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Old 05-12-2002, 06:00 PM   #61
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Martin C
I just finished reading your setup giude and I want to tell you it is the easiest to understand (chassis tuning) book I have read. Maybe you could add a chapter on upper link lengths. I know the 414M has longer upper links than the 414X and I read that the Yokomo guys are lengthening their links also. When would you alter the lengths and what would it change?
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Old 05-12-2002, 08:25 PM   #62
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Thankyou Trips, rcruv, impactplayr and also mcrisp.

1) If I would need to place spacers (eg. O-rings) below the pistons to vary droop, I think I might give it up. It is just too messy and the thing is that I may not get it right the first time. I cannot imagine myself repeating the whole procedure again to readjust a different droop. I think I would just vary the shock ends.

2) So droop is measured from the bottom of the hub carriers, then is it true that droop quotations are different for different cars, say 4mm for one is not the same as 4mm for another? I figure I remove the tires and I can do the measurements with just a ride height gauge.

3) mcrisp, I always thought as tires warm up their traction increases. Are you pointing out that as tires overheat instead of just merely warm up, they lose traction? I really want to sort this out. When a 4wd sedan loses rear traction towards the middle of the run, I always ascribe the effects are due to the culprit of the front tires. The front tires steer left and right and naturally they warm up more than the rear tires. Then the front tires traction increase relatively to the rears and the front assumes more traction and the rear breaks loose comparatively. I always use this theory to explain the phenomenon. Now this rear toe-in business making the rear tires overheat causing the car to lose rear traction really has got me confused.
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Old 05-12-2002, 09:15 PM   #63
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Ottoman :

Thanks for the suggestion and feedback. I keep a list of ideas as I will continue to add to the book.

The shorter the upper link the more the camber will change when the suspension is compressed. Having the camber change more will reduce straight line acceleration but can help increase traction in the corners. I actually like to use a shorter upper link on the rear of my 414M. You should try both and go with what works for your overall setup.

Mandy:
Instead of measuring droop, I actually like to measure the "up-travel", because this can be measured the same on every car. Up-travel is the distance the chassis raises up from rest to just before the tires come off of the ground. So if I have 3mm of up-travel then the chassis will raise up 3mm before the tires come off the ground at that end of the car.

I agree that having to change spacers in the shocks to too much work. The losi is a good car, but the foundation for the droop screws needs to be changed.

Tires overheating: It is true that front tires work very hard and can overheat as well. For example if you drive around your track in a clockwise manner the front left tire take a lot of abuse and can overheat. But the rear left tire could also overheat as it also takes a lot of abuse. For example at my home track (which is a carpet track) I have found that if I use 3 degrees rear toe the rear tires overheat at the 4 min mark. If I use 2.5 degrees of rear toe the tires are fine to the end. I have also found that when I run a front one-way this makes it easier to overheat the rear tires given the additional load on the rear tires due to the increased steering the front one-way provides. I am not saying that 3 degrees of rear toe in is too much. But for my track and my setup and the tires/inserts I use 2.5 degrees works more consistently.

I hope this helps.

Last edited by mcrisp; 05-12-2002 at 09:21 PM.
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Old 05-13-2002, 12:22 AM   #64
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Wow, using limiters is going to be pretty annoying with the Losi shocks. To get into the right ballpark, the rear shocks become so short at full extension that it's impossible to get the spring perches onto the shafts. I had to cut down the height of the spring perches just to be able to get them on. Putting them on and off with springs there is going to be REAL fun... At least I left enough room on the shock ends to get most of my adjustment there so I won't be opening the shocks much. I'm thinking I might want to look into Yokomo shocks for the car, from the setup sheets on the Yokomo website it seems they're close to the correct length.

Martin,

I noticed on your website that you've attended some races here in the U.S. I was wondering if you were planning to come to any this season?

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Old 05-13-2002, 02:44 AM   #65
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Mcrisp thankyou very much.
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Old 05-13-2002, 09:06 AM   #66
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Hi Trips

I went to three races so far this year in the states including the Triple crown race at RC Madness, the Trinity 2k2 Race in Maryland and the ROAR carpet nats in california. I will also be going to the ROAR paved on-road nats in July.
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Old 05-13-2002, 09:52 AM   #67
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Martin
Great book! Downloaded that before I went on vacation. Still reading, but I have a question. I notice you avoided tires Can you comment on foams vs rubber. Also I just had 180 turn on my nitro car in handling between tracks. My Xray remained the same, but MTX-2 went from off power push to off power oversteer. The only change was the foams and track. Ended up with the softer fronts on the rear! Was running purple (F) and double purple (R) or 40 (F) and 42 (R). suggestions?? New to foams. Electric I run a soft to med tire with Yok firm inserts.

Thanks
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Old 05-13-2002, 10:26 AM   #68
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Hi RC Nitro

Thanks for the feedback on the book and suggestions for topics. Always appreciated.

I am going to assume that you used foam tires on both the electric and Nitro cars.

In general foam tires will provide more grip than rubber tires. (I like both types of tires) As a result of this grip the amount of weight transfer you had with rubber tires will be increased with foam tires. Even though when you let off the power with rubber tires you are not transferring too much weight to the front end of the car, with the extra grip of foam tires, the wight transfer is increased and you are transferring even more weight to the front of your car. Yes it is true that the rear tires also have more grip, but the increased weight transfer to the front tires has taken the "balance" out of your car. In other words the front suspension can't handle the increased weight transfer caused by the foam tires. To fix this you should either go with a harder compound front tire or stiffen the front suspension to reduce the weight transfer to the front. You can refer to the book on how to stiffen the front end. Depending on how stiff your springs are I would start with increasing your front springs and shock oil. You can fine tune this with the caster and camber and roll center. If the car is flipping I would raise the roll center.

