Liberty's Kraton V4 speed project

[GMballistic]

Breaking 100
Having hit 94.5 mph on 6s the question is can I squeeze out 5.6 more mph out of this thing with the stock electronics? (no add on's like cap packs)
Even if this rig won't go any faster with this ESC I have been very impressed with this BLX 185 system!

-Liberty

I too have been impressed with the stock system, ...my current PB is 99mph on the stock motor/ESC combo with no cap packs etc and that was done without using my Panther Graphene battery.

I expect it will break into triple digits with that battery but I definitely feel like the ESC is what is holding me back hence why I bought an MM2 the other week. I'm running at a ROSSA event this weekend on the stock motor/ESC as I think that'll be my best chance to max it out, ...after that I'll be starting to change from it.

 

[LibertyMKiii]

I too have been impressed with the stock system, ...my current PB is 99mph on the stock motor/ESC combo with no cap packs etc and that was done without using my Panther Graphene battery.

I expect it will break into triple digits with that battery but I definitely feel like the ESC is what is holding me back hence why I bought an MM2 the other week. I'm running at a ROSSA event this weekend on the stock motor/ESC as I think that'll be my best chance to max it out, ...after that I'll be starting to change from it.

Sweet man! I wish I could attend that event! I also have a MM2 sitting on the shelf and the Cap Pack I built. Sort-of saving that stuff for the Limitless. I want to keep this Kraton stock, and will likely go back to being a basher once the Limitless comes out.

-Liberty

 

[GMballistic]

Sweet man! I wish I could attend that event! I also have a MM2 sitting on the shelf and the Cap Pack I built. Sort-of saving that stuff for the Limitless. I want to keep this Kraton stock, and will likely go back to being a basher once the Limitless comes out.
-Liberty

Yeah UK might be a bit far for you to attend.

It does make sense for you to save that stuff for the Limitless and then return the Kraton to a basher.
If I get a Limitless it won't be for a long time but if I did I'd definitely be aiming for some very big numbers with that as it looks so capable. Be interesting to see what sort of high speed numbers the first speed runners with them start getting and if any find a GT body or similar to fit or if that's even necessary to achieve 150+mph.

 

[LibertyMKiii]

Yeah UK might be a bit far for you to attend.

It does make sense for you to save that stuff for the Limitless and then return the Kraton to a basher.
If I get a Limitless it won't be for a long time but if I did I'd definitely be aiming for some very big numbers with that as it looks so capable. Be interesting to see what sort of high speed numbers the first speed runners with them start getting and if any find a GT body or similar to fit or if that's even necessary to achieve 150+mph.

I suspect most will get stuck in the 120-135 range until they go full bodied. Since 1/7 scale length bodies are non-existent... those of us with fiberglass skills may be the only ones going real fast

 

[jondilly1974]

There really are only 2 good options GRP and BSR forms(that can handle over 100mph reliably). This location construction site would eat up BSR foams pretty bad. (I have several in the garage but wont use them on this car & road)
Gears can compensate for tires, but my issue is power against aerodynamic drag. Removing the wing along with the wheelie bar may be a good start for reducing drag. Could be just enough to get that extra 5+mph.

-Liberty

I’m having trouble finding enough space to keep my throttle open long enough to get to 60. I have to baby the throttle to 45ish before I pull too hard or else I get a wheelie, which turns into a cartwheel or backflip. ??

 

[cootertwo]

And then with more space needed comes the more range problem..... on and on. It's sorta similar to all the stuff they have to go through at the real land speed record challenges, like Bonneville, etc. Always something else to get that few extra mph.

 

[LibertyMKiii]

And then with more space needed comes the more range problem..... on and on. It's sorta similar to all the stuff they have to go through at the real land speed record challenges, like Bonneville, etc. Always something else to get that few extra mph.

Couldn't agree more!

I’m having trouble finding enough space to keep my throttle open long enough to get to 60. I have to baby the throttle to 45ish before I pull too hard or else I get a wheelie, which turns into a cartwheel or backflip. ??

I know it looks easy in videos and this sounds silly, but it really takes some practice on smoothly applying the throttle at the correct rate to keep the rig in control. Driving on 4s is a piece of cake but 6s and 8s are considerably more difficult.

 

[jondilly1974]

Couldn't agree more!



I know it looks easy in videos and this sounds silly, but it really takes some practice on smoothly applying the throttle at the correct rate to keep the rig in control. Driving on 4s is a piece of cake but 6s and 8s are considerably more difficult.

