Limitless Rot's 140+ mph Limitless GT build log

[jondilly1974]

I am not sure how practical something like this would be. I am not a big fan of ladders, definitely not that i am missing some toe-stability. A raised plateau like this would be awesome and this one is advertised as 'foldable'

View attachment 165397

I myself am most curious how good this motor with (2x)2x4S will run. I do wanna make a big leap in PB with this config.

A baker rack wouldn’t be impossible but it’s far from convenient IMO. I would much rather just use a standard step ladder, or if you want a larger platform, use a podium style ladder like James McCoy uses.

 

[rotauq]

Added some epoxy & glass fiber reinforcements to the body and made a start with the underbody aero:

 

[rotauq]

I was a bit pre-occupied with upgrading my FG Marder (to belted 4x4/brushless). FG is awesome, but any little change requires it to be completely disassembled. As it's nearly finished i am re-focussing on my limitless.

Done a couple of runs with my TP 5840L/Corvette C8 body (with rear wheel extenders) and it runs straight as an arrow. The car gives confidence, which i still lack myself. Even standing behind my car i've still not really given it 'full pulls'.

What i did do was, compare the voltage sag of 8S on 2x 6200mAh vs 4x 6200mAh. I didn't keep the logs but benchmark runs showed a promising + ~2.5V/ ~50A

When I pushed harder I was getting weird rpm readings:

Peaking 45070rpm is basically no load rpm? All grubscrews were locktited and after the run as wel. Motor coolribs scraped and my cupsock (waterhose) destroyed.

After looking for alternative Pinocchio spools, carbon or other, none easily ship to the EU. So i figured i'd make my own from 8mm steel. I made it 2cm longer which makes it compatible with the front dogbone. I actually still consider to add a third bearing at the end, pretty sure that would kill a lot of resonance. Further paths could be to raise the rear and front diffs some more to improve the alignment:

 

[LibertyMKiii]

I was a bit pre-occupied with upgrading my FG Marder (to belted 4x4/brushless). FG is awesome, but any little change requires it to be completely disassembled. As it's nearly finished i am re-focussing on my limitless.

Done a couple of runs with my TP 5840L/Corvette C8 body (with rear wheel extenders) and it runs straight as an arrow. The car gives confidence, which i still lack myself. Even standing behind my car i've still not really given it 'full pulls'.

What i did do was, compare the voltage sag of 8S on 2x 6200mAh vs 4x 6200mAh. I didn't keep the logs but benchmark runs showed a promising + ~2.5V/ ~50A

When I pushed harder I was getting weird rpm readings:
View attachment 170714
Peaking 45070rpm is basically no load rpm? All grubscrews were locktited and after the run as wel. Motor coolribs scraped and my cupsock (waterhose) destroyed.

After looking for alternative Pinocchio spools, carbon or other, none easily ship to the EU. So i figured i'd make my own from 8mm steel. I made it 2cm longer which makes it compatible with the front dogbone. I actually still consider to add a third bearing at the end, pretty sure that would kill a lot of resonance. Further paths could be to raise the rear and front diffs some more to improve the alignment:

View attachment 170713

Can't really explain the no load rpms the logs recorded, but I like the idea of a bearing carrier to support that Pinocchio shaft.
I suspect harmonics and vibrations are to blame with the odd rpm readings near the end. A high speed camera watching the rear shaft sure would tell a story.

I had read before that some misalignment is a good thing, but maybe using the rubber o-rings and things that we do mitigate the slop might resolve the issues of a straight alignment dog bone setup as they want to bounce and chatter.

 

[rotauq]

Can't really explain the no load rpms the logs recorded, but I like the idea of a bearing carrier to support that Pinocchio shaft.
I suspect harmonics and vibrations are to blame with the odd rpm readings near the end. A high speed camera watching the rear shaft sure would tell a story.

I had read before that some misalignment is a good thing, but maybe using the rubber o-rings and things that we do mitigate the slop might resolve the issues of a straight alignment dog bone setup as they want to bounce and chatter.

Good point. Perfect alignment could indeed enhance harmonics as the wear and tear on the cups and bones would match the rotating forces. My guess it's also part of the source. Extending Pinocchio's nose did increase the angle some more vs the 10cm scorched spool..

