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Old 05-05-2014, 04:42 PM   #361
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Piston holes vs oil viscosity was discussed a few pages back in this thread.

It relates to high speed vs low speed response. Low speed being weight transfer and high speed being bump response.

I tried a front gear diff recently in my bd7 and I have ran them in the passed.

Front diff had no chatter with regular CVDs at full lock and less drive pin wear compared with a spool. Chatter isn't an issue with DCJs.

On track results gear diff more turn in, slightly smoother to drive but less corner exit steering.

In field was faster but the high speed sweepers I was loosing time.
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Old 05-06-2014, 12:56 AM   #362
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It has been brought to my attention that spur gear diameter has an effect on handling. Never thought about this before. I just figured we were shooting for a certain FDR and we were good. So, what can one expect to feel by switching to a larger spur gear versus a smaller one?
The spur size itself won't affect the handling, but it changes the position of the motor which can affect it. Motor further back will give more steering into the corner with the back end more likely to step out. Should give more rear traction on the power, which is useful in a RWD but not necessarily helpful in a 4WD where even loading across all four wheels gives the best traction.
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Old 05-06-2014, 09:24 AM   #363
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Just giving an update here. I widened the rear a bit and also made the car a bit longer. Its exactly what I was looking for, even on a much looser track. All I needed was a tad bit and I found it!

Thanks, Martin
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Old 05-07-2014, 06:46 AM   #364
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So I have a question in regards to anti dive and caster. I run anti dive on my car and it really helped calm down the steering and prevent traction rolling. But having anti dive also reduces castor. The way I read the castor section in rc workbench is that less castor will increase initial turn in and decrease mid corner steering. This contradics what I am seeing with the anti dive on my car. So my question is, does castor (in the small range we are talking about) have so little affect on the car that the change in front hinge pin angle over powers it?
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Old 05-07-2014, 05:46 PM   #365
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Has anyone discussed what setup changes one should make when the temperature of the asphalt changes?

Cheers.
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Old 05-08-2014, 12:38 PM   #366
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Originally Posted by Nathan Wilson View Post
Can you please explain why you recommend more damping in the rear to give more steering off and neutral power. Thanks
The theory behind it is as follows. By slowing down how fast the rear end squats it keeps more weight over the front tires giving more steering. I have to say however that in applying this to my full size race car, I am experiencing the opposite results. It seems that when I go with less dampening in the rear on my full sized race car the rear rolls more quickly in the rear in the middle of the corner, giving more steering by taking away some rear grip.

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I am curious what the advantages/disadvantages of running a front gear diff with the 1-2.5 million weight oil versus a spool are and when would you use this? Also why change the pistons in the shock as opposed to just changing to a thicker or thinner oil? Thanks!
First let me talk about the heavy diff oil versus a spool. For the longest time I have always run a spool as I have liked the extra acceleration on on power steering it gives me compared to even a 2m diff oil. However it finally dawned on me that I was spinning the front tires a lot more. This leads to wearing out or over heating the front tires too early leading to a push at the end of a run. This really only applies to modified. It also dawned on me that I was actually not able to really pull full throttle without spinning the front tires, so I started to explore using a 2m diff oil. What I found was I really did not give up much if any on corner exit acceleration, and in fact gained some other advantages. I was not abusing the front tires as much so the car was more consistent at the end of the run. Also I found the car had a little more steering and rolled through the middle of the corner better.

Now lets talk about your piston question. The size of the piston not only affects the amount of dampening but affects the high speed dampening. A large hole with thicker oil will have less high speed dampening than a smaller hole with thinner oil when their low speed dampening is the same.

The high speed dampening is when you hit bumps, curbs etc. The low speed dampening is when you are transitioning side to side into and out of corners, or when you are braking and accelerating.

High speed dampening is very very important to keep the tires from bouncing along the driving surface. If your tires are bouncing too much then you are loosing grip.

