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Author Topic: 2nd Battery box and Chute doors.......................  (Read 4586 times)
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Sumner
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« on: February 02, 2008, 11:03:20 PM »

While I was waiting for some fittings to finish the fuel tank and water tanks................

     

I built a second battery box for the data logging computer...................

     

.................... and worked...............

     


.................. and worked..............

     

.............on chute doors and still didn't get them finished, but ............




 they are coming along,

If you want to see more pictures and a description of what i did it all starts here:

http://purplesagetradingpost.com/sumner/bvillecar-2/construction%20page-94.html

c ya,

Sum
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« Reply #1 on: February 03, 2008, 12:23:06 AM »

I didn't think it was possible for someone to over-engineer a battery hold-down strap, but at least we're sure that neither of them will wiggle loose! grin

Just like the old MG motto - "Safety Fast".
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« Reply #2 on: February 03, 2008, 06:02:09 PM »

Wow, Sum...

Having just gone through our parachute door design and having just read yours I can honestly say that is one amazing and beautiful piece of thinking, designing and making. Great to follow.

How much fun was that? I so hope it works well in race mode, that'll just be the cat's whiskers.

Sure we wont know the finer points of its operation until a speed test but I wish to add a list of thoughts:

The first question I have is the concept of "neutral" position being actually parallel with the car's axis. Is not the air actually traveling at your 7 degree line at the surface of your car and hence maybe neutral is yet to be parallel yet at this point?

I am only theorising here (and Jack's concerns of theoretical solutions not withstanding) but think that the air coming in through the gaps at the front of the doors wont actually be enough to fill the gap in the airflow made by the body of the car (different sectional area) therefore creating a lower pressure zone between the doors causing them to want to bow in towards the parachute...

The air pushing the door on the inside of the door due to this new angle will presumably limit this and want to push it back to a degree but may not this set up a flapping motion...? Will the spring act as a damper for this?

Also the air closing the gap behind the car will likely to be turbulent and so quite unpredictable in direction around the doors leading to further flapping possibilities.

I am concerned about flapping not just because of the potential vibration and damage this may cause, but because they will act like a tailplane and try to steer your car unpredictably. I guess the saving grace to that is that they are only opened when the chute is out which should have a bigger stabilising force in a straight line.

I am not trying to be a wowser Sum, really I want to participate in this fantastic design game you have set up.

Reverend H+

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Sumner
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« Reply #3 on: February 03, 2008, 10:56:50 PM »

Wow, Sum...

Having just gone through our parachute door design and having just read yours I can honestly say that is one amazing and beautiful piece of thinking, designing and making. Great to follow.

How much fun was that? I so hope it works well in race mode, that'll just be the cat's whiskers.

Sure we wont know the finer points of its operation until a speed test but I wish to add a list of thoughts:

The first question I have is the concept of "neutral" position being actually parallel with the car's axis. Is not the air actually traveling at your 7 degree line at the surface of your car and hence maybe neutral is yet to be parallel yet at this point?

I am only theorising here (and Jack's concerns of theoretical solutions not withstanding) but think that the air coming in through the gaps at the front of the doors wont actually be enough to fill the gap in the airflow made by the body of the car (different sectional area) therefore creating a lower pressure zone between the doors causing them to want to bow in towards the parachute...

The air pushing the door on the inside of the door due to this new angle will presumably limit this and want to push it back to a degree but may not this set up a flapping motion...? Will the spring act as a damper for this?

Also the air closing the gap behind the car will likely to be turbulent and so quite unpredictable in direction around the doors leading to further flapping possibilities.

I am concerned about flapping not just because of the potential vibration and damage this may cause, but because they will act like a tailplane and try to steer your car unpredictably. I guess the saving grace to that is that they are only opened when the chute is out which should have a bigger stabilising force in a straight line.

I am not trying to be a wowser Sum, really I want to participate in this fantastic design game you have set up.

Reverend H+

Hey so many questions and so few answers  cool.  Thanks for taking the time to look it over and think about it and comment on it.  I've even got some other questions that worry me that you didn't mention.  One thing is I think I have a way to maybe lock the doors in the open position if they ever get there  cry.  One thing we don't have to worry about is wondering how they will react in the 200+ mph range  cheesy.  The car will have a lot of runs much under that while I can test these out.

I'm going to move the chute line attach points further back.  I don't want them so far into the car with the chute flapping around and having to worry about the lines rubbing on something in the rear of the car.  I don't know how I figured the angle a while back and was so far off from where the back of the car would really be.  In fack I told Rex it wouldn't go as far back as in his sketches.  Now his sketches are probably pretty close to how far the rear of the car is behind the rear axle.

Hey don't you have a car to get ready??  Sure wish I was going to be there to watch it go down the salt the first time, oh well, next year will have to do,

Sum
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« Reply #4 on: February 03, 2008, 11:46:27 PM »

Sum,

I've read the whole build writeup at your site and am a big fan, like so many others.

After looking at some spin videos and reading the posts on the parachute threads I wonder about you opening the chute in a spin and the tether line catching on the door tearing it open beyond your set point or off the car with the attachment point deep inside the car.  While not adding or subtracting from the spin or control of the chute it will cause mucho damage to the door(s).

To help the doors open and hold them there you could make a spring loaded latch that goes over-center and helps open the doors and hold them open.  Locate it in the rear 1/3 of the door.

