Jerold's Limitless Build

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Good point, messing with the ESC throttle curve is more accurate and easier than trying it on the RadioLink. I can add just a touch of negative exponential curve, ... I think that is negative? Either way make it look like that. Got it.

You're describing a bump stop. Which, on a real car, prevents you from smashing your axle/control arm/whatever into the frame, which is bad. Riding on the bump stops (done that before) does stiffen the suspension but effectively makes an infinite spring rate and makes the ride super choppy and uncontrollable on a rough road. Small bumps under throttle or braking causes the car to skip and dart.

The nitro tubing is installed in the rear, which ash you described, is a PITA to install. Raz made it look so easy. But I either didn't use enough of it or it's too soft for the amount of down force I have.

I have a lot of ABS plastic and can try the discs like you have. Or I might be able to just buy some plastic washers and split them and wedge them on to the shaft. What do they look like installed? Do they sit under the spring above the spring cup or inside the spring stacked up?
They sit inside the spring stacked up. IIRC I have either 3 or 4 on the rears which limits the suspension travel to something like 2mm with zero droop. I have one less on the front but quite a bit of droop dialed in. This ensures that my car is always raked no matter how hard I press down on the rear and the front never bottoms out.

You are correct that setups like this are less than ideal for rough or choppy roads. I guess my reply to that would be - rough and choppy roads are less than ideal for speed running and will definitely make finding an ideal setup tricky, to say the least.
 
They sit inside the spring stacked up. IIRC I have either 3 or 4 on the rears which limits the suspension travel to something like 2mm with zero droop. I have one less on the front but quite a bit of droop dialed in. This ensures that my car is always raked no matter how hard I press down on the rear and the front never bottoms out.

You are correct that setups like this are less than ideal for rough or choppy roads. I guess my reply to that would be - rough and choppy roads are less than ideal for speed running and will definitely make finding an ideal setup tricky, to say the least.
The road is great for a 1:1 scale, but OK for 1:7 scale. It has a few utility covers and such that can be a bit of an obstacle.
 
A Bit More Work and Some Confusion
First things first. I was hoping to get the mods down then give it a test weekend but it happens to be the one weekend a year it rains in Nor Cal. :cry:
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Too Much Down Force
After the last run I concluded that I have too much down force and the chassis is pan slapping the ground. There were some suggestions about adjustments and nitro tubing. However, I have already have max preload and the nitro tubing is already install on the rear shocks. So I think it's a matter of too much down force. I'm not really cornering so I only need enough to keep it on the ground and going straight.

@Diem Turner had a slick idea with some spacers, which I'm going to try next if this doesn't work. It seems like a pretty simple idea to implement, just cut some plastic washer/spacers and stick them in there. They will act like a bump stop and limit the travel.

To address this, the first thing I did was to reduce the aero. Cut the front by about a 1/3 and the back by about 1/2.
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This gives the front more down force and still has a bit on the back. In Raz's Speed Secrets series he cuts the front to about 1/5 and the back flat. That will get me a few MPH but I'm just not that confident in my driving skills at this point.

Driveshaft Clearance
After the last run I also found out that my fancy Raz Shifrin CF drive shafts are rubbing on the down braces. When you buy them the instructions are very straight forwards that you need to remove your down braces or modify them.

The rear one was very minor and only in one spot. I know the drive shave is balanced so I'm thinking the diff cups are a bit whacked. I took out a bit more material on the rear down brace and will save the drive cups for another day.

The front drive shaft has a nice ring on it. It's really only surface scratch, but you can see it rubbed enough to make it all the way around. Since I moved the servo mount to the front down brace (see post #46) and took out some material, the brace moves a bit. Apparently enough to interfere with the drive shaft.
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So I remade my servo mount to include a 3rd mounting point and stiffen the down brace at the same time. It's a bit larger and has more holes, but the same idea. It uses the two "mounting holes" and I drilled a new one at the bottom.

