G-Shock Ratings?

Moderator: Mike Everman

Post Reply
Lugebob
Posts: 33
Joined: Sat Jan 08, 2005 3:43 am
Antipspambot question: 0
Location: Waldorf, Md USA
Contact:

G-Shock Ratings?

Post by Lugebob » Tue Jan 18, 2005 2:27 am

Does anyone have a clue (even roughly) what kind of g shock load a spinning turbine can withstand? Does the inflight g-load data relate to instantanous shock at all???

I am running a JetCat P200. if it matters

Here is why.. reference my earlier post on the Jet Luge... The jet luge is a skateboard that goes bump every time it hits a crack or stone or makes an abrupt landing.. lol. I dont want these shocks to send the rotor spewing chunks.. at 112,000 rpm. I need to select some shock mounts for this but every shock mount manufacturer want to know the Fragility Factor stated in G's..

Got a clue? I really need to know so I will even pay for the answer if you can provide proof.

thanks
bob
Bob Swartz
Work Hard Play Harder

Stephen H
Posts: 328
Joined: Mon Oct 06, 2003 6:51 pm
Antipspambot question: 125
Location: New Zealand

Re: G-Shock Ratings?

Post by Stephen H » Tue Jan 18, 2005 8:15 am

or you could just add a simple suspension system to the luge??

Lugebob
Posts: 33
Joined: Sat Jan 08, 2005 3:43 am
Antipspambot question: 0
Location: Waldorf, Md USA
Contact:

Re: G-Shock Ratings?

Post by Lugebob » Wed Jan 19, 2005 12:03 am

I wished it were that easy. There is no such simple suspension. Many have been tried and only one has ever worked and it cost over $4K to build. The problem with a suspension is the a streetluge is lean steered. You steer it by leaning into a turn. All of the designs but one changes the steering angle of the skateboard truck dynamically to the road conditionand you have no idea on how it will steer from bump to bump.

thanks for the tip anyway
Attachments
suspensionluge.gif
The only one that ever worked made by Dr Jarret Ewanek (dr gofast) for The Sanfrancisco Big Air Contest.
suspensionluge.gif (25.81 KiB) Viewed 8619 times
Bob Swartz
Work Hard Play Harder

Mike Everman
Posts: 4934
Joined: Fri Oct 31, 2003 7:25 am
Antipspambot question: 0
Location: santa barbara, CA
Contact:

Re: G-Shock Ratings?

Post by Mike Everman » Wed Jan 19, 2005 12:37 am

I believe Stephen means a suspension for the engine, which makes a lot of sense. I'd look into some of the shocks and swing arm sets you can get for decent RC off road cars. Very nice hardware surprisingly cheap, shocks with adjustable damping and spring rate and such. Cool.
Mike
__________________________
Follow my technical science blog at: http://mikeeverman.com/
Get alerts for the above on twitter at: http://twitter.com/mikeeverman

Eric
Posts: 1859
Joined: Sat Oct 04, 2003 1:17 am
Antipspambot question: 0
Location: United States
Contact:

Re: G-Shock Ratings?

Post by Eric » Wed Jan 19, 2005 3:22 am

I dont know if you have ever seen what an exploding turbine can do, but depending on size the results can be quite horrific. One old physics book that I found showed a picture where a research lab spooled a small turbine up to operating speed (encased in a anti frag enclosure made of about 12" of lead bricks, and a humongous concrete cover. Well anyway the thing exploded, sending the lead bricks through the walls, a few into a nearby house, and the concrete top went flying through the ceiling and finally stopped 2 floors up. It was a pretty heavy one, not anything that could be fit on a luge, but even anything close to that large of a failure would be very very bad.

Without access to the data, I would say that the inflight g-load would be the maximum g-load from banking and turning, and turbulance, probably giving a certian g-load for what could be withstood for a certian period of time, this however should not be mistaken for an instantaneous shock, wich will have much larger value.

