Chute mounts

[Bob Drury]

  Doug, I was just making a generalized statement using fourteen feet as most chutes are that size.
  The point is that unless you are running a unsprung vehicle with a lot of rear downforce (like a Drag Racing Funny Car or Top Fueler), you are asking for trouble mounting a chute to the rear end.
  Moving the attachment point higher puts the angle of the tag line closer to the instant center of the vehicle.
  Obviously if the vehicle is only running say 150 mph, the hit at the chute blossoming will be a lot easier than at say 200 mph.
  Why ask a question if you don't want a answer?             Bob

[rgn]

It looks like if you stood this one on end the driver could be the first privateer into space?  

Thanks to Larry and also Kiwi Sid (via pm) for taking the time to answer some of my questions, and educate me better.  I still have a lot to learn in all aspects of LSR.  

These are just my personal opinions, naive as they may be.  (please don't shoot me in the torso, or the head):  

A chute is designed to decelerate a vehicle or person or thing, and assist it-them to a safe and hopefully graceful conclusion to a journey.  If a chute is unsettling a vehicle it isn't doing it's job, and is potentially causing problems (accidents) not preventing them.  

In skydiving we liked to load our chutes as they gave us more control, the chutes were then less affected by wind gusts thermal activity etc.  A lightly loaded ram-air parachute (large square footage in relation to suspended weight) will be easily affected by the fore mentioned environment variables, and collapse, or be ravaged by the forces of nature.  That is why students are only allowed to jump in moderate conditions.

Sid offered me some really valuable real-world insights into the vehicles that travel at the upper envelope speed.  People have died because their vehicles couldn't be stopped.  What I'm hearing is that the slower vehicles are getting into trouble because the parachute is doing too much?  The chute should assist and not detract from a vehicles journey, and my opinion in relation to sport skydiving and base jumping has always been that one incident is one too many.

As I said to Sid, I have a great book (albeit pretty much unread) pertaining to this subject of parachute recovery systems... It's called Parachute recovery Systems, by T.W. Knacke.  (lol).

I'm reading it now and I'm sure the maths is in there to calculate what a vehicle needs.  I would advise any of you interested to buy it from my old supplier:  http://www.paragear.com/templates/parachute.asp?group=23

The parachute manual by Dan Poynter is also considered the bible in terms of reference.

I'm sure contained within there is a more scientific way of determining what sort and size chute is applicable for each application.  For example starting on page 5-3 there is a table pertaining to Parachute type in relation to shape, opening force, average angle of oscillation, drag coef.

Attached at the bottom, is a shot of the page I just mentioned.  The book is all about the physics and maths.  

I personally think that a combination of this type of information, coupled with empirical real world experience and expertise from the LSR community, you will be able to eliminate many of the problems that have been described here and elsewhere.  Suppliers generally mean the best, but they often don't really know what you need, I've always felt responsibility for your own safety is your own. (I've survived many a thousand deployment).

My gut feeling is that you are over-chuting (sq area) in the lower speed classes, and this is what is causing problems to a great degree.  If deployment of your chute is not something you look forward to, go smaller?

Higher speed vehicles I'm interested in hearing more about, as I think this is perhaps another world?  Cheers.

[jdincau]

rgn
     I think you will find most of us go to a supplier who is familiar with land speed raceing (Diest, Stroud, DJ Safety etc.) asking for a recomendation. They ask about the speed range and vehicle weight in order to supply something appropriate. The people who get in trouble are buying old drag race chutes on ebay, racingjunk.com and the like with no clue as to what can go wrong.

[Jon]

My process for buying a chute was;
Search for and read as much as I could find on this forum about chutes and suppliers.
Write down the suppliers that get constantly recommended
Write down all the stuff I learnt about chutes, mounting, teather lengths, speed and weight effects etc.
Emailed a couple of the suppliers saying I weighed x kg, wanted to go y mph can I have a chute.
The guy who asked a $hitload of questions about the things I had read and demanded answers then explained to me what I would need to do for mounts etc befor he offered to make a chute got my confidence and I followed his recommendations.

I am 100% responsible for my safety, I didn't trust my knowledge so found someone who's knowledge I did trust.

Cheers
jon

[Bob Drury]

  Look at it from this standpoint:  If you have had a persistent headache for a few days and mention it to a group of friends, you will get all sorts of advice but in your mind you know you should consult with a Doctor.
  When you see the Doctor, he needs to know ALL of the simptoms you have noticed.
  The same is true when ordering a Parachute.
  The Vendor needs to know ALL of the facts pertaining to its usage.
  I highly recomend that you buy from the Manufacturer and not thru a secondary Dealer.
  Ask them any questions you may have and listen to what they have to say.
  Advice from others is nice but its not their Ass on the line................   Bob

[Tman]

I ran the ballpark numbers for our lakester based off the equation in Strouds catalog, even conservatively it was off the chart for the standard drag race type chutes.