This is all done by hand, no mill nor CNC, so it's a bit rough in the looks department, but it works.
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This is what it looks like attached to the down brace, note drive shaft clearance tunnel and the nut on the bottom.
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And the other side.
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While I had everything apart I threw in some more caster to help it track straight, or at least that's the idea. Which, according to my Viso skills says it's about 20° of Caster, yikes! I will find out how it works when I hit the road. Which means I need to go through my alignment again. :cool:
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Cleaning Old Thread Lock
I had to remove a few parts to get this done and a lot of metal on metal screws, with nasty old gummed up threadlock on them. I didn't want to put them back in like that. I mean technically it should help keep the screw in there, but it can get pretty hard to put them back in and it's a mess. So I had to find a way to clean up the screws or buy new ones. Since I'm cheap, I'm going to clean them.

I tried a wire brush, but that's not very good. Simple Green does nothing. I thought about brake clean or the ultrasonic cleaner, but it's more stuff to drag out and/or clean up.

In the end I used my mini-torch and a wire brush. Grip the head of the screw with the Vise Grips and heat it till it smokes, then brush the crap out of it. They are super clean after that, but really hot.

For all the metalurgist, no it didn't get hot enough long enough to temper them or change the grain structure.

My Confusion
Don't you hate it when you have one screw left over? In this case I had a M3x12 Cap head screw and I was missing the top nose cone screw.:unsure:
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To fix this mess I was working on I had to pull the center brace, front and rear down braces, PPS Spool cap, move the motor out and remove the spool, the nose cone, left rear body mount and the front brace support (above the control arms). So it could have been just about anywhere.

There was no threadlock on the screw, so I knew it goes into plastic and it's a cap screw, so it not underneath the car.

I had another nose cone screw, but being a bit anal retentive I had to figure out where the to other screw went and what I missed or messed up. I was just about to post a "What Screw is This" thread and I had an idea.

I looked through the schematics and found that it's an M3x12mm screw (PN AR723312), then started looking for all the placed it goes. It turns out that used the nose cone screw to secure the top of the front brace.
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Problem solved!

It's all back together, waiting to be aligned, get new servo endpoint adjustments and a throttle curve.
 
Awesome build thread you have here.very extensive .and you detailed it pretty well.now I understand when you said there wasn't much.in my build thread .my 3 pages doesn't come close to the journey you went through on yours .I believe over 10 pages long and I'm sure there's more ..I my self just started my build thread just about a little while ago and I hope when I'm done it's a journey that helps someone that wants to do the same...we might not think about it but our build threads are also instructional to those who follow us and want to do the same.mean while we are like the student we are learning as we build .we search for advice and hope our ideas work .i my self enjoyed reading your progress actually learned things I didn't know .I thank you for that.again awesome build .👍✌️
 
Awesome build thread you have here.very extensive .and you detailed it pretty well.now I understand when you said there wasn't much.in my build thread .my 3 pages doesn't come close to the journey you went through on yours .I believe over 10 pages long and I'm sure there's more ..I my self just started my build thread just about a little while ago and I hope when I'm done it's a journey that helps someone that wants to do the same...we might not think about it but our build threads are also instructional to those who follow us and want to do the same.mean while we are like the student we are learning as we build .we search for advice and hope our ideas work .i my self enjoyed reading your progress actually learned things I didn't know .I thank you for that.again awesome build .👍✌️
Thanks you. Just about everything I learned about this process I got from this exact forum and people here. It's truly a great community.

Admittedly it's a selfish thread as I documented a lot of stuff so I would remember later. I also might over engineer/analyze things just a little bit and it's more of journal than a build thread. But if other's learn from my mistakes and discoveries, I'm happy to contribute to their delinquency.

As a spectator, looking at my build thread, it's probably a bit wordy and sometimes less is more if you want someone to actually ready it. There are a few other people that read the details, but I'm sure most just look at the pictures. Which is OK too.
 