The win should mostly be the 'solid' spool and the shorter dogbone.

 

[LibertyMKiii]

These harmonics and vibrations really do impact the performance in a bad way. These little shockwaves in the driveline translate back into the motor and the ESC freaks out seeing odd back EMF readings. A smooth running driveline is one of the keys to high speeds.

I have wondered about a design that would act much like a 1:1 car drive shaft rubber coupler that isolates vibrations and takes the larger shock/impacts. It would be introducing a new failure point and additional rotational mass into the system, but might be beneficial.

The more I see on dog bone setups the more I am glad my 200+ build has belts

 

[rotauq]

These harmonics and vibrations really do impact the performance in a bad way. These little shockwaves in the driveline translate back into the motor and the ESC freaks out seeing odd back EMF readings. A smooth running driveline is one of the keys to high speeds.

I have wondered about a design that would act much like a 1:1 car drive shaft rubber coupler that isolates vibrations and takes the larger shock/impacts. It would be introducing a new failure point and additional rotational mass into the system, but might be beneficial.

View attachment 170739

The more I see on dog bone setups the more I am glad my 200+ build has belts

Belted has some advantages. I also suspect it to be much more efficient. On my 10kg FG i've not yet manged to pull more than 4000W (XLX2/5694-1000kv). I also like how elegantly FG managed to loop the belt basically flat on the chassis bottom. Might be a option for your build too:

I 1:1 car diff coupler like that would be 'calmer'. No clashing of cups and dogbones. FG has thick rubber socks which also dampen the clashing some. So far my best result is some waterhose over the cup and then fill it with some shoo goo. It held great everywhere except at the Pinocchio side.

Whiles drawing my first quick prototype i figured clamping it on the top brace would be good, seems to work fine:

 

[LibertyMKiii]

Belted has some advantages. I also suspect it to be much more efficient. On my 10kg FG i've not yet manged to pull more than 4000W (XLX2/5694-1000kv). I also like how elegantly FG managed to loop the belt basically flat on the chassis bottom. Might be a option for your build too:

View attachment 170744

I 1:1 car diff coupler like that would be 'calmer'. No clashing of cups and dogbones. FG has thick rubber socks which also dampen the clashing some. So far my best result is some waterhose over the cup and then fill it with some shoo goo. It held great everywhere except at the Pinocchio side.

Whiles drawing my first quick prototype i figured clamping it on the top brace would be good, seems to work fine:

View attachment 170763

I would need a longer belt, which does not exist so I would have to re-design. With that said I do like how they did that!

Would another PPS bearing carrier work or would it need to be machined down?

 

[rotauq]

I would need a longer belt, which does not exist so I would have to re-design. With that said I do like how they did that!

Would another PPS bearing carrier work or would it need to be machined down?

An extra PPS bearing carrier would be ideal, but as you already expected it's on uneven ground and would require to be machined down. Just gonna start with some 3d print prototypes and see where it leads to

 

[rotauq]

Even though my testrun ended up in some unintended gymnastics,

(Do check this magnificent landing if you've not seen it)

It was actually an ideal testscenario for my my PLA 'pinocchio noseclamp'. Logs now look really clean even with the in-air low load max rpm. Satisfied with the concept i've done some improvements on the design. Carrying the receiver and bridging it to the pps motor mount.

In the meantime, as it's raining constantly, i figured i'd take on my cable management:

Redid all my front lights:

And the rear lights:

Lighted powerbuttons; left cooling/lights , right ESC power

As it's become a bit complex, i made my own wiring diagram:

I also made a smaller spoiler. The old one will get it's second life as a snowshovel in my crawler:

Some sideglow to make it more visible.

The wrapping in the rear is part of the body i am considering to cut off. I feel like the gaping at the wheels is too much making the C8 struggle at high speeds. Rear lights also include a pulsing lights which are not visible on the picture:

 

[Sandracer_NL]

1. 3d print is next level
2. cable management is nice and clean
3. lighting looks better
4. power button looks real nice
5. shovel is sweet, hopefully some snow this winter
6. power diagram…

 

[Edough13]

Some amazing work for sure @rotauq pretty intense with all the wiring and lights etc I don't imagine that's easy to setup and keep tucked and Purdy at all. Love the re purpose with the spoiler to a snow plow also that's awesome!

