HRE Unveils New Carbon Fiber Wheels
#47
11-10-2008 | 03:10 PM
Former Vendor
Joined: Oct 2008
Posts: 148
From: Vista, CA
Rep Power: 0
7075??
Alpine_997
Be careful with 7075. I love the material and we used it all the time in aerospace. It isn't so good at holding its strength at high temps and after temperature exposure. Good for bicycles. Not good for wheels and brake temperatures. Believe me, if it were a good for wheels, we'd be using it.
Alan
Be careful with 7075. I love the material and we used it all the time in aerospace. It isn't so good at holding its strength at high temps and after temperature exposure. Good for bicycles. Not good for wheels and brake temperatures. Believe me, if it were a good for wheels, we'd be using it.
Alan
I guess everyone is entitled to their own personal style and this wheel is not my personal style.. No right or wrong just indifferent.
GEE-BEE sucks to hear about your accident and your wheels. You are much cooler about it than some would be.
I think before CF for me I would go with higher lighter weight aluminum such at T7075 if I were to spend the kind of money CF demands.
Benjamin - exactly.
GEE-BEE sucks to hear about your accident and your wheels. You are much cooler about it than some would be.
I think before CF for me I would go with higher lighter weight aluminum such at T7075 if I were to spend the kind of money CF demands.
Benjamin - exactly.
Last edited by HRE_Alan; 11-10-2008 at 03:13 PM.
#49
11-10-2008 | 06:31 PM
Registered User
Joined: Dec 2006
Posts: 3,116
From: Palos Verdes
Rep Power: 254
Thank you for taking time to answer. Back to the issue of carbon fiber wheel, it seems there is no advantage as far as weight/durability between this carbon fiber/aluminum combination wheel, or carbon/magnesium combination wheel (Dymag), versus a magnesium wheel?
Benjamin,
I agree with you wholeheartedly (except for your criticism of us of course!!
)
It is unfortunate that in one breath HRE is criticized for making wheels that are "too heavy" while our "competition" is applauded for making wheels that are irresponsibly light weight. And now we introduce a material that can get us to a lower weight safely and we're being criticized.
If you notice, the weights of our 1pc forged aluminum wheels are in-line with our quality competitors, namely BBS and Champion. Why is this? It's because the same physics that apply to them apply to me. I can make a 17lb wheel any day of the week, but that doesn't mean it is safe to go on a 997TT. Oh... but they've tested it. Not enough. It turns out that it helps if you test to the correct load rating for the application and the use the right spec. We actually multiply the designated TUV load rating by a factor of safety before designing the wheel to that spec. Why? We've found that simply going off of max axle load isn't enough. Not even close. If it were that easy to make them lightweight, wouldn't Porsche do it themselves? Do any of us have more resources than Porsche? I don't think so.
This shows the difference between good marketing and good engineering. We'll stick to the good engineering. We want to be in business for the long haul. We're not going to sell a bunch of wheels and then going running off with all the money once the fatigure failures begin... and they will begin. It just takes time.
So on to carbon. It turns out that the stiffness of the carbon barrel is actually much higher than the stiffness of the aluminum barrel. In fact, in fatigue, the barrels are load rated MUCH higher than the aluminum center simply because you have to design the rim around impact. Okay... so is it brittle and is it going to shatter into a million pieces under impact. Nope. If you hit a curb or something you'll definitely damage it, but you'll have a localized failure which is what you want and should expect.
As for us not knowing and/or not caring, I want to extend an invitation to you to visit HRE anytime. I can give you a personal tour (above and beyond my normal tours) and show you how we do it and why we do it that way. I think you'll be impressed by our knowledge and expertise, our capabilities, our honesty and the most of all the integrity that is simply infused in all of us here.
If you want to criticize us after that, feel free. I welcome constructive criticism. It keeps us moving forward. I just prefer it is based on facts and reality.
My $.51.
Thanks,
Alan
I agree with you wholeheartedly (except for your criticism of us of course!!
)It is unfortunate that in one breath HRE is criticized for making wheels that are "too heavy" while our "competition" is applauded for making wheels that are irresponsibly light weight. And now we introduce a material that can get us to a lower weight safely and we're being criticized.
If you notice, the weights of our 1pc forged aluminum wheels are in-line with our quality competitors, namely BBS and Champion. Why is this? It's because the same physics that apply to them apply to me. I can make a 17lb wheel any day of the week, but that doesn't mean it is safe to go on a 997TT. Oh... but they've tested it. Not enough. It turns out that it helps if you test to the correct load rating for the application and the use the right spec. We actually multiply the designated TUV load rating by a factor of safety before designing the wheel to that spec. Why? We've found that simply going off of max axle load isn't enough. Not even close. If it were that easy to make them lightweight, wouldn't Porsche do it themselves? Do any of us have more resources than Porsche? I don't think so.
This shows the difference between good marketing and good engineering. We'll stick to the good engineering. We want to be in business for the long haul. We're not going to sell a bunch of wheels and then going running off with all the money once the fatigure failures begin... and they will begin. It just takes time.