Thanks you. Just about everything I learned about this process I got from this exact forum and people here. It's truly a great community.

Admittedly it's a selfish thread as I documented a lot of stuff so I would remember later. I also might over engineer/analyze things just a little bit and it's more of journal than a build thread. But if other's learn from my mistakes and discoveries, I'm happy to contribute to their delinquency.

As a spectator, looking at my build thread, it's probably a bit wordy and sometimes less is more if you want someone to actually ready it. There are a few other people that read the details, but I'm sure most just look at the pictures. Which is OK too.
You did your thing.a build thread is a journal.its a story and not everyone does there threads the same nor should they.they all suppose to be unique.yours is .I wish I had organized mine better but I still have time .I'm just updating as I move forward and I may miss some tiny details and maybey I might not explain things the best but point is I'm moving forward and I can allways go back if needed and edit .build threads are meant to be read not just flip through them and look at photos.if that was the case then we wouldn't be able to write anything and it would be more or less a album with pics..read is in thread right? Many here like to read and when we have conversations on here we type and people read ..anyways enough of my bla bla bla lol 😴🥱 before I bore u and others ..I enjoyed read your Bible🤟😁
 
Control-Z
A new solution for a stock body Limitless V1 with and XLX2. The body lower and fits better and the XLX2 is on the pan!
View attachment 245289
End swapping the ESC
I started this a while back and I've been getting busy with other stuff and some travel. However when I finally got it done I found out that the wires didn't really fit under the stock Limitless body. That combined with a few other annoyances made me scrap that idea. Control-Z

Custom Double Wide
My first thought was to double up the battery tray, side by side, and create a custom battery tray. Then I can just put the XLX2 on the other side. My plan was perfect but a bit daunting. I prototyped the tray created from 3/8" ABS and it fit both of the monster batteries. Securing it to the pan and the weird angles was a bit much but doable. Also I have to figure out some way to secure them, which was getting a bit weird. Then get an aluminum tray made but no one makes M3 Nutserts that don't require a special tool and a 5 ton press. Ok to I hit too many walls . . Control-Z, again
View attachment 245290

New Servo Mount
I started looking at the gigantic electronics box and servo mount. Then I started thinking there must be a way to save some space. The solution is to mount the servo the down brace.

My mock up looks good and plenty of space. Then use my XLX2 center brace to hold the electronics. Less weight up top, the body sits lower and shorter wires.
View attachment 245291
With a bunch of time and CAD work I had a design, then went to Send Cut Send to get an estimate, which is pretty cheap.

View attachment 245288
However, they have a $29 min and I didn't want to drop $30 on a part that may not fit nor work. So it's off to Home Depot for some bar stock. Good thing too my holes were just a bit off and I had to give them a bit of love with the drill.

I cut off a chunk of bar stock and drilled my holes screwed it in and everything work. But I didn't get the fancy shape, but it's a prototype. I used an electronics box from a Mojave and made a dual antenna mount (ignore the crappy tubes). The antenna sit inside the body and are higher than stock.








This is with everything in there. Ignore the messy wiring, that will get cleaned up. It turns out my Mojave box is too small for the Castle link and all my wires, so I'm probably going to chop up Limitless box and use that. Also trim down the center tray a bit or more likely I will get a better one that is stronger, that POS tends to bend because of the right angles. I swear it bent sitting on my bench.
View attachment 245292

What Left
Loctite everything
Clean up my wiring with Limitless box
Properly mount the XLX2
New chassis brace?
Who makes this/Where can I get one?​

View attachment 245294
SFR, he sells very limited amounts. I have the other style brace. I wouldn’t recommend it! There was so much chassis flex. Very thin carbon fiber. Look into scorched instead.
 
SFR, he sells very limited amounts. I have the other style brace. I wouldn’t recommend it! There was so much chassis flex. Very thin carbon fiber. Look into scorched instead.
Thank you. I liked the vertical rails because I thought they would have more stiffness up and down.

