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Old 05-15-2002, 03:25 PM   #76
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Mcrisp: When will you have the hardcopy of Touring Car Chassis Setup Guide in stock?
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Old 05-15-2002, 04:37 PM   #77
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RC Nitro

"Proper" gears are designed with an involute profile so that the point of contact between the teeth does not change as the gears rotate. The gears we use have a flat tooth profile for reasons of economics. This means that the teeth must slide across each other as they rotate. Bigger teeth have to slide more relative to each other so are theoretically less efficient. On the other hand a smaller tooth will distort more if loading is very high making the samll teeth less efficient. I think you are right about the main factor being the ability to fine tune ratios though.

BTW I'm 5 weeks and 7 3 hour exams off being a mechanical engineer.

Mcrisp: moving the wing backwards will put a higher percentage of downforce from the wing on the rear wheels but not neccesarily more rear downforce as the wing could become less effective. The shape of the bodywork will determine whether you get an increase or decrease in downforce from moving the wing.
On a proper racing car moving the wing back put it in cleaner air so downforce increases. Our wings don't work as true wings though. They work by obstructing air flow rather than accelerating airflow over one face to acheive the pressure differential. This is why the current 2wd offroad cars all mount the wings directly behind the rear bodywork and not up high in clear air. Moving the wing back in this situation can actually lose rear end grip.

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Old 05-16-2002, 03:50 AM   #78
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RC Nitro. I am certain you know I didn't mean a formal triangle when I meationed triangle. It was just using an extreme analogy to illustrate a point. So what's the minimum teeth a gear could have?

Now you are teasing me. Of course it's the transmission I was referring to when I talked about efficiency. A 64 pitch gear sitting on a pit table under a sun screen of course wouldn't be more efficient than a 48 pitch gear sitting in a hobby shop cabinet.

mcrisp this is not being sarcastic or anyting. This is a serious and sincere question. Do tires increase traction on warming but then reverse and lose traction if overheated? I want a very short answer this time.
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Old 05-16-2002, 04:40 AM   #79
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Quote:
Originally posted by mandy
RC Nitro. I am certain you know I didn't mean a formal triangle when I meationed triangle. It was just using an extreme analogy to illustrate a point. So what's the minimum teeth a gear could have?
Yes I did, but it was 6 am and I only had 3 hrs sleep. Daughter was sick the night before and I wa up a lot. I read my post last night and realized I was a bit strong. Sorry Your example is valid and a good way to point out the logic! I need to think more out of the box. ie not be so blasted logical.

Min diameter of a gear is based on tooth angle. YOu measure the distance between two gear teeth "V" shape and to center line of that is alpha (a). Formula is z=2/ sin^2 a. For a 20 degree angle that is ~ 17 teeth. There are other factors involved too.

Quote:

Now you are teasing me. Of course it's the transmission I was referring to when I talked about efficiency. A 64 pitch gear sitting on a pit table under a sun screen of course wouldn't be more efficient than a 48 pitch gear sitting in a hobby shop cabinet.
Actually I had someone try to convice me that single gears had an efficiency ratio....
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mcrisp this is not being sarcastic or anyting. This is a serious and sincere question. Do tires increase traction on warming but then reverse and lose traction if overheated? I want a very short answer this time.
Yes Short enough
To a point. I am an ex full scale racers. Ever notice Trans Am racers or the NASCAR guys doing small turns at low speed? This is to heat up a cold tire. Cold tires are like hards with hard inserts. But Martin is right, when you get tires to hot, like toward the end of a race and the rubber is worn down they will get that greasy feeling and it is not linear either You get accelerated wear with an overheated tire as they are now to soft. Like soft and soft inserts on a hot day. Work great for about 2 laps and then yuck!

Last edited by RC Nitro; 05-16-2002 at 04:44 AM.
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Old 05-16-2002, 04:49 AM   #80
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Mandy, I think you and rcnitro may be getting a bit confused.
I don't think rcnitro is teasing you.

In engineering calculations gears are usually taken as being 100% efficient because with an involute tooth profile as used in most applications they theoretically are as there is no relative movement between the gear teeth at the point of contact so no frictional losses. This is what rc nitro means when he says gears don't have an efficiency ratio.

