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post #1712 of (permalink) Old 06-29-2013, 01:47 PM Thread Starter
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DKShrimporium's Avatar
Join Date: Nov 2004
Location: PA/MD/DE tristate area
Posts: 1,409
FD2013 project 01

Let's start with the backstory, with this project.

DK tries very hard to appreciate good people, in her life. And not just focus on herself. Very high up her list is her father-in-law, who happens to be a grown-up Pennsylvania farm boy. Mebbe it's 'cause we're two of a kind, we both MUST do projects, and keep active.

Well, recently, FIL had retinal surgery. They plastered back down his retina to the back of his eyeball, pushed against it while it healed with a bubble of nitrogen (I'm guessing), and sent him home to heal, admonishing him NO JOLTS. Jolting could tear loose the retina, causing permanent blindness.

He's an OUTDOOR project junkie. Gardening, mowing, landscaping, that sort of thing. He does a lot of mowing, on a riding mower.

Said mower used to have a suspension system in the seat, which had worn out. The suspension system consisted of a scissors frame, connected to a single air piston and two heavy duty tension springs. Aside from the piston wearing out, the mounting piece within the mechanism for the springs was inexplicably made of aluminum. Over time, the springs pulled clear through their mounting holes, like a grabby infant ripping a big hoop earring from a momma's pierced ear, tearing the earlobe. There was no salvaging the part, and DK saw no point in buying a replacement as there was a design flaw in her mind that would simply repeat history.

DK wanted a replacement suspension system that would mimic a high-end air suspension seat, but not at the four digit cost. She wanted to get to a solution for about a Ben Franklin note.

She dug back in her cob-webby squirrely brain and thought about all the stuff she learned about air pistons when she researched them for the BSCC Lid Levitation project. As in that project, mounting considerations were a bear, in the lawn tractor seat real estate. There was no place to mount a pair of air shocks where they would not be in the way, have impossible mounting positions, and furthermore, due to the nature of mowing, the pistons would be exposed to a lot of dirt, aging the seals easily. They were just a lot of technical hurdles, to use.

She cruised high and low, searching for a solution, and came upon these things that are secondary suspension tools, called air bags. Yes, air bags. Also called air springs. But they are not air cylinder pistons, they are more like balloons made of fiber-reinforced structural rubber polymer material. They are designed to provide secondary suspension cushion to back up struts or air pistons in cars, trucks, motorcycles, etc.

A cruise through trucking, motorcycling, and car parts places in cyberspace eventually led her to some with specifications that she thought might work.

She spent a week taking apart the mower and seat, studying the real estate and geometries and mechanical relationships. The real estate was very tightly engineered, and it would be a challenge, but there was one site she thought might work for mounting.

Since said mower is a five-digit piece of equipment (that would be: $$,$$$.$$) and not hers, she was very conservative in her approach to alterations, insisting any she did would be reversible and not alter the engineering too much. The machine is well engineered, meaning all the parts are integrated and the spaces, too, so it's always a bugger to upset that and try to keep the original efficiencies.

So here is the project array, which came in just under a Ben. Her work on WetWedding took her to some pneumatics works, and a pneumatics parts vendor, which she used for these parts. Yes, shrimp became related to this project.

Another example of airbags in bikes. Good pics.

And another.

And here the air springs are used in some dude's thesis, in an air suspension design for a wheelchair. Advanced geeks only on this link.

Both the motorcycle dudes and the thesis dude speak of pressure accumulators inline with these airsprings to get really controlled air suspension function. DK has a sense of pressure accumulators, since basically a well tank is a large one, and she was forced to learn all about them in her install of WetWedding! So of course, now DK is obsessing on gettin' her an accumulator in her pneumatic system.


Last edited by DKShrimporium; 05-21-2015 at 02:00 PM.
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