The scorched is a good suggestion, I'll need to make sure it works with my servo mount. From the pictures it looks like it might be a little tight.
 
Strange Weather, Springs, Bump Stops, New Fans, an Unrelated BEC and a Custom Case
I'm starting to thing that California broke off in the last earthquake and floated north to replace Seattle. Don't get me wrong Seattle is nice but it's not good weather for speed runs. It's been 3 weeks of pretty much solid rain, which I haven't seen since the '80s.

Right about now all you snow bounders are like yah yah yah, grow a pair, our rain is frozen and it's stays still the spring. :unsure:

Anyway, on to the car.

Springs and Bump Stops
During the last runs I noticed the splitter was dragging the ground, so I tuned up the aero (cut it down). But I also got some new higher rate springs and installed bump stops in the front.

The original front springs are pretty soft (ARA330600) which are 27 lbs/in. There are also two more options from Arrma the medium springs (ARA330630) at 32 lbs/in and the firm springs (ARA330631) at 38lbs/in. There are also new springs from Perfect Pass, coming soon and I have no idea what the spring rate is.
IMG_4982.jpg
I just went for the firm ones. The worst it will do is bounce a bit. In theory, it should also be more stable and reduce the over steer, not that I do a lot of drifting. They are like $7, so if I don't like them I can skip Starbucks that day and buy the medium springs.

Installing them wasn't bad, but adjusting the preload was a little tricky. The driver's left side went just fine because as I tighten the adjustment ring, the shock cap gets tighter. The driver right side was the opposite. When I tightened the adjustment ring, the shock cap loosened. Oops. I manged to get a wrench on the shock body and deal with it. They are in and look straight.

In addition to that I added some "bump stops". For the rear I used nitro tubing and it was a pain in the A-double-S and messy too. This time around I figured I would try something different. I found some grommets at Lowes Hillman part number 884626 that were pretty thick and made of rubber. Don't pay attention to the picture on the website they look more like stacked cylinders than a split donut.
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Once installed I have about 6mm of travel with a nice soft bottom. The float freely on the shock shaft and were WAY easier to install. The only trick is you have to give the spring perch a bit of love to get it on there. I could have trimmed the bottom "cylinder a bit if needed, but in the end the fit fine and I'm expecting they will work very well.

This picture shows the upper half of the grommet. It sits deep in the spring perch.
IMG_4985 (2).jpg

New Fans

I'm not talking about subscribers here, it's cooling fans. There aren't a lot of options for the 1717 motor basically a Castle fan, ebay or custom. I was running the Castle Fan, which work OK but it could be better and move more air. These guys were doing a super sale on Ebay and figured I would give it a try. Putting it on is a little strange, because you have to fit everything, then disassemble it to put lock tight in there and readjust it. Hopefully everything stays in place.

IMG_4983.jpg

They have JST connectors on the fans, so I just spliced some male ends onto it and plugged it into the receiver. They power on and move air but I won't know how they work until I get out and run again. I'm sure they aren't a great piece of engineering but we will see how they do.

Eventually I will probably just mount some 40mm 12V server fans on the pan next to the motor. It's a simple option but takes a bit more planning and a 3rd battery or BEC.

I've heard from others to just run a fan battery because it will degrade performance to use the main batteries. The cheap fans are like 7W max draw. So 7W out of my 500W is about 1.4%. So yeah it might degrade performance, but at my speeds it's not going to matter much if any.

Unrelated BEC
I also installed the Castle 2.0 20Amp BEC in my crawler with the ProTek RC 1KTBL servo. It was no small task. You can read about the details here
https://www.arrmaforum.com/threads/castle-bec-2-0-wiring.58530/.

