Kronos XTR Horatio's XTR Build

[Niekname]

For the kick up, maybe you could create a plastic "wedge"? don't see why it wouldn't work, maybe you would also need a custom skid plate to make it look somewhat normal. Just an idea. And do you already have a layout in mind?

 

[Horatio]

For the kick up, maybe you could create a plastic "wedge"? don't see why it wouldn't work, maybe you would also need a custom skid plate to make it look somewhat normal. Just an idea. And do you already have a layout in mind?

You're right - I could alter the kick up, purely by adding/removing wedge shaped spacers under the pivot blocks.

On 4WD off road cars, the kick up seems to vary from as little as 1° to 6°.

The main impact on this angle is on the overall caster angle. But I can add some of the lost caster on the upper arms.

Reducing kick up is normal for on-road cars, so 0° isn't wrong as such, it just isn't typical for a 4WD off roader. I may even find I have more responsive steering. For speed runs, I don't think I'll be negatively impacted by the absence of kick up at all. The only mild inconvenience is mitigating the steering linkage geometry due to the changes, but future Horatio can figure that out.

Perhaps for off road stuff, I'll be looking enviously at the Scorched carbon/alloy hybrid chassis for Kraton, wishing that they did something like that for Kronos.

I have a good idea in my mind what it's all going to look like. The motor will be closer to the centre line, and slightly further forward. This will make way for more powerful, longer, 6000w TP motor/s.

The steering servo will be moved in, where previously there was a dogbone, and it will be straight, rather than on the wonk.

The radio box will no longer be part of the servo mount. It will be a separate, mounted and waterproof item.

The battery mount will be removed, along with the side guards. These may not be put back on and replaced with something else.

The rear part of the chassis will be more generously proportioned, possibly to make room for 2 batteries and a larger ESC.

The transmissions will be running with alloy cases, with ceramic oversized bearings.

It's all a matter of money, the time to earn that money, then the time to smuggle in parts, then the time to fettle those parts into an operational thing.

But my XTR is going to be faster. I want it to be demonstrably the fastest 6S Monster Truggy.

 

[VaporTrail]

Absolutely legendary!!

definitely going to be checking in on this. I've been kicking around the idea of a CF chassis to really get the weight down on the Shogun. As it stands, I believe weight is her biggest enemy in terms of performance. If I can lose around a1.5lbs (or .68 kilos for our British Imperialists ), I really think the Shogun will have a major improvement.

I've also been on the lookout for a CF chassis for my 4Tec 2.0. That's another one that can perform well, but the weight makes it a bit dodgy in the turns.

 

[Horatio]

Absolutely legendary!!

definitely going to be checking in on this. I've been kicking around the idea of a CF chassis to really get the weight down on the Shogun. As it stands, I believe weight is her biggest enemy in terms of performance. If I can lose around a1.5lbs (or .68 kilos for our British Imperialists ), I really think the Shogun will have a major improvement.

I've also been on the lookout for a CF chassis for my 4Tec 2.0. That's another one that can perform well, but the weight makes it a bit dodgy in the turns.

It's going to be fun.

Shedding some heft, improving weight distribution, increasing stiffness and making the drive train more efficient will definitely result in more mph.

The 5mm chassis will be significantly stiffer, but will also be lighter.

Having lighter, harder, straighter centre drive dog bones will yield instant results, but also with hardened pins, will improve the wear rate. As pins go a funny shape, this robs power.

I'm not sure how much lighter things will be, but it will be interesting to see before and after weights.

Lighter titanium dog bones will also be less rotating mass.

Replacing the composite nylon transmission cases with alloy items will unfortunately add some weight back on, but cnc precision parts should aid the drive efficiency with better mesh and larger, smoother bearings.

Now I need to start looking for some more Onyx lipos.....£££

 

[Horatio]

When I looked at purchasing a rig I looked at Kronos kagama Asuga was able to find titanium driveshafts for Kronos Asuga but only front for kagama if I recall correctly. I think 85.5 & 110 length are same as the buggy, think you may have rear measurement wrong. I used tworks 84.5mm in front for sworkz, rear 112mm from mugen on my buggy. When looking for Kronos shafts Of top my head scorched do 85mm & 168mm rear, I believe Kronos 85.5 & 170mm.

