Speed Calculator

Could you please add the dimensions of the Jammin X2 CRT diffs, they're not the typical truggy ratio: ring=10t, crown=45t.

[ikpthegame]

it would also help to know what xtm those are from.

[pinkpanda3310]

Originally Posted by BrianG

Panda: Thanks for that info! I assume the LST1 and RC8T are CVDs, and the XTM is a true dogbone?

Looks like I'm gonna have to add a seperate center CVD and CVD axle sections or pages. Otherwise, those measurements won't make much sense when applied to the current dogbone picture. Does anyone have a good clear picture of a center CVD and an axle CVD? All of mine are in vehicles and are not in "picture condition". Ideally, a clear, large (bigger is better for me to edit), well-lit image with a white background. PM me if you have pictures and/or can take some and I'll supply my email addy to send them to.

BTW: I am adding the following as a note to myself since my development PC is off and I don't feel like turning it on just for this:
Ofna Hyper 7 F/R:
D1: 97/104
D2: 90/97
D3: 4.8
D4: 3
D5: 7.9
D6: 12.7

I tried to put spaces in to make it look like columns but the post didn't come out that way

Yes the xtm is a true dog bone and the others are cvd's. I'll attempt some photo's for you tonight but my photography isn't good

Originally Posted by ikpthegame

it would also help to know what xtm those are from.

Only the first is xtm- mammoth part # mv3559. I saw on the interweb it was 192mm but when I got it in hand it said 182.5mm. I don't know why there is a difference???

[BrianG]

I did some snooping around for various CVD units and it seems that there is so much variation in design that creating a page to list all the possible measurements will be next to useless. So, unless I get a really good idea on how to do it effectively and without confusion, I think I'll stick to documenting just dogbones. Those are a lot easier to measure and quantify.

[Mozzy]

Does this seem right??
I have taken this data from when my CRT had the Neu 1515 2.5D F in it running 5S.

Input data:

Enter Front/Rear Differential Gear Ratio (?):3.30769230 Jammin CRT 43/13
Enter Transmission Gear Ratio (?):1 Direct drive or centre diff 1/1
Enter Additional Gear Ratio (?):1 Select preset other ratio
Enter Spur Gear tooth count (?):62 Truggy CRT (Mod 1)
Enter Pinion Gear tooth count (?):16
Enter total battery voltage (?):18.5v
Enter kv rating of brushless motor (?):1700
Enter tire diameter in inches (?):5.65 Crimefighter MTR 1/8 scale truck
Enter the added radius of tire
"ballooning" in inches (?):2 My standard radius is nearly 3. I didn't think this was correct.
Enter Current draw in amps (?):0
Enter motor resistance in Ω (?):0

Results:

Spur/Pinion Reduction Ratio (?): 3.88 : 1
Total Reduction Ratio (?): 12.81731 : 1
Tire Circumference (?): 30.32 inches (770.04 mm)
Rollout (?): 2.37:1
Total Motor Speed (?): 31450 RPM
Theoretical Maximum Vehicle Speed (?): 70.44 mph (113.16 km/h)
Calculated Loaded KV Value (?): 1700
Calculated KT Constant (?): 0.8 oz-in/A
Calculated Motor Torque (?): Amperage not specified...
Calculated Axle Torque (?): Amperage not specified...
Calculated Motor Power (?): Amperage not specified...

[BrianG]

As said in the other thread you started, 3" of ballooning is way off. That would make your tires look like pizza cutters, and should not be happening on a base speed of ~40mph - there simply isn't enough tire speed with that gearing you posted. Use a ballooning value around .5 for the gearing you are at.

[BrianG]

Triscuit:
The motor list is already pretty large so I hesitate to add more.


Aero:
A database-driven design would be perfect for this application except for two things:

A) I have not written much PHP (I'm an ASP developer). My server runs Apache with PHP. I could upgrade to an IIS/SQL server, but M$ stuff costs too much. Also, I'd have to take time to become proficient with PHP.

B) These pages would be limited to online use only. Not a big deal I guess since most people don't download and use it offline, but the capability is there to do so.