Long story short I had to make a special wiring harness. The problem is now every other servo looks weak.
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Custom Gear Case
Since we have a lot of indoor time these days I created a custom case for some gear. The short story is, I'm more organized. The long story is in the link below.
https://www.arrmaforum.com/threads/case-for-the-camera-gear.58838/
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New Day, New Runs

New Day
Finally after weeks of rain I got outside. Don't get me wrong I love the rain, in fact I love any weather. One of the perks of living in the Bay Area is the weather is typically 60-80 and sunny. It's like having good macaroni and cheese; all the time, everyday and that's all you get eat. It's great, but it's most boring thing you can imagine. Nothing changes... ever. So a little bit of weather is welcome.

Yah, I know all you snow bound people, yah, keep whining snowflake. :eek:

New Runs
This is a bit of a repeat from the Speed Runners ~ How Fast Did You Go Today? Go to that thread to see the video.

I'm definitely getting used to the car and the speed. I'm getting more than 3 Secs of wide open throttle. I would say the biggest improvement was setting the D/R for the steering, it took way a lot of squirrelliness.

In a nut shell, I had 4 good runs, all over 120 MPH (my old PB) with a new PB of 125 MPH.

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The changes to the aero and springs seem to work great. I marked the scratches in the pan with a black Sharpie and didn't see much of anything new afterwards. This is clipped this from one of the runs.
Clearance.jpg

As you can see I've got forward rake 3/8-1/2 in (9-12mm) of clearance in the front. You can also see the trail of crap coming from the back form the rear spoiler, which is kind of cool to see in the video, it looks like a rocket flying past the camera.

The new servo mount seems to work good. There is no additional wear on the front drive shaft but I will need to keep an eye on it.

The full caster setting is also very good. Caster is what makes your wheel return to center when your driving. The car tracks much straighter, or wants to go straight.

I had 4 runs recorded between 122 & 125. There was a fifth run that I didn't set the GPS. :banghead: It was a solid run too, probably in the same speed range. All the pulls were 3+ seconds of open throttle too. Given the consistency of the runs I may have reached the limit of this configuration. Meaning I need to cut down on drag, like less aero, better bearings, harder tires, etc.. Or I need to start gearing up.

The drive train is bone stock with a 32T pinion. Then put this into a speed calc and got 137MPH using 6S to estimate the batteries under load. I'm withing 90% of that target. At this point I'm feeling pretty good about gearing up. I'm thinking of moving up to 36T pinion and looking for a mid 130... assuming I have the room for it.
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Broken Stuff
Some time after the 125MPH run I lost the front drive system. it's either at diff or a drive cup grub screw. I will need to pull this apart an figure it out. Either way I've got some wrenching to do.

Data Logs
Below is the throttle and power out from the data log. I'm still giving it a bit of punch at the top end and probably need to adjust my throttle curve, which I never did. However, I only had 1 ESC error.

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Looking at my max amps peaked at 527 A. This is the same curve from above where I ramped the throttle at ~40%. All the other runs < 500A.
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The motor temp was not good. However, I did do three back to back runs. Over all I don't like the new fan setup. It's noisy and doesn't seem to push that much air. I might try to change to some better fans and/or try to create some sort of plenum to direct the air towards the motor.
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My voltage sag wasn't great either. It dropped to 22.4V, which wasn't the fastest run
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Some Data Log Notes
The data logs are interesting and do tell a story. However, they aren't the entire picture nor are they that accurate. The resolution of my data log is 5S and I don't know the precision and accuracy of the samples. i.e. 8 bit ADC vs 20 bit ADC and what is the margin of error on that. Because high precision ADC cost more that the ESC, I suspect they are fairly low end ADCs and a lot of the data is interpolated by software. Which is still useful but I don't believe it to be the gospel either.

I went through the logs and noticed that temperature changes after the run. So my max temp (214 °F) occurred long after my run was done. The running temp was ~172, which is reasonable. However, temperature readings are not exactly instantaneous. It takes time for heat to travel and sensors to adjust. Which means my running temp is somewhere between the two.