(an example would be the nifty USB keychain I just got, it says its rated to something like 1200 G shock, you might first think HOLY CRAP thats a durrable key chain, but when you calculate how much it would deform, the velocity of the keychain, and how long the impact event will last, you will find that it would be equivalent to being dropped on a hard floor from 10 or so feet)

Instantaneous shock is a totally different thing than what would be experienced in flight, even turbulance is essentially soft because it is just compressible airflow. If you drop a basketball on the ground it squishes out as it impacts, reducing the maximum shock to a fairly small level, if you have an object that is solid, even a small drop could have a huge shock value, depending on how much the ground / object deform, ie running full speed into a concrete wall vs running full speed into a mattress. I would say the amount of acceleration applied perpendicularly to the engine that would cause it to explode would be very small.

You also have to figure that the engine will be exerting a large gyroscopic effect, if you are planning on suspension.

Generally I would say putting a turbine on something that will be exposed to shocks and bumps is a bad idea. However if you are going to do it, use large wheels, something nice and shock absorbant, have suspension system for your luge, and then have a shock dampening mount to a plate to which the engine shock dampening tower could be mounted. And while you are at it, you can put the engine in a fragment absorbent enclosure such as ones used by turbofans to keep rouge fan blades from flying out the side of the engine and into the passenger compartment. Why not just put something like a pulsejet on it and not have to worry about super suspension systems?

Eric
Image

Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

Lugebob
Posts: 33
Joined: Sat Jan 08, 2005 3:43 am
Antipspambot question: 0
Location: Waldorf, Md USA
Contact:

Re: G-Shock Ratings?

Post by Lugebob » Wed Jan 19, 2005 4:45 am

Thanks Eric, I have initiated contact with a Shock Mount Expert From LORD Corportation that does alot of aerospace and transportation shock and vibration dampening designs. I know this is a problem. that is why I asked and am making sure it is as right as it can be... measure twice cut once.. but in this case I am measuring many times from many points of view. to include yours.

I am using the largest highest quality "Luge Wheels" made. 101mm diameter 78a durometer wheels QTY 6. Although I cannot control all conditions I will hand pick my roads with a closer inspection than normal. A suspended luge is out of the question but the purpose of this discussion was the shock mounting of the Turbine and or Turbine mount to the Luge. I am going to see if a mount can be designed to reduce 100g half signwave pulse to 20 g's half sinewave, until I can rent or borrow a data logging accelerometer to get real values. I get this start value from knowing the properties of the axles that I bend hitting stuff.

Now as far as containment.. Yea this is scarey stuff. I was prepared to build a containement vessel but was told that these turbines are built to meet the

AMA requirement 533 in Durability
Engine design and construction must minimise the development of an unsafe condition of the engine between overhaul periods. The design of the compressor and turbine rotor cases must provide for the containment of damage from rotor blade failure.

Yes I am betting alot on the fact that it will meet that standard.

Good thing my 1st test road (mile long street out front) is fresh paved butter.

Thanks for making me think harder.

bob
Bob Swartz
Work Hard Play Harder

tufty
Posts: 846
Joined: Wed Dec 24, 2003 12:12 pm
Antipspambot question: 0
Location: France
Contact:

Re: G-Shock Ratings?

Post by tufty » Wed Jan 19, 2005 7:15 am

Are there restrictions on the size and type of wheels you can use? If not, one might want to look into a system similar to the dirtsurfer rather than 'standard' trucks which would, I believe, allow for mounting of a workable suspension system. Relevant patents include AU750255 and WO0205911 which should give you enough to go on to find the rest.

Just a thought

Simon

Lugebob
Posts: 33
Joined: Sat Jan 08, 2005 3:43 am
Antipspambot question: 0
Location: Waldorf, Md USA
Contact:

Re: G-Shock Ratings?

Post by Lugebob » Thu Jan 20, 2005 2:40 am

Yep. Since I plan on still traveling to races and running in the normal gravity competitions the Luge without turbine must follow all the rules. largest wheel diameter is 101mm using 608 bearings, and the 78a durometer urethane is the fastest. I will bolt the Turbine powered power pack, fuel tank and throttle on for demo's.