 

[jondilly1974]

I need to redo my wiring soon as I usually locate it all on the T2T brace, which makes gear changes a PITA. Time to redo both rigs.

 

[rotauq]

1. 3d print is next level
2. cable management is nice and clean
3. lighting looks better
4. power button looks real nice
5. shovel is sweet, hopefully some snow this winter
6. power diagram…

90% of my day job is making functional drawings, so a wire diagram was an easy task. Running so many signalleads and most of all lots of different voltages i think it was a smart thing to do. I am not 20 anymore it's getting harder and harder to remember everything.

I need to redo my wiring soon as I usually locate it all on the T2T brace, which makes gear changes a PITA. Time to redo both rigs.

I now have it all wrapped, exact lenghts, parallel to the T2T brace. I got a few velcro straps to extra secure it. I am really happy how it all worked out. I can almost remove all parts, leaving the wiring all intact.

 

[rotauq]

While prepping the limitless for a few high expectation run(s) at airport on monday, I decided not to go for the Protoform C8 body. It has to run with wheel hub extenders and i don't trust those at real high speeds.

So I decided to get me the Bittydesign Seven65 as it could be delivered within a few days. With my colorblindness & adequate sight I set my requirements full on visibility. A must to be able to see it and it's direction at long distance at dusk and preferably plenty of wide front light to be capable at actual night runs.

I think i can call it successful. It's starting to look more and more like my water-cooled PC I also think the powerbuttons at the rear, which needed to be redesigned came out both nice and functional. I painted it black, with some gunsmoke added. Might not be best for daylight visibility but it blocks stray light.

The bittydesign body (McLaren 720s I think) not only looks good, it fits amazingly tight. It hardly needs reinforcement and even the spoiler is solid. (unlike the floppy protoform) I might even keep it for a while.

ps. I have been meaning to realign the arrmaforum stickers, but they really are too sticky and leave a lot of residue.

 

[Malice]

That looks awesome

 

[Edough13]

Amazing job @rotauq! Looks like a night club on wheels

 

[jondilly1974]

While prepping the limitless for a few high expectation run(s) at airport on monday, I decided not to go for the Protoform C8 body. It has to run with wheel hub extenders and i don't trust those at real high speeds.

So I decided to get me the Bittydesign Seven65 as it could be delivered within a few days. With my colorblindness & adequate sight I set my requirements full on visibility. A must to be able to see it and it's direction at long distance at dusk and preferably plenty of wide front light to be capable at actual night runs.

View attachment 173242View attachment 173243
View attachment 173240
View attachment 173241

I think i can call it successful. It's starting to look more and more like my water-cooled PC I also think the powerbuttons at the rear, which needed to be redesigned came out both nice and functional. I painted it black, with some gunsmoke added. Might not be best for daylight visibility but it blocks stray light.

The bittydesign body (McLaren 720s I think) not only looks good, it fits amazingly tight. It hardly needs reinforcement and even the spoiler is solid. (unlike the floppy protoform) I might even keep it for a while.

ps. I have been meaning to realign the arrmaforum stickers, but they really are too sticky and leave a lot of residue.

I really am looking forward to seeing some big numbers from your runway passes.

 

[Doom!]

Please bring her home in one piece, she's a real looker! Good luck Monday!

 

[rotauq]

I really am looking forward to seeing some big numbers from your runway passes.

I am still in doubt what numbers to aim for. It's more than twice the distance i've ever run before.
Work in the morning will be hectic and a toe-checkup at the hospital, so i likely have only about 1.5 hour to do some runs.

I don't wanna do spur changes on site, just pinions. (27T-46T)
I'll bring:
2x 4S 6000 G+
4x 4S 6200 Racings (parallel?)
2x 3S 6200 Racings (warm up/trackfeel)
1x Turnigy heaterbag
Laptop for datalog check (gear up or down)
extra set of tires
general tools

So the question is, will i start with a 150 'banker' run and then go up or directly aim opportunistically for 170