The full data log is attached for those that are interested. The summary is below.
RunSpeedBatterySetupMin VoltsAmpsWattsMtr Temp
1122CNHL Racing Series 9500mAh 4S 90C8S24473.310962
111.5​
2124CNHL Racing Series 9500mAh 4S 90C8S24.6458.511277
159.6​
3123CNHL Racing Series 9500mAh 4S 90C8S22.4494.712545
172.3​
4N/ACNHL Racing Series 9500mAh 4S 90C8S30.7475.411989
136.8​
5125CNHL Racing Series 9500mAh 4S 90C8S23.1527.112150
166.5​
6120SMC Graphine Extreme V2, 7700mAh 4S 40C8S32.6466.711912
108.7​
7120SMC Graphine Extreme V2, 7700mAh 4S 40C8S26.1433211901
145.9​
 

Attachments

  • 20230121.zip
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Front Diff inspection
I pulled the front diff. It wasn't as bad as I thought, but it is a lot of little screws that I need to remember where the go. For the most part I try to put them back in the hole they came out of and for the rest I put them in small bins and labeled them. So when I put it back together it's a matter of how good my notes are and can I read my own handwriting.

The Failure
I would estimate the input shaft was spinning about 52,000 RPM when it failed. Which is quite a high RPM for any bearing.

The failure started with the front input shaft bearing. The inner seal spun and split it onto at least two pieces. The little "C" shaped bit should be part of the "O" shaped bit. There seems to be a little bit missing too?
IMG_5009.jpg


From there, I'm sure the bearing was quite unhappy, maybe the shards of metal jammed it up or vibrated it's way out. Whatever it was, the insides were now outside.
IMG_4998.jpg


Inspection
Looking at the front race it, looks OK except for a few small scars, but a new housing is only $12. So it's getting replaced.
IMG_5017.jpg


The ring and pinion look OK. They have some wear but nothing that is worth $60 at this point. The innards of the diff housing were a bit light on grease. It's going to get spun out of the gears anyway and I'm not sure how to get grease to stay in the gears, rather than on the walls.

Note: The brown tinge that looks like rust is just some weird artifact of the lighting.
IMG_5018.jpg


Part List
They don't have all the parts locally so I have to wait a bit, but I should be back on the road as soon they come in.

DescriptionPart NumberCost
Inner Pinion BearingARA610017$7.99
Outer Pinion BearingARA610019$7.99
Pinion ARA310468$13.99
SpurARA310441$22.99
HousingARA310854$11.99
Total$27.97
 
New Fan, Not Bottoming Out, More speed runs, and Burnt Connector
The data log is attached in the ZIP file.

New Fan
There is a problem with the Castle 1717, which is the only fan that exists for that motor is a single 40mm fan from Castle. It works OK, but there should be better options.
1676764072038.png

When I first started this project (1 year ago) I had ordered a Yeah Racing through the LHS. It looks like this Power Hobby fan. It completely envelopes the motor, has heat fins, it interfered with the motor wires and it was a touch too small. Too small can be fixed by making it fit, but the problem is there is no room for the the screws to hold it down. With that I set it aside and tried other options.

I tried one of the China specials from Ebay. It's worked, sort of but didn't really move much air. The mount is jinky and the fans are crap. The only way to position it was high up near the body and there was no space around it to gather air and nothing to direct the air. I wanted to try something different.

After the mediocre Castle fan, and the China fan disaster I figured what could it hurt. I took the Yeah Racing fan shroud and butchered it until it fit. Loose the back plate, chop the sides to just below the opening and chamfer the back corner to clear the wires.
1676765160606.png

But I had no way to mount it. So I took some zip ties and used the fins to lock them in. The angle of the fins keep the zip tie secure enough that I can move the car with the fan. Figure that was good enough till I crash. :rolleyes:
1676763745185.jpeg


What I'm considering doing it just mounting two fans to the pan, next the motor. I could always throw a piece of plastic/lexan on top/sides to direct the air towards the motor. Let me know what you think of that idea?
1676766430233.png


Not Bottoming Out
After some previous runs and scrapping the belly, I stiffened the front springs (hardest springs I could find) and added a grommet to the lower shock shaft to prevent the shock from bottoming out.

