Limitless Yet another GT build

[K-BASH]

Thats a great idea! I'll measure later - but I wonder if the caster shims would work there (snip off the ears). Might be too big if memory serves. I like this a lot, though. Thank you for sharing!

The stuff I was looking at in Raz's videos he seems to use quite a bit. Its got a red outer lining and a black center. Almost kind of looks like low pressure hydraulic line - but the color is more vivid. And it looks like there are sections and not one piece. No springs. I see it a lot in his earlier videos - I figured he'd evolved away from it - but I saw it in a pretty recent one, too.

I'm excited to get it out there - but I'm in the midwest and winter is pretty much here. So I've got a few months to kill before I can rip it.

Thinking outside the box,,it's things like this that makes me love the hobby so much.even if it don't work,great thery an then built well an looks like it could work.A+ for creativity,this isn't fakebook where everyone talks $hit to each other...Great group of older speedrunners on here..welcome an if this dual 1721 setup works it'll change the speedrunning game fosho...really hope it'll run um without issues,makes perfect sense to me,lighter fluid in diff would let them breath a little better opposed to heavy fluid .I'm in st louis,what, part of midwest you in??

 

[Tirefryer426]

Thinking outside the box,,it's things like this that makes me love the hobby so much.even if it don't work,great thery an then built well an looks like it could work.A+ for creativity,this isn't fakebook where everyone talks $hit to each other...Great group of older speedrunners on here..welcome an if this dual 1721 setup works it'll change the speedrunning game fosho...really hope it'll run um without issues,makes perfect sense to me,lighter fluid in diff would let them breath a little better opposed to heavy fluid .I'm in st louis,what, part of midwest you in??

I'm over in Omaha. For sure this is way more civil than the other place. haha.

I think having something a little different is the main reason I built the car. And it was fun to work out. Got the design simplified so that there are only two custom parts and only three holes that needed drilled in the chassis. My dad is a machinist, so it was also fun to be able to involve him in making the parts.
The diff fluid will for sure be trial and error. Originally I was going with 1 mil in the center. I want the two halves to share power as much as possible, and I don't want one side to be able to dramatically run away from the other. Then I think I start to have the problems Mike has with his car. So I figure start in the middle-ish and work up or down. I thought for a second lighter fluid would potentially help with blow overs, but the more I think about it the less I think it would help. Once an aero blowever starts at higher speeds a power cut or diff slip isn't going to stop it. BUT - I am starting to think about trying to make some aero disruptors like what they use in Nascar.

On paper I think the car has a ton of potential. Gonna take the driver a while to get there, though! Lot of awesome experience here to draw from.

 

[Diem Turner]

I'm over in Omaha. For sure this is way more civil than the other place. haha.

I think having something a little different is the main reason I built the car. And it was fun to work out. Got the design simplified so that there are only two custom parts and only three holes that needed drilled in the chassis. My dad is a machinist, so it was also fun to be able to involve him in making the parts.
The diff fluid will for sure be trial and error. Originally I was going with 1 mil in the center. I want the two halves to share power as much as possible, and I don't want one side to be able to dramatically run away from the other. Then I think I start to have the problems Mike has with his car. So I figure start in the middle-ish and work up or down. I thought for a second lighter fluid would potentially help with blow overs, but the more I think about it the less I think it would help. Once an aero blowever starts at higher speeds a power cut or diff slip isn't going to stop it. BUT - I am starting to think about trying to make some aero disruptors like what they use in Nascar.

On paper I think the car has a ton of potential. Gonna take the driver a while to get there, though! Lot of awesome experience here to draw from.

FWIW, from my own observations blow overs seem to be more dependent on suspension setup than anything else. As long as you can guarantee that the rear of your car remains higher than the front, that should take care of most (if not all) of it. Press down as hard as you can on the rear of the car and if your chassis goes anywhere near level, add more suspension limiting. That's my take anyways.

 

[LibertyMKiii]

Great build and like others said I am happy to see people trying things.
Something you might talk to your dad about is how he might implement a drive shaft damper in the system.

The ESCs "feel" harmonics and feedback from the other motor. The ESC thinks this is some issue with the motor and can dial back the power. I think a damper in the system might be the solution to get both systems to open up for full power. (my belief on why Raz's dual castle setup didn't go faster)

I think something like we do for drive shaft couplers is the way to go but have not figure out how to make it 1/7 scale and still strong enough...

 

[K-BASH]

I'm over in Omaha. For sure this is way more civil than the other place. haha.

