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Old 04-27-2014, 08:24 AM   #376
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Uploaded another model Xray XB4.


Quote:
Originally Posted by ads0021 View Post
That's what I thought unfortunately.

The car is 70mm wide inc components. Much narower wieght. Slightly longer though. I think the main difference is the torque of the motor as it accelerates acts much further forward and give much more drive to the front end.

I have already designed it, (mostly in solidworks) made it and have been running it for a few months.

My problem is that these changes in motor position and decreasing the width have had such a large effect that using rc crew chief will work but I have lost all comparisons to a normal setup.

I think the best thing is to get my base setup on the software then compare it to the numbers you would expect to see from a normal lay out.

This might help me to understand what effects the changes are having.
As long as the motor is mounted transverse and between the axles the torque reaction shouldn't affect the fore/aft weight transfer.

What you have done is reduce the MMI (Mass Moment of Inertia) in roll but may have actually increased in pitch and yaw because the chassis is longer. The MMI is a function of the distance from the centre of gravity squared so a small change can make a significant difference. If this is the case then transitions in weight transfer will occur faster in roll but slower in pitch/yaw.

Using solid works you should be able to get the MMI properties directly out of the program. You may already have them if you have assigned mass properties to all the components. If you feel ambitious you could just build a simple model of the major components chassis, motor, batteries, ESC receiver and servo so you could compare the standard T4 layout to the one you are experimenting with.

Hope that helps.
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Old 04-28-2014, 02:38 AM   #377
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Quote:
Originally Posted by ads0021 View Post
I really love this software. Have got the demo and will be getting any day. Good videos too.

I have an unusual problem though. I am testing some ideas in weight distribution in an xray t4. Central motor possition and the whole car is 70mm wide.

I have found it make a huge difference to how the car handles.

Is there anyway to take this into account on rc crewchief?
Are you sure its the weight layout making the difference? Chassis flex makes a huge difference to TC handling and your layout is certain to have very different flex characteristics to a normal TC. It looks very stiff from the pictures you've posted.

I did my own project with similar aims, except I reduced the weight spread in all directions since spreading the weight out a long way front/rear can have a negative effect on handling:

New car project TC6-C

Overall I found a decent improvement in laptimes, but I'd kept the flex similar to the original car (after a couple of iterations of top-decks).
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Old 05-12-2014, 08:58 AM   #378
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Started a Youtube series on Setup and use of RC Crew Chief.

Episode 1 - Setup Basics
https://www.youtube.com/watch?v=2OnVziwkWeA

Episode 2 - Weight Transfer Balance
https://www.youtube.com/watch?v=u4DC...D6qh_i1Zt5fiqQ

Even if you don't have the program you will learn something. Several more episodes to come. I'm trying to do this in small sections so it doesn't get to long winded.

Stay tuned for more. Subscribe to the "RCCrewChief" youtube channel to get notices as new Episodes are added.
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Old 05-13-2014, 04:17 PM   #379
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Hi Bob,

Does shocks and shock rebound have an effect on the ride frequency?
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Old 05-14-2014, 05:22 PM   #380
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Sorry for the slow response it's been a long day. A car's suspension is treated as a mass-spring-damper system. The mass and the spring establish the frequency of oscillation. The damper determines how slowly or quickly the oscillations dissipated.

So to answer your question in an idealized system the shocks do not affect the ride frequency.
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Old 05-14-2014, 09:59 PM   #381
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Thanks Bob.
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Old 05-20-2014, 06:15 PM   #382
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Setup Basics Tutorial Episode 3 - Responsiveness (Overall Stiffness) is up on Youtube.

http://youtu.be/HnhydAFK_Yk

Should have Episode 4 - Camber and Camber Gain uploaded tomorrow.
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Old 05-21-2014, 09:12 AM   #383
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Episode 4 - Camber and Camber Gain is up. It's very important to watch the Setup Basics Series in order as video builds on the previous one. Even if you don't have the program I guarantee watching the series will improve your setup knowledge.

https://www.youtube.com/watch?v=HLcB6rfeQzY
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Old 06-05-2014, 09:10 AM   #384
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What is the "Dbar" parameter in the Wire type ARB setup page? Is it equivalent to the Dwire parameter?
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Old 06-05-2014, 12:31 PM   #385
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Quote:
Originally Posted by Silverexpress View Post
What is the "Dbar" parameter in the Wire type ARB setup page? Is it equivalent to the Dwire parameter?
That is correct. Thanks for pointing that out. I have a Maintenance release coming out shortly so I will change the Name in the ARB Table to Dwire so everything matches.
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Old 06-05-2014, 01:45 PM   #386
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Thanks for the quick reply, Bob. Also, in the Dynamic page, if I change the ride height this should also affect the droop. It is because the shock body is mounted to the chassis and the entire assembly moves relative to the shock piston shaft.

Last edited by Silverexpress; 06-06-2014 at 09:20 AM.
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Old 06-05-2014, 03:36 PM   #387
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Quote:
Originally Posted by Silverexpress View Post
Thanks for the quick reply, Bob. Also, in the Dynamic page, if I change the ride height this should also affect the droop. This is so because the shock body is mounted to the chassis and the entire assembly moves relative to the shock piston shaft.
not really being a individual adjustment ( it would but being that most touring chassis have more droop available than they need you would need to readjust to correct)
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Old 06-05-2014, 04:36 PM   #388
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You are right a ride height change affects droop settings. It will also affect camber and track width. The approach I have taken in creating RC Crew Chief is that you want to see the effect making one change has. That is why the droop doesn`t change as I assume you would adjust it after making a ride height change. That is also the way I would approach a change like that at the track.
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Old 06-06-2014, 09:36 AM   #389
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The reason why I brought up droop is because during a days worth of racing (2 to 3 heats + main) I'll repeatedly change my tires to accommodate the changing track conditions. For example, early on when the clay track is wet I'll choose slicks. As the day goes on and the track becomes drier and chewed up, I'll gradually change into treaded tires. A slick will have a smaller diameter than let say a pinned rounded tire. Sometimes there's almost a 5 mm difference in diameter!

Re-adjusting the springs to the setup height will affect the distance of the shock limiters relative to the bottom of the shock body. This increased change will have a noticeable adverse braking effect especially for a mid motor setup. Likewise for turns, the outside rear wheel will have an increased LLT.
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Old 06-06-2014, 02:38 PM   #390
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I totally understand what you are saying. I was thinking in terms of a TC where it is easy to reset the droop when making a ride height or tire diameter change.

If you haven't already done this the best way to model the effect will be to have two different setups. One for slicks and one for treaded tires. If you maintain the ride height the same between the two models then the difference in the droop would be 1/2 the difference in the tire diameter. So for example if the slicks are 80 dia and droop is 12mm, then for the treaded tire that is say 85mm dia the droop setting would be 14.5mm.

I'll put your suggestion on the list for a future update.
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