Landracing Forum
Thrust-powered Land Speed information => Discussions on absolute land speed records => Topic started by: Blue on January 23, 2009, 07:18:59 PM
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I'd like to clear up some myths that circulated outside of our team about Sonic Arrow's skid brake. Just like the myth of forged aluminum wheels somehow being superior to a lighter and stronger material and manufacturing technique, the skid brake fostered a lot of misconceptions.
Most teams use a series of different braking technologies for the high speeds of the ALSR. Terminal braking below 200-300 mph is typically accomplished with wheel brakes. Breedlove departed from this practice with a skid brake. Although some questioned the effectiveness, I have seen the telemetry that showed its performance at a constant -.28 G from 210 mph to 0. This compares well with Thrust SSC's -.23 G with significantly more wheel drag.
The advantages of the skid are:
1. It has no chance of flat-spotting the tires, skidding a solid wheel would result in significant imbalance for any subsequent run;
2. It "polishes" the desert: the track left behind was smoother and harder than the surrounding playa;
3. It can be designed to fail-safe extend and require power to retract (Sonic Arrow was originally set up to power extend and fail retracted, something I changed as soon as I saw it).
4. It induces no mechanical or aerodynamic wheel drag during the run (aerodynamic wheel drag from the brakes and the "playa scrapers" had a significant effect on wheel speed vs. vehicle speed for Thrust).
5. It cannot wear out, burn out, or overheat (the thermal load goes into the playa).
These advantages are not necessarily true for any skid brake, Breedlove's design was very innovative.
The only disadvantage I ever saw was that the skid was directionally fixed, and unloaded the steering. So a driver had to choose between braking force and steering authority. I would change this on any new design so that the brake steered with the front steering and control was maintained. This should be transparent to the driver.
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Eric,
I was there when Craig ran at Bonneville (not sure if he used it there though) and Black Rock and I have to say it always seemed to work very well. Point 3 is the most relevant one for me. A steerable version sounds even better.
Robin
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Eric
Great in depth technical info in the Sonic Arrow's skid plate. I was at Black Rock helping the SOA team and at his Rio Vista shop through the build stages. I know how the original skid plate worked Dennis showed me a lot on he mechanicals of the car. You and your team all you have done to improve it and other fatal flaws with your advanced skills made it more stable. The info you posted here helps us to learn much more in that area of braking. How are you and your team coming along on your new ALSR design?
Here is Dennis and crew after front wheel removal when they had trouble with dust buildup between the wheels. My Dad and Dennis going over things before a run in the morning
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Great in depth technical info in the Sonic Arrow's skid plate. I was at Black Rock helping the SOA team and at his Rio Vista shop through the build stages. I know how the original skid plate worked Dennis showed me a lot on he mechanicals of the car.
This is going to sound a little strange, but according to the records we were able to reassemble and interviews we had with several former team members, there were at least 3, maybe 4 full turnovers of the SOA team between 1996 and 1999. Who was Dennis and what did he do?
The info you posted here helps us to learn much more in that area of braking. How are you and your team coming along on your new ALSR design?
It's proceeding well, it is a much simpler design than both Bloodhound and AI5R. Money, of course, is the limiter for every program.
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Great in depth technical info in the Sonic Arrow's skid plate. I was at Black Rock helping the SOA team and at his Rio Vista shop through the build stages. I know how the original skid plate worked Dennis showed me a lot on he mechanicals of the car.
This is going to sound a little strange, but according to the records we were able to reassemble and interviews we had with several former team members, there were at least 3, maybe 4 full turnovers of the SOA team between 1996 and 1999. Who was Dennis and what did he do?
The info you posted here helps us to learn much more in that area of braking. How are you and your team coming along on your new ALSR design?
It's proceeding well, it is a much simpler design than both Bloodhound and AI5R. Money, of course, is the limiter for every program.
