Other Computer Aided Handlpole Design

[eeerieski]

For waternut, and everybody else too I guess...

In many of my models small local stresses may seem severe, weld fillets would likely reduce many of these stress concentrations. I simply used 500lbs as the applied force and the overextended model has stops welded to the bottom tube and their bearing faces constrained.
First up is the overextended model, looks like a limiting strap would be necessary.

Next up is the side pancake , looks to be a non-issue

Finally is the pole slam on the hood, keep in mind none of these dimensions are exact and are general approximations.

 

[Jake6488]

looks like some good work keep it up

 

[swapmeet]

Really cool stuff man. I'm about to embark on building an adjustable pole out of a beat up AC unit. Very cool to see where your seeing stress etc.

I think the 'ugly base' comment was based on the round tube base vs a more traditional boxed base.
FWIW, i'd be intrested in seeing your results based on actual material sizes available. I just purchased 2" tube with 1/8" wall, and 2" Schedule 40 to slide the 1/8" wall inside of. The difference is 1/16". I'll cut slots on on the horizontal of the schedule 40 to take up the 1/16" of 'slack'.

Since i'm using a existing AC steering base and pole base so my situation won't be testable on your software. But maybe you can play with the idea of an adjustable pole as mentioned above in conjunctioin with your 'ugly base'.

 

[eeerieski]

If someone were to want a boxed base, I'm sure a small cap of .125" or thinner plate/sheet aluminum could be welded over the bottom few inches or even the entire length.

As for the adjustable feature,to make the main structural portion of the pole adjustable in length would add weight, cost, and another potential failure point(s). Yes it is do-able but I am trying to stay away from it. Its also occurred to me that it would be doubly difficult to design an adjustable length pole where the tubes are curved.

There are more ways of adjusting length than just the pole, take for example the hinge bracket, It could be designed such that the hinge holes are not aligned along the horizontal axis of the bracket (rotate the bracket 180 degrees to change the pivot point forward or back by I'm guessing up to +-1". Turnplate length is another -3". Handlebar bend is -2" even the axis of the turnplate could be moved forward to get -2". Thats 9" of adjustability without touching the pole, -8"/+1" assuming stock overall length. I have a -2 AC 750sx pole I could try to model as a comparison.

Keep in mind that my latest bare fixed length model is a mere 3.6lbs. I'm a fan of the KISS mentality and am trying very hard to stay away from "if it isn't broke then it doesn't have enough features yet. "

 

[AusAndrew]

How have you constrained the pole in the pancake loadcase? Would have expected more stress...

Also have you considered that the thinner tube might fail in buckling/crushing rather than just yielding? FEA won't spot that...

Andrew

 

[Dustin Mustangs]

Buckling for the side loading scenario should deff be looked into considering the unsupported length of the main members. I don't have any fancy software handy but I would be willing to bet that you could find a more efficient cross section than dual tube. Maybe you are going with it for reasons other than strength to weight ratio though.

Cool post...

 

[swapmeet]

I'm already useing an adjustable -2.5 to -3.5 Xmetal turn plate with straight bars. The flipable pole bracket is an intresting thought and shouldn't be tough to manufacture. I understand your goals and design philosophy. I'm a fan of the RRP style poles and willing to take on the addtional weight to have it adjustable in that manner.

I plan on adding a slight bend after the adjustable portion where the tubes slide within each other. The majority of the poles on the market do not have a sweeping bend across the length of the pole. Its typically straight with a bend near the steering plate.

Had you planned on doing an arc from one end to the other?

 

[Mark44]

The pole is only as strong as the fiberglass its attached too at its base.

Mark44

 

[eeerieski]

How have you constrained the pole in the pancake loadcase? Would have expected more stress...

Also have you considered that the thinner tube might fail in buckling/crushing rather than just yielding? FEA won't spot that...

Andrew

Side pancake constraints are a pinned connection at the base and 500lbs applied sideways at the handle end.

Hood slam is probably what you are curious about, Pinned connection at the base and I extruded some temporary flats on the tubes so I could apply another pinned connection halfway between the handlebars and the base hinge. I then applied 500lbs down at the handles.

I had considered buckling and am unsure of a correct way to go about analyzing it, sometimes a working prototype needs to be built to make sure it doesn't fail in unexpected ways.

More efficient than tubes? Are you referring to something similar to AC Racing Superjet poles where they use a press-break bent sheet of Al? Or maybe extruded box tubing? Aluminum round tubing is pretty strong light and relatively cheap already.

Has anyone seen a Team Bill/Highroller/Goose Break? What wall thickness tubing do those poles use? The only aftermerket pole I've seen pictures of broken was near the handle bars where an unsupported cast flat section cracked in half.