So on to carbon. It turns out that the stiffness of the carbon barrel is actually much higher than the stiffness of the aluminum barrel. In fact, in fatigue, the barrels are load rated MUCH higher than the aluminum center simply because you have to design the rim around impact. Okay... so is it brittle and is it going to shatter into a million pieces under impact. Nope. If you hit a curb or something you'll definitely damage it, but you'll have a localized failure which is what you want and should expect.
As for us not knowing and/or not caring, I want to extend an invitation to you to visit HRE anytime. I can give you a personal tour (above and beyond my normal tours) and show you how we do it and why we do it that way. I think you'll be impressed by our knowledge and expertise, our capabilities, our honesty and the most of all the integrity that is simply infused in all of us here.
If you want to criticize us after that, feel free. I welcome constructive criticism. It keeps us moving forward. I just prefer it is based on facts and reality.
My $.51.
Thanks,
Alan
Last edited by cannga; 11-10-2008 at 06:45 PM.
#50
11-10-2008 | 06:45 PM
Former Vendor
Joined: Oct 2008
Posts: 148
From: Vista, CA
Rep Power: 0
mag vs carbon?
Cannga,
As an engineer I love magnesium and we're always looking for a good forged magnesium option to offer. Basically the only good forged mag option I know of now comes on the Carrera GT from the factory. BBS and others are ending their mag options for the track due to problems. F1 obviously runs mag but durability past one race isn't exactly the concern.
As for comparison to carbon/aluminum, without doing some actual engineering to check my info first, i'll take a chance and open myself up to ridicule and say off the top of my head that I think the weight and cost would be about the same. I also think the mag rim would be susceptible to impact, not to mention corrosion (although you can mitigate this if you do it properly). I do think the cost of forged mag would be similar to carbon though.
I am not a fan of cast mag as it just doesn't have the strength needed. Forged aluminum pretty much gets you there without any of the problems.
On a side note, your red 997TT is absolutely hot.
Alan
As an engineer I love magnesium and we're always looking for a good forged magnesium option to offer. Basically the only good forged mag option I know of now comes on the Carrera GT from the factory. BBS and others are ending their mag options for the track due to problems. F1 obviously runs mag but durability past one race isn't exactly the concern.
As for comparison to carbon/aluminum, without doing some actual engineering to check my info first, i'll take a chance and open myself up to ridicule and say off the top of my head that I think the weight and cost would be about the same. I also think the mag rim would be susceptible to impact, not to mention corrosion (although you can mitigate this if you do it properly). I do think the cost of forged mag would be similar to carbon though.
I am not a fan of cast mag as it just doesn't have the strength needed. Forged aluminum pretty much gets you there without any of the problems.
On a side note, your red 997TT is absolutely hot.
Alan
#51
11-10-2008 | 06:58 PM
Banned
Joined: Feb 2005
Posts: 166
From: Manhattan Beach, CA
Rep Power: 27
Dymag Cf Barrel
Moment of inertia facts
<O:p</O:p
Determination of moment of inertia for a wheel is very difficult because the “normal” calculations are for a thin wall cylinder or solid rod, the calculation being a function of the mass multiplied by the square of the radius. With the Dymag carbon / magnesium wheel being of different materials and different masses as you radiate out from the hub, then the calculation needs to take on some assumptions.
<O:p</O:p
Therefore if we take the whole wheel, then the basic formula is:
<O:p</O:p
MOI = ½ mr²
<O:p
If the carbon barrel alone is measured versus a metal rim it would be:
<O:p</O:p
MOI = mr²
<O:p
So because of the radius being squared in each calculation, the greater the diameter of any wheel then the greater the effect of reducing the MOI.
<O:p</O:p
As you can see if we use the generally accepted first formula then we are very conservative in our result, especially if we compare the Dymag wheel with an aluminium centred wheel where we could be as much as 50% greater on MOI than in reality! Hence the importance of measuring MOI of 2 wheels accurately on the same machine to make any comparison.
<O:p</O:p
Porsche 997 rear wheel comparison<O:p></O:p>
<O:p</O:p
Comparing a 19x11.5” Porsche 997 Carrera S wheel with a Dymag carbon/magnesium 19x12” wheel.
<O:p</O:p
Porsche: 30lb x19” M=30lb, R=9.5”
<O:p</O:p
Therefore: ½ x 30 x 9.5² = 1,353.75 lb/in² MOI
<O:p</O:p
Dymag: 19lb x 19” M=19lb, R=9.5”
Therefore: ½ x 19 x 9.5² = 857.375 lb/in² MOI which is 63% of the MOI of the Porsche wheel.
<O:p</O:p
Why is this important?
<O:p</O:p
Consider 2 factors of the wheel in use, rotating and steering.