I think having something a little different is the main reason I built the car. And it was fun to work out. Got the design simplified so that there are only two custom parts and only three holes that needed drilled in the chassis. My dad is a machinist, so it was also fun to be able to involve him in making the parts.
The diff fluid will for sure be trial and error. Originally I was going with 1 mil in the center. I want the two halves to share power as much as possible, and I don't want one side to be able to dramatically run away from the other. Then I think I start to have the problems Mike has with his car. So I figure start in the middle-ish and work up or down. I thought for a second lighter fluid would potentially help with blow overs, but the more I think about it the less I think it would help. Once an aero blowever starts at higher speeds a power cut or diff slip isn't going to stop it. BUT - I am starting to think about trying to make some aero disruptors like what they use in Nascar.

On paper I think the car has a ton of potential. Gonna take the driver a while to get there, though! Lot of awesome experience here to draw from.

Lol I totally agree with you there.i grew up just south of Lincoln, Nebraska is unlike any other place I've ever been an love going back there to see family...I actually just inherited a bunch of farm ground that's been in the family forever...got all my grain out the field,I now fires are super bad up there right now.

 

[Tirefryer426]

Great idea!

We have been kicking around a few ideas. One of them was exactly this instead of a differential. My concern with the damper was that it was going to be harder to tune (and its not easy to make) Reason being is that there will definitely be power consumption difference between the front and the rear systems. So in my mind, a damper like this would eventually reach its limit and essentially go full lock and transmit feedback. It might still be enough if it were made of the right material even at full bind/lock. Definitely be better than being mechanically connected to the same drive gear. Its on the table for sure if the diff idea chokes. This could even be a next step after I get the gearing worked out between the front and the rear to tune the amp draw to be close together. Could try making it out of a tire?

We were looking at leveraging a heavy spring in a case instead of the diff. Talked about doing a slipper clutch.

We may still do this - but another option on the table was going belt drive. It would eliminate a lot of the bad harmonics in the drive line. But it makes gearing changes pretty much a no go. The car would have to be built for its theoretical top speed target and the power dialed back with trim limits in the transmitter. So instead of gearing up you would dial a few % points back in on the TX. What I'm not sure about is whether or not that is harder on the ESCs to run that way. I've been under the assumption thats why people don't do it that way currently. Just gear the car for what you want it to do and dial the power in with the electronics.

Great build and like others said I am happy to see people trying things.
Something you might talk to your dad about is how he might implement a drive shaft damper in the system.

The ESCs "feel" harmonics and feedback from the other motor. The ESC things this is some issue with the motor and can dial back the power. I think a damper in the system might be the solution to get both systems to open up for full power. (my belief on why Raz's dual castle setup didn't go faster)

I think something like we do for drive shaft couplers is the way to go but have not figure out how to make it 1/7 scale and still strong enough...
View attachment 256431

Lol I totally agree with you there.i grew up just south of Lincoln, Nebraska is unlike any other place I've ever been an love going back there to see family...I actually just inherited a bunch of farm ground that's been in the family forever...got all my grain out the field,I now fires are super bad up there right now.

Thats awesome! My SO is from Davey, a little north of Lincoln. Might be looking at a few roads out that way as possibilities in case the road I have picked out doesn't cut it.
Its been a crazy dry year. There might have even been a burn ban.

 

[LibertyMKiii]

Great idea!

We have been kicking around a few ideas. One of them was exactly this instead of a differential. My concern with the damper was that it was going to be harder to tune (and its not easy to make) Reason being is that there will definitely be power consumption difference between the front and the rear systems. So in my mind, a damper like this would eventually reach its limit and essentially go full lock and transmit feedback. It might still be enough if it were made of the right material even at full bind/lock. Definitely be better than being mechanically connected to the same drive gear. Its on the table for sure if the diff idea chokes. This could even be a next step after I get the gearing worked out between the front and the rear to tune the amp draw to be close together. Could try making it out of a tire?

We were looking at leveraging a heavy spring in a case instead of the diff. Talked about doing a slipper clutch.

We may still do this - but another option on the table was going belt drive. It would eliminate a lot of the bad harmonics in the drive line. But it makes gearing changes pretty much a no go. The car would have to be built for its theoretical top speed target and the power dialed back with trim limits in the transmitter. So instead of gearing up you would dial a few % points back in on the TX. What I'm not sure about is whether or not that is harder on the ESCs to run that way. I've been under the assumption thats why people don't do it that way currently. Just gear the car for what you want it to do and dial the power in with the electronics.



