sub trim

Old 02-15-2007, 08:22 PM
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Default sub trim

What is sub trim and when is needed?
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Old 02-15-2007, 09:04 PM
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Originally Posted by rockdog200
What is sub trim and when is needed?
this is to set the servo dead striate then when runing the car use your normal trim. its like a fine tune thing and is very useful when you play with your radio and understand how it works.
read the book it should tell you a bit more in detail.
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Old 02-16-2007, 07:56 AM
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in short, the subtrim takes the endpoints with it when it is moved, whereas the trim just moves the center.

in more detail...

i actually do most of my trimming with the subtrim. when my car quits tracking straight, it's usually a physical tweak (l/r) that's introduced to the steering mechanism (from a crash). when this happens, your endpoints often shift along with the center, so using only the trim to center the car back up will result in assymetric end points. the better radios allow you to configure one of the quick buttons to be whatever you want. i assign one to subtrim, and i use it frequently.

most people prefer to trim the center with the standard trim function, and use a second operation (epa) to readjust the travel balance.

i like to have my trim set to zero at most times (and let the subtrim fall where it may), so that the actual epa values (l/r) are a direct representation of the amount of servo throw each way. that way i can make sure the speed/resolution is similar in both directions.
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Old 02-16-2007, 09:29 AM
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upon many requests...

trimming with subtrim combines steps 3 (centering) and 4 (rebalancing epa's). there are cases where only the center needs adjusted (where epa's didn't shift), but this is less frequent.
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Old 02-16-2007, 02:37 PM
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Seaball king of subtrim




Also the CEO of Failure inc. LOL








I love Seaball
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Old 02-16-2007, 03:24 PM
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Originally Posted by seaball
in short, the subtrim takes the endpoints with it when it is moved, whereas the trim just moves the center.

in more detail...

i actually do most of my trimming with the subtrim. when my car quits tracking straight, it's usually a physical tweak (l/r) that's introduced to the steering mechanism (from a crash). when this happens, your endpoints often shift along with the center, so using only the trim to center the car back up will result in assymetric end points. the better radios allow you to configure one of the quick buttons to be whatever you want. i assign one to subtrim, and i use it frequently.

most people prefer to trim the center with the standard trim function, and use a second operation (epa) to readjust the travel balance.

i like to have my trim set to zero at most times (and let the subtrim fall where it may), so that the actual epa values (l/r) are a direct representation of the amount of servo throw each way. that way i can make sure the speed/resolution is similar in both directions.
Wow! I had no idea... Thanks seaball!
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Old 04-08-2007, 05:53 PM
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Question here...................

Is it a bad idea to adjust the servo link *you know that little 1" turnbuckle/rod end combo deal the servo connects to* to make the truck/car track straight? Or do you guys keep it EXACTLY as the manual has it set then adjust from there?
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Old 04-08-2007, 09:30 PM
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Originally Posted by K_King
Is it a bad idea to adjust the servo link *you know that little 1" turnbuckle/rod end combo deal the servo connects to* to make the truck/car track straight? Or do you guys keep it EXACTLY as the manual has it set then adjust from there?
it's actually a great idea to play with this, provided you have a goal in mind here. the servo link is what i usually adjust to get the l/r end points the same. nothing about our steering geometry is linear, so the ideal length of the servo pushrod is relative to your end points (steering throw).

using a small servo horn, the linkage will almost hyperextend one way or the other if your throw is large. adjusting the link for the best symetry is a good idea.
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Old 04-08-2007, 09:32 PM
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Originally Posted by K_King
Question here...................

Is it a bad idea to adjust the servo link *you know that little 1" turnbuckle/rod end combo deal the servo connects to* to make the truck/car track straight? Or do you guys keep it EXACTLY as the manual has it set then adjust from there?
1) Zero out all steering trims (regular and sub-trims)

2) Set the servo horn/servo saver to the angle that the kit specifies, using the sub-trim

3) Set the steering rack/steering arms to center using the steering link (the one that goes to the servo).

4) Make sure the outer steering links are the same lengths (close to the specified length from the kit).

5) Set toe as desired (per desired setup) and make sure that the outer links stay the same length.

6) Test drive...adjust steering link (servo link) to make the car track straight.

Once the car goes straight, you shouldn't have to mess with the sub-trim unless you change the servo or servo saver.
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Old 04-08-2007, 10:12 PM
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After you zero everything out, make sure the L/R balance is even too. After you have set the car up, check the L/R steering throw on a Hudy or Integy gauge. If it is off, don't change the radio L/R, change the little shorty linkage and make sure it is perfect. If you don't do this, you will have uneven ackerman. Make sure to rest your camber, toe, etc. and recheck often. Not as noticable on my 1/8 scale car but was a royal PITA on my electric sedan. Once I found it and fixed it, the car was perfect. Bottom line is you want to like for your L/R trim to be within 3-4% of each other.
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Old 04-08-2007, 10:22 PM
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The ackerman won't uneven, the steering throw will be. Ackerman doesn't change due to steering throw, it's part of the steering geometry.

But yeah...that should have been

7) Make sure the steering throw is even by adjusting the EPA for right and left turns.
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Old 04-08-2007, 10:24 PM
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Yeah I was thinking, hey I cant just pop this off and loosen or tighten lol.

But I didnt know if that affected the steering geometry in any way (for whatever reason). Im just trying to have all of my controller settings as close to 0 as possible (isnt everyone? :P)
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Old 04-08-2007, 10:30 PM
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Most cars I've seen, you can turn the steering to one side or the other and access the link.

It's just one of the PITA setup deals you only have to do once when you first build the car. It's a big deal though that the steering linkage is "split" evenly (equal L/R throws) starting at the servo/link/arms. If it's offset there, you'll never get it straight and evenly trimmed out.
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