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Originally Posted by Adam B View Post
It has been brought to my attention that spur gear diameter has an effect on handling. Never thought about this before. I just figured we were shooting for a certain FDR and we were good. So, what can one expect to feel by switching to a larger spur gear versus a smaller one?
I have heard the same thing, but in my testing I have not been able to actually feel a difference. Perhaps the top pros can feel the difference, but I can't.
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Old 05-08-2014, 12:45 PM   #367
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Quote:
Originally Posted by frozenpod View Post
Piston holes vs oil viscosity was discussed a few pages back in this thread.

It relates to high speed vs low speed response. Low speed being weight transfer and high speed being bump response.

I tried a front gear diff recently in my bd7 and I have ran them in the passed.

Front diff had no chatter with regular CVDs at full lock and less drive pin wear compared with a spool. Chatter isn't an issue with DCJs.

On track results gear diff more turn in, slightly smoother to drive but less corner exit steering.

In field was faster but the high speed sweepers I was loosing time.
Great Explanation!

Quote:
Originally Posted by daleburr View Post
The spur size itself won't affect the handling, but it changes the position of the motor which can affect it. Motor further back will give more steering into the corner with the back end more likely to step out. Should give more rear traction on the power, which is useful in a RWD but not necessarily helpful in a 4WD where even loading across all four wheels gives the best traction.
Yes...good point re: having weight further back due to a small spur.

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Originally Posted by hyujmn View Post
Just giving an update here. I widened the rear a bit and also made the car a bit longer. Its exactly what I was looking for, even on a much looser track. All I needed was a tad bit and I found it!

Thanks, Martin
Awesome! Glad that helped.

Quote:
Originally Posted by theproffesor View Post
So I have a question in regards to anti dive and caster. I run anti dive on my car and it really helped calm down the steering and prevent traction rolling. But having anti dive also reduces castor. The way I read the castor section in rc workbench is that less castor will increase initial turn in and decrease mid corner steering. This contradics what I am seeing with the anti dive on my car. So my question is, does castor (in the small range we are talking about) have so little affect on the car that the change in front hinge pin angle over powers it?
If you were to just reduce caster you would see slightly more turn in and less mid corner. But because you are also adding anti-dive that is reducing the weight transfer to the front tires on turn-in which is taking away some initial steering, compared to just reducing the caster.

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Originally Posted by EDWARD2003 View Post
Has anyone discussed what setup changes one should make when the temperature of the asphalt changes?

Cheers.
This is a good topic. I have always performed better on carpet than asphalt so I may not be the best one to answer this. In general I have found there is a sweet spot for asphalt temps that produce the most grip. Too cold and you have not grip,...too hot and you also have no grip. So you will need to adjust your settings to allow for more or less grip as the temps change.
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Old 05-10-2014, 05:59 AM   #368
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Great Explanation!
Thanks.
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Old 05-10-2014, 07:29 AM   #369
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quick question about camber links: I apologize if its been asked already.

I understand how angle affects the amount of roll & the length affects how fast but my question is:

What affect does raising the inside the same amount as the outside have?

say, raising both the inside and outside both 1mm.
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Old 05-12-2014, 05:59 AM   #370
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Hey Matin

Something I don't get.
My car feels good, is consistand and has good fast times.
With Sorex (32/36) Tires I have no issue's. But with the Ride REX34 tires I have a "groove of death" at all the four tires of my car.... I just don't understand.
Does it have to do with the airgap? With the additive, with my set-up? I check the glue every run, so that should not be the problem.

My set-up can be found at:
http://www.petitrc.com/reglages/schu...er20140427.pdf

Hope you can give me some directions or ideas.

Thanks in advance.