Here’s link to Scorched shafts, on sale atm

https://scorchedparts.co.uk/product...e-drive-shaft-notorious-outcast-typhon-senton

115.5/ 141.5 kagama

Memory correct only able find driveshaft correct length for front on kagama. But here’s link to tworks shafts, if ordering them they took a month to arrive.

https://www.rc-tworks.com/search?q=titanium+driveshaft+

You were right - having measured, mine are 85mm between the pins for the front and 175mm for the rear.

I can happily lose about 5mm, due to moving the diff inwards. Well the Scorched item is available 168mm, so it's a tad on the short side. For the front 82mm would be about spot on.

 

[Nelson.81]

You're right - I could alter the kick up, purely by adding/removing wedge shaped spacers under the pivot blocks.

On 4WD off road cars, the kick up seems to vary from as little as 1° to 6°.

The main impact on this angle is on the overall caster angle. But I can add some of the lost caster on the upper arms.

Reducing kick up is normal for on-road cars, so 0° isn't wrong as such, it just isn't typical for a 4WD off roader. I may even find I have more responsive steering. For speed runs, I don't think I'll be negatively impacted by the absence of kick up at all. The only mild inconvenience is mitigating the steering linkage geometry due to the changes, but future Horatio can figure that out.

Perhaps for off road stuff, I'll be looking enviously at the Scorched carbon/alloy hybrid chassis for Kraton, wishing that they did something like that for Kronos.

I have a good idea in my mind what it's all going to look like. The motor will be closer to the centre line, and slightly further forward. This will make way for more powerful, longer, 6000w TP motor/s.

The steering servo will be moved in, where previously there was a dogbone, and it will be straight, rather than on the wonk.

The radio box will no longer be part of the servo mount. It will be a separate, mounted and waterproof item.

The battery mount will be removed, along with the side guards. These may not be put back on and replaced with something else.

The rear part of the chassis will be more generously proportioned, possibly to make room for 2 batteries and a larger ESC.

The transmissions will be running with alloy cases, with ceramic oversized bearings.

It's all a matter of money, the time to earn that money, then the time to smuggle in parts, then the time to fettle those parts into an operational thing.

But my XTR is going to be faster. I want it to be demonstrably the fastest 6S Monster

You were right - having measured, mine are 85mm between the pins for the front and 175mm for the rear.

I can happily lose about 5mm, due to moving the diff inwards. Well the Scorched item is available 168mm, so it's a tad on the short side. For the front 82mm would be about spot on.

Need pull it out & measure it 170.5mm I still believe 168mm will work. I’ll be trying it in mine with couple orings when funds permit.

These showed up today also, not happy, been on the case to eBay see what happens.

 

[Horatio]

Need pull it out & measure it 170.5mm I still believe 168mm will work. I’ll be trying it in mine with couple orings when funds permit.

These showed up today also, not happy, been on the case to eBay see what happens.

View attachment 6866

View attachment 6867

Well that sucks! Wtf are those? PayPal refund? It looks like he put his old droop screws into the doodad and kept the domed ones.

"Dude. I know where you live. Refund me immediately".

I feel bad about it because I shared that link. It seemed a legit way to save £5.

Any how,

And:

A slightly worrying thing is that they specify the ends of the shafts are 8mm balls.

The Corally drive shafts appear to be 7mm. I've measured the internal size of the outdrives from the centre diff, and they appear to be 7.8mm.

8mm ball ends might be too big. That would be a shame, because then I'd have to faff about changing my hardened diff outputs - and they're still mint. I'd also have to 'upgrade' my transmission inputs.

Only one way to find out......

 

[Nelson.81]

Well that sucks! Wtf are those? PayPal refund? It looks like he put his old droop screws into the doodad and kept the domed ones.

"Dude. I know where you live. Refund me immediately".

I feel bad about it because I shared that link. It seemed a legit way to save £5.

