airframefixer
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| posted on 16/1/08 at 06:48 PM |
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Delinquent
I believe your old man is referring to AC130 sol gel treatment.
You can buy from pacific coast composites. comes in a two part kit which gets mixed and applied to the surface. The bond primer is big dollars last
time I checked and it has a really short life. they mainly use heat cured film adhesives with this system, which necessitate a hot bonder (a machine
that schedules and applies a current to a heat blanket in vacuum bag).
Keep in mind though that this is a repair method, it might not pass muster for manufacturing. Carrol Smith even said it "bonding is not for
us". For myself at least, I can think of few places were the dollars would go a lot further than being able to bond metal. driver training and
tires come to mind.
Andrew
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Puk
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| posted on 16/1/08 at 07:09 PM |
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quote:
Originally posted by airframefixer
Delinquent
I believe your old man is referring to AC130 sol gel treatment.
Keep in mind though that this is a repair method, it might not pass muster for manufacturing. Carrol Smith even said it "bonding is not for
us".
Andrew
Ok - well I'll chase that up. Also got a lead on some adhesive from a company called Lord.
Structural Adhesive
Any one interested in car design will be familiar with Carol Smith and would be foolish to disregard his advice. That said he was writing at least 10
years ago, Tune to Win dates back to '78. He might not feel that glues aint for us if he were writing today.
Whist we stand on the shoulders of giants we don't need to slavishly copy the - after all Enzo used to insist that the "horse comes before
the cart" and Porsche always put his engines out the back.
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
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Delinquent
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| posted on 16/1/08 at 07:55 PM |
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quote:
Originally posted by airframefixer
Delinquent
I believe your old man is referring to AC130 sol gel treatment.
You can buy from pacific coast composites. comes in a two part kit which gets mixed and applied to the surface. The bond primer is big dollars last
time I checked and it has a really short life. they mainly use heat cured film adhesives with this system, which necessitate a hot bonder (a machine
that schedules and applies a current to a heat blanket in vacuum bag).
Keep in mind though that this is a repair method, it might not pass muster for manufacturing. Carrol Smith even said it "bonding is not for
us". For myself at least, I can think of few places were the dollars would go a lot further than being able to bond metal. driver training and
tires come to mind.
Andrew
May do, he specified Boegel as the brand name only. The bonding primer and bonding adhesive do indeed go out of date reasonably rapidly, though in
that instance is of course to meet aviation standards which are (understandably!) overly stringent to say the least.
They don't generally use film adhesive or any form of hot bonding there, all cold cure mixes so one less thing to worry about!
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kb58
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| posted on 16/1/08 at 08:09 PM |
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With all the discussion on liquid adhesives, has there been enough advancement in double-sided tapes that they could work, too?
That said, I could see a practical problem of how to line up the panel "just right" before letting it touch the chassis. I wonder if the
stuff could grab onto the panel so hard that it would get destroyed pulling it off - if it went on misaligned.
Regardless of adhesive type is the implications of coolant/brake fluid/oil/gas dissolving the adhesive, tape or otherwise. I still think a few rivets
in the corners are good insurance.
I was thinking the same thing about Carroll Smith. The guy knew everything, but his comments were based upon the adhesive technology at the time.
It's natural to assume that newer better adhesives are out now. However, his comments on metal properies apply as much today as they did
then.
[Edited on 1/16/08 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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I-man
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| posted on 16/1/08 at 08:45 PM |
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Hi Guys,
Here is a link of a dutch guy who built a 7 with an alum chassis,
Hope it helps your discussion
http://www.geocities.com/MotorCity/7630/chassis.html
I-man
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Joe T
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| posted on 26/1/08 at 03:17 PM |
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Pondering on this I think I would also need some sort of mechanical backup in the event of a bonding failure, I am sure manufactureres will have
calculated and compensated etc.
But if I was experimenting with my own stuff, I would build that in.
Most that have seen the RCR chassis in the flesh have marvelled at its design, weld quality and complete lack of distoriton. As for weight I think it
would depend on the application, but to me they seem no heavier than equivellent spaceframes when we have had to move stuff around.
Cheers
Joe T
Costin Roadster Project
Work in progress
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scotmac
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| posted on 9/3/08 at 03:39 PM |
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I have long finished the chassis of my RH L/W, fully strengthened and bonded.
