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Old 04-25-2006, 03:54 PM   #10111
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Had a test and tune session last night with my R40. I have converted it to run in the 1 horsepower class we have here. Running a TOP X-12 (1 hp) with OS MTX3 header and Associated pipe from the RTR RC10 truck.

The track we run on has 2 tight hairpin type corners where you slow down significantly so I needed quite a bit of low end snap. I am still using the Mugen clutch, but found some interesting results if you want low end snap:

1. Ensure you are gearing 1st gear right. If you are trying to pull a high 1st gear ratio your clutch will slip. I dropped down to a 20 tooth 1st pinion and reduced some clutch slip right there.

2. Ensure that your 2 speed is not shifting too early. If you get into 2nd too early you can drag your clutch by it trying to pull too high a ratio out of its torque band.

3. With the following setting I got the car to where it will break traction under acceleration from a relatively slow speed corner.

0.8mm clutch gap.
Yellow mugen shoe.
0.6mm on adjuster nut, MTX4 spring.

In fact I can make the rear wheels break out under acceleration now if I want. The tall clutch gap is they key.
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Old 04-25-2006, 03:58 PM   #10112
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Quote:
Originally Posted by AMGRacer
Thats part of your problem right there. You should go to at least 0.5 to 0.6 as a starting point if you are using any of the more modern powerful engines.

BTW the HPI stock spring is lighter than the stock MTX3 and MTX4 clutch springs, not stiffer.
Ive got a powerful motor and a gap that large didnt work whatsoever for me. In fact my motor makes a lot of torque. So im wondering why Ive never been able to get any sort of engagement really on 2-3 different clutch setups.

But ive seen people build their first centax on an r40 and have it engage fine. Its really kinda baffling.

Yeah it seems all the mtx springs I tried seemed to be heavier. Im going to run that one that nitrothugg suggested. Thanks for the info.
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Old 04-25-2006, 04:00 PM   #10113
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Quote:
Originally Posted by AMGRacer
Had a test and tune session last night with my R40. I have converted it to run in the 1 horsepower class we have here. Running a TOP X-12 (1 hp) with OS MTX3 header and Associated pipe from the RTR RC10 truck.

The track we run on has 2 tight hairpin type corners where you slow down significantly so I needed quite a bit of low end snap. I am still using the Mugen clutch, but found some interesting results if you want low end snap:

1. Ensure you are gearing 1st gear right. If you are trying to pull a high 1st gear ratio your clutch will slip. I dropped down to a 20 tooth 1st pinion and reduced some clutch slip right there.

2. Ensure that your 2 speed is not shifting too early. If you get into 2nd too early you can drag your clutch by it trying to pull too high a ratio out of its torque band.

3. With the following setting I got the car to where it will break traction under acceleration from a relatively slow speed corner.

0.8mm clutch gap.
Yellow mugen shoe.
0.6mm on adjuster nut, MTX4 spring.

In fact I can make the rear wheels break out under acceleration now if I want. The tall clutch gap is they key.
Well isnt low engagement all about smooth accerlation and not breaking traction. I can set my clutch like normal and rev like crazy and itll snap hard , break some traction and go , but I dont like reving 20-30% rpm to get it to just move.

Last edited by Artificial-I; 04-25-2006 at 04:15 PM.
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Old 04-25-2006, 06:36 PM   #10114
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Quote:
Originally Posted by Artificial-I
Ive got a powerful motor and a gap that large didnt work whatsoever for me. In fact my motor makes a lot of torque. So im wondering why Ive never been able to get any sort of engagement really on 2-3 different clutch setups.

But ive seen people build their first centax on an r40 and have it engage fine. Its really kinda baffling.

Yeah it seems all the mtx springs I tried seemed to be heavier. Im going to run that one that nitrothugg suggested. Thanks for the info.
Dunno I cant explain it since I will never be at the track with these people. Basically clutch setup works along with MANY other factors including, pipe, engine tune, plug selection, tire choice, track layout etc etc. The tracks we have here in Australia are quite different to US tracks usually, they are more european style in the main (well the ones I run at anyways).

