OV9

Funny old Thursday afternoon, when an international chemical manufacturer takes an interest in some stupid shit I'm doing at the garage

OK, so I've been playing around with some ideas for chassis stiffening (separate thread on it's way for the metalwork side of that), and one thing that caught my attention was the use of closed cell polyurethane foam to fill hollow sections (e.g. chassis rails, wishbones, push rods etc). The idea came from the world of boats where people use this PU foam for buoyancy but also to strengthen hollow aluminium masts. The principle is the same as various other composites - combine something strong in tension with something strong in compression and get more than the sum of the parts.

I should add at this point that we're not talking about the expanding foam builders use - that's open cell foam. It has little strength, and is moisture cured, so wouldn't ever properly set inside a tube anyway. This is the 2-part foam that I also happen to use for moulding race seats - it's called LD40.

Anyway, I started looking into this, and apparently it's also something American hot rodders do to their wibbly-wobbly road car chassis. But with pretty mixed success. The big problem seems to be trapped moisture causing internal corrosion, but I also suspect that poor application in some cases has caused uneven distribution, leading to weak points that quickly break and render the whole endeavour pointless.

So I spent a little time working out a) an anti-corrosion strategy (using a primer that will also promote adhesion, which in turn will also improve strength), b) a reliable delivery mechanism and c) what additives I could use in the foam to improve compressive strength.

As it turns out, chemical modification of closed cell PU foam is a hot topic at the moment (who knew? ) and the latest round of scientific papers around the use of a group of chemicals called polyhedral oligomeric silsesquioxanes was only published last month. Combined with the use of some physical nano-fillers, I reckon I can double the compressive strength of the foam with only a negligible weight penalty.

So far so good, but you can't just pop down to B&Q to buy polyhedral oligomeric silsesquioxanes (or 50 micron hollow glass microspheres, for that matter!). So I did what any sensible person would do and phoned an industrial manufacturer of PU foam.

This is where things took a bit of an odd turn. The technical sales people had no idea what I was talking about, and I ended up speaking to one of their senior chemists (I may have failed to disavow them of the notion that I was planning to buy industrial quantities of their products ). Given that I'm neither a materials scientist nor a qualified chemist, I held my own remarkably well in a 10 minute conversation, and somehow gave the impression that, rather than an idiot playing with random chemicals in his garage, I was actually a competent person to conduct formal R&D on a novel product.

Not only that, but he was genuinely enthused by my idea and wants to "work together" on development

The upshot is that he's introduced me to a whole range of alternative PU foam bases that are an order of magnitude stronger than LD40, and will produce small batches of whatever special formulation I want. All free. Yay.

Now all this is pretty exciting in itself. I've somehow managed to blag freebee support for my silly project from a proper commercial lab! But then I started reading the data sheets for these alternative foams and doing some fag packet sums. The numbers are so crazy I thought I'd got the decimal point in the wrong place. With the additives, we're looking at compressive strengths double that of concrete and tensile strength in excess of oak. At a density less than half of water.

So I suspect this might have other applications beyond just making my little racecar a tiny bit faster...

Lots to do now - not least fitting a more accurate gauge to my hydraulic press for testing purposes. I have no idea what's already out there, but I may have accidentally stumbled on something actually quite good.

Amazing when the bloke in his shed pulls out a major discovery, ahead of the big players in science Well done that man.

That sounds like a fun project with possibly good uses.

I understood approximately 1% of that but good darts - and be careful where the IP goes!

So is it the strength of the foam you want to improve solely or is it other aspects of it also?

Merc have been doing this since the 80s but I’m guessing you are trying to do something much better than before.

Dave!

Strength is the absolute top priority (closely followed by strength relative to density), but I'm also considering hygroscopicity, longevity, and mode of failure (ductile better than brittle).

Ultimately there's nothing fundamentally new in what I'm doing - just combining known materials and techniques from a variety of industry sectors (plus some research stuff) in a novel way.

Re. Automotive uses - PU foam has been used for years in cars, but primarily for its acoustic and NVH dampening qualities. I understand that Lexus has been using PU foam sandwich plates in structural applications recently (this is also something common in the construction industry).
What theyre not doing is using the super-strong Pu foam bases (their stuff is closer to my LD40), using the modifying additives, or designing it for an in-situ, mid-service life application.

Nefarious wrote: Fri Mar 26, 2021 9:47 am Strength is the absolute top priority (closely followed by strength relative to density), but I'm also considering hygroscopicity, longevity, and mode of failure (ductile better than brittle).

Ultimately there's nothing fundamentally new in what I'm doing - just combining known materials and techniques from a variety of industry sectors (plus some research stuff) in a novel way.

