Speed Calculator

[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.

[Triscuit]

Would you be able to update this with maybe these motors? http://hobbyking.com/hobbyking/store...sp?search=KD36 i would greatly appreciate it but as it is it is a simple calculator and seems to work good thanks :)

[Aero]

Hello BrianG, its great to see added shock and dogbone info to the calculator/pages, part#'s would be great as well. The designation(?) numbers look to be somehow misplaced but that could be my computer..? I'd like to add more dogbones and maybe shocks, i have a few(..), and also got a few to add that i got emailed from generis once. No secret that i've been looking for some certain dims of dogbones, but now rather end up 'fetching' dogbones to suit the purpose, which Neo and others from esav.com began to do in practice.

And I like to add nitro ruster+nitro stampede 32p gearings (conversion-related), 1 HW motor, and maybe some more stuff. The motor spec listing is great too, as always you do awesome stuff, but the best thing is you are keeping up the good work!! I can add the data here, or thru email, after easter holidays..2+ weeks

I contacted David Gray from progressive rc to salute him on his earlier work, they have a nice and huge comprehensive list of specs on a-z stuff, that also can be sorted, and has a mighty-fine capacity/cost column. I suggested a sort of slight teaming up with you, he was hm intrigued ? when i suggested he contacted you, but hesitated as the amounts of work to ask/do was a big pile as well, that noone deserve. He see obstacles when it came to the web interface/design, and i have a hint that you're great with that part

the things i had in mind (to sugest) was a database look-up connection, and i was thinking of the option for people to ADD info to the listing, preferably only by having a log-in(..).or whatever in between, a mix of a calculator and a database. As i recall you writing too much data would not be wishable to a point ? Even though progressiverc's data maybe isnt all up to date/relevant, that would be a giant leap in usefulness, and probably end up as the most comprehensive listing of rc data and calculations possible..just venting some ideas thats all. so you could think about contacting him, if you wish or not, no probs..i just saw some potential thats all (consider it passed on from here ). Sorry I can't really myself add help in this matter, so to speak not really my fields.

feel more than free to remove the quote below, after you read it. (and get into a .com fight.. ) . I may remove it myself, if i get told to do so by david. It serves as display honest intentions only.

aero


"Thanks for the kind and detailed response.

I have certainly seen and used this very handy and well done calculator. I appreciate the idea and may look to contact Brian, but it is hard to ask for such large favors J.
---
I am glad you have found the data useful.

We think alike, but unfortunately my web programming skills are tapped, and the current incarnation represents the limit of my ability/time at the moment. I am waiting for the right opportunity or volunteer to make the next logical step to a database system that would be easier to update and add to, hopefully with member logins to update for multiple editors.

Thanks for your recommendation and best wishes!

Regards,
David Gray
ProgressiveRC"
----
http://www.progressiverc.com/index.p...d=13&Itemid=18

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

[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...

[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...

[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.

[nitrostarter]

Correct, the X2 truggy has 43/10 differentials.