Lost Sight of Limitless Turning Around and Smacked Into A Rock

[Diem Turner]

Thank you for the information. I might be using a crappy speed calculator since it only asks about my gearing and diff gearing, motor kv, and tire diameter. This is the data from the pass itself:
-Current: 305.8 amps
-Max RPM: 39,438
-Voltage: Min 27v
Avg 32.9v
Max 33.8v

https://scriptasylum.com/rc_speed/top_speed.html

This is the speed calculator I use and, once you get voltage sag correctly dialed in, it's really accurate. One thing you don't want to forget is when inputting motor KV, start at 80% of the KV value of the motor. It will probably require a little bit of tweaking but that should get you in the ballpark. The KV rating of all motors is freestanding, not accounting for load. A 1650KV motor is realistically closer to 1320KV and so forth.

Here's a typical calculation for an Infraction V2 with 2.8 ratio diffs and a 2400KV motor.

Just for the record, this car did indeed max out at 122mph.

 

[GTRider610]

That one seems a bit more in depth than the one I’ve been using. To be fair the one I was using was spot on for most other gearing scenarios. This is the one I’ve been using https://www.radiocontrolinfo.com/information/rc-calculators/rc-car-calculator/. I just did a test on the one you use for 8s pass and my gearing. Got 146mph and similar rpms to my pass.

 

[Diem Turner]

That one seems a bit more in depth than the one I’ve been using. To be fair the one I was using was spot on for most other gearing scenarios. This is the one I’ve been using https://www.radiocontrolinfo.com/information/rc-calculators/rc-car-calculator/. I just did a test on the one you use for 8s pass and my gearing. Got 146mph and similar rpms to my pass.

View attachment 226233

You're calculating at 30V which is pretty ambitious, if not to say unrealistic. 27-28V is probably more like what you're going to see IRL under full load. Set it for 8 cells, 3.5V per cell for a start.

Edit: Oh, so you did actually hit 146mph? I might have had this thread confused with a different one. In that case, my bad. One thing that does start becoming a difficult to calculate variable is wind resistance. Once you get up there, air becomes more like driving through a cheesecake

 

[rotauq]

You're calculating at 30V which is pretty ambitious, if not to say unrealistic. 27-28V is probably more like what you're going to see IRL under full load. Set it for 8 cells, 3.5V per cell for a start.

Edit: Oh, so you did actually hit 146mph? I might have had this thread confused with a different one. In that case, my bad. One thing that does start becoming a difficult to calculate variable is wind resistance. Once you get up there, air becomes more like driving through a cheesecake

Nah, his pass was 137 whereas the calculator predicted 146.

Thank you for the information. I might be using a crappy speed calculator since it only asks about my gearing and diff gearing, motor kv, and tire diameter. This is the data from the pass itself:
-Current: 305.8 amps
-Max RPM: 39,438
-Voltage: Min 27v
Avg 32.9v
Max 33.8v

Most important is how the voltage does after your minimum (likely the point the esc gives 100% power out). Does it increase, is it stable or volatile. Best just copy in you log zoomed in at the 12s you did the run. We'll also be able to tell if you are smooth enough on the throttle. A big part of battery sag can be caused by your trigger finger. (not much doubt there though, getting up 137 means you got some feeling there)

300A is not accessive load yet, meaning your motor can handle more. But when your gearing (thus load) increases, voltage sag and motor inefficiency will increase. It's all about finding that sweetspot.

 

[Diem Turner]

Nah, his pass was 137 whereas the calculator predicted 146.

Most important is how the voltage does after your minimum (likely the point the esc gives 100% power out). Does it increase, is it stable or volatile. Best just copy in you log zoomed in at the 12s you did the run. We'll also be able to tell if you are smooth enough on the throttle. A big part of battery sag can be caused by your trigger finger. (not much doubt there though, getting up 137 means you got some feeling there)

300A is not accessive load yet, meaning your motor can handle more. But when your gearing (thus load) increases, voltage sag and motor inefficiency will increase. It's all about finding that sweetspot.

Ok, then this was the thread I thought it was and my original suggestion to bump the voltage down to 27-28V stands. Don't get too hung up on what the data log says about RPMs as those aren't super accurate.

This is what I get when I calculate his case (the amps can be left out as they're not relevant to speed calculation, only power output). Fairly spot on, no?

 

[rotauq]

Ok, then this was the thread I thought it was and my original suggestion to bump the voltage down to 27-28V stands. Don't get too hung up on what the data log says about RPMs as those aren't super accurate.

This is what I get when I calculate his case (the amps can be left out as they're not relevant to speed calculation, only power output). Fairly spot on, no?
View attachment 226240

Seems spot on.
I use my own excel sheet to thinker with the numbers.

Using the speed calculator is just one thing though, understanding what and why those variables do or don't is another.

 

[Diem Turner]

Seems spot on.
I use my own excel sheet to thinker with the numbers.

Using the speed calculator is just one thing though, understanding what and why those variables do or don't is another.

100% and I by no means lay claim to understanding it all. I go on 2 parts logical deduction, 1 part understanding, 3 parts intuition and a dash of luck.

 

[GTRider610]

Noted on the voltage input. Makes sense why my speeds on that calculator were so high at first. I tried to zoom into the logs from the 137 run as best as I can. This was my first 8s pass on foams, so I was pretty nervous and I'm sure it will show that in my throttle curve.