Calculated transmission losses usually relate to other factors such as churning losses from oil in the transmission and bevel gears which can't use an involute profile. Belts also have a theoretical loss that can be calculated.

Tyres provide optimum traction at an optimum temperature. Too hot or too cold wil result in a loss of traction.
Heat is generated by the tyre carcass flexing. If a tyre gets too hot a harder insert will reduce flex and increase traction. If the tyre is too cold a softer insert will help. This will only make a small difference though. You must have the right tyre to start with.
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Old 05-16-2002, 04:51 AM   #81
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Looks like rcnitros just replied
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Old 05-16-2002, 04:55 AM   #82
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Quote:
Originally posted by dw
RC Nitro

"Proper" gears are designed with an involute profile so that the point of contact between the teeth does not change as the gears rotate. The gears we use have a flat tooth profile for reasons of economics. This means that the teeth must slide across each other as they rotate. Bigger teeth have to slide more relative to each other so are theoretically less efficient. On the other hand a smaller tooth will distort more if loading is very high making the samll teeth less efficient. I think you are right about the main factor being the ability to fine tune ratios though.
I did realize that, was just trying to save the boring tech for us engineers I figured I would leave out base circle, pitch diamenter, etc out of the equation. I had a chat with a friend that is a machinist and to make our gears the right way is to expensive for the gain.
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BTW I'm 5 weeks and 7 3 hour exams off being a mechanical engineer.
Congrats Dude!!!!! Finished my 8 years of night school in 92.
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Old 05-16-2002, 05:00 AM   #83
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Quote:
Originally posted by dw
Looks like rcnitros just replied


Well said responce! You must be in Europe, as you said tyres vs tires.
John
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Old 05-16-2002, 07:35 PM   #84
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Mandy : Yes

BW : good luck on those exams! I agree with you about the wings, but I would think, that in general with the touring car bodies (e.g. stratus), moving the wing a little further rearward would increase the rear downforce.

smash123: I expect to have a new batch in about 1 month. The reason for the delay, is I am going to print a very large volume and the cover is being re-designed.
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Old 05-17-2002, 03:29 AM   #85
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mcrisp

Great book, great deal of information and most important easy to undestand!! Thank you very much


Are you going to release a third version? What will the differences/addition?


Thanks again


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Old 05-17-2002, 08:39 AM   #86
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Hi nnick,

Thanks for the feedback on the book. As with a lot of products, I will be releasing new versions of the book from time to time. I keep a running list of ideas to improve the book. I don't have a specific time-table for the next version yet.

If you feel like sending me some ideas for the next book, please feel free. You can find my email on my website.

By the way, the book is selling all over the world, but you are the first one from Greece!!

After reading about the worlds I really wish I had spent the money to go. It looks like a great track, and the competition looks very close.

Thanks again,
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Old 05-18-2002, 03:38 AM   #87
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mcrisp, awesome work. I race a XXXS on pavemant-no VHT. Here's one for ya, how do softer wheels affect handling vs. stiffer wheels. Team Orion makes some really soft wheels where they almost feel like rubber. I'm thinking wheels should be as stiff as possible so there won't be any runout when power is applied to them, is this correct? Now it's just the inside of the wheel that is super soft not the outside.
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Old 05-18-2002, 10:48 AM   #88
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ok here comes a newbie dumb qestion....is there any link where i can read up on this roll centre?....

im totally confused with the jargon u all are using....


Thanks.
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Old 05-18-2002, 10:54 AM   #89
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Dragon,

http://www.mpowered-racing.com is the home of the mpowered chassis tuning guide. It's probably the best investment you can make in R/C racing.

There's also this site: http://gallery.uunet.be/heremanss/ but having read both I think the mpowered guide is more understandable and made more sense to me.

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Old 05-18-2002, 12:19 PM   #90
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Personally I prefer the gallery... one.

I've now read both, and I don't fully agree with the analysis of the handling in the M-powered one (particularly on caster) - I'm not an engineer, so I'm not saying mcrisp has the facts wrong, it's that when I apply the things I get different results with my chassis.

And the gallery... one is free.
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