small curve in the throttle, it's capable of so much more if a guy could plant the power, 8s is no joke, she's a violent car

Copy that! 8S - 1500kv = insane torque. Nicely done.

 

[AngrySection8]

Copy that! 8S - 1500kv = insane torque. Nicely done.

Here's a 6s run on a different buggy, had to do a 0-55 on it though as it only tops at 58mph, castle 6s esc, 2200kv but the older non sensored one, running grp's for tires, this car hooked well hence the much higher g rating, ironically it did the exact same time but again 0-55 not 60

And here's the log from the asuga, as you can see it wasn't even working, there's a lot left on the table with it but no sense turning it up if it's just gonna blow the tires off

 

[Horatio]

Here's a 6s run on a different buggy, had to do a 0-55 on it though as it only tops at 58mph, castle 6s esc, 2200kv but the older non sensored one, running grp's for tires, this car hooked well hence the much higher g rating, ironically it did the exact same time but again 0-55 not 60

View attachment 6196

And here's the log from the asuga, as you can see it wasn't even working, there's a lot left on the table with it but no sense turning it up if it's just gonna blow the tires off

Loving the 1.24g