Any how, View attachment 6868
And:
View attachment 6869
A slightly worrying thing is that they specify the ends of the shafts are 8mm balls.

The Corally drive shafts appear to be 7mm. I've measured the internal size of the outdrives from the centre diff, and they appear to be 7.8mm.

8mm ball ends might be too big. That would be a shame, because then I'd have to faff about changing my hardened diff outputs - and they're still mint. I'd also have to 'upgrade' my transmission inputs.

Only one way to find out......

So not wanting to waste money on ordering something that don’t fit, I have scorched shafts in basket , I went & pulled my own out . I could make up couple mm with orings but not 7mm. On this occasion corally measured correctly 85.5 fr 170.5 rear, seems you’ve managed to stretch & shrink your shafts you definitely need go titanium lol. Hope they fit the cups or we both be needing new diff and or cups. But where Theres a will there’s a way I’m hoping they fit without changing up things maybe a Dremel inside the cup but they do look close to 8mm. Scorched do diff outdrives fit 5mm shaft which what corally looks like, and I know a arrma spool fits corally so guessing diff would to with maybe shorter front shaft, might have to use scorched 80mm front shaft if comes to it.

Droop screws turned out they are avid ones just for 1:10. They similar to ones I would have ordered from AliExpress just not as round a dome head , but the AliExpress they not as big a dome as the avid 1:8. The avid 1:10 worked a little cheaper than the Ali ones which out stock everywhere atm neway, so just stick with avid ones they still fit.Not what I thought they where but not been robbed either. But whilst looking saw nylon ended ones might protect your carbon chassis.

Vid link to spark with arrma spool fitted if interested.

 

[Horatio]

So not wanting to waste money on ordering something that don’t fit, I have scorched shafts in basket , I went & pulled my own out . I could make up couple mm with orings but not 7mm. On this occasion corally measured correctly 85.5 fr 170.5 rear, seems you’ve managed to stretch & shrink your shafts you definitely need go titanium lol. Hope they fit the cups or we both be needing new diff and or cups. But where Theres a will there’s a way I’m hoping they fit without changing up things maybe a Dremel inside the cup but they do look close to 8mm. Scorched do diff outdrives fit 5mm shaft which what corally looks like, and I know a arrma spool fits corally so guessing diff would to with maybe shorter front shaft, might have to use scorched 80mm front shaft if comes to it.

Droop screws turned out they are avid ones just for 1:10. They similar to ones I would have ordered from AliExpress just not as round a dome head , but the AliExpress they not as big a dome as the avid 1:8. The avid 1:10 worked a little cheaper than the Ali ones which out stock everywhere atm neway, so just stick with avid ones they still fit.Not what I thought they where but not been robbed either. But whilst looking saw nylon ended ones might protect your carbon chassis.

Vid link to spark with arrma spool fitted if interested.

View attachment 6873

View attachment 6874

View attachment 6875

View attachment 6876

View attachment 6877

Cheers!

Yeah, Corally helpfully printed the wrong dimensions - a simple cut and paste error I should imagine.

I'm pulling the trigger on the Titanium centre driveshafts. I can make them work by carefully positioning the centre diff.

I'll be calculating the how much shorter I can go with them tonight. SOH CAH TOA. The joy of trigonometry.

 

[Horatio]

Horrible geeky maths time.

I'll spare the calculations and just give the results.

FRONT

The front driveshaft has a stock length of:
85mm (Hypotenuse)
Angle: (12.0°)
This gives us a triangle:

A=17.7mm (distance motor mount needs to move over to centre driveline)
B=83.1mm (new driveshaft length)
C=85.0mm (stock driveshaft length)

Shaft length can decrease by 2mm

REAR

The rear driveshaft has a stock length of:
175mm (Hypotenuse)
Angle: 5.8°
This gives a triangle:

A=17.7mm
B=174.1mm
C=175.0mm

Shaft length can decrease by 1mm.

Conclusion:

Total driveshaft lengths (when added together) need to equal as close to 257mm as possible.

Motor mount would then have to move rearwards by as much as 6mm, with corresponding 6mm longer front driveshaft - from 83 to 89mm.

