R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 04-08-2009, 11:58 AM   #16
Tech Adept
 
Join Date: Mar 2009
Location: Metro New York
Posts: 139
Default

BobW,

In terms of measuring the CG height, I have seen a Go-Cart Setup software that requires a scale measurement at all four wheels level, and another scale measurement with the rear wheels raised about 1 foot up on blocks (on top of the scales).

I have not derived the math, but it seems the eight measurements of static weight allows one to compute the center of gravity from left to right, front to rear using scales. Since my little brother races midgets, I would be interested in discussing this derivation, although I have been too lazy to do the math myself.

I suspect this also allows one to calculate CG height.

Last edited by SystemTheory; 04-08-2009 at 12:05 PM. Reason: Height Comment Added
SystemTheory is offline   Reply With Quote
Old 04-08-2009, 12:32 PM   #17
Tech Adept
 
Join Date: Aug 2006
Posts: 242
Default

Thanks for the program, is very interesting, now is time to work with it, and take measurements to my car.

Greetings, Luis c.
__________________
## NOSRAM ## YOKOMO BD5W ## BMI DB12RR+ ##
luic is offline   Reply With Quote
Old 04-08-2009, 01:39 PM   #18
Tech Addict
 
BobW's Avatar
 
Join Date: Mar 2004
Location: Kingston, Ontario
Posts: 600
Trader Rating: 1 (100%+)
Default

Your CG method sounds like a great idea. Just need 4 accurate scales and a level surface. You might need to know the angle of the chassis as well. Have to do the math and see.

I've thought about taking this program to the next level which would require knowing the CG. Then you could build a 3D model and look at weight transfer under cornering and acceleration/deceleration. This is a big step though.
BobW is offline   Reply With Quote
Old 04-08-2009, 02:48 PM   #19
Tech Elite
 
Skiddins's Avatar
 
Join Date: Feb 2006
Location: Windsor, UK
Posts: 4,761
Default

I have tried to use it and it all started promisingly, but somewhere along the line I managed to input some data that the programm disagreed with.
I got an error about non intersecting circles (I think, it was last night).

Only problem is it wouldn't allow me to correct the mistake. Every time I tried to close the error box it immediatly realises something is wrong and brings the error box up again.

Skiddins
__________________
Xray T4'18, T4'14 (Wet Car)
Xray X12 2018
Xray X1'16
wlrc.co.uk (West London Racing Centre)
RCDisco.co.uk
Skiddins is offline   Reply With Quote
Old 04-08-2009, 03:09 PM   #20
Tech Addict
 
BobW's Avatar
 
Join Date: Mar 2004
Location: Kingston, Ontario
Posts: 600
Trader Rating: 1 (100%+)
Default

Easy fix Skiddins. If the program is still running press ctrl-alt-del to bring up the task manager, select the RollCentre program and then click End Task to stop the program. Restart the program and then you should be good to go.

If you are building a new model you should click the "New Model" button. Give the model a name, copy the numbers from an existing model and then start playing. That way you won't mess up one of the existing models in the database.

If this doesn't work let me know.
BobW is offline   Reply With Quote
Old 04-08-2009, 08:57 PM   #21
Tech Champion
 
Join Date: Feb 2003
Location: Sydney, Australia
Posts: 5,310
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by BobW View Post
Go to the model page and select the "Rear Suspension" radio button and then click on the "Alternate Outer Positions" button this will open a window where you can enter other positions for the outer camberlink. These positions are entered as offsets from the base point so a 1mm shim would have a horoffset of zero and a vertoffset of 1.0. A 1 mm shim is pretty small so it may be hard to click on it in the setup page. The other way to do it would be to increase the value for LKing on the model page by 1mm.
Yep after looking at it for a bit I worked out the "Lking" approch and bumped it up to 35mm.

I spent some time trying different geometry and came to a balance I like the look of so will give it a run on the weekend.

Once again thanks for this cool little program.
__________________
Blade: Andro Treiber H 79g AN
FH: Donic Bluefire M3 Max Blk
BH: Donic Bluefire M2 Max Red
Powered by Falco
Dragonfire is offline   Reply With Quote
Old 04-09-2009, 05:25 AM   #22
Tech Addict
 
BobW's Avatar
 
Join Date: Mar 2004
Location: Kingston, Ontario
Posts: 600
Trader Rating: 1 (100%+)
Default

That's great Dragonfire. I probably should have included a basic user's manual but it seems like those who have tried it are getting the hang of it.

Just checked the file hosting site and it's been downloaded 127 times. That's awesome. I wasn't sure how this program would be received but it looks like it's useful.

Hope your setup changes work. I made some significant changes to my car for our club race on Tuesday to increase front grip and free up the rear and it did just what I expected.

Enjoy.
BobW is offline   Reply With Quote
Old 04-09-2009, 06:39 AM   #23
Tech Champion
 
Join Date: Feb 2003
Location: Sydney, Australia
Posts: 5,310
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by BobW View Post
That's great Dragonfire. I probably should have included a basic user's manual but it seems like those who have tried it are getting the hang of it.

Just checked the file hosting site and it's been downloaded 127 times. That's awesome. I wasn't sure how this program would be received but it looks like it's useful.

Hope your setup changes work. I made some significant changes to my car for our club race on Tuesday to increase front grip and free up the rear and it did just what I expected.