Robert
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Old 05-12-2014, 08:01 AM   #371
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Finally subscribed! Thanks Martin
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Old 05-12-2014, 10:11 AM   #372
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Martin, I have been working on getting an old TC3 to be hooked up as a VTA car. I have been dialing it in pretty good, though I have one issue that keeps rearing it's head... the car has a tendency to break loose about mid-corner on fast sweepers. I'm running asphalt and the car is great everywhere else, seems pretty fast through the infield. but when I'm running the sweeper (coming off the straight) at full throttle, as you should in slow VTA, this is where I have problems. If I feather / pump the throttle I can usually drive around the problem. But I'm losing time by doing this. What are some initial changes to consider? I was thinking of going a bit wider in the rear by shimming the hexes. My main concern is to not add so much rear traction that I slow the car in the infield, right now the rotation through there is good. I'm very close to getting the car right. If you need my current set up I can post next time, just looking for an answer or two to work with at the moment. Thank you!
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Old 05-13-2014, 12:53 PM   #373
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Quote:
Originally Posted by C&B RC View Post
quick question about camber links: I apologize if its been asked already.

I understand how angle affects the amount of roll & the length affects how fast but my question is:

What affect does raising the inside the same amount as the outside have?

say, raising both the inside and outside both 1mm.
I think I answered that, but like you I don't want to go through all the postings to find it

By raising both the roll center is lowered very slightly. This is because the instance center moves further away from the car and then when you draw a line from the instance center to the center of the wheel on the other side, the intersection with the center line of the car is slightly lower. But it is only a small change and it is less than the amount of spacers you add. For example I did the math (with chassis dimension assumptions) and raising the upper link 2mm both inboard and outboard will only lower the rc about 1mm.

Quote:
Originally Posted by Robert_K View Post
Hey Matin

Something I don't get.
My car feels good, is consistand and has good fast times.
With Sorex (32/36) Tires I have no issue's. But with the Ride REX34 tires I have a "groove of death" at all the four tires of my car.... I just don't understand.
Does it have to do with the airgap? With the additive, with my set-up? I check the glue every run, so that should not be the problem.

My set-up can be found at:
http://www.petitrc.com/reglages/schu...er20140427.pdf

Hope you can give me some directions or ideas.

Thanks in advance.

Robert
I am not sure what you mean by "groove of death" can you describe that further?

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Finally subscribed! Thanks Martin
Quote:
Originally Posted by nf_ekt View Post
Martin, I have been working on getting an old TC3 to be hooked up as a VTA car. I have been dialing it in pretty good, though I have one issue that keeps rearing it's head... the car has a tendency to break loose about mid-corner on fast sweepers. I'm running asphalt and the car is great everywhere else, seems pretty fast through the infield. but when I'm running the sweeper (coming off the straight) at full throttle, as you should in slow VTA, this is where I have problems. If I feather / pump the throttle I can usually drive around the problem. But I'm losing time by doing this. What are some initial changes to consider? I was thinking of going a bit wider in the rear by shimming the hexes. My main concern is to not add so much rear traction that I slow the car in the infield, right now the rotation through there is good. I'm very close to getting the car right. If you need my current set up I can post next time, just looking for an answer or two to work with at the moment. Thank you!
hard to give you accurate advice without knowing how the rest of your car is setup, but notwithstanding that, here are some things to consider that should take away some steering in the sweeper, but still keep your infield steering very similar.

1) add more ackerman and remove any toe out you have on the front. This should smooth out the turn in as well as take away a little mid corner steering. It may not affect the mid corner too much however as your steering angle is likely not that great if it is a wide sweeper.
2) reduce your rear uptravel/droop a little. For example if you have 3 mm of droop, then try 2.5mm. This will reduce the weight transfer a little to your front tires as you get off the throttle.
3) Go up on your front shock oil a small amount. Like from 400 to 500 cst. This will slow down the weight transfer to the front so it is not as abrupt and can potentially smooth out that off throttle transition that seems to be where your issues start.

hope this helps.
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Old 05-13-2014, 12:54 PM   #374
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Finally subscribed! Thanks Martin
Awesome! spread the word
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Old 05-13-2014, 01:32 PM   #375
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I think my friend RK is referring to groove of death, as the premature wear on the inner sides of the tires

In my experience this more of an insert issue associated manly with some pre-mount spec tires

But I'm sure there are some things you can advise him of on setup ?
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