Limitless Danyrc Limitless build

[Danyrc]

Long time RC hobbyist first time Arrma owner. Decided to build a Limitless for speed runs (something around 120 mph) and some bashing occasionally. This is the list of parts already bought, some have arrived, other are still in the mail or backordered.

Castle MMX8S 1717 1650kv combo (installed)
My old Futaba 4pls but just in case I have a brand new RC6GS V2
PPS motor mount (installed)
PPS diff mount (backordered)
PPS diff cover plate (waiting shipment)
DS 3225sg 35Kg steel coreless HV servo (installed)
Arrma front shock springs 35mm 32lbf/in (installed)
SFR carbon fiber side skirts (installed), front splitter (installed) front and rear air dams (waiting shipment)
RCAWD Rear Center Dogbone 103.5mm
Arrma Center Driveshaft High Speed Support Set (installed)
Alza Racing Motor 40mm Fan Mounting base, Motor Fan Base - Dual 40mm and Dual 40mm Aluminium Fan Cover (installed)
Two 40x40x28mm 12V Ultra High Speed Fans with an incredible stupid high airflow of 31.3 CFM each with a dedicated 3S 2200mah lipo (installed)
Avid Aura ball bearings kit (installed)
Arrma 29T and 39T Spool gears
Dozens of 5mm bore Mod 1 pinion gears from 17t to 36t.
GRP S5 tires.
Skyrc GSM-105 (new gen with 10Hz update frecuency)
Sunpadow 6s lipos 5100mah 60C and Sunpadow 4s lipos 7300mah 70C

Setup
Opened two holes to the upper front arms for easy access to the Droop screws.
Front toe 0 degree.
Rear toe stock
Caster increased by moving two clips to the front of the upper front arms. Front Camber 0 degree, had to add 2mm plastic washers to the upper pivot balls.
Rear Camber 0 degree.
Ride height 8mm front, 22mm rear.
Droop 0mm front and rear.
Shocks, 3000 cst silicone oil all around, stiffer springs on the front. Front shocks moved to the upper hole in the shock tower, preload around 60%, rear shocks at outer hole of tower giving more stiffness, preload all the way down.
Planning to change diff silicone oil to at least 100k front and 20k rear.

I haven't had the oportunity to do any speedrun due to a very high winds here in South Florida during the last weeks but I've had bashing a couple of times on 6s speeding to 80mph at times and the car runs very smooth.
Any recommendations for my build?

 

[Danyrc]

I'm going to put limitters on the rear shocks made from some rubber tubes to try to eliminatethe rear end going below the front under acceleration. Does anybody know which length is the best? I know @GMballistic make them for his cars.

 

[Cahnno]

This is a well thought out build , good job!!

 

[Danyrc]

After trial and error I made the limiters. They are approx 12mm and take around 60% of the shocks shafts length, that way with my setup the rear end will never be higher than the front.

 

[Danyrc]

A little clip just to show you how powerful these 31.3 CFM fans are. They hover all over the table.

 

[LibertyMKiii]

Sounds like you have done your homework and set the car up well.

Only thing I would change is the batteries and connectors. If you want to go really fast CNHL or SMC V2 6400mAh packs are the only ones to go for. (should be in stock again soon)
QS8 anti-spark connectors are pretty awesome.

 

[Danyrc]

Sounds like you have done your homework and set the car up well.

Only thing I would change is the batteries and connectors. If you want to go really fast CNHL or SMC V2 6400mAh packs are the only ones to go for. (should be in stock again soon)
QS8 anti-spark connectors are pretty awesome.

Thanks. I used the XT90 because that's what I have in my other cars but you are correct about the QS8 being better suited for the Limitless, I will put them on the list. About the batteries I really appreciate your response, I know the hipe now for the CHNL and SMC. Are they really better than others? I've had used dozen of different lipo brands in my 20 years in the RC world and what I have learned is that it's always hit or miss. I have no proof but I bet there is not more than two or three real lipo manufacturers in China supplying all the vendors we buy from, they just pack them and put their brand name on their final product. I don't trust any battery that says it has more than 60C. I'm not an expert by any means but I don't believe a 6000mAh battery at 100C can give you 600 Amps not even for 1 second burst, there is no "normal" ESC that can stand that power nor any 10AWG wire or its insulation. I would appreciate the explanation from somebody knowledgeable about electric systems.

 

[GMballistic]

I'm going to put limitters on the rear shocks made from some rubber tubes to try to eliminatethe rear end going below the front under acceleration. Does anybody know which length is the best? I know @GMballistic make them for his cars.

I should have measured them when I made mine but it was the same process as you've now done, ...just trial and error to see what worked best giving me the ride height set up I wanted.

