Injuries: Is it really the 450?

dkg wrote:

Comparing the performance specs between stock 2012 Honda 250 / 450, you get the following: HP approx: 38 to 55 approx a 45% increase for the...

Comparing the performance specs between stock 2012 Honda 250 / 450, you get the following:

HP approx: 38 to 55 approx a 45% increase for the 450
Weight: 222 to 238 approx a 7% increase for the 450
P/W ratio: 5.8 to 4.3 approx 34% increase for the 450

Assuming that in race machines relatively linear performance increases are available across the machines, then the percentage increase is the most notable. Clearly the 450 has significant performance increase over the 250. However, there is no direct correlation between lap times and performance increase. This kind of calls into question the assertion that the 450 performance is the cause of the injuries as the performance increase of the bike is not resulting in a linear decrease in lap times. The performance is there but is not being used in all cases to maximum advantage. Kind of like driving your Ferrari in rush hour traffic, you can go 200mph, but other factors limit this ability.

Some comments have considered the gyroscopic effect. Not being a physicist, I did some quick looking at this. What I learned is that a motorcycle has 3 primary points of inertia. The two wheels and the crank/flywheel effect. Relevant variables in this area would be in the internal engine components. However, the nonlinear variable in this case would be the rotational speed of the engine. The 450 has roughly a 7-10 percent increase in weight in these components. (very rough estimate). However this maybe offset by the higher rpm of a 250. Tire/wheel combos may have some minor increase in inertia in favor of the 450, however, I do not think the actual math would support a highly significant gyroscopic increase in the 450.

I find it hard to blame all the carnage on the bike, and like others I don't think the classes will change. Personally, I tend to think that most of the carnage is attributable to other factors including, bad luck, rider error, track conditions, etc. I respect the opinions of those with a different perspective. I simply don't see enough events to say it is the bike that is to blame. It may have some effect but probably isn't the causative factor.

Faceaz wrote:

You started to get there, but I think fell short in your analysis (as I probably will as well). Math / Physics is interesting for me...

You started to get there, but I think fell short in your analysis (as I probably will as well). Math / Physics is interesting for me, but I'm far short claiming to know it well. The Gyroscopic effect is referred to Rotational Inertia. I pulled a 06 yz450f crank / piston off the shelf as well as a 05 yz250f. I don't have any flywheels, but I feel comfortable plugging an extra .5lbs for the 450.

The 250 combination - crank, piston, comes to 6.5 lbs
- it's diameter is 4.1" & width of 2.2"

The 450 combination - crank, piston, .5 for the flywheel comes to 8.9 lbs or a 37% increase in mass
- it's diameter is 4.6" & width of 2.5"

Plugging it into a online formula I found for calculating ratational inertia of wheels. The 450 has a rotational interia of .007 & the 250 a intertia of .004. The rotational inertia of the 450 is approx. 75% greater than the 250 - that's pretty huge.

dkg wrote:

Wow, didn't realize it was that great of a percentage differential, I thought it would be much less (in the area of 10%). Boy was I...

Wow, didn't realize it was that great of a percentage differential, I thought it would be much less (in the area of 10%). Boy was I wrong. Thank you for the effort. Math/Physics is of interest to me, I get the theory, but sometimes those advanced equations look a little too much like Greek for me to exert the effort to figure them out.

I suspect I was a little too quick to discount the gyro/rotational inertia effect, especially with that big of a difference. Ever use one of those gyroscopic exercise balls? Little inner ball in a plastic shell used to develop the forearms and wrists. The more I think about it, even that minor weight was able to produce a fairly strong force. Perhaps this effect is what we are seeing in crashes such as James in Colorado this year (not using this for any other purpose than example) during that sequence it seemed he was really trying to bring the bike back up, however, once it started going he simply could not exert enough force to straighten it out. I am sure there are other examples out there.

It would be interesting to see the calculations out of the manufacturers on what exactly is going on.

Hank_Thrill wrote:

Look, when examining the injury rates of the sport today, you cannot dissect individual crashes and expect to explain the big picture. That's like a social...

Look, when examining the injury rates of the sport today, you cannot dissect individual crashes and expect to explain the big picture. That's like a social researcher trying to understand the high violent crime rate in a big city by cherry picking ten murders.

Instead, to explain the big picture - in this case really high injury rates in the sport, particularly the 450 class - you identify one, or very few, variables, or casual factors. In this case, 450s are the more powerful, and much heavier - especially considering gyroscopic force - compared to the 250f machines, and two-strokes of the past. The only variables differing between the 450 class and the 250 class are the machines, rider experience, and number events competed in each year.