Thanks for the info. I’m having fun either way, but I just wish the nose would stay down so I could floor it ?I know I could put some weights there, but I don’t want to add silly weights. I’d rather learn to drive it better, like you are implying here. ??

 

[LibertyMKiii]

I have been wanting a scale set ever since I got into this hobby. Should be a great tool for my various speed rigs. In this picture I have made no changes. Pretty surprised how close to balanced it was given the heavy Graphene pack and my sloppy "wing it" suspension pre-load adjustments.

 

[BashingBrian]

So cool...??

Can you balance it up some more just by adjusting the pre-load..?? or do you need to add/remove weight..??

 

[LibertyMKiii]

So cool...??

Can you balance it up some more just by adjusting the pre-load..?? or do you need to add/remove weight..??

You could adjust placement of the battery, droop screws, and preload. I am thinking this will be more useful with the Limitless and dream build that both will run 2 large batteries. Also Esc placement is more open on those.

 

[Erstadw]

I used 9/16" brass tube I found at my lhs. Fit pretty snug over the o-ring. Pin in the spool hasn`t come out since. I think it was around four bucks for a 12 inch piece. Cant remember how long I cut it. I just measured the space between the two mounts and made it 1 or 2mm shorter.

 

[LibertyMKiii]

Tried running tonight without the wing and wheelie bar. Back end kept getting lose on me, so that wing must be needed after all with this body shape.
Either way I picked up 2 mph but feel like it is at its limit with this factory ESC.

96.1 mph

 

[jondilly1974]

So to get to over 100, have you considered a little taller tire?

 

[DoNoHarm]

That truck looks so weird with those tires ?? i find it hilarious that it passed 90. Good luck on triple figures dude.

 

[LibertyMKiii]

So to get to over 100, have you considered a little taller tire?

The aftermarket does not currently have a good solution.
GRP is 98mm
Arrma Hoons are 100mm
BSR foams are 103.5mm

Many people have taken the GRP 1/8 tires well into the 150 range so there is no problem running them at higher speeds.

The issue is the ESC as mentioned in the video.
To get slightly nerdy here..... You have "X" air resistance at 100mph and it requires "Y" horsepower to push through that resistance with a given objects aerodynamics.
work in man's world is often described in horsepower in electricity 1 hp is equal to 746 watts.
We don't really know the output of this BLX 185 esc, but lets say its true output is 185 amps.
We also know voltage sag occurs somewhere around 0.5v to 0.9 volts during a speed run per cell.
So we will say my fully charged 6s LiPo is outputting 21v under a full load at 96mph
185 amps x 21 volts = 3885 watts
3885 watts less thermal and electrical efficiencies (best motors are around 90% efficient)
3885 * 0.9= 3496.5 watts (the rest was turned into heat in the ESC, wires, connectors, and motor)
I wont get into mechanical losses but those exist.
3496 watts / 746 = 4.68 hp

So to go faster I need more watts, which do the work.

Ways to get more watts?
1. Higher voltage or less sag (more mAh)
2. More Amps out of the esc or change to aftermarket solutions like Castle
3. More aerodynamic shape could take that same 4.68hp and do more with it because it suffers form less air resistance.

This is assuming the gearing of the car is setup for more speed (which mine is)

 

[jondilly1974]

So you don’t think a taller tire like a Duratrax Bandito would give you a speed advantage, assuming it holds up at 100mph? It’s the same as gearing up. Hard to believe nobody makes a tire worth running that isn’t 120mm. I see a need for one. Who will fill the void?

 

[Mr.Duke]

The 1/5th scale GRP tires are 118mm diameter but you'll also have to factor in the square adapters that run about $50 for the set.

 

[LibertyMKiii]

The 1/5th scale GRP tires are 118mm diameter but you'll also have to factor in the square adapters that run about $50 for the set.

I won't run these tires for several reasons.
1. They are significantly heavier.
2. They are worse aerodynamically and will slow the car down.
3. No one can seem to run these and go much over the 105-115 range (talking 8s cars outputting 9kW or more), versus 150+ on the 1/8 scale version.
4. I see lots of "blow outs" on other people's videos using these.

Too many negatives. The best option is some custom foam tires on 1/5 wheels. I have the wheels from a 1/5 Losi 5ive, but would need to cut it more narrow and then have BSR John to make the foam for me. (but this sort of thing would be for my dream build not this Kraton) I believe I am satisfied with the results of the Kraton and speed. Waiting now for the Limitless.