<O:p</O:p
To rotate the wheel, the work energy required is calculated as force of net angular position change = ½ MOI x angular velocity², strictly speaking it is Force net θ = Δ( ½ MOI ω²)
<O:p</O:p
Which in English means that the energy consumption goes up as a function of the moment of inertia x the square of the speed, or as you go quicker it takes much more energy! This equation also shows that both acceleration and braking are both effected significantly by a reduction in MOI
<O:p</O:p
Steering changes are even easier to understand. The change in direction is governed by the momentum of the wheel which is calculated as the MOI x angular velocity, so in the above example, the Porsche on the Dymag wheel will use 47% less energy input to steer the car, either driver or power steering input, this is why the car feels “lighter” to drive and more responsive to steering input.
<O:p</O:p
Rule of thumb calculations
<O:p</O:p
This is a minefield of assumptions!! 2 of the old tuning rules of thumb were that 6lb weight saved on a car was equal to 1 bhp and that 1lb of rotating weight was worth 10lb of static weight, so in the Porsche example above, we are saving 11lb per wheel, x 10 = 110lb x 4 = 440lb ÷6 = 73.33 bhp we think this is probably excessive as the 10 factor does not take into account the diameter of the rotating part. A carbon propshaft would not have the same effect for example.
<O:p</O:p
We have been stating that the rotating/static weight factor is about 6:1, this would give a result as above of 44bhp, which is roughly the gain effect that Parr Porsche said about the original tests of the carbon car wheels on the 996 GT3 RS!!
<O:p</O:p
Power to weight calculation<O:p></O:p>
<O:p</O:p
Now if we take the Porsche wheels, the 997 Carrera S weighs 3131lbs and has 355 bhp, which gives it a power to weight ratio of 8.82:1 or, if you lose 8.82 lbs it is equivalent to 1bhp equivalent gained.
<O:p</O:p
So if we take the Dymag 6x factor for the carbon wheels then saving11lb per wheel x 6, x 4 wheels ÷ 8.82 lb/bhp = 29.93 bhp an important 8.43% power gain simply by bolting on different wheels. <O:p></O:p>
<O:p</O:p
But if we take the sometimes accepted10x rotating to static weight factor this figure comes to 49.88 bhp
<O:p</O:p
Obviously using this type of formula, the more power to weight ratio, the bigger the wheel effect on performance – not too surprising really!
Fuel saving and emissions reduction<O:p></O:p>
<O:p</O:p
The best estimates available for fuel and emissions savings by using carbon wheels are between 3.0% and 8.0% fuel savings. The increased % would be with stop – start driving for the obvious reasons of overcoming inertia and momentum. Also air drag factors mask the wheels performance at higher & more consistent speeds.
<O:p</O:p
Emissions are much more difficult to calculate, especially when taking into account warm up and urban type cycles of car use. However as gasoline produces an average of 2.35kg per litre of fuel at the tailpipe, then it is safe to assume an initial saving of emissions to match fuel consumption. Again urban cycles will show a greater effect from the carbon wheel. So if the average car produces 165g of CO2 per km (at 7litres per 100km) the carbon wheels may reduce this to nearly 151g, a 9% improvement.
<O:p</O:p
The fuel and emissions savings/reductions caused by carbon wheels need much more work. It is not possible to calculate these effects due to the other rotating components of the car which contribute to the overall moment of inertia, plus there are effects on non-rotating parts such as suspension where lighter wheels would give softer settings which require less energy to use the car in normal road conditions due to the reduction in energy losses with tyre deflections.
<O:p</O:p
Conclusion
<O:p</O:p
Carbon rims have a noticeable effect on a car’s performance and handling, the variations in moment of inertia of the complete system are not well enough researched to give absolute figures of the improvements that the wheels give. That the improvement is significant is beyond doubt, the independent testing and standards agencies now need to make these evaluations, equally condemning many of the very heavy aftermarket products.
<O:p</O:p
#53
11-10-2008 | 07:19 PM
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Joined: Jul 2003
Posts: 5,113
From: Dallas, TX
Rep Power: 256
I think the collaboration between Dymag and HRE will only make the product better than it was before, and will give it additional credibility. I'm definitely more excited about having a CF rim option than before.
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Pardon me.... calculations.
#55
03-31-2009 | 10:24 AM
Back at the 2008 SEMA show, Vivid Racing blogged about the new Carbon Fiber wheels HRE was releasing in cooperation with Dymag. These new wheels are available in the CF40 and CF43 design which is a HRE 1 piece Monoblock forged center and a Dymag Carbon Fiber outter barrel. Extremely lightweight, very strong, and fashionable, these wheels will be for the elite. Applications will be available for the following vehicles:
- Aston Martin DBS and Vantage V8
- Audi R8 and RS6
- Chevrolet ZR1 and Z06
- Ferrari F430 and F430 Scuderia
- Ford GT
- Lamborghini Gallardo
- Mercedes CLK63 Black and SL65 Black
- Nissan GTR
- Porsche 996TT, 997 Narrow Body, and 997TT
Last edited by vividracing; 04-01-2009 at 02:38 PM.
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