As @LibertyMKiii mentioned looks like you've been doing your homework and I like your build. That said I'd definitely change those ESC/battery connectors as that will end up holding you back. I use 8mm bullets mainly but do have a set of OSE 8's on the Limitless.

 

[LibertyMKiii]

Thanks. I used the XT90 because that's what I have in my other cars but you are correct about the QS8 being better suited for the Limitless, I will put them on the list. About the batteries I really appreciate your response, I know the hipe now for the CHNL and SMC. Are they really better than others? I've had used dozen of different lipo brands in my 20 years in the RC world and what I have learned is that it's always hit or miss. I have no proof but I bet there is not more than two or three real lipo manufacturers in China supplying all the vendors we buy from, they just pack them and put their brand name on their final product. I don't trust any battery that says it has more than 60C. I'm not an expert by any means but I don't believe a 6000mAh battery at 100C can give you 600 Amps not even for 1 second burst, there is no "normal" ESC that can stand that power nor any 10AWG wire or its insulation. I would appreciate the explanation from somebody knowledgeable about electric systems.

I would like to do more testing of a mid range LiPo like a Turnigy Heavy Duty versus an SMC to see the difference.... A friend of mine has gone 159 with Turnigy HD packs. They are one of the best bang for the buck LiPos in my opinion.

With that said I did compare a Zeee 6000mAh 80c cheap amazon LiPo to the SMC V2 150c pack. With zero other changes to my car I picked up 7 mph and significantly less voltage drop. You don't need the best of the best batteries to go 100 mph, but when you want to go beyond 120mph a good battery will help a lot and eventually the xt90 solder joints will melt

In the data logs from my MMX8s it pegs a maximum reading at 399a. The XLX 2 can read beyond 600amps... I have seen it a few times. Are their logs accurate? We hope so....

 

[Notoriousone]

Nice work, the car looks great. As said, swap connectors to 8mm, and maybe better Lipos. The other thing I would do is make the nitro tubing on shock shafts longer, you don't need that much travel in the rear shocks for speedruns. I'll post a pic later of how mine are, I have about 3 mm of shock shaft visible at the top, and stiff tubing but after a 130mph run the nitro will compress from the forces pushing down on it, increasing the shock travel. I raise the tubing up again after the run. This will happen so don't leave much room on those shafts

 

[Danyrc]

I would like to do more testing of a mid range LiPo like a Turnigy Heavy Duty versus an SMC to see the difference.... A friend of mine has gone 159 with Turnigy HD packs. They are one of the best bang for the buck LiPos in my opinion.

With that said I did compare a Zeee 6000mAh 80c cheap amazon LiPo to the SMC V2 150c pack. With zero other changes to my car I picked up 7 mph and significantly less voltage drop. You don't need the best of the best batteries to go 100 mph, but when you want to go beyond 120mph a good battery will help a lot and eventually the xt90 solder joints will melt

In the data logs from my MMX8s it pegs a maximum reading at 399a. The XLX 2 can read beyond 600amps... I have seen it a few times. Are their logs accurate? We hope so....

Thanks for the info. Looking for better connectors and when economy allows better batteries

Nice work, the car looks great. As said, swap connectors to 8mm, and maybe better Lipos. The other thing I would do is make the nitro tubing on shock shafts longer, you don't need that much travel in the rear shocks for speedruns. I'll post a pic later of how mine are, I have about 3 mm of shock shaft visible at the top, and stiff tubing but after a 130mph run the nitro will compress from the forces pushing down on it, increasing the shock travel. I raise the tubing up again after the run. This will happen so don't leave much room on those shafts

Thanks for the heads-up. Looking again I realized there is still too much travel, I'll make a new ones. Will keep you posted.

 

[rotauq]

Thanks. I used the XT90 because that's what I have in my other cars but you are correct about the QS8 being better suited for the Limitless, I will put them on the list. About the batteries I really appreciate your response, I know the hipe now for the CHNL and SMC. Are they really better than others? I've had used dozen of different lipo brands in my 20 years in the RC world and what I have learned is that it's always hit or miss. I have no proof but I bet there is not more than two or three real lipo manufacturers in China supplying all the vendors we buy from, they just pack them and put their brand name on their final product. I don't trust any battery that says it has more than 60C. I'm not an expert by any means but I don't believe a 6000mAh battery at 100C can give you 600 Amps not even for 1 second burst, there is no "normal" ESC that can stand that power nor any 10AWG wire or its insulation. I would appreciate the explanation from somebody knowledgeable about electric systems.