The disadvantage of moving the motor rearwards is less space for longer can motors and more rearward weight bias, but these are comparative minor points compared with power robbing, 12° driveline angles.

In full size vehicles, these angles are not recommended to exceed >2°!!

The planned modifications are not subtle, and whilst I want to endeavour to keep the Kronos XTR's inherent handling characteristics, already I'm seeing reasons where certain trades have to be made for the best quality components.

Principally, weight distribution and kick-up.

These are minor trades to make for lower weight, less rotating mass, greater efficiency and greater stiffness.

 

[Horatio]

So it begins.....

 

[Nelson.81]

View attachment 6883
So it begins.....

I’ll let you be the Guinea pig see if shafts fit the cups before ordering mine . Good luck with it.

 

[Horatio]

I’ll let you be the Guinea pig see if shafts fit the cups before ordering mine . Good luck with it.

Erm, ok.

I spoke to Dave from Scorched parts.

The 8mm ball won't fit the Corally diff outs, which are 7.8mm and the Corally dog bones are 7.6mm - designed to be a clearance fit.

Dave stated that if the diff outs are 5mm shaft, his ones may work. So, basically take the diff apart and the Scorched diff outs, with an 8mm cup may work.

I also discussed the pins, thinking that if he supplied the driveshafts, I could possibly get them machined down to 7.6mm ball and then send them back to get the pins pressed in.

But, it looks like I need to go back to the drawing board with the driveshafts - or modify the diff. Or just replace the center diff entirely. There are still plenty of options, including upgrading the entire motor mount assembly.

Interestingly, the first thing Dave asked was - how much kick up are you running? "As soon as you start hitting some speed, you'll notice excessive wear on your front driveshaft. This is because of the kick up". To mitigate it on the Arrma cars - including the limitless - they recommended the Trident speed running shafts.

When I told him I was running 0° kick up, he said 'you'll be fine then - like with the Hobao' which also runs 0°, being an inherently on-road car, rather than an Inbetweener like the Arrmas.

Basically, with the limitless, if you want to go super fast like with a Hobao V2E - you need those Trident shaft and Pinocchio centre spool (224mph fast!!).

Meanwhile, back at planet knobhead:

546!! Crikey! It's not that far off the weight of my Baja 5B stock SS chassis - and 75g heavier than my current 5B chassis....!

So, now it's time to swot up on diff outputs and see if any of the Scorched parts will fit our freaky Corally diffs.

 

[Nelson.81]

Erm, ok.

I spoke to Dave from Scorched parts.

The 8mm ball won't fit the Corally diff outs, which are 7.8mm and the Corally dog bones are 7.6mm - designed to be a clearance fit.

Dave stated that if the diff outs are 5mm shaft, his ones may work. So, basically take the diff apart and the Scorched diff outs, with an 8mm cup may work.

I also discussed the pins, thinking that if he supplied the driveshafts, I could possibly get them machined down to 7.6mm ball and then send them back to get the pins pressed in.

But, it looks like I need to go back to the drawing board with the driveshafts - or modify the diff. Or just replace the center diff entirely. There are still plenty of options, including upgrading the entire motor mount assembly.

Interestingly, the first thing Dave asked was - how much kick up are you running? "As soon as you start hitting some speed, you'll notice excessive wear on your front driveshaft. This is because of the kick up". To mitigate it on the Arrma cars - including the limitless - they recommended the Trident speed running shafts.

When I told him I was running 0° kick up, he said 'you'll be fine then - like with the Hobao' which also runs 0°, being an inherently on-road car, rather than an Inbetweener like the Arrmas.

Basically, with the limitless, if you want to go super fast like with a Hobao V2E - you need those Trident shaft and Pinocchio centre spool (224mph fast!!).

View attachment 6888

Meanwhile, back at planet knobhead:

View attachment 6889
View attachment 6890
546!! Crikey! It's not that far off the weight of my Baja 5B stock SS chassis - and 75g heavier than my current 5B chassis....!

