Limitless Rep's Limitless

[RepEvox]

After a 2 year Covid hiatus, I finally got back to rebuilding my Limitless that I crashed into a curb...it still needs some work, mainly need a few sets of new tires, paint/trim a new body, rear shock setup with rubber bumps, possibly fix front diff pinion because it seems to skip teeth, and modify this wing by trimming a piece off and moving the plastic wing rearward. I'll probably need to invest in a GPS and other odds and ends to really make this professional like shortening the ESC wires and recrimping.

Right now, she is really well balanced down the middle, with a decent weight bias towards the front with the motor and battery moved as far as I could. This is much lighter weight than my previous build with the 7075 JustBashIt chassis and 2 4s batteries. I don't think that matters much, but I like to think it improved my power to weight ratio. I think the way I positioned all the parts is pretty decent and it keeps the area between the wheels empty. Maybe that helps diffuse the air better?

Build List:
Scorched RC full length chassis, battery mounts, and body posts
Perfect Pass carbon fiber kit, most importantly the chassis brace, steering plate, and splitter
PPS single motor mount and center diff holder
Front/rear diff lockers, white lithium greased, shimmed
2x Kraton 134mm shafts for center driveshafts, small pieces of silicone in the drive cups
TP5670CM 2510kV, has the sleeved rotor for a higher max RPM
XLX2 with cap bank, QS8
Powerhobby 8s 6000mAh QS8, strapped in and outdoor velcro'd
Savox 2290SG
Radiolink RC6GS with 3W signal repeater and R8EF receiver

I'll learn fast if this setup works to my liking. I am hoping the servo is fast/torquey enough at speed, single 8s can exceed load requirement, and whether or not it still drives straight. If I really wanted to push it, I would invest in the dual motor setup with same electronics or potentially just do parallel 8s to feed more current. I am not a fan of series.

I haven't driven this past 120mph since it isn't geared tall yet, but I intend to take it to a clean, pedestrian and car vacant road. I will have to get used to speedrunning again and push it to my personal limits first, then when I'm comfortable I may start taking videos of any impressive speed numbers. I bought a DJI air unit which is an FPV camera designed for quadcopters. With a little bit of jury rigging, I'm sure I can mount it to a body and get some cool onboard footage which I think could be unique. A gopro may also fit, but I think I may have trouble stablizing and bracing the camera. I'm thinking I'll need to mount any camera to my chassis brace.

Let me know your thoughts and any suggestions!

 

[rotauq]

Nice setup:

- Somehow the 5670CM looks like its smaller on the picture, maybe due to the big chassis.
- I am unsure about the Kraton centershafts, limitled amps the battery can deliver, these will be your bottlenecks. Definately with that big motor.

I've ran the dji air unit (vista) on my limitless. It does get really hot, so it will require active cooling if you mount it on the inside of the body. The camera can't be on the inside, even clear lexan will still give fuzzy images. I ended up mounted mine above the rear wing.

 

[ArrmaPOWA]

That motor will wreak havoc on your electonics... I lost an xlx2 and a 4s lipo within the first 5 runs with the 5670cm because i was overgeared slightly. Start with extremely mild gearing and be prepared to purchase the absolute BEST lipos on earth to keep voltage up. On 6s, i ran the same mph with a pinion 16t smaller than the spur than i did with a 7 tooth p/s difference

 

[LibertyMKiii]

First of all great build and look killer!

Regarding the motor.... I have not tried it myself, but it is said the 6-pole (56mm and 58mm motors) do not play well with the XLX2 and higher rpms. What I have been told is over 1300kv is risky. It isn't noticeable with minimal amperage loads (speeds under 100mph) but when geared high it will show the problem.

I'd recommend getting the perfect pass carbon shafts at some point.

 

[RepEvox]

I would assume the sleeved rotor pulls more amps and I was concerned about the 6-pole. My XLX2 throws the 'excessive load' error frequently. I may just have to be content with this setup for now since it would easily be another $1k to rearrange this for dual motors (1721?).