Enjoy.
I am doing some testing on saturday so I will do back to back runs and compare the results...
__________________
Blade: Andro Treiber H 79g AN
FH: Donic Bluefire M3 Max Blk
BH: Donic Bluefire M2 Max Red
Powered by Falco
Dragonfire is offline   Reply With Quote
Old 04-09-2009, 10:11 AM   #24
Tech Fanatic
 
flatspunout's Avatar
 
Join Date: Jul 2007
Location: Somewhere between raising hell and Amazing Grace
Posts: 759
Trader Rating: 38 (100%+)
Default

This is a really neat tool but I have some questions:

Is the chassis width measured at the widest point or at the front/rear?
Does the program take into account inboard toe/antisquat/antidive? I only see one variable for hingepin mount location...this kind of leads to my next question: are the hingepin location measurements for the front taken looking at the front, and for the rear looking at the rear?
How about that basic user manual?

Thanks!

-rocky b
flatspunout is offline   Reply With Quote
Old 04-09-2009, 05:34 PM   #25
Tech Addict
 
BobW's Avatar
 
Join Date: Mar 2004
Location: Kingston, Ontario
Posts: 600
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by flatspunout View Post
This is a really neat tool but I have some questions:

Is the chassis width measured at the widest point or at the front/rear?
Does the program take into account inboard toe/antisquat/antidive? I only see one variable for hingepin mount location...this kind of leads to my next question: are the hingepin location measurements for the front taken looking at the front, and for the rear looking at the rear?
How about that basic user manual?

Thanks!

-rocky b
Chassis width really doesn't do anything at this point. Just draws the line in the graphics to scale.

Toe/AntiSquat/antidive is not included When I measure up I just use the average value. So for instance for the rear hinge pin location with 3 deg toe-in I set the hinge pin X1 coordinate to the average distance when you measure the hinge pin at it narrowest and widest point. The same would apply to antisquat/anti dive. If you have a 1mm shim under the front or rear hinge pin mount then I would add .5mm to the measured Y1 value with no shims.

Both views would be looking at the car from the front

Hope that helps

Last edited by BobW; 04-09-2009 at 05:35 PM. Reason: Addition
BobW is offline   Reply With Quote
Old 04-10-2009, 02:26 AM   #26
Tech Fanatic
 
flatspunout's Avatar
 
Join Date: Jul 2007
Location: Somewhere between raising hell and Amazing Grace
Posts: 759
Trader Rating: 38 (100%+)
Default

Thanks that's the info I was looking for!

-rocky b
flatspunout is offline   Reply With Quote
Old 04-10-2009, 12:04 PM   #27
Tech Regular
 
inconceivable's Avatar
 
Join Date: Jan 2008
Posts: 331
Trader Rating: 3 (100%+)
Default

Very cool tool and if what I'm seeing is accurate I may have finally found my front end gremlin ..... can't wait to test the new setup.

One quick question .... While in the setup screen, if I choose a different "Alternate Inner Position", say more outward (toward the tire). Does the program take into account the fact that the LCambLnk measurement would have to change ? In this example I suppose the LCambLnk would become shorter to retain the same camber. Or, do I need to remeasure it and input the new LCambLnk variable to see the actual affect ? Hope this makes sense.

Thanks again for a GREAT tool !
__________________
"And now the Matador shall dance with the blind shoe maker"
"America is all about speed. Hot, nasty, badass speed. - Eleanor Roosevelt, 1936"
inconceivable is offline   Reply With Quote
Old 04-10-2009, 02:32 PM   #28
Tech Addict
 
BobW's Avatar
 
Join Date: Mar 2004
Location: Kingston, Ontario
Posts: 600
Trader Rating: 1 (100%+)
Default

When in the setup screen the program recalculates the LCambLnk value.
BobW is offline   Reply With Quote
Old 04-10-2009, 05:46 PM   #29
Tech Adept
 
Join Date: Mar 2009
Location: Metro New York
Posts: 139
Default

I took a cursory look at weight transfer dynamics under cornering forces. It is fairly complex, and a further complication is that the push/loose condition is a dynamic point on the tire load curves, which require an empirical tire model.

But a simple calculation, such as weight transfer in a 2g turn, might be helpful during tuning and setup to gain insight into the process. In the book Chassis Engineering, the author uses a 1g full scale cornering rate to show the change in tire loads under a standard comparison with different setups.
SystemTheory is offline   Reply With Quote
Old 04-10-2009, 06:50 PM   #30
Tech Addict
 
BobW's Avatar
 
Join Date: Mar 2004
Location: Kingston, Ontario
Posts: 600
Trader Rating: 1 (100%+)
Default

The next level I'm considering is a 3D model static model. Then like you say you could look at weight transfer under constant accel/decel and lateral cornering forces. Now that I can function in VB I might start working on it. Really depends on if this program is found to be useful.

The math doesn't scare me, it's the easy part. The biggest challenge is having a good 3D graphical display. That's what will take all the time.

The ultimate version would be a 3D dynamic.
BobW is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Team Losi JRXS Type-R Andrew Gray Electric On-Road 13454 07-11-2017 08:26 PM
XXX-CR Thread Matt Howard Electric Off-Road 5778 04-03-2017 01:45 PM
Tamiya TRF416 / TRF416WE / TRF416X academygaz Electric On-Road 10619 01-01-2015 04:36 PM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 02:09 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net