Eric
Dennis Craig is one of the original chassis fabricators of SOA Sonic Arrow along with Pete Ogden not sure if Pete's last name is spelled right. Dennis was the main front wheel suspension assembler and helped clocking of the steering he was with the team until it disbanded not long after the 97 runs when money ran out on the effort. I know on your new project the bad economy its hard to find a solid sponsor to help support an effort as the ALSR. It seams the British have no problems of resources and sponsorship dollars on there effort. I just wish we could land a solid financial sponsors here in America as the British team has in there country
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Jim,
Do you have Dennis and Pete's contact information? I would like to get their recollections and comments on many areas of the original build.
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Jim,
Do you have Dennis and Pete's contact information? I would like to get their recollections and comments on many areas of the original build.
Bump to next post
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Eric
I just sent information to your e-mail please send back comformation thank you
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Well, we use non-skid brakes.
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Well, we use non-skid brakes.
With all respect, I don't think there is any type of ALB that would prevent intermittent sliding at 150-300 mph with the resulting uneven radial wear of a solid wheel. Even with a 50Hz system, the response and modulation is simply not fast enough to keep up with the rotational velocity of a 24 to 40" wheel. Most racing and commercial aviation systems use only 20 Hz, the military uses 50 for the smaller diameter wheels and higher landing speeds common to fighters.
Im<HO it is far better to bypass the whole issue and transfer the braking energy directly into the playa with a skid brake. Certainly, any braking should be power-off = brake; i.e. fail safe. When I took on the Breedlove car for Steve Fossett the brake was power-on, spring-retract: the opposite of fail-safe. It was one of the first things we changed.
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The only disadvantage I ever saw was that the skid was directionally fixed, and unloaded the steering. So a driver had to choose between braking force and steering authority. I would change this on any new design so that the brake steered with the front steering and control was maintained. This should be transparent to the driver.
It would seem easier to move the skid to the rear and limit the downforce to a fraction of the rear wheel weight. The drag vs CG bias would help straighten a spin, just have to make sure it can't dig in any direction.
Agreed the front steering should remain unaffected.
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I'd want to approach that idea very slowly. Lock up the rear on a bike and you're probably down. Lock up the rears on a car and you're probably around. A skid is the same as locking up the tires. That's why the skid on the front is much more stable.
Pete
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Usually I chase ideas around fairly well before a build. The thought was a percentage of the rear weight to keep all wheels turning and capable of stability. That does limit the available braking greatly. The question is, would it be enough.
The front skid concerns me if a flat spin has just started, it would tend to straighten you out but going backwards. I guess an extra chute could be added in the front. 8-) or lots bigger tail feathers.
I have had a rear lock on an engine sieze a couple of times (that little bike in the picture was one). Not fun, but I would have been in much worse shape had the front wheel suddenly stopped.
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Looks like a spambot to me.
Pete
removed :cheers:
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Gosh! All those years in Japan & I never saw any Spam!
Mike
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Mike, I found one of them this morning and removed it -- thanks for tipping me off about #2. It's gone.
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Well, well, there he (was) again this morning, so I've tried a new tack -- a ban on his various addresses. Let's see if it works this time. If you're wondering what the heck I mean -- there's been a spambot showing up around here recently. It appears to be the same one each time - so that's why I'm trying an address ban.
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Like this one??? http://www.landracing.com/forum/index.php/topic,7604.msg79419/topicseen.html#new (http://www.landracing.com/forum/index.php/topic,7604.msg79419/topicseen.html#new)
Mike
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Would that be the "racing post trophy" one - that I just now nuked?
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Jon Sure appreciate all the work you do to keep our favorite website running. Again super THANKS :cheers: :cheers: :cheers: :cheers: :cheers: :cheers: :cheers:
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It seems to me that a skid plate located farther rearward than the centers of the rear wheels would not unload the front end. This suggests that ability to steer would not be diminished. I agree with y'all that the "power off default" condition should be to apply that brake.