I don't think the perfect pass shafts will fit this build. I would have to buy equal length custom shafts out of titanium i.e. scorched RC.

As for the air unit, I will definitely be adding a fan and separate battery pack to power it. Then I can decide where to mount it, the wing seems like a decent place for it. I'm not really satisfied with the current wing setup I have. It's floppy and it still uses the shaved plastic wing. I'd like to potentially upgrade the braces to aluminum and make my own wing.

 

[Diem Turner]

I would assume the sleeved rotor pulls more amps and I was concerned about the 6-pole. My XLX2 throws the 'excessive load' error frequently. I may just have to be content with this setup for now since it would easily be another $1k to rearrange this for dual motors (1721?).

I don't think the perfect pass shafts will fit this build. I would have to buy equal length custom shafts out of titanium i.e. scorched RC.

As for the air unit, I will definitely be adding a fan and separate battery pack to power it. Then I can decide where to mount it, the wing seems like a decent place for it. I'm not really satisfied with the current wing setup I have. It's floppy and it still uses the shaved plastic wing. I'd like to potentially upgrade the braces to aluminum and make my own wing.

As has already been mentioned, that motor is a risky proposition. Raz killed an XLX2 with a 5870 1920KV in short order. I'm not sure I quite understand your dislike for series connection of batteries; at its core an 8S lipo is nothing more than two 4S lipos in series. But, as always, to each their own.

To address the drive shaft issue you could install a Pinocchio spool to segment your driveline into three shorter components which should help with vibration.

That's a nice looking build you have there though

 

[SrC]

After a 2 year Covid hiatus, I finally got back to rebuilding my Limitless that I crashed into a curb...it still needs some work, mainly need a few sets of new tires, paint/trim a new body, rear shock setup with rubber bumps, possibly fix front diff pinion because it seems to skip teeth, and modify this wing by trimming a piece off and moving the plastic wing rearward. I'll probably need to invest in a GPS and other odds and ends to really make this professional like shortening the ESC wires and recrimping.

Right now, she is really well balanced down the middle, with a decent weight bias towards the front with the motor and battery moved as far as I could. This is much lighter weight than my previous build with the 7075 JustBashIt chassis and 2 4s batteries. I don't think that matters much, but I like to think it improved my power to weight ratio. I think the way I positioned all the parts is pretty decent and it keeps the area between the wheels empty. Maybe that helps diffuse the air better?

Build List:
Scorched RC full length chassis, battery mounts, and body posts
Perfect Pass carbon fiber kit, most importantly the chassis brace, steering plate, and splitter
PPS single motor mount and center diff holder
Front/rear diff lockers, white lithium greased, shimmed
2x Kraton 134mm shafts for center driveshafts, small pieces of silicone in the drive cups
TP5670CM 2510kV, has the sleeved rotor for a higher max RPM
XLX2 with cap bank, QS8
Powerhobby 8s 6000mAh QS8, strapped in and outdoor velcro'd
Savox 2290SG
Radiolink RC6GS with 3W signal repeater and R8EF receiver

View attachment 229254

I'll learn fast if this setup works to my liking. I am hoping the servo is fast/torquey enough at speed, single 8s can exceed load requirement, and whether or not it still drives straight. If I really wanted to push it, I would invest in the dual motor setup with same electronics or potentially just do parallel 8s to feed more current. I am not a fan of series.

I haven't driven this past 120mph since it isn't geared tall yet, but I intend to take it to a clean, pedestrian and car vacant road. I will have to get used to speedrunning again and push it to my personal limits first, then when I'm comfortable I may start taking videos of any impressive speed numbers. I bought a DJI air unit which is an FPV camera designed for quadcopters. With a little bit of jury rigging, I'm sure I can mount it to a body and get some cool onboard footage which I think could be unique. A gopro may also fit, but I think I may have trouble stablizing and bracing the camera. I'm thinking I'll need to mount any camera to my chassis brace.