I have not yet done any torsional rigidity testing, nor weighed the chassis, so i will not join the steel vs aluminum debate just yet.
However, in terms of bonding adhesive, i am using Fusor 112B/113B from (The) Lord . It has a lap-shear-strength of 18.6 MPa and a Torsional Impact
Resistance of 106 in-lb. It is made for putting together auto body panels.
The specs for them can be found here:
http://www.lord.com/Home/ProductsServices/Adhesives/FusorAutomotiveAftermarketProducts/Products/MetalAdhesives/tabid/3400/Default.aspx
In terms of prep, all i do is run over the sections to be bonded w/ an electric sander w/ coarse paper on it. This gives me a nice metal to metal
adhesion, which is really all they require for this adhesive. The adhesive is made w/ small glass beads to ensure the correct optimal bonding distance
between the metal. It has a "work time" cure of 70 minutes at 70deg(f) and a full cure of 8 hours at 70deg(f). They have a "quick
curing" version that has a "work time" cure of 40 minutes, but still requires 8 hours for full cure.
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scotmac
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| posted on 9/3/08 at 04:00 PM |
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Sorry, let me amend that. The lap-sheer rating of 18.6 MPa was an adhesive failure point. However, the 106 lb-in Torsional Impact Resistance was w/
"No adhesive failure". ie, the actual value is unknown, somewhere *greater-than* 106 lb-in.
Specs:
http://www.lordfulfillment.com/upload/UI3002.pdf
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Puk
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| posted on 9/3/08 at 04:20 PM |
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Hi Scotmac - can you let us know what materials you bonded and how did you support the bond during the cure?
Cheers,
Puk
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
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scotmac
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| posted on 9/3/08 at 05:53 PM |
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The adhesive works for almost any metal. It will even bond aluminum to steel. But all my strengthening was done w/ 6061-T6. I supported via rivets,
bolts, and clamps. At this point, i now have a great selection of about 10 different clamps, almost of which are the rachet style or a
high-clamp-force screw style.
[Edited on 10/3/08 by scotmac]
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scotmac
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| posted on 9/3/08 at 06:08 PM |
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And note, the RH L/W is only a debacle in the un-strengthened form. It is actually a good "base" for an aluminum monocoque. What you do w/
that base is up to you.
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Wragie
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| posted on 24/8/08 at 11:00 PM |
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Just caught this last post but the LW is not a good start. It's a good example of how not to cut holes or rivet and a few other things in
aluminium. There are a lot of things that would have to be fixed if you hope to make it last. And none of this has to do with strength just the way
they did things.
It's too bad though if done right it could be what they claimed.
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Joe T
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| posted on 26/8/08 at 09:31 AM |
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At the moment I have a bare RCR70 Aluminium moncoque chassis sitting on my wheelfree ramp, if anyone wants to come and inspect it they are more than
welcome.
Did anyone have a good look at the new Lotus Aluminium chassis at the motorshow, any thoughts, comments?
Cheers
Joe T
Cheers
Joe T
Costin Roadster Project
Work in progress
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Theshed
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| posted on 26/8/08 at 02:13 PM |
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Bonding and rivets
Having lurked I have plucked up the courage to show how you can spend six years going off at a tangent.
The photo is of my build which started off with locost dimensions. It will have a rear mounted Maserati V8 knocking out 375 bhp through a sequential
dog box - Locost it has not been! Suspension is from a Lola champ car.
I make all my own machined parts in my shed - very very slowly!
This is the central tub. There is a sub-tub at the front. The rear will end in a machined plate thereafter a tube or two to support the transaxle.
Main panels are honeycombe. Internal panels stiffeners etc are all 2024T3 Alclad. Panels where not folded (a nightmare) are joined by bonded joiners
using araldite 420 and riveted with Aerospace rivets - mainly monel. I do spend a lot of time cleaning off any oxide and abrading with scotch-brite
and/or wet and dry and then clean everything up with Mek. I did a test strip and a 1 inch lap joint (with no rivets) tore at the metal before the
joint broke. Not all that scientific though!
Its probably obvious but there is a glass fiber bit that covers all you can see.