So, that leaves a client-side solution (data held in jscript multi-dimensional arrays) which requires me to hand-enter the data. As nice as it would be to partner up with someone to offer that level of data, I don't think it will happen soon.

You have to remember my whole site started with a simple one-page calc to estimate speed. It was primarily for me so I wouldn't have to mess with a calculator every time I wanted to mess with things, but I published it online in case others wanted to use it. Incidentally, this really started out as a program I wrote for the HP48GX calculator, but then ported it to Excel (mainly for GUI speed), then to HTML (so I can access it anywhere).


drkdgglr:
Sure, I'll add it to the next revision.

[Arct1k]

I would have thought that your would put the data into a local MySql db or Excel and then use a script generator to build the jscript arrays?

Just a thought...

[BrianG]

That is a possibility, and something like I was considering when developing Mike's brushless selector guide. I ended up using an XML scheme for that, but wouldn't work well for this. Any scheme that "wrote" the arrays would require either a daily automatic task/job, or something I'd have to "run" each time something changed. Either way, I'd still have to learn PHP - not just learn it, but be proficient to avoid issues like cross-site scripting, SQL injection, etc. And I'm not even sure what level of capabilities my server offers. And, I have to make sure the code is portable in case I ever switch servers.

I'd be more than happy to take the time to go through all this effort if I could get my hourly wage that I get at work.

[thzero]

Personally I prefer ASP.NET backed by MySQL. But its not nearly as portable as PHP as far as webhosting goes. And definetely not downloadable.

Plenty of frameworks for PHP that do the bulk of the work as far as cross-site scripting, etc.

Originally Posted by BrianG

That is a possibility, and something like I was considering when developing Mike's brushless selector guide. I ended up using an XML scheme for that, but wouldn't work well for this. Any scheme that "wrote" the arrays would require either a daily automatic task/job, or something I'd have to "run" each time something changed. Either way, I'd still have to learn PHP - not just learn it, but be proficient to avoid issues like cross-site scripting, SQL injection, etc. And I'm not even sure what level of capabilities my server offers. And, I have to make sure the code is portable in case I ever switch servers.

I'd be more than happy to take the time to go through all this effort if I could get my hourly wage that I get at work.

[Arct1k]

I was thinking more for the existing stuff - I know is all in arrays at the moment...

You could replicate something like you did for you picture generator...

[Bmr4life]

This will be my Jammin X2 CRT with a 2200kv on 4S.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 48
Pinion Tooth Count: 14
Total Voltage: 14.8
Motor KV: 2200
Tire Diameter (inches): 5.65
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.006
Spur/Pinion Ratio: 3.43 : 1
Total Ratio: 11.34066 : 1
Tire Circumference (inches): 17.75 inches (450.85 mm)
Rollout: 1.57:1
Total Motor Speed: 32560 RPM
Vehicle Speed: 48.26 mph (77.52 km/h)
Effective KV Value: 2200
KT constant: 0.61 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

[scarletboa]

Originally Posted by Bmr4life

This will be my Jammin X2 CRT with a 2200kv on 4S.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 48
Pinion Tooth Count: 14
Total Voltage: 14.8
Motor KV: 2200
Tire Diameter (inches): 5.65
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.006
Spur/Pinion Ratio: 3.43 : 1
Total Ratio: 11.34066 : 1
Tire Circumference (inches): 17.75 inches (450.85 mm)
Rollout: 1.57:1
Total Motor Speed: 32560 RPM
Vehicle Speed: 48.26 mph (77.52 km/h)
Effective KV Value: 2200
KT constant: 0.61 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

I run a 15t pinion in my CRT x2 with that same motor and 4s lipo and It goes between 38 and 40mph. I think you might have made a mistake in the differential ratio.
Btw, the motor only gets up to 140f running in tall Grass in 80f ambient temps. For this truggy, 15/48 is the sweet spot.

[Arct1k]

Maybe a bit fast as with 48mph you are sure to get balooning which will push you even faster... This might be closer to a 60mph geared setup...

[nitrostarter]

Correct, the X2 truggy has 43/10 differentials.