Thats awesome! My SO is from Davey, a little north of Lincoln. Might be looking at a few roads out that way as possibilities in case the road I have picked out doesn't cut it.
Its been a crazy dry year. There might have even been a burn ban.

Yes I think your fluid diff may do the job well. Glad you had already thought about these things.
My 200+ build is what you talked about gearing is limited so changing the voltage and KV is part of the equation.

 

[K-BASH]

Great idea!

We have been kicking around a few ideas. One of them was exactly this instead of a differential. My concern with the damper was that it was going to be harder to tune (and its not easy to make) Reason being is that there will definitely be power consumption difference between the front and the rear systems. So in my mind, a damper like this would eventually reach its limit and essentially go full lock and transmit feedback. It might still be enough if it were made of the right material even at full bind/lock. Definitely be better than being mechanically connected to the same drive gear. Its on the table for sure if the diff idea chokes. This could even be a next step after I get the gearing worked out between the front and the rear to tune the amp draw to be close together. Could try making it out of a tire?

We were looking at leveraging a heavy spring in a case instead of the diff. Talked about doing a slipper clutch.

We may still do this - but another option on the table was going belt drive. It would eliminate a lot of the bad harmonics in the drive line. But it makes gearing changes pretty much a no go. The car would have to be built for its theoretical top speed target and the power dialed back with trim limits in the transmitter. So instead of gearing up you would dial a few % points back in on the TX. What I'm not sure about is whether or not that is harder on the ESCs to run that way. I've been under the assumption thats why people don't do it that way currently. Just gear the car for what you want it to do and dial the power in with the electronics.



Thats awesome! My SO is from Davey, a little north of Lincoln. Might be looking at a few roads out that way as possibilities in case the road I have picked out doesn't cut it.
Its been a crazy dry year. There might have even been a burn ban.

I'm from small town off 77 called Cortland between Lincoln an Beatrice....straight ,flat roads ..just hard to find smooth sections..I bet down along the river would be good place to check out..Iowa probly has smoother roads...there's alot of open roads with little traffic out that way..we used to go to Henry dorrly park an zoo yearly for fam reunions...
Wonder how a belt driven setup would work,could double as a clutch for the 2 1721s.only someone from NEB would come up with ideas like this..lol some very intelligent folks in the husker state

 

[Tirefryer426]

I'm from small town off 77 called Cortland between Lincoln an Beatrice....straight ,flat roads ..just hard to find smooth sections..I bet down along the river would be good place to check out..Iowa probly has smoother roads...there's alot of open roads with little traffic out that way..we used to go to Henry dorrly park an zoo yearly for fam reunions...
Wonder how a belt driven setup would work,could double as a clutch for the 2 1721s.only someone from NEB would come up with ideas like this..lol some very intelligent folks in the husker state

Thats crazy! Small world.
And its funny you mention down by the river - thats exactly where my front runner for a road is. This is up north a bit by Boyer Chute.
But its a mile and a half long, flat, straight, no curbs or trees - and almost no traffic. The only hesitation is that there are a few spots that might be too 'dippy'.

 

[K-BASH]

Thats crazy! Small world.
And its funny you mention down by the river - thats exactly where my front runner for a road is. This is up north a bit by Boyer Chute.
But its a mile and a half long, flat, straight, no curbs or trees - and almost no traffic. The only hesitation is that there are a few spots that might be too 'dippy'.

View attachment 256480

Hamburg is probly little over an hr south of you right??I imagine in between the bluffs down in that flat bottoms by Rockport, hamburg area would probly be goood..when ya drive down Nebraska highways they all seam to have sections with the dips.lol I can hear it in my head going down a Nebraska highway...out in that area is God's country.very special place to me...kinda like going to your first huskers game kinda special.usely make it out there every year for harvest...couldn't make it this year thou...

 

[Tirefryer426]

Hamburg is probly little over an hr south of you right??I imagine in between the bluffs down in that flat bottoms by Rockport, hamburg area would probly be goood..when ya drive down Nebraska highways they all seam to have sections with the dips.lol I can hear it in my head going down a Nebraska highway...out in that area is God's country.very special place to me...kinda like going to your first huskers game kinda special.usely make it out there every year for harvest...couldn't make it this year thou...

Yup, just a hair over an hour from here. I may go look out that way. I'm making a list of candidates and then in spring I'm going to go do some passes on my motorcycle to try and find a clean section and a good line. Really hoping the road above will work since its not far from where I live.

 

[Tex Koder]

Great build and like others said I am happy to see people trying things.
Something you might talk to your dad about is how he might implement a drive shaft damper in the system.