Now as far as the Dirtsurfer goes... what a wonderful simple design that just plain works and is very fast. I rode one in the Hot Heels Race in Austria a couple of years ago. I am not even good at standing on a skateboard and this thing was easy to learn. I have seen them also race in Ohio. Nice machines but no go for my design if I plan to race it.. Maybe next version.

thanks
ps what country holds those patents. I was unable to find in USA search.

bob
Bob Swartz
Work Hard Play Harder

tufty
Posts: 846
Joined: Wed Dec 24, 2003 12:12 pm
Antipspambot question: 0
Location: France
Contact:

Re: G-Shock Ratings?

Post by tufty » Thu Jan 20, 2005 11:17 am

Lugebob wrote: ps what country holds those patents. I was unable to find in USA search.
Espacenet is the place to go, lousy search and presentaation but 'hackable'

I've attached the patents themselves.

Simon
Attachments
AU750255.pdf
(441.17 KiB) Downloaded 363 times
WO0205911.pdf
(550.71 KiB) Downloaded 403 times

Stephen H
Posts: 328
Joined: Mon Oct 06, 2003 6:51 pm
Antipspambot question: 125
Location: New Zealand

Re: G-Shock Ratings?

Post by Stephen H » Thu Jan 20, 2005 11:51 am

if you just want it for demos why not use a pulsejet? much louder to amaze people and cheaper and should handel bumps ok if you keep the fuel going all the time!

larry cottrill
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Antipspambot question: 0
Location: Mingo, Iowa USA
Contact:

Re: G-Shock Ratings?

Post by larry cottrill » Thu Jan 20, 2005 2:51 pm

Bob -

Here's an article of mine on using pulsejets in a vehicle. The article is a little dated, now, but might be good enough to get you thinking about some of the design issues you'd need to address:

http://www.jetzilla.com/Vol01Num01/jetZ ... #Article_1

Good luck!
L Cottrill

Lugebob
Posts: 33
Joined: Sat Jan 08, 2005 3:43 am
Antipspambot question: 0
Location: Waldorf, Md USA
Contact:

Re: G-Shock Ratings?

Post by Lugebob » Fri Jan 21, 2005 2:04 am

Thanks for the article, that was very informative... I will take another look at pulse jets for sure... The luge may be a good test bed for a small pulse-jet to augment the speed, but there is alot to learn. I am concerned about the thrust to system weight... With the turbine I will have about 8 minutes full throttle run time with 50 lbs of thrust in a 13 lbs package "wet"
this includes fuel ,turbine, batteries, computers, valves filters, and mount, starter..... and I will continue with this design until I get to exhausted to continue.. Already in this by alot of money, with prospective sponsors already knocking at hte door.

I will look more... even if it is just one more way to push a luge it would be fun. how much time and thrust would I get from one of the small pulsejets runing off one of the propane torch canisters? Could the airflow from an already rolling luge be enough to start it, so I could fire it off in motion.. without a blower. even 10 lbs of thrust would give a good show for a minute or so.. going down a hill.


thank you again..
bob
Bob Swartz
Work Hard Play Harder

Stephen H
Posts: 328
Joined: Mon Oct 06, 2003 6:51 pm
Antipspambot question: 125
Location: New Zealand

Re: G-Shock Ratings?

Post by Stephen H » Mon Jan 24, 2005 5:13 am

you mean the small canisters used for camping stoves and lights? they dont have enough fuel going though them to power a pulsejet, i would sugest getting a liquid system so you dont need a big propane tank! using a pump straight into the CC.
this includes fuel ,turbine, batteries, computers, valves filters, and mount, starter
pulesjets dont need turbines, batteries, computers, valve fulters or starters on board, you need the pulsejet, fuel and spark plug.. if you want to start it infront of people you might have a problim!

Post Reply