 

[eeerieski]

Most hulls are arced so why not the handlepole too? The arc would only be in the open span, the handlebar end would be left straight, in the model straight for 8".
It is not that hard or expensive to put a slight arc in aluminum with the harbor freight tubing roller:

 

[Waternut]

In many of my models small local stresses may seem severe, weld fillets would likely reduce many of these stress concentrations.

eerieski: Actually the welds will increase the stress concentration. The reason for this is the weld is insanely stiff and the surrounding material will be very weak by comparison. This is made worse by the welding process as welding destroys whatever heat treating the original metal had. So instead of 6061-T6, you'll be at 6061-0 after welding which is less than half the strength and stiffness of -T6. With the large stiffness difference, you'll be more prone to stress cracking around the weld. You can reduce some of the effects by re-heat treating the pole but you'll still have a problem. Just as an FYI... this is why you don't see welding on structural components on aircraft.

To everyone else: I keep hearing all this stuff about floatation in the handlepole. What's the big advantage to this? Is it only beneficial when the ski is on the verge of sinking or what?

 

[Boris]

To everyone else: I keep hearing all this stuff about floatation in the handlepole. What's the big advantage to this? Is it only beneficial when the ski is on the verge of sinking or what?

Think of what happens to a ski that is upside down in the surf with a 3" extended keel.
The OEM RN pole has it's weaknesses but the fact that it helps right a ski is a big reason why I run one. Since this project has the potential to give us a whole new pole and not just another RRP remake, I thought I would ask about flotation.

 

[eeerieski]

eerieski: Actually the welds will increase the stress concentration. The reason for this is the weld is insanely stiff and the surrounding material will be very weak by comparison. This is made worse by the welding process as welding destroys whatever heat treating the original metal had. So instead of 6061-T6, you'll be at 6061-0 after welding which is less than half the strength and stiffness of -T6. With the large stiffness difference, you'll be more prone to stress cracking around the weld. You can reduce some of the effects by re-heat treating the pole but you'll still have a problem. Just as an FYI... this is why you don't see welding on structural components on aircraft.

Very true, I do know this but hadn't considered it. I think this falls into the prototype test category. Damn if I had a MIG+spoolgun or AC TIG...
Found this cool pic showing the effects:

 

[eeerieski]

Think of what happens to a ski that is upside down in the surf with a 3" extended keel.
The OEM RN pole has it's weaknesses but the fact that it helps right a ski is a big reason why I run one. Since this project has the potential to give us a whole new pole and not just another RRP remake, I thought I would ask about flotation.

I'm thinking the easiest way to add flotation would be to skin over between the tubes and fill with 2lb foam, Or add non-structural tubes for cables to snake through and seal off the main tubes +2lb foam. Maybe a big chunk of blue house foam up near the steering would help.

 

[Boris]

I think a total redesign would be a better solution.
Not ting on your efforts it's just that I have something totally different in mind.
A single tube wrapped by styrofoam and a composite shell sort of like the OEM pole but with a stiffener between the top and bottom cast pieces.
Flotation, strength, a breather tube and somewhere to rout the cables all in one.

 

[Mark44]

h

Look all the peeps trying to be engineers. :Banane37: :thinkerg:

Mark44

 

[eeerieski]

Am I one of those peeps? I'm taking my final 2 classes to get my BS.

As for the spring, It occurred to me that a gas spring would work wonderfully in this application due to the design constraints.

 

[kevbo]

There are dozens of custom poles around. Their success is/was based 100% on looks. An adjustable length pole is useful, the RRP pole is nice but expensive, heavy, and has no functional pad. It would not be difficult to improve but it would have to look "cool" for anyone to buy it. Instead of yet another pole, try to design a releasable brake for for the pivot that is somewhat universal. A lot of riders (with sore backs) would buy one of those. Another useful item would be a bolt on extended nozzle that would make trim work better, everyone wants to do a backflip. This industry is small and the participants are fickle to say the least. It takes a lot of product hype to get any volume at all.

 

[Dustin Mustangs]

More efficient than tubes?

A tube is efficient, no arguing that. Two parallel tubes are not (at least with how these will be loaded). Consider your second moment of area for purely lateral or purely vertical loadings on a dual tube cross section versus a cross section with a single hollow member or even one with a web. Same with a torsional loading.

Your design looks cool as hell though (esp the last one) and I would consider that just as important as strength to weight ratio when it comes to how a product like this would sell.

 

[eeerieski]

A tube is efficient, no arguing that. Two parallel tubes are not (at least with how these will be loaded). Consider your second moment of area for purely lateral or purely vertical loadings on a dual tube cross section versus a cross section with a single hollow member or even one with a web. Same with a torsional loading.

Your design looks cool as hell though (esp the last one) and I would consider that just as important as strength to weight ratio when it comes to how a product like this would sell.

It's a balancing act between strength, weight, cost, function and marketability/looks (an engineer's life). A single hollow member would work great, now find me one that would work for a comparable cost to standard tubing. As for the web, one or 2 series of webs could be added to join the tubes together (if that's what you intended) if the plain dual tube design proved insufficient in practice.

It all comes down to a lack of carnage experiences from others with this style/type of pole. I was primarily designing the solid model to see how it would look/work and the FEA models are sort of a bonus to point out glaring issues with the design. I appreciate the input and should probably play around with different tubing setups to humor you guys.