The nitro car is a much heavier car than the electric car and as a result this further accentuates the weight transfer. This could be the reason why you did not see the same problem with the electric car as the nitro car. (again assuming you ran foams on both cars).

Having said all of that, in general drivers like to run a harder foam on the front and softer foam on the rear. A very common carpet combination is TRC PLAID in the font and TC PURPLE in the rear. The PLAID is good because the outer edge of the tire is a harder compound which helps prevent the front end from diving too much in the corner and giving you too much steering.
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Old 05-13-2002, 06:36 PM   #69
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I've asked this question in another thread but that thread is a bit too quiet and static. I would like to ask the question again here.

I run the mr4tc world's edition. I've been using the stock recommendations of the 2-hole pistons. Many people advise me to use the 3-hole (each hole being smaller than that of the 2-hole) pistons instead, saying that the chassis will roll less and 'less lazy' around the corners. I fully understand the logic.

Has anyone used the 3-hole pistons in mr4tc and find that there is really so much a difference? I want to change to the 3-hole pistons but thinking that if the effect is not much different, it ain't worth the the trouble (huge work, and oily too).
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Old 05-14-2002, 07:56 AM   #70
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Quote:
Originally posted by mcrisp
I am going to assume that you used foam tires on both the electric and Nitro cars.

Actually I run rubber on the electric. The car is running well and the handling suits me right now so I have not changed. (Soft tire with firm insert.)

I did not know that foams had more grip. 85% of the nitro drivers are using foams so I am having to switch to keep up. I see what you are saying now. I normally play with the car with rubber and race on foam. I like to pratice doing figure 8's but I run the rubber as to not wear the foams down. I see that I need 2 setups if I do this. I just got 2 new sets of foams softer for the front. With rubber I have off power push. Been reading your book . I think some of my problem is the increased speed of the nitro and the lack of slowdown when you let off the throttle. Because as the race progressive and I get my rhythm, the rear get looser, lots of trailing throttle oversteer! Worse with the foams.

Quote:
If the car is flipping I would raise the roll center.
No traction rolls yet..........

Thanks for the tire tips
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Old 05-14-2002, 11:14 PM   #71
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What effect do different wing placements have on the handling of the car?

Switching from 64 pitch to 48 pitch (and same gear ratio) will have the same gear ratio right? Just confirming.
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Old 05-14-2002, 11:24 PM   #72
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Aurra Sing

Wing Placements : The further you move the wing towards the rear of the car the more rear down-force you will get. The more angle you have on the wing the more down-force you will get.

Yep : the ratio on the gears is the same.
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Old 05-15-2002, 02:57 AM   #73
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The ratio is the same. The efficiency is different. 200:100 and 20:10 has the same ratio but the former has higher efficiency. That's why 64 pitch has higher efficiency than 46.

The use of 64 pitch to get more versatility in gear ratios is really a myth in my opinion. It is more eficient to put it in short. It is smoother. It resembles a bigger and 'rounder' circle.46 pitch has the advantage in being more resistant to wear.

As the number of teeth decreases, the gear resembles less of a circle. Imagine a gear with 3 tooth. It really is a triangle. It is then far from being 'round'.

mcrisp thankyou again so much on your input on the rear toe-in business......but the more I think about it the more I believe my theory is correct. If tires lose traction on warming, what are tire-warmers for? Unless you can point out 'warm' and 'overheat' are on opposite sides of the spectrum.
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Old 05-15-2002, 04:35 AM   #74
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Quote:
Originally posted by mandy
The ratio is the same. The efficiency is different. 200:100 and 20:10 has the same ratio but the former has higher efficiency. That's why 64 pitch has higher efficiency than 46.

The use of 64 pitch to get more versatility in gear ratios is really a myth in my opinion. It is more eficient to put it in short. It is smoother. It resembles a bigger and 'rounder' circle.46 pitch has the advantage in being more resistant to wear.

As the number of teeth decreases, the gear resembles less of a circle. Imagine a gear with 3 tooth. It really is a triangle. It is then far from being 'round'.
Mandy I disagree with you "circle" statement. gears do not become a square or triangle. There is a minimum number of teeth for any gear size. As I am a Mechanical Engineer I know how gears are designed. All are cut form a base circle. 64 pitch will give you a finer ratio between gears over 48 pitch. However 48 has larger teeth they have more load bearing capacity. Ever notice that nitro's run 48 not 64. This is due to load bearing capicity. In efficiency, you must be refering to the transmission. As gears themselves do not have an efficiency ratio.

Not trying to start a war here

I run both nitro and electric. In nitro you have the option of 48 or 48 Where as the electric you have 64/48 or 32 in trucks. Really depends on the application. I have found 48 to work better for MY situation as the tacks I run on, parking lots, are not always clean and I loose less spurs at 48
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Old 05-15-2002, 06:48 AM   #75
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Default Overheating Tires

HI Mandy,

Yes it is true that tirewarmers heat up tires, but in most real car racing these tirewarmers do not put as much heat into the tires as actually racing the car around the track. (e.g. F1)

Tire companies provide a range of tire "compounds" that reach their "traction peak" at different tempurature ranges. For example the Take-off tires have the following tires and corresponding track surface tempurature ranges.

Tire Temp Range (Centigrade)
CS-22 0-30
CS-27 10-50
CS-32 20-60
CS-37 40-70

For example, if you tried to use a CS-22 with a track temp of 50 (C), the tire compound would quickly overheat and you will loose traction. This overheating issue is exactly why they have multiple tire compunds.

I hope this helps.
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