Let me know your thoughts and any suggestions!

What a nice neat job there. Thinking outside the box. Different. Lean and mean.
Chassis balance/Bias/Crossweight is so very important with these rigs. They hook up great when done correctly.

 

[LibertyMKiii]

I would assume the sleeved rotor pulls more amps and I was concerned about the 6-pole. My XLX2 throws the 'excessive load' error frequently. I may just have to be content with this setup for now since it would easily be another $1k to rearrange this for dual motors (1721?).

I don't think the perfect pass shafts will fit this build. I would have to buy equal length custom shafts out of titanium i.e. scorched RC.

As for the air unit, I will definitely be adding a fan and separate battery pack to power it. Then I can decide where to mount it, the wing seems like a decent place for it. I'm not really satisfied with the current wing setup I have. It's floppy and it still uses the shaved plastic wing. I'd like to potentially upgrade the braces to aluminum and make my own wing.

You could re-drill the motor mount position for the regular limitless motor mount position (if it is already not provided)
The sleeved rotor isn't the big issue it is the ESC does not know how to read the back EMF from the 6 pole 1/5 scale motors correctly.

If you only want to bash with it and want to keep the setup the same there is a leopard 1/5 scale 1340kv motor that is a 4 pole.
That would be a relatively low cost option to fix the issue but keep things similar to how they are.

 

[RepEvox]

As has already been mentioned, that motor is a risky proposition. Raz killed an XLX2 with a 5870 1920KV in short order. I'm not sure I quite understand your dislike for series connection of batteries; at its core an 8S lipo is nothing more than two 4S lipos in series. But, as always, to each their own.

To address the drive shaft issue you could install a Pinocchio spool to segment your driveline into three shorter components which should help with vibration.

That's a nice looking build you have there though

I appreciate the advice. I've seen the pinocchio and it's on my list of parts I'd definitely buy if I want to push this to its limits. Right now I'm just trying to have fun with it. Regarding the dislike for series, it's more of a personal pet peeve. Have to charge twice, plug in twice, unplug twice, etc. 1 8s tabbed together is cheaper, cleaner, and probably performs cooler.

You could re-drill the motor mount position for the regular limitless motor mount position (if it is already not provided)
The sleeved rotor isn't the big issue it is the ESC does not know how to read the back EMF from the 6 pole 1/5 scale motors correctly.

If you only want to bash with it and want to keep the setup the same there is a leopard 1/5 scale 1340kv motor that is a 4 pole.
That would be a relatively low cost option to fix the issue but keep things similar to how they are.

This chassis came with 4 motor mount positions. Basically left/right and then forward/rear, but still uses the normal length shafts. I drilled my own holes to use the equal length shafts and so I could mount the motor as is.

 

[rotauq]

As for the air unit, I will definitely be adding a fan and separate battery pack to power it. Then I can decide where to mount it, the wing seems like a decent place for it. I'm not really satisfied with the current wing setup I have. It's floppy and it still uses the shaved plastic wing. I'd like to potentially upgrade the braces to aluminum and make my own wing.

This is how i had mounted it (2 year old pics from my buildlog)
3D printed FPV tower / dynamic wing prototype was obviously fragile but it worked great.
As you can I mounted mine outside so it was cooled by driving.

I am unsure if the air unit need an arming signal to start recording. (I only have vista's without onboard recording)
If so you will have to access the OSD at least once to disable arming feature to make it leave the pit mode. If you keep the 5.8ghz broadcasting power low, it should not get hot, assuming you don't wanna use fpv glasses.

 

[RepEvox]

Very cool, I didn't check your build thread, but do you use the goggles ever? I have a DJI FPV so it would be easy to do though not very safe. Not sure I would be comfortable driving it without rear view or the potential for feed loss. It occasionally happens with the FPV, but the worst thing that usually happens is the drone corrects itself as opposed to a 20lb car flying at 100mph.