[Avanti Kid]

I bought my most recent chute from Jim Deist before he died, he asked how much my Avanti weighed and what speed will we be doing, then he used his software program to design my chute, my car weighs 4,200 lbs and goal top speed was 220 mph, after receiving this chute for two years at Bonneville we have used it at 216 mph with no problems at all.  The interesting thing about using a chute at high speed is each car is a little different, thats why you should start deploying it at lower speeds to see if its attached correctly at the rear of car, then progress in jumps of 25 mph faster to check it out and some cars like my brothers Pantera at 210 mph you have to drive into the chute at max power, if you get out of the power band the Pantera will quickly spin out (years ago I spun it out at 180 mph) because of the change on it suspension system, but on the other hand my Avanti at 216 mph, we can get out of the throttle and coast, then deploy the chute with no problems, I prefer getting out of the power band if possible to take the load of the chute from hitting the engine connecting rods, (this could be bad), take care, Dave 

[Hooley]

The chute on the orange studebaker seems to work fine. I put it level with the cam shaft. I have put a secound one one for running the mile tracks. Need more practice with two chutes.

   If any is going to the Wilmington Mile next week, Bob Stroud is having a seminar on land speed chutes. It is Sat evening at one of the motels. See the ECTA page for more info.    http://www.landracing.com/forum/index.php/topic,11377.0.html

              Hooley

[SPARKY]

Thanks guys  for all your input,  learned things---I had a miss conception about mounting pin dia.-- thanks Jon---I called Bob and he does not want his teathers to see more than 1 inch with at least a 1/2" grade 8 in spool if one is used.  Thanks  now to noodle out where to put the pilot chute tubes  ---we are leaning towrd the top  the air up there should be a little cleaner due to the rake.

[Jon]

I was going to point my pilot chute tubes up at about 15degrees as well as mounting them high Sparky.

One thing that I noticed when looking at all the chute threads on this forum is there's heaps of pics where the pilot chute looks like it's dragging on the ground before it starts to pull out the main.

I've since gone to a drag style pilot chute in the main chute tube to make my build simpler (&i was running out of roomin a closed tail) so my pilot chute will come out horizontal but still reasonably high up.

This is what I made up before going away from specifoc pilot tubes;


I used about 2/3 of the spring Bob supplied.
The crosshole is to hold the spring compressed to almost bind while the chute is put in.
The ears support the spring to full extension.
It will throw the pilot chute and the Dbag pull line about 30' when not attached to anything.

It's just sitting on a wall rail, if it's a use to you I'll post it.

Cheers
jon

[SPARKY]

One of the things that I had learned to do with the old system was to "cock" the spring pilot chute in such a maner as for it to deploy at an angle to travel---got it into clean air---it worked so well I am having second thoughts about this new system 

[Stan Back]

Ours is a little different . . .

[Tman]

Ours is a little different . . .

Ours OR YOU!?!?!?

[kiwi belly tank]

Lakesters & liners don't typically have the big dead air area stuck to the back of the vehicle like the wide body stuff does so finding good air to put a pilot into isn't normally an issue. What can become an issue for them due to long line length is the chute blossoming early & hitting the end of tow line too hard. This can cost you a chute or in some cases, a lot more. I found a little electrical tape around the shroud lines can prevent that.
Write your info on your laundry, if you happen to loose something out there, theres a good chance you'll get it back.
  Sid.

[hitz]

lots of prattle on here.

Got my chute from Stroud. I installed it per his instructions. It worked fine at 150. It's designed for 230 Crankshaft height location is a WAG for a V/8.

To find the correct CG.

Make a "U" shaped lift fixure with holes drilled in the uprights at ~2" spacing, install eye bolts at your best guess (in drilled holes). Guess a little high. Make a speader bar. You can probably use a notched 2X4 to keep the chains apart at the width of the uprights and bring the chains up to a common lifting point. Test lift and move the "U" attachment fore and aft untill the car balances. Make sure the suited driver or equal dead weight is in the seat and the fluids are up. That should be your CG. Put a semi permanent mark where the "U" touches. The "U" uprights should be verticle at ths point and the chains hanging neatly. Matching steel eyed cables are best but may be hard to come by. Move the eye bolts down on uprights untill you can move the car end up and down a few inchs by hand. Put a couple of drops of oil where the chain meets the eye bolts. That spot  should be the verticle height of the CG. There are other ways to do this but this way is probably easiest to carry out without errors. If you don't agree that this method will work, let me know.
 
 Bob Stroud has probably seen more problems from misinstalled car chutes than any other man alive. Listen to experiance.

hitz