View attachment 6891

So, now it's time to swot up on diff outputs and see if any of the Scorched parts will fit our freaky Corally diffs.

Should have tried twisting his arm to make some for corally, other aftermarket manufacturers are starting to jump on the corally band wagon but still not the same amount upgrades available as is for other manufacturers yet unfortunately. If 5mm outdrive cups fit could just drop in arrma spool or diff they look like they will fit with a shorter front driveshaft.

Don’t think they do anything for truggy, but could maybe check lengths tworks offers see if the way doing it with there shafts as your willing to move diff location.

 

[Horatio]

Should have tried twisting his arm to make some for corally, other aftermarket manufacturers are starting to jump on the corally band wagon but still not the same amount upgrades available as is for other manufacturers yet unfortunately. If 5mm outdrive cups fit could just drop in arrma spool or diff they look like they will fit with a shorter front driveshaft.

Don’t think they do anything for truggy, but could maybe check lengths tworks offers see if the way doing it with there shafts as your willing to move diff location.

Where there's a will.......

Dave made it clear he doesn't do 'one offs'. I get it. The chap would be bogged down constantly.

However. During the course of our conversation - he didn't come across as negative towards Corally and I dropped enough hints.

I said "I look enviously through the Scorched catalogue of parts for Arrma rigs, and I'm beginning to wish I'd got a Kraton [pure lies, obviously]."

It can't be lost on him that there are quite a few Corally owners now.

Mind you - good luck trying to find out how long anything is - because Corally won't know!

The 7075 XTR chassis is an incredibly risky 3mm thick.

This means the jump to 5mm results in a 40% thicker chassis. It will be much stiffer, so likely won't be needing the centre brace.

It's going to be interesting if it works out lighter. Minus the bracing and side guards, I reckon it will be.

Edit to add:

The 'cups' going into the transmission will need changing, too.

Dave reassured by saying 'there are much more expensive hobbies'.

The trouble is, I already do those as well!

 

[Horatio]

Fair dinkum!

Here's the spec of the Kronos rear centre dogbone drive shaft from an Aussie site:

 

[Horatio]

More interesting complications.

The first issue is obviously ensuring the 'cups' or as I would describe them - 'input/output drives' are compatible with 8mm ball ended driveshafts. It turns out Corally items, when new and unworn are 7.8mm. I've got some worn ones which are showing 8.0mm at a push, so would be a (very) close interference fit.

The driveshafts themselves are nominally 7.8mm, but my worn examples are 7.6mm.

So, Scorched do 8mm 'cups' onto 5mm shafts, that would be compatible with the 13t input into front/rear transmissions.

That's where the good news ends, because the centre diff uses 6mm shaft, one piece, output drives. It's these that are the problem. Scorched don't do these (not yet).

Reluctantly, the super-duper titanium centre driveline from Scorched will have to be put on hold, as an entire new centre diff assembly will be required. This is something I may be open to, once I've had a chance to see how much better (or not) my homemade chassis concept is.

So for now - my entire drive will be standard items - even the dogbones - front and rear, as they're going to work - no issue. The front dog bones being 2mm longer is merely 1mm per end - nothing in dogbone terms. Better too long than too short!

My chassis, mounting positions, radio box, steering servo mount etc - will all be new.

Angle of the dangle

Next issue - steering plate. It's mounted onto the transmission case with approximately 6° angle, to offset the kick up.

To ensure the steering assembly meets the chassis at right angles, I need to modify the angle of this plate.

Either by

• bending the 7075
• Filing the transmission case
• adding a wedge

The clearance between the bellcranks and the upper arm pin brace is very slight as it is.

Removing this angle will bring it even closer to the pin brace and may necessitate machining of the brace.

Front droop.

The 7075 chassis has a significant amount of machining on the droop ears, with a downward angle.

Cutting the 5mm Carbon with such an angle will not be easy without risking delamination.

Or - I run with a lot less droop at the front. Basically none.

Milling.

The 7075 chassis has milled areas of relief for the spur - 2.5mm - and front and rear crowns - 2mm.

Achieving this without a milling machine will require a very, very steady hand with the Dremel and a very good side cutter tool.