Geo
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Sumner
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« Reply #5 on: February 04, 2008, 12:20:26 AM »

................
To help the doors open and hold them there you could make a spring loaded latch that goes over-center and helps open the doors and hold them open.  Locate it in the rear 1/3 of the door............Geo

Yep, something along those lines is what I have in mind.  Lets not talk about spinning.  I hope to avoid that with a car that is about 23 feet long.  If and when you do spin there is a pretty good chance something will need to be fixed.  Heck when Hooley spun in 2006 it caved the driver's side door in.  Luckily someone had a toilet plunger and we got it pulled back out  cool.

Thanks for following the build and looking over my shoulder,

Sum
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« Reply #6 on: February 04, 2008, 02:50:22 AM »

I'm surprised anyone could understand what he was saying Sum ......going on like the Mystic Oracle....
Quote
The first question I have is the concept of "neutral" position being actually parallel with the car's axis

huh?....

anyway.....thank god someone has distracted the doomsayers away from our 'chute doors.....

I am constantly amazed at your "one-man" efforts Sum....

Quote
Hey don't you have a car to get ready??

too right , I've been at it today , all day, now I'm back jerkin' around with the tail-pipe angry angry angry that lovely little tip poking out at the tail of our car is unsupported all the way from in front of the axle....and now because of the chute bay and the new floor in the tail section I have to remake it ........and that's a PITA!

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« Reply #7 on: February 04, 2008, 02:58:43 AM »

Wow I like it Alot, looks complicated though, think I will stick to two wheels,Oi whats that pile of washers on the left stud of the battery hold down tsk tsk. Seriously though Nice Nice.What is the Orange car in the pictures on your site looks like a Jensen Interceptor?
« Last Edit: February 04, 2008, 11:07:45 AM by oz » Logged

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« Reply #8 on: February 04, 2008, 04:12:24 AM »

The opening doors for sure violate the smooth air flow when underway.
Consider it to be a speed brake and all is swell.
Remember it is going to take power to do that and consider where it is always going to come from with out fail.
With a suitable linkage, all of the considerations mentioned for holding them open can be accomplished with the energy you have available from the pulling forces on the lanyard after it is deployed.
If the proper anchor height is buried within the doors you have to consider what a side load is going to do.
Unlike a relatively short vehicle that can sometimes be saved from a spin with the pull from the chute, a proper balanced and aero package will try to straighten out on it's own if the human error is just removed from the problem.
The human failure has the tendency to pull the slowing chute too late into a sideways adventure to bring it back into line smoothly.
If the doors are going to act as a speed brake in any case, remember the air flow is on all sides.
If the hinge action opened them up and down, the lanyard would be much more able to move side to side (cross wind) without hitting the hatches.
The hatches can also be made to open wider with the pull from the lanyard if they don't have to fight limit stops without damage if required
If the chute goes way up and down, that usually means the vehicle has lost contact with the ground and the health of the doors is of little concern.
Bike liners have a required automatic deployment feature when the ride angle is beyond normal limits and a car might do well to consider it.
Build it like you are going 100mph faster than you ever will and you can call it the "COMFORT ZONE". undecided
 
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« Reply #9 on: February 04, 2008, 04:03:22 PM »

Wow I like it Alot, looks complicated though, think I will stick to two wheels,Oi whats that pile of washers on the left stud of the battery hold down tsk tsk. Seriously though Nice Nice.What is the Orange car in the pictures on your site looks like a Jensen Interceptor?

Hey that is only one nut and maybe 2 washers  cheesy.

The car is a '73 Datsun Z that belongs to a young hot rodder.  He was trying to put a 75 injected Z motor in it (first year they were injected) I took one look at the wiring mess and talked him into putting a small bock chevy I had in it.  Hopefully it will be on the road in a week.  We are waiting on a drive shaft.  Hopefully the exhaust will be done tonight.  Then just a little wiring and some plumbing and we should be ready for a test ride.

This has become my other job........... the other being building the lakester.

c ya,

Sum
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« Reply #10 on: February 05, 2008, 07:33:00 PM »

Oi whats that pile of washers on the left stud of the battery hold down tsk tsk.

Be nice, Oz - those aren't washers - they're clearly precision stamped shims!

And I doubt if they're going to slow the car down any.
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« Reply #11 on: February 05, 2008, 10:22:08 PM »

Oi whats that pile of washers on the left stud of the battery hold down tsk tsk.

...........they're clearly precision stamped shims!......................

Yep on special order from China,

Sum
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« Reply #12 on: February 06, 2008, 07:00:51 PM »

I thought you made everything on that car!  Do you mean to tell me that I can get genuine Sumner Battery Strap Precision Stamped Shims through an outside supplier? 

What's the world coming to . . . grin

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Well, I guess we're making a LOT of progress . . .  rolleyes

We are NOT rebuilding . . . We are reloading.

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« Reply #13 on: February 06, 2008, 07:43:00 PM »

For those who don't know Sumner has a secret Fab shop located in a cave in upper Blanding Utah. It's called AHSHIT MFG. and has special prices for racers. Chrome is xtra. grin evil
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« Reply #14 on: February 06, 2008, 08:43:12 PM »

That is in China!  I was there for a spell.   

Buh  lahn ding, Eeuu tahh

Ah sheet MFG

Lo ban    Sum "how" nur

I think there are a bunch of nuts, including me, and quite a few watchers.

Actually those hinges look beautifully fascinating.  Nice work!
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