Re. Automotive uses - PU foam has been used for years in cars, but primarily for its acoustic and NVH dampening qualities. I understand that Lexus has been using PU foam sandwich plates in structural applications recently (this is also something common in the construction industry).
What theyre not doing is using the super-strong Pu foam bases (their stuff is closer to my LD40), using the modifying additives, or designing it for an in-situ, mid-service life application.

I'd guess the cost/benefit ratio is not right for them to make something notable stronger/more durable given that they only legally have a limited warranty to worry about, various safety standards they only have to meet rather than wholly exceed, etc.

Your use case is a bit different to theirs

Great stuff! I've never known someone to have so many schemes and ideas! I just about manage to lurch from one day to the next with dealing with normal life.

Keep us up to date, could certainly have applications in civil engineering so if you need any advice on that sphere I may be able to help.

Cool

duncs500 wrote: Fri Mar 26, 2021 9:56 am Great stuff! I've never known someone to have so many schemes and ideas! I just about manage to lurch from one day to the next with dealing with normal life.

Keep us up to date, could certainly have applications in civil engineering so if you need any advice on that sphere I may be able to help.

That's because he retired young, remember?

You could make some very light bikes with that too.

Whenever a piece of agricultural equipment gets leaky perished tyres I just fill them with PU foam and then they’re good until the tyre just deconstructs itself

Awesome work.

Hacking a material which can be dissolved by a chemical and removed would be a big benefit. On the box section at the back of the Merc it has a sense foam in its full length, the metal inside is perfect so no water ingress etc but if it had become rusty then welding it would be a nightmare. You would need to remove the lot.

Sounds like a really cool project !!!

Dave!

I take it this is on your Westfield, not the ff?

Dave - these are the major drawbacks. It is very much a one-shot-deal. It is absolutely not removable afterwards and it is *probably* unweldable (although different chemical modifiers might make the foam element sufficiently heat resistant to allow it). I'm not overly concerned with the unweldability at the moment - not least because elsewhere I've also been playing with 3M 9323 (aka helicopter glue), which provides a perfectly workable alternative to welding in many applications.

James (?) - the thought started with the FF (I'm in the middle of some other chassis stiffening work). Mostly because the technical regulations are so limiting to what I'm allowed to do, it forces you to think outside the box! That said, if my testing goes the way I expect it to, the Westifield will probably be the first guinea pig!

Very

Reminds me of a uni lab session where we were split into teams, each given spaghetti and paper and glue guns - 60mins to build a bridge over a gap. Winner would be the one that held the heaviest weight - destructive test.

Teams were building fancy cantilever stuff - we made a toblerone tube and started to fill it with hot-melt glue. About half way through - when we had already received 2-3 glue replenishment runs - they realised what was going on and disqualified us for wasting uni supplies.

Somewhere a parallel conversation is happening where a senior chemist is having a conversation with his boss. “No - a motor racing team. No - I am talking to the team owner ”

I am sure you’re thinking about the IP so won’t even mention it.
Again.

Sounds great application.

Reminds me of Leak sandwich speakers - they used woofer which was a foam coated in thick foil which was over 100 times stiffer than same weight of paper for same area.

Sounds like an awesome project you've got going.

I imagine large chemical companies, just like large autmotive companies, are full of curious geeks repressed by the collosal inertia that almost always pervades these places. The bloke is probably delighted to support something cool.

A decade or more ago a friend of mine experimented with a foam filled lotus chassis, apparently it was a fantastic improvement. Except for when you needed to access the coolant, electrical and AC lines that occupy those spaces and the expense of doing it on a line at several.... some, cars a day.

You may also need access to a very very very clever structural analysis person to model what that extra material does in the virtual world. Stuff that is hard to model will easily go into the too hard basket for a lot of applications.

I think the lexus NVH panel may be https://acousteel.com/about/, clever stuff, but expensive and has it's own set of compromises.

Best of luck you POS (Polyhedral Oligarchs Siquoasaxepainthings)

Nefarious wrote: Fri Mar 26, 2021 12:09 pm Dave - these are the major drawbacks. It is very much a one-shot-deal. It is absolutely not removable afterwards and it is *probably* unweldable (although different chemical modifiers might make the foam element sufficiently heat resistant to allow it). I'm not overly concerned with the unweldability at the moment - not least because elsewhere I've also been playing with 3M 9323 (aka helicopter glue), which provides a perfectly workable alternative to welding in many applications.

James (?) - the thought started with the FF (I'm in the middle of some other chassis stiffening work). Mostly because the technical regulations are so limiting to what I'm allowed to do, it forces you to think outside the box! That said, if my testing goes the way I expect it to, the Westifield will probably be the first guinea pig!

Jordan, not James- it’s not the worst I’ve been called Would it not concern you if they decide what you’ve done gets outlawed you’ve then got a chassis full of foam to try and clean out?

Because of your breakins......

https://m.youtube.com/watch?v=WVy5Vm43X_A

Just an idea.

Dave!