I can mitigate the spur clearance by swapping the 52t spur for the 46t item. It likely won't need any milled relief, being 47.8mm, vs 53.9mm.

 

[Nelson.81]

Fair dinkum!

Here's the spec of the Kronos rear centre dogbone drive shaft from an Aussie site:

If your making custom chassis you could use any diff bulkhead you want really if you’d be willing to make your own shock towers also. Came across a page on Facebook kit rc doing custom carbon work, some nice looking bits might be of interest.

More interesting complications.

The first issue is obviously ensuring the 'cups' or as I would describe them - 'input/output drives' are compatible with 8mm ball ended driveshafts. It turns out Corally items, when new and unworn are 7.8mm. I've got some worn ones which are showing 8.0mm at a push, so would be a (very) close interference fit.

The driveshafts themselves are nominally 7.8mm, but my worn examples are 7.6mm.

So, Scorched do 8mm 'cups' onto 5mm shafts, that would be compatible with the 13t input into front/rear transmissions.

View attachment 6897

That's where the good news ends, because the centre diff uses 6mm shaft, one piece, output drives. It's these that are the problem. Scorched don't do these (not yet).

Reluctantly, the super-duper titanium centre driveline from Scorched will have to be put on hold, as an entire new centre diff assembly will be required. This is something I may be open to, once I've had a chance to see how much better (or not) my homemade chassis concept is.

So for now - my entire drive will be standard items - even the dogbones - front and rear, as they're going to work - no issue. The front dog bones being 2mm longer is merely 1mm per end - nothing in dogbone terms. Better too long than too short!

My chassis, mounting positions, radio box, steering servo mount etc - will all be new.

Angle of the dangle

Next issue - steering plate. It's mounted onto the transmission case with approximately 6° angle, to offset the kick up.

To ensure the steering assembly meets the chassis at right angles, I need to modify the angle of this plate.

Either by

• bending the 7075
• Filing the transmission case
• adding a wedge

The clearance between the bellcranks and the upper arm pin brace is very slight as it is.

View attachment 6898
Removing this angle will bring it even closer to the pin brace and may necessitate machining of the brace.

Front droop.

The 7075 chassis has a significant amount of machining on the droop ears, with a downward angle.

View attachment 6899

Cutting the 5mm Carbon with such an angle will not be easy without risking delamination.

Or - I run with a lot less droop at the front. Basically none.

Milling.

The 7075 chassis has milled areas of relief for the spur - 2.5mm - and front and rear crowns - 2mm.

Achieving this without a milling machine will require a very, very steady hand with the Dremel and a very good side cutter tool.

I can mitigate the spur clearance by swapping the 52t spur for the 46t item. It likely won't need any milled relief, being 47.8mm, vs 53.9mm.

i mentioned those 5mm outdrives before if they fit along with an arrma centre spool(if spool fits I guess diff does also) , if watch that vid I posted arrma spool drop’s straight in corally chassis.

If your making custom carbon chassis, you could drop in any bulkhead diff case you want really, if willing make own shock towers also fit around it. Came across a page on FB do custom carbon work for one off projects stuff looks decent maybe of interest.

 

[Horatio]

i mentioned those 5mm outdrives before if they fit along with an arrma centre spool(if spool fits I guess diff does also) , if watch that vid I posted arrma spool drop’s straight in corally chassis.

If your making custom carbon chassis, you could drop in any bulkhead diff case you want really, if willing make own shock towers also fit around it. Came across a page on FB do custom carbon work for one off projects stuff looks decent maybe of interest.

View attachment 6893

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View attachment 6896

Kit RC look amazing. I hope they have a website.

It may seem odd to folk, but I don't do book face.

 

[Nelson.81]

Kit RC look amazing. I hope they have a website.

It may seem odd to folk, but I don't do book face.

They don’t seem to, you need to message them through Facebook messenger. Maybe steal/borrow someone else phone for a bit. Or I could maybe drop them a message for you maybe chat by email or some other way if you’d like.

Here’s their contact info & couple reviews & pics.