This seems to have solved the problem. It's hard to see in the photo, but I marked all the scraps with a Sharpe and I don't seen any new scraps for the most part. There might be a few little nicks or dots, but nothing like it was. I will go over the boo-boos better with fresh Sharpe later.
RC_Pan.jpg


However, road turtles (AKA raised pavement markers) are still a problem. This is just from driving over them at low speed, turning around. I don't have a good solution, but I'm glad they are softer than my car.
1676766885475.jpeg

More Runs
Long story short new PB with two runs at 131 mph. Also a 130 mph , 127 mph and one I didn't have my GPS on for, which I swear was the fastest.

The video of one of the 131's is below. I sent it down range then lost sight of it in the shadows. A bit of elevation fixed that problem.

In this configuration I bumped the pinion to 36T with the stock 34T center spool. Honestly I was expecting a bit more than 131, but I'm happy with that.

However it seems to be maxed out again, which what I don't understand. Although, what the math says and what reality is depends on a lot of factors.

My road is 1676 feet (google maps), I'm using about 1200 feet of that, so I know I need to work on keeping in it a bit longer. I can see the RPM still climbing when I get out off the throttle.
1676770691829.png


The data log shows full throttle for about 3 Secs on the good runs. Each one is pretty consistent and no excessive load errors, I did modify the throttle curve just a bit to taper at on the high end. My braking is at 50% now. I could probably bump that up and get more throttle time.

Throttle was 100% each time Current, RPM were consistent. The temp kept climbing but I was running about 2 mins between runs. The big gap in the middle I set a time for 5 mins and let the car cool. This is probably a good method. Not the motor gets hotter after the run. It take time for the internals to heat up and register.
1676768124009.png
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One very odd thing I observed was a random voltage drop. Before the third run the voltage dropped to 17.2V (2.15V/cell) for some odd reason. Throttle was about 20% at best. Maybe there is a short some where that I don't see?
1676768400009.png


Burnt Connector
Maybe this has to do with the random voltage drop, I dunno, but it's odd. I figured this out when I was discharging my batteries and the connector didn't seat correctly. The picture is after I cleaned it up a bit so I could connect to it and discharge the batteries to storage.

Maybe there was some grease or oil in there? I'm sure they were fully seated, I learned that lesson before.

Anyway, I will have to change both connectors, batteries and ESC.

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Thanks for reading and feedback is welcome!
 

Attachments

  • 20230212.zip
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New Fan, Not Bottoming Out, More speed runs, and Burnt Connector
The data log is attached in the ZIP file.

New Fan
There is a problem with the Castle 1717, which is the only fan that exists for that motor is a single 40mm fan from Castle. It works OK, but there should be better options.
View attachment 279340
When I first started this project (1 year ago) I had ordered a Yeah Racing through the LHS. It looks like this Power Hobby fan. It completely envelopes the motor, has heat fins, it interfered with the motor wires and it was a touch too small. Too small can be fixed by making it fit, but the problem is there is no room for the the screws to hold it down. With that I set it aside and tried other options.

I tried one of the China specials from Ebay. It's worked, sort of but didn't really move much air. The mount is jinky and the fans are crap. The only way to position it was high up near the body and there was no space around it to gather air and nothing to direct the air. I wanted to try something different.

After the mediocre Castle fan, and the China fan disaster I figured what could it hurt. I took the Yeah Racing fan shroud and butchered it until it fit. Loose the back plate, chop the sides to just below the opening and chamfer the back corner to clear the wires.
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But I had no way to mount it. So I took some zip ties and used the fins to lock them in. The angle of the fins keep the zip tie secure enough that I can move the car with the fan. Figure that was good enough till I crash. :rolleyes:
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What I'm considering doing it just mounting two fans to the pan, next the motor. I could always throw a piece of plastic/lexan on top/sides to direct the air towards the motor. Let me know what you think of that idea?
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Not Bottoming Out
After some previous runs and scrapping the belly, I stiffened the front springs (hardest springs I could find) and added a grommet to the lower shock shaft to prevent the shock from bottoming out.