The ESCs "feel" harmonics and feedback from the other motor. The ESC thinks this is some issue with the motor and can dial back the power. I think a damper in the system might be the solution to get both systems to open up for full power. (my belief on why Raz's dual castle setup didn't go faster)

I think something like we do for drive shaft couplers is the way to go but have not figure out how to make it 1/7 scale and still strong enough...
View attachment 256431

This is something that needs to be custom 3D printed out of TPU and using 2mm screws..

 

[Dan B.]

What about a different approach to controlling a dual motor setup? Instead of focusing on drivetrain solutions to mask or somehow smooth out deviations from motor to motor, why has no one done this with electronics, some kind of hardware/software that buffers and synchs the outputs of two “paired” ESC’s? Before you say “because an ESC that can control two motors simultaneously doesn’t exist,” I would submit that although that is true the tech must surely exist to regulate each ESC /motor leg to perform on par with the other. A primary controller running two ESC’s, one for each motor. Some kind of ECU running the two ESC’s? A good processor could sort this out, methinks. Just spitballing…
Not suggesting this for your build, @Tirefryer426 , just throwing an idea out there.

 

[Diem Turner]

What about a different approach to controlling a dual motor setup? Instead of focusing on drivetrain solutions to mask or somehow smooth out deviations from motor to motor, why has no one done this with electronics, some kind of hardware/software that buffers and synchs the outputs of two “paired” ESC’s? Before you say “because an ESC that can control two motors simultaneously doesn’t exist,” I would submit that although that is true the tech must surely exist to regulate each ESC /motor leg to perform on par with the other. A primary controller running two ESC’s, one for each motor. Some kind of ECU running the two ESC’s? A good processor could sort this out, methinks. Just spitballing…
Not suggesting this for your build, @Tirefryer426 , just throwing an idea out there.

Because I'm waaay too stupid to do anything like that.

 

[Cereal_killer]

No hate. I wish you the best of luck. I just don’t wanna see an (estimated) $2500+ build get smashed. Just try to gear for 100mph to start. Trust me. Don’t be in a rush. If you have to make a correction it’s nice to know how the car responds. If it doesn’t respond well then it’s better to have it happen at 100 or so than 150+.

+1
We have all have wrecked at one point, some more than others! Including me.. it gets very frustrating sometimes and you just want to sell your stuff! “Been there” lol but if it’s one thing I’ve finally learned about is what @LicketySplit said don’t be in a rush.. start with 4S and move up as you get more comfortable. I failed to learn that first time around. But there is a ton of willing people out here that guide you in the right direction if needed!

 

[Dan B.]

Because I'm waaay too stupid to do anything like that.

Me too, man. But I know someone who may not be. I’m going to run the idea by him the next time we speak. Then I’m going to fire up a big fatty, make a White Russian, and try to nod at the appropriate times in his explanation of why or why not this could work.
And to clarify, at least as far as Arrma Forum is concerned, I find you to be one of the sharpest tools in the shed here.

 

[Diem Turner]

Me too, man. But I know someone who may not be. I’m going to run the idea by him the next time we speak. Then I’m going to fire up a big fatty, make a White Russian, and try to nod at the appropriate times in his explanation of why or why not this could work.
And to clarify, at least as far as Arrma Forum is concerned, I find you to be one of the sharpest tools in the shed here.

I appreciate the kind words brother. We're all just learning together here as we go along. Making observations, reporting back, listening to others, tweaking our positions.

I can't wait to hear about what you guys (or he, whatever the case may be) come up with. I'll be here waiting to say clever things like, "Well that's just, like, your opinion man!!".

You just made me realize how much I miss White Russians

 

[Dan B.]

I appreciate the kind words brother. We're all just learning together here as we go along. Making observations, reporting back, listening to others, tweaking our positions.

I can't wait to hear about what you guys (or he, whatever the case may be) come up with. I'll be here waiting to say clever things like, "Well that's just, like, your opinion man!!".

You just made me realize how much I miss White Russians

Maybe I’m overthinking the approach. Maybe CC should just design a dual ESC with one processor and dual motor outputs. Yeah, that would be easier…. The whole dual motor speed running segment would be so happy!

 

[Diem Turner]

Maybe I’m overthinking the approach. Maybe CC should just design a dual ESC with one processor and dual motor outputs. Yeah, that would be easier…. The whole dual motor speed running segment would be so happy!
View attachment 257367

That's going to be a seriously big ESC

 

[Dan B.]

That's going to be a seriously big ESC

Agreed, but the overall footprint might be the same or even smaller than the two XLX2’s that are currently required.