 

[Diem Turner]

Noted on the voltage input. Makes sense why my speeds on that calculator were so high at first. I tried to zoom into the logs from the 137 run as best as I can. This was my first 8s pass on foams, so I was pretty nervous and I'm sure it will show that in my throttle curve.

View attachment 226282

Ah gotcha. You can lock the vertical axis in the "view" menu. That will prevent your view from being cut off at the top/bottom.

 

[GTRider610]

Motor mount and spool didn't show today. Looks like that ETA is now Tues or Wed. Gonna use the stock spool and mount for now to get the car dialed. Painted the wing a bright yellow to try and match the front/avoid me from hitting anymore peoples landscaping. Waiting on the clear coat to dry before mounting. She's almost ready to start dialing back in via test passes.

 

[Diem Turner]

Motor mount and spool didn't show today. Looks like that ETA is now Tues or Wed. Gonna use the stock spool and mount for now to get the car dialed. Painted the wing a bright yellow to try and match the front/avoid me from hitting anymore peoples landscaping. Waiting on the clear coat to dry before mounting. She's almost ready to start dialing back in via test passes.

View attachment 226312

You mean you painted it yellow so people's landscaping could see you coming and not jump out in front of it.

 

[GTRider610]

You mean you painted it yellow so people's landscaping could see you coming and not jump out in front of it.

I like your logic.

 

[rotauq]

Noted on the voltage input. Makes sense why my speeds on that calculator were so high at first. I tried to zoom into the logs from the 137 run as best as I can. This was my first 8s pass on foams, so I was pretty nervous and I'm sure it will show that in my throttle curve.

View attachment 226282

Without vertical axis locked it's hard to tell what the voltage is doing. But even without i am quite sure your rpm was still increasing. Ideally you want to have the curve go flat before you brake. If you had given it 2-3s longer at max throttle you would have passed 140 imho.

Your throttle input is indeed initially cautious with maybe a little much buildup at the end. Current-line is quite steep at 181-183.

 

[GTRider610]

Without vertical axis locked it's hard to tell what the voltage is doing. But even without i am quite sure your rpm was still increasing. Ideally you want to have the curve go flat before you brake. If you had given it 2-3s longer at max throttle you would have passed 140 imho.

Your throttle input is indeed initially cautious with maybe a little much buildup at the end. Current-line is quite steep at 181-183.

I agree. I was def very much puckered since it was my first time going full send on foams. Didn't go bad just heard a bunch of horror stories. Hopefully this week I can hold WOT a bit longer and see what happens.

 

[rotauq]

For our 3S challenge i just switched from foams back to GRP's. It's the other way around for me.
Foams not being that grippy is a good thing as they will temper your trigger finger too.
Most important difference to me is the breaking. On foams I've set my braking power up 70%

 

[AIan]

You mean you painted it yellow so people's landscaping could see you coming and not jump out in front of it.

I’d put a horn on it too then landscaping can hear you and move out the damn way!!

 

[GTRider610]

For our 3S challenge i just switched from foams back to GRP's. It's the other way around for me.
Foams not being that grippy is a good thing as they will temper your trigger finger too.
Most important difference to me is the breaking. On foams I've set my braking power up 70%

Noted. Hopefully I can keep it in 1 piece long enough to see.
Well got her back together, but seems like there is still a problem with the suspension. Rebuilt the whole car and somehow the grub screw on the same side as before just spins and won’t bring the car down anymore than about half the height of the other side. I replaced the A arm and grub screw on the problem side and it does the exact same thing as before. I’m assuming something is bent creating a height difference, but I have no idea. My only guess is a bend in the front shock tower? Everything looks normal and it’s driving me nuts. I rebuilt the whole thing and it’s still acting up lol.

 

[GTRider610]

I started replacing the other sides A arms and suspension components and noticed a very uneven sag in the A arms from the original to all the replaced stuff. The shocks are off and droop screws are backed all the way out and threaded just enough to not fall out and get lost. I'm trying to figure out what is causing it since nothing is standing out too much. I am slowly just stripping and replacing everything in the front end until I figure it out. I had most of the parts already to do that. I would just need a shock tower at most. Figured swapping to a brand new chassis would eliminate this problem, but apparently not lol.

 

[Diem Turner]

I started replacing the other sides A arms and suspension components and noticed a very uneven sag in the A arms from the original to all the replaced stuff. The shocks are off and droop screws are backed all the way out and threaded just enough to not fall out and get lost. I'm trying to figure out what is causing it since nothing is standing out too much. I am slowly just stripping and replacing everything in the front end until I figure it out. I had most of the parts already to do that. I would just need a shock tower at most. Figured swapping to a brand new chassis would eliminate this problem, but apparently not lol.

View attachment 226415

Yeah, that looks off bro, I feel ya. I wish I had any idea what it is. Just a shot in the dark...have you tried removing the sway bar?

 

[cduna]

Speedrunning is this way..expect to total car out everytime, then when it happens ya won't be so upset.ive totaled out many,I push them to an past there limits..this was my worst,lost everything, but motor.car ranaway on its own 70mph into curb.1000ish $ loss

View attachment 224955

This pic makes me want to cry but then again it’s garage time to bring her back to life !