I am officially spooked to drive this with the motor seeing as multiple people told me it would explode my electronics. What dual motor setup would you all recommend? 1721? TP4070CM? I'm not really trying to get 205mph, but my pockets are burning a hole and I want something to work on.

I'm already starting to talk to people to see if I can get my hands on 8s2p packs and I have a bunch of parts in my shopping carts.

 

[Diem Turner]

Either would surely be fun, though I'm not sure I'd recommend going the dual motor route just for s & giggles if I haven't, at least somewhat, plumbed the depths of a single motor setup. I'm not trying to talk you out of it, but when you get into the ridiculous amounts of torque that are generated by dual motor setups you begin creating a lot of new problem relating to the drivetrain and the strain you're putting it under. I think that was the primary impetus for Raz creating his PP CF drive shafts because he was shearing the cross pins off of everything with a dual 1717 setup. He blew a lot of diffs, both with and without diff lockers. You'll probably be changing diff input bearings every few runs...I guess my point is you'll want to spend at least as much money and time on bullet proofing your drivetrain to the extent that this is possible. But please, don't let me deter you from going balls out
The 1721 is sensored and ridiculously smooth that Raz pulled 192mph on 8S parallel with on a single motor. I've gotten my Infraction to 122mph on 3S parallel with the 1721. On balance, Raz got a dual 1717 to 198mph but I could understand if you had misgivings about the Kevlar wrapped rotors. If going the TP route the 4070CM would surely be a great choice too, though I'd probably go with the 4080CM, but that's just my personal preference.

 

[RepEvox]

I think I'll take your advice and make a few smaller orders for a single 1721 build to start out with. The dual motor setup feels like an itch to be scratched so I'll resist the impulse for now. I think I'll keep my motor mount placement and order a full set of titanium driveshafts from scorched along with a new wing. In the meantime I'll keep my eye out for the new TP motors and competitor's options. Maybe James Mccoy will shed some light on his setup; I think he alluded to it, telling me to stay tuned when I made a comment on his 204mph run.

 

[rotauq]

Very cool, I didn't check your build thread, but do you use the goggles ever? I have a DJI FPV so it would be easy to do though not very safe. Not sure I would be comfortable driving it without rear view or the potential for feed loss. It occasionally happens with the FPV, but the worst thing that usually happens is the drone corrects itself as opposed to a 20lb car flying at 100mph.

I've done some FPV driving. DJI range goes further than radio range on high power.
For speedrunning you do need a spotter for safety, it's not really handy... except for turning the car around out of sight
For bashing/exploring it's simular to drone flying. I've done many runs in my garden.

 

[RepEvox]

Here's a small update before I get my next batch of upgrades in. I'm going to try to find a clean way of holding the 2 antennae 90 degrees apart as shown. Waiting on the new wing to show up and my GPM aluminum parts that may help stiffen everything up if I decide to use them. My radio is also complete. I bought a 3W 2.4GHz repeater, but had to add a small DC/DC switcher board to boost the 2s lipo receiver pack to 12VDC. This combined with the air receiver should meet my range requirements without having to stand on a 50ft ladder. I am playing around with the features on the radio to make the Limitless easier to control without having to use the $75 perfect pass. All radios have a built in a throttle speed, so I think this combined with a steady finger and creeping up the end points will help me get used to speedrunning again. Oh and I installed new BSR tires and some rubber bump stops on the rear shocks. I cut a slit in them so I can remove them and trim them as needed, hopefully they don't pop out.

I still have a few things to do as the parts come in. Install wing, new ti driveshafts x 6, reshim diffs, zero trim on steering and adjust turnbuckles, paint and cut new body, play around with GPM aluminum parts for stiffening, install 30CFM 50mm fans and motor heatsink.