This seems to have solved the problem. It's hard to see in the photo, but I marked all the scraps with a Sharpe and I don't seen any new scraps for the most part. There might be a few little nicks or dots, but nothing like it was. I will go over the boo-boos better with fresh Sharpe later.
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However, road turtles (AKA raised pavement markers) are still a problem. This is just from driving over them at low speed, turning around. I don't have a good solution, but I'm glad they are softer than my car.
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More Runs
Long story short new PB with two runs at 131 mph. Also a 130 mph , 127 mph and one I didn't have my GPS on for, which I swear was the fastest.

The video of one of the 131's is below. I sent it down range then lost sight of it in the shadows. A bit of elevation fixed that problem.

In this configuration I bumped the pinion to 36T with the stock 34T center spool. Honestly I was expecting a bit more than 131, but I'm happy with that.

However it seems to be maxed out again, which what I don't understand. Although, what the math says and what reality is depends on a lot of factors.

My road is 1676 feet (google maps), I'm using about 1200 feet of that, so I know I need to work on keeping in it a bit longer. I can see the RPM still climbing when I get out off the throttle.
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The data log shows full throttle for about 3 Secs on the good runs. Each one is pretty consistent and no excessive load errors, I did modify the throttle curve just a bit to taper at on the high end. My braking is at 50% now. I could probably bump that up and get more throttle time.

Throttle was 100% each time Current, RPM were consistent. The temp kept climbing but I was running about 2 mins between runs. The big gap in the middle I set a time for 5 mins and let the car cool. This is probably a good method. Not the motor gets hotter after the run. It take time for the internals to heat up and register.
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One very odd thing I observed was a random voltage drop. Before the third run the voltage dropped to 17.2V (2.15V/cell) for some odd reason. Throttle was about 20% at best. Maybe there is a short some where that I don't see?
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Burnt Connector
Maybe this has to do with the random voltage drop, I dunno, but it's odd. I figured this out when I was discharging my batteries and the connector didn't seat correctly. The picture is after I cleaned it up a bit so I could connect to it and discharge the batteries to storage.

Maybe there was some grease or oil in there? I'm sure they were fully seated, I learned that lesson before.

Anyway, I will have to change both connectors, batteries and ESC.

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Thanks for reading and feedback is welcome!

I believe there's a 3D Dual-fan Chassis Mount out there.. Do you have access to a 3D printer?
 
I believe there's a 3D Dual-fan Chassis Mount out there.. Do you have access to a 3D printer?
No but I might be able to finagle one, it depends on how complex it is. I can always just pay a service if it seems like it will work.

Do you have link?
Is this the one?

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https://www.thingiverse.com/thing:5086838

Might be backwards from my setup, but I might be able to modify it. Looks like some else reversed it.
 
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TBH,
I'm skeptical how much fans help with the temperature since the internal cabin of the limitless is pretty small and doesn't allow for much airflow. I think all the fans are doing is recirculating hot air around the motor. I never seemed to have a problem but I don't do too many back to back runs (3 at the most) so I've removed my temperature sensor and my server fan....
 
TBH,
I'm skeptical how much fans help with the temperature since the internal cabin of the limitless is pretty small and doesn't allow for much airflow. I think all the fans are doing is recirculating hot air around the motor. I never seemed to have a problem but I don't do too many back to back runs (3 at the most) so I've removed my temperature sensor and my server fan....
Some say this is the solution to your problem.install this on top of your rig and you'll no longer ever ever have a cooling problem 👍🤣🤣🤣

Screenshot_20230219-050155.png
 
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