Six-Axis Vibration Testing

The biggest reason is that the vendor request it done on a six axis machine.

The four axis machine may locate the problem. It still may not. The greater range of motion of the 6 axis machine will be closer to operational motion.

First point is that these buggies had been manufactured for kids. Second point --- driving conditions for dune are believed to be much more worse than for highway.

I do agree with ozzb, in any case you have to meet any vendor's requests to secure needed safety level.

six axis - x,y,z, plus pitch, roll, yaw

what I would do, though, is put the buggy on a single axis vibrator, and test one axis at a time.

It seems the manufacturer has taken short cuts in the manufacture of his product, or doesn't completely understand the rigours of the application those buggies can be put in to.

Sounds like they have just supplied the inline fuel filter floating in free space and not secured it to the frame, along with the fuel line, its short cuts like these that gives the biggest problems on those machines, it may be ok for a lawn mower to free mount a weight like a fuel filter, not a machine like that, given the accelerations those "free weights" can achieve, they will break loose quite easily.

If your going to build a 6-axis machine, allow for enough "throw" length if your going to dynamically test the product to cater for enough accel/decel forces.

I concur. Better engineering up-front saves much later on. Never mind the law suit when one of these catch fire.

Goto YouTube and do a search for "Buggy Racing" or "Donald 500" you should get a feel for the dynamics these "Real" ones go through.

I know the Donald one is there, and quite a few American Off Road too

A first remark there are only 3 axis to define our world in 3D, but on each one you can have two vectors: one being a force projection and the other being a moment projection one.

I totally agree with the request of the vendor since when the mobile moves in space and a dune trip is on a 3D surface any possible combination of forces and moments can occur. It is thus compulsory to check the behaviour under similar conditions. The problem you could be confronted with is the magnitude of accelerations and frequencies your test rig must generate. I ask myself if the vendor made real field measurements with accelerometers and data loggers to get an information about what happens with the buggie in the real world. If this information is available then you can get from it the dynamic limits for the test rig.

In order to avoid any problem after delivery I would ask the client to give a VERY detailed specification concerning the dynamics he wants to impose to his mobile.

I may suggest to take about 30 to 50 % reserves since even with a specification it is better to have the possibility to go over fixed limits.

Although it should be a not too heavy buggie the use of hydraulics could be the best solution from the overall cost point of view. If frequencies are not too high it could be possible to use even pneumatic servo-systems.

Why bother testing I would secure the filter and line and be done with it unless that has been tried or not possible. Just a thought.

good luck,Crusty

I apologize but my answer was partial. I would suggest you have a look at the hexapods used in flight simulators. If you want I can give you the coordinates of a manufacturer building currently such devices. The advantage of hexapods is that only cylinders are used but the 3 components of force and moment can be build.

The manufacturer who is supplying such systems is in Europe. I do not know where you are located so that I cannot estimate if you are or not interested in this information. There are also American companies making same products but at a much higher prices.

I am the one who posted this question. I forgot to sign in when posting.

I am located in Toronto Canada. My client is willing to pay for the cost of the testing which is very expensive if I outsource it but it may be worthwhile for my company to buy the machine since we will be doing this testing for some time to come.

I would appreciate the information on the hexapod simulator or six-axis simulator.

Thanks for all the input.

As I said above, make sure you have enough throw distance and speed.

Off Road shockers very closely run in the meters per mS speeds.

a 16" external bypass, external cannister shocker going from fully extended to almost fully compressed in about 20ms, or simulation of travelling at 250km/h (or faster they are getting) and hitting 1 all mighty pot-hole, alot of stresses and strain you have to incorporate.

Its no use buying a machine that is not capable of the worst extreams, cause thats the place most problem occur.

Dune Buggies for kids according to original message.

Do you believe that "simulation of travelling at 250km/h" is realistic?

yes I do

there will be someone who buys it and does something stupid and returns it when something goes wrong.

Whats the possible speed of the buggy when someone uses metanol and nitros?

Also the impact after dropping from the top of a sand dune?

Whats the possability of driving off the top of a dune and falling 10 or more meters (airborne) ??

I have done this with mine and flattened the roof down by 1/2 height on the drivers side, no matter the size of the product, the same things can happen to them

you have to look at the most extreme when you want to do this type of testing, including (if shockers are even used) stroking the suspension from top stop to the bottom stop (or further)

I understand you point and under such conditions I would NOT suggest a 6 vectors test but the following procedure:

a- let the product fall from at least 25 m (possible height of a dune = height of a 8 floors high building)

b- project it with 250 km/h against a concrete wall.

c- recover the rests of the driver and ask how he feels.

Any way if the vehicle will resist the test the supplier can be sure it will stay ok under normal conditions of may be 30 to 60 km/h and jumps or falls of 1 to 3m.

I agree we have to take a very large reserve of safety for the car, if the buggy will have after successful tests the weight of a Sherman no matter it kept the tests.

When a product is sold there are in the manual some limits specified as speed, for instance. If the customer does not respect those limits the supplier is not responsible for what happens. In general as far as I know the car supplier is only considered as responsible for an accident if it happened within the limits and the product did not respond to the specification. If the user did change the characteristics he is fully responsible for the results he will obtain not the supplier.

But of course I may be wrong as usual I do not claim to know all or the best.

30km/h off the top of a 50 meter high dune, turn the wheel and roll down the hill at the max angle at which sand will "just" hold its place, close to distructive test that is completely possible.

Dunes that high and I think higher I have driven on, down between Portland and Nelson (Victoria, Australia)

This type of action would possibly need 6-axis testing as you roll, you would stress the buggy on all axis... and the unfortunate passengers.