If faster and heavier machines did not explain higher injury rates, and the more spine crushing severe injuries, we would expect to see the same injury rates that we are seeing today all throughout the 80's and 90's on much slower bikes of the past. Faster machines are not the sole cause of injuries, but may explain the higher injury rates we are witnessing (big difference between the two). Thus, if you cherry pick individual crashes, the explanation larger bikes result in higher injury rates may or may not explain that particular crash. There are always exceptions to the rule (e.g., someone having their life saved by not wearing a seatbelt, despite seatbelts overall drastically increasing the odds of surviving a crash). Injuries have been around since this sport begin, but the higher injuries we are seeing today may be explained by the bikes being raced today. To determine what kind of increase in injury rates are due to the machines (15% or 50%), a serious study would have to be done.

sam111 wrote:

[i]"When examining the injury rates of the sport today, you cannot dissect individual crashes and expect to explain the big picture."[/i] You can't examine [i]"two out...

"When examining the injury rates of the sport today, you cannot dissect individual crashes and expect to explain the big picture." You can't examine "two out of the last three years" and establish a "trend" either.

As Jeffro503 said "the 450's let a rider choose how fast he really wants to go." Strictly speaking, I don't think you can blame the bikes for allowing the riders to push the limit of what is physically possible. By twisting the throttle, they are choosing to go that fast. Also, lets not forget that rider talent and skill are still the main determinants of speed on the track.

Although I think that the four strokes have contributed to the higher race speeds seen in pro racing today, I am still not convinced the crashes and injuries this year are a direct result of the extra power and weight of the 450's.

Hank_Thrill wrote:

You are absolutely right about not coming to conclusions based on the past two out of three years in the 450 class. What concerns me is...

You are absolutely right about not coming to conclusions based on the past two out of three years in the 450 class. What concerns me is that during the 1990's I can only recall two professionals suffering spinal injuries, Doug Henry, and Jeff Emig (I'm sure there are some lesser known professionals). However, over the past five years spinal injuries to professional racers have blown through the roof, despite technological advances like the Leatt brace. I just thank God we haven't seen a higher number of riders becoming paralyzed. I really hope 2013 turns out more like 2011 and all the motogladiators stay healthy.

As far as the riders determining their own fate. These guys are going to go as fast as possible on whatever machines you give them, especially those in contention for race wins and titles. This is why I think it is important for the AMA to step in and slow the bikes down. I would gladly sacrifice as a spectator the pace slowing down 2-3 seconds a lap if it meant the superstars of the sport could race together for more than a few months out of the year. Or, I didn't have to read stories like Nick Wey and Hahn online every other month. Plus, don't people come on here every year wishing the supercross lap times were longer?

I get the feeling from watching races since the switch to 450's in 2006, that a lot of 450 riders realize you can sustain that "red zone" level of intensity and pace throughout the span of a series (e.g., Reed and Villopoto in Arlington, TX; Dungey and Villopoto at Steel City during the first moto). Even going back to 2006, Ricky and James would play a chess matches with each other, then turn up the pace tremendously towards the winding laps of the main (though, that was probably more due to race strategy). San Diego, 2006 is a good example. K-Dub is another good example of 450 pros staying in the yellow zone, as opposed to riding in the red zone all the time. We all know he has the skill to run just as fast as anybody out there on a supercross track, but it all depends on his mood and location (Huston and Vegas usually do the trick for him lol). You seem to recognize the new technology has led to a fast pace, but faster paces don't lead to increasing the odds of injury when you hit the ground?

Ps.
This has been a really good thread. Nice, formal, and informative. Kudos to those for figuring out the rotating inertia of the engines. I remember Canard saying the 450 felt about 50lbs heavier than the 250f he raced, based on the rotational mass.

Faceaz wrote:

Allot of current 4 strokes don't have a counter balancer. I understand your logic of increasing, but it only works if you think a spinning crank...

Allot of current 4 strokes don't have a counter balancer. I understand your logic of increasing, but it only works if you think a spinning crank can defy gravity & move the bike directly upwards. The panic rev is all about rotating mass around the rear wheel. The rear axle acts as a pivot point, with the wheel containing it's own mass to force the rest of the bike around. The distance of the crank from rear wheel increases it's pivotal torque to work against the wheel. The increased mass of the crank combined with the pivotal torque / leverage arm (distance from the wheel to the crank), means the crank has much greater influence in fighting the rotational mass of the wheel.

UpTiTe wrote:

The jump Reed crashed on was not big at all and the 250 2 strokes would have been jumping it. Reed said the crash was caused...

The jump Reed crashed on was not big at all and the 250 2 strokes would have been jumping it. Reed said the crash was caused by changing up lines and the soft dirt slowed his progress down. It had nothing to do with the bike having to much power, especially considering he was jumping it fine all night before that.

I agree 100% that a 450 in the hands of a less talented rider is dangerous, but I don't believe that it is in the hands of a top pro.

Faceaz wrote:

Allot of current 4 strokes don't have a counter balancer. I understand your logic of increasing, but it only works if you think a spinning crank...