For what it is worth if I was starting again and/or building a roadcar I would never go this route - it is too lonely by half.
I am reasonably confident that this will not fall apart too quickly. I have one suspension pick up that makes me nervous to look at....
I am not convinced that "surgical" cleanliness and an oven are essentials. I could however be spectacularly wrong!
I have given up answering questions on when this will be finished but I have gone far too far to give up!
Oh bugger - a forum virgin how do I attach a photo??? I have stuck in in the photo section under Theshed - Incidently in the background is the shed
itself!
John
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mr henderson
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| posted on 26/8/08 at 05:14 PM |
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Hi John
Welcome to the forum. I haven't looked at your pics yet, my broadband is down to dialup speeds and those are some big pictures!
Regarding posting pics, there are some tutorials on the forum but I find it much easier to open a photobucket free account, then you can upload your
pics and resize them (something under 100k is more friendly) then link to them in your posts here
John
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Theshed
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| posted on 26/8/08 at 09:01 PM |
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Yes - sorry about the photos I will try and re-size them- sounds like a good diversion from work!
I have stuck a few pics of what was at the time a half completed sub-tub to which most but not all of the front suspension is mounted. That bit is now
very nearly finished and I am just about to join the two big bits together. Exciting bit!!
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Wragie
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| posted on 26/8/08 at 09:32 PM |
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quote:
Originally posted by Theshed
Yes - sorry about the photos I will try and re-size them- sounds like a good diversion from work!
I have stuck a few pics of what was at the time a half completed sub-tub to which most but not all of the front suspension is mounted. That bit is now
very nearly finished and I am just about to join the two big bits together. Exciting bit!!
That is very nice. I see you have the flanging, corners and so on done the proper way. Aviation background?
what are you paying per sheet for the panels? Last time I was brave enough to check the balsa core was about $1000 a sheet.
Dave
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Theshed
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| posted on 26/8/08 at 10:21 PM |
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No aviation background (bodge it and bang it is my usual fare) but next project might be a plane = swiftly followed by a divorce I suspect. I did get
a lot of info from home build aircraft sites.
I have gradually learned more as I went along - the thicker honeycomb is "commercial grade" and was £200 for an 8' x 4 ' sheet
with 1.2mm NS4 skins and 1/4 cells. Plan A was to make tubular front and rear sub-frames. For reasons that I now forget I decided to make a front
sub-frame in honeycomb. I got a taste for the exotic so the thinner honeycomb is 7075 t6 shins 1mm thick with 1/4 cells ( that cost £400 for a sheet).
Having learned something about this stuff I now know (hindsight is great) that I should have had much thicker sheets with smaller cells and thinner
high grade skins.
Whilst I agree with all those who have warned against the exotic in favour of the proven I could not ressit the challenge of something daft....if it
collapses under its own weight I will be the first to admit to stupidity....
I butted in to join the debate on bonding and riveting. I do not think that riveting would ever squeeze out all of the glue. If you look across a
riveted panel it is slightly wavy. I suspect that by aviation standards the bond is shocking in that it varies in thickness. However for mere mortals
I know that you need a chisel to force such a joint apart.
I am not sure that the fact that you cannot undo a bonded panel is a major downside. Most of my joints were pinned for months or even years before
being finally bonded - it is a slow process! You spot mistakes before they are irreversible - usually...
My "sub-tub" is accurate to a few thou in most places. It is all made from one piece of material bent into the shape you see. I really
made a mess of that first time around....long story!
Whilst I have struggled (and made some serious errors) I do think that a "locost" could be made with two side panels of honeycomb. Side
impact would be improved (has anybody ever seen a t-boned locost?). Serious thought would need to be given to suspension loads. Could be fun!
John
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Wragie
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| posted on 26/8/08 at 10:41 PM |
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Don't worry about taking it apart that's not as bad as you think. Just get a heat gun, looks like a hair drier on steroids, and a paint
scraper. Most adhesives let loose around 150-200c (depends on brand of goop used). Gently heat, and pry a section at a time. As long as you keep the
temp under about 300c it doesn't affect the aluminium.
The panels are very strong, we used balsa cored panels for cargo floors. The alum core stuff you used is even stronger.
Dave
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