A Mercedes and a Dacia can be built in the same factory too. Bad analogy, I know. I just want to make the point that they all come from the same factory is not a valid point. You and your siblings come from the same parents, so you certainly are equally proficient in math...

In mass manufacturing their is always a spread in quality, even for the exact same make. A lithium extractor can be worn, an operator could still be drunk in the morning a raw material supplier can fluctuate in quality, so many variables. On the other side there are the customers (not us, but all them brands) and they pay a certain price based on quality criteria (sometimes even fines when not met) The answer is a game of statistics. Batch sampling, cherry picking the excellent among the good. If you can sell 10% of your products for double the price, you will cherry pick. A random Zeee battery might actually be the best battery in the world, a rare gem in an adequate batch that was shipped to Zeee.

So you are not necessarily playing for a better battery, but certainly get a battery that meets the criteria of the brand/type. Which you will only put to test when heavily geared up and a esc/motor combo that doesn't bottleneck before the battery does.

 

[Danyrc]

Nice work, the car looks great. As said, swap connectors to 8mm, and maybe better Lipos. The other thing I would do is make the nitro tubing on shock shafts longer, you don't need that much travel in the rear shocks for speedruns. I'll post a pic later of how mine are, I have about 3 mm of shock shaft visible at the top, and stiff tubing but after a 130mph run the nitro will compress from the forces pushing down on it, increasing the shock travel. I raise the tubing up again after the run. This will happen so don't leave much room on those shafts

Done. New longer limiters installed. Left before and right after your advice

 

[Danyrc]

MMX8S fan installed, I used a little bit less powerful fan of 23.78 CFM and 0.66A because this fan will be connected to the balance connector of the main 6S battery or one of the two 4S when running 8S.

 

[Danyrc]

I have a question for @LibertyMKiii , @GMballistic and @Notoriousone
Would be reasonable installing just a male QS8 on the ESC and using this QS8-XT90 series adapter ?
I don't want to look cheap but in that way I would not have to change all my lipo's XT90 connectors. I have other rigs using the same batteries, I would have to change all my connectors (including all ESCs and charger cables to QS8) and that would be a litte expensive.

 

[LibertyMKiii]

I think you need to seriously consider having a speed set of batteries.
When you get faster and start pulling high amps xt90's are a ticking time bomb. Adapters can be just as bad....

Think of this scenario..... The car is doing 110mph and the xt90 small 3.5mm connection melts, the ESC looses power, and you no longer have brakes. The car crashes into a curb at 100+ speeds and is a total loss.

With that said I have done 119mph on xt90s. So this is a do as I say not as a I do sort of thing lol

***** edit
I would almost rather see it the other way around where QS8 is on the battery and speed setup and then you use an adapter to convert this to a xt90 in the lower power rigs. Adapters on the charger with low amps wouldn't be an issue.

 

[Danyrc]

I think you need to seriously consider having a speed set of batteries.
When you get faster and start pulling high amps xt90's are a ticking time bomb. Adapters can be just as bad....

Think of this scenario..... The car is doing 110mph and the xt90 small 3.5mm connection melts, the ESC looses power, and you no longer have brakes. The car crashes into a curb at 100+ speeds and is a total loss.

With that said I have done 119mph on xt90s. So this is a do as I say not as a I do sort of thing lol

***** edit
I would almost rather see it the other way around where QS8 is on the battery and speed setup and then you use an adapter to convert this to a xt90 in the lower power rigs. Adapters on the charger with low amps wouldn't be an issue.

Thanks. I know what you mean. I do speedruns with my Kyosho Inferno GT2 at 108mph on 6s and never had problems with the XT90s but the Inferno is just 8.5 lbs, the Limitless is heavier and will use 8s half of the time.

 

[GMballistic]

I decided along time ago now to just run everything on Castle 8mm bullets, ...doesn't matter what it is; basher, speed runner, 2S, 3S etc etc everything gets those bullets fitted.
For my Limitless it still has batteries (4S) with Castle 8mm bullets on but they connect in series to an OSE 8mm anti spark plug just before the ESC.

If you're serious about speed runs then it just makes sense.

 

[Danyrc]

Ok boys you are right. I'm going to swap all my lipos to QS8. I pulled the trigger and bought these. 10 pair QS8 connectors

 

[Danyrc]

Following the advice of some respected members here is an update of my build.
- QS8 connectors.
- 2 SMC True Spec Extreme Graphene V2 22.2V-6400mAh-150C
- Kill Mode cap pack with XT90 connector.
- Scorched center driveshafts.
- Aluminum chassis braces.
- Aluminum center brace.
- Carbon fiber battery trays.
- Waiting for GP5 front and rear differentials.