Allot of current 4 strokes don't have a counter balancer. I understand your logic of increasing, but it only works if you think a spinning crank can defy gravity & move the bike directly upwards. The panic rev is all about rotating mass around the rear wheel. The rear axle acts as a pivot point, with the wheel containing it's own mass to force the rest of the bike around. The distance of the crank from rear wheel increases it's pivotal torque to work against the wheel. The increased mass of the crank combined with the pivotal torque / leverage arm (distance from the wheel to the crank), means the crank has much greater influence in fighting the rotational mass of the wheel.

unknownmxr wrote:

this is getting too abstract, but it doesn't matter where the torque is applied since the bike is in free fall. The rear wheel has a...

this is getting too abstract, but it doesn't matter where the torque is applied since the bike is in free fall.
The rear wheel has a larger diameter than the crank, but it is spinning at a vastly reduced rate. Maybe about 10% of crank rpm.

Overdrive wrote:

The conversation at the end of this video between James and Malcolm is very interesting. James says on the 250 2t you feel like your going...

The conversation at the end of this video between James and Malcolm is very interesting. James says on the 250 2t you feel like your going fast but in reality when he looks down he's really not going that fast compared to the 450's.

To me that says when you hit the ground your not as likely to get hurt when your not going as fast. Draw your own conclusions, but watching James on a 2 stroke is amazing, fast or slow.....

rcm406 wrote:

Just look at the 250 class for the obvious answer! Who's hurt? Dean, that's it right? Why is it that riders in the 450 class are...

Just look at the 250 class for the obvious answer! Who's hurt? Dean, that's it right? Why is it that riders in the 450 class are dropping like flies and hardly anyone is injured in the 250 class.

lapper wrote:

Based on a casual observation of this years injuries, it would be easy to blame the 450. I'm not going to debate the physics of the...

Based on a casual observation of this years injuries, it would be easy to blame the 450. I'm not going to debate the physics of the 450's additional weight and power. I'm sure it's a contributing factor. However, there's lots more to consider.

1. Notice the 2nd moto lap times are all 2-5 seconds slower regardless of category. Rider fatigue is probably part of the explanation, but so is track conditions. The tracks get rougher as the day goes on and the track condition for the 450's is always rougher than the 250's (yes, there was one exception this year) . Bigger bikes, faster speeds on a rougher track. I hate to say more crashes are to be expected, but they are.

2. 250 riders are still building their resume for a 450 ride. They're more willing to ride hurt and/or postpone getting the inevitable surgery. Just give me a shot and tape it up. I'll be fine. A top 450 rider who misses a year for a surgery / recovery will probably still find a ride. A top 5 250 rider who misses a year will be lucky to get any support. Dean Wilson is a good example. He's is one of the top 250 riders moving up and he still tried to ride with a bad shoulder. Once he accepted he had to have surgery, he had both shoulders done. Would Dean have gotten more offers for better contracts with a top 3 250 finish this year? Absolutely. However, If he postponed the surgery and somehow made it through the year, he'd be another out for the season injured 450 rider within the next few years.

3. Injuries can be cumulative. Typically, a 450 rider has more years racing and therefore probably more minor injuries. That minor ACL tear as a 250 rider becomes a torn ACL as a 450 rider. How many times have we heard "I've had this problem for years, and I finally had to have it fixed".

None of these are the sole reason, because there is no single reason, including the size / power of a 450. I'm hoping this was just a fluke season and the moto gods smile on all the riders next year. The 450 class will be awesome!

rcm406 wrote:

Just look at the 250 class for the obvious answer! Who's hurt? Dean, that's it right? Why is it that riders in the 450 class are...

Just look at the 250 class for the obvious answer! Who's hurt? Dean, that's it right? Why is it that riders in the 450 class are dropping like flies and hardly anyone is injured in the 250 class.

sam111 wrote:

For all anybody knows, the injuries this year could have been caused by nothing more than bad luck. As [i]UpTiTe[/i] pointed out on the first page...

For all anybody knows, the injuries this year could have been caused by nothing more than bad luck. As UpTiTe pointed out on the first page, most of them were the result of freak accidents or common rider errors unrelated to bike horsepower or weight anyway. The evolution of the 4 strokes has elevated the pace of pro racing, but, at this point in time, it is impossible to conclude whether they are responsible for the recent spike in injuries or not. One year of disproportionate casualties does not necessarily equate to a trend.

I'm no physicist, but it seems to me the guys doing the calculations don't know nearly enough about what they are saying for their findings to have any credibility. A panic rev is not that effective at lifting the front on any bike (2 or 4 stroke, 250 or 450), and I don't think it was ever going to save Reed anyway.

Motocross83 wrote:

Panic revving does have a slight effect but it's by no means a get out of jail free card, regardless of the bike. More a last...

Panic revving does have a slight effect but it's by no means a get out of jail free card, regardless of the bike. More a last ditch effort if things have gone tits up. It also tends to happen naturally anyway as soon as the bike falls away out from under you. The throttle gets wound open because you don't have time to re-grip (although as already stated, by that point you want it wound open anyway). What happened with James at Daytona would've happened on any other bike, in almost exactly the same way imo.