Just passing along what works for me, feel free to try it if you think it will help.
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Old 04-25-2006, 06:43 PM   #10115
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Quote:
Originally Posted by Artificial-I
Well isnt low engagement all about smooth accerlation and not breaking traction. I can set my clutch like normal and rev like crazy and itll snap hard , break some traction and go , but I dont like reving 20-30% rpm to get it to just move.
Well it depends on driving style and such. What you need to remember is that with electric cars they make maximum torque at 0 rpm, whereas with nitro cars maximum torque is achieved far further up the RPM scale, more near the top. So in fact you want your clutch to engage as far up the RPM band as you can get it while still making sufficient grip. In fact in 1:1 drag racing maximum acceleration is achieved with around 7% wheelspin, NOT as would be commonly assumed 0% wheelspin.

I achieve maximum laptimes when my clutch is slightly snatching grip from the rear tires on acceleration from a slower corner. Oversteer makes the car turn in more when exiting the corner, if done in a controlled manner.

Now my descriptions can make it sounds as if my car is an uncontrolled monster, it is difficult to convey the subtleties of what I am talking about in text.
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Old 04-25-2006, 09:04 PM   #10116
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Yeah it could be a good setting but im just trying to achieve almost instant clutch engagement from any sort of tiny throttle blip.

I did drive it though with a very snappy drive one time with the mugen grey. Id rev up and the car would just tear out of the corner. But I have like slow transistions , 180's , chicanes you name it. Ill have to bring a video camera next time and do some filming to see the torture this cars goes through , just think of an electric track.

But its horrid with a high engaging clutch at my track youll hear my car mid corner , REEEEEEEEE....and its just at the same speed. Once it finally engages it can throw the car out of the turn. I get high temps from it due to this and can only think how badly its wearing down whatever clutch disc I had to grab.

Basically im trying to get my setup to do what the top driver at my track runs. He uses a very smooth driving style with a low clutch engagement.

Did you ever get the R40 clutch to engage low? As well were those settings for the mugen?

I noticed someone else in a centax thread saying they hated only 2 centax clutches , one was the r40 the other was the reflex. I think its just something that cant be overcome unless you want high rev and hard bite. Which maybe its what hpi wanted for us. But Im not used to this driving style at all and Ive always driven all my cars with basically instant clutch engagement. Im thinking hpi really needs to dig down on this car and not worry about weight placement. But fix the few problems that lurk on this car.
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Old 04-25-2006, 11:38 PM   #10117
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You might find that a higher engagement for the clutch is what you need now that you switched to the front spool. You can dive into the corners really hard and yank it around the apex with the throttle. You could also try gearing down a bit to keep the rpm's higher.
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Old 04-26-2006, 12:21 AM   #10118
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Is a harder (mugen) or softer (GS or HPI)clutch spring going to help clutch engagement? i'm running a Mugen hard spring now with much better results.

My clutch nut wound down the threads last race and caused it to start slipping again. I took it apart and screwed it up more and fixed the problem. If that thing would stay put I think alot of the slipping issues would go away. I don't want to thread lock it cause I'm not entirely confident of the position it should be in.
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Old 04-26-2006, 02:33 AM   #10119
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Quote:
Originally Posted by Artificial-I
Yeah it could be a good setting but im just trying to achieve almost instant clutch engagement from any sort of tiny throttle blip.

I did drive it though with a very snappy drive one time with the mugen grey. Id rev up and the car would just tear out of the corner. But I have like slow transistions , 180's , chicanes you name it. Ill have to bring a video camera next time and do some filming to see the torture this cars goes through , just think of an electric track.

But its horrid with a high engaging clutch at my track youll hear my car mid corner , REEEEEEEEE....and its just at the same speed. Once it finally engages it can throw the car out of the turn. I get high temps from it due to this and can only think how badly its wearing down whatever clutch disc I had to grab.

Basically im trying to get my setup to do what the top driver at my track runs. He uses a very smooth driving style with a low clutch engagement.

Did you ever get the R40 clutch to engage low? As well were those settings for the mugen?

I noticed someone else in a centax thread saying they hated only 2 centax clutches , one was the r40 the other was the reflex. I think its just something that cant be overcome unless you want high rev and hard bite. Which maybe its what hpi wanted for us. But Im not used to this driving style at all and Ive always driven all my cars with basically instant clutch engagement. Im thinking hpi really needs to dig down on this car and not worry about weight placement. But fix the few problems that lurk on this car.
I can get the R40 stock clutch to engage quite low, but as previously discussed the stock shoe is quite slippy and a low setting is quite pointless with that much slip. I really cannot see how engaging the motor at the slight blip of the throttle is going to be that good for laptimes, but also I have never seen your track.

Basically most centax clutches are not really designed for low RPM response/engagement so you will find that their springs prevent useful movement of the clutch shoe even with the adjuster nut set very loose. You will need a quite soft spring, or grind a coil off an existing spring. The problem you will also find is that if the shoe moves too early there will be insufficient bite. Basically you will need to do some experimenting.

But also I would encourage you to watch some RC videos, especially the Winternats videos. That track is fairly tight (well for my part of the world) and you can hear the way they have their clutches set. They are kicking in at quite high RPM and still they have a "sobbing" sound as the clutch bite fights against the tire grip.
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Old 04-26-2006, 11:52 AM   #10120
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I got the winternats video. Ill watch it again to see your talking about. But my track has terrible traction.

Have you ever driven a 3 shoe clutch like the old racer2. You can get those things to engage at pretty much very low rpm. Its just what im used to and allows you to be smooth on the throttle and saves gas , increases cooling.
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Old 04-26-2006, 12:22 PM   #10121
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Quote:
Thats part of your problem right there. You should go to at least 0.5 to 0.6 as a starting point if you are using any of the more modern powerful engines.
How do you get the gap that big. I removed all the spacers now. Ive only got the clutchbell and bearings bolted down and my max only goes to 0.48mm
(this is with the mugen grey shoe fitted and the nut set to 0.6mm
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Old 04-26-2006, 09:53 PM   #10122
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Quote:
Originally Posted by ProE
How do you get the gap that big. I removed all the spacers now. Ive only got the clutchbell and bearings bolted down and my max only goes to 0.48mm
(this is with the mugen grey shoe fitted and the nut set to 0.6mm
You shim between the end of the SG shaft and the thrust bearing holder with some of the little tiny shims that come with the car.
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Old 04-26-2006, 10:01 PM   #10123
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Quote:
Originally Posted by Artificial-I
I got the winternats video. Ill watch it again to see your talking about. But my track has terrible traction.

Have you ever driven a 3 shoe clutch like the old racer2. You can get those things to engage at pretty much very low rpm. Its just what im used to and allows you to be smooth on the throttle and saves gas , increases cooling.
The old racer 2 had a 2 shoe "HPI racing clutch" assembly with 3 optional holes to use and a wrap around spring. These clutches are fine and work quite well, but as they engage very low you can never get a good deal of punch from them. Plus you will notice that they always slip even with low power motors, and they only do it worse as you get higher power motors.

These sort of clutches seem to be popular on RTRs and off road vehicles where the available traction to the wheels is only a fraction of what we have with on-road cars.

A smooth engaging clutch that engages at low RPM can be a good thing, but you really need to set the engagement point of the clutch to the point where the motor is starting to produce good power to be really fast. A clutch that engages too low can in fact overheat a motor and use more gas as you cause it to "chug" trying to pull the car along far outside of its torque band.

I will try and get some video of my car in action with a clutch that engages about 25% of the way up the throw, and you will see that I can drive it very smoothly. It is just that the first 25% of the throttle is not used, you smoothly use the remaining 75%. It is an acquired art to train your finger to work like this. Some drivers do the "double tap" out of a corner to get a similar smooth effect.
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Old 04-26-2006, 10:26 PM   #10124
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Yeah , its been awhile since I broke out the racer2. Built the clutch during assembly and havent touched it in like 8 years. Still works great.

I guess reason why I bring it up is , im shooting for that type of engagement. It doesnt seem to slip much to me.

Also I just checked out another r40, the r40 would need to be revved full throttle and would take 1-2 seconds to engage....talk about bad. LOL. Even then it didnt have much snap.
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Old 04-27-2006, 12:36 AM   #10125
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Here's a clip my friend put together of me runnin at one of my local tracks. Didn't have enough mem to catch a guy runnin his R40 that I was helping him tune though. Track was a bit dusty to go any faster though sunday it will be better hopefully.

http://media.putfile.com/Warmup-in-Bridgeport
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