Polycarbonate and fuel

[latheboy]

After reading Adams thread where he's making a plenum and having a clear lid like mine, i thought i'd show you how fully sick it is.

1st was just a 10mm thick piece of polycarbonate, this cracked and failed.
Failure wasn't from the caps being too tight, it was the fuel and pressure plus poor design.
At the centre of each carb you can see a stain on the poly.

http://i1226.photobucket.com/albums/ee405/latheboy179/IMAG0157_zpsf78e9cf5.jpg (http://s1226.photobucket.com/user/latheboy179/media/IMAG0157_zpsf78e9cf5.jpg.html)

2nd was the same as below with a slightly different mounting set up. This one cracked and stained too.

This is the 3rd clear lid i made with a Al clamp plate and spacers around each counter sunk cap screw.
Chemical sealed too so the poly was full floating. There was 20 set ups in making this clamp plate and poly lid.

http://i1226.photobucket.com/albums/ee405/latheboy179/Newcover4.jpg (http://s1226.photobucket.com/user/latheboy179/media/Newcover4.jpg.html)

I have been using this lid for about a year and have had no cracking issues.
The problem I have is Standoff/Reversion.

Standoff/Reversion (very simple) is when the valve is open and the fuel and air is rushing towards the cylinder, then when the valve shuts the fuel and air bounce backwards out of the carb and hits the far side of the plenum/air box/ pods.

It now looks like this.

http://i1226.photobucket.com/albums/ee405/latheboy179/IMAG0155_zpsb466112a.jpg (http://s1226.photobucket.com/user/latheboy179/media/IMAG0155_zpsb466112a.jpg.html)

Pretty shit if i do say so myself!

If anyone is thinking of doing something like this, Perspex is shit, don't bother with it.

Have a think about polycarbonate, but try and not have it in the firing line of the carbs. It will turn to perspex when in contact with Fuel.

Hardened glass (I think) is the way forward. I will need to do a redesign of my plenum to make this work.

I can't comment on other clear plastics, Geoff (freak) used something for his clutch cover and reckons it's good. I don't remember what it was, started with "M".




I will be removing the clear lid and making a new flat Ally plate instead untill i can find a better solution.
Hardened glass is an option but getting it cut to my specs is the hard part, +/- 2mm is not good enough for me.

[Redmohawk]

I got a local glazer that will cut 12mm hardened shop front glass to size but I didnt ask what his tolerances were I'd hope they were better than +/- 2 mm though. From what he said cutting wasnt a big issue but holes $$$$ So I thought I'd buy a drill and give it a bash

[TonyOW31]

If you want glass cut really accurately, get it waterjet cut.

[GammaBoy]

Or make a template out of rubber and cut it yourself with a sandblaster.

[latheboy]

Can't cut hardened glass with a waterjet, it shatters it...

Can cut normal glass though, then get it hardened.


Sandblaster ya reckon Gamma.... Might talk to some people

[Large]

Ya need little fucking wipers in there Ivan

[GammaBoy]

Yeah, its a technique custom guys use to chop laminated windscreens.

[latheboy]

Ya need little fucking wipers in there Ivan

Water injection just to clean the screen.....


Yeah, its a technique custom guys use to chop laminated windscreens.

Cool, Gibbo will know someone....

[Large]

Or put double glass in, with some blue fluid and plastic fishies.

Always thought that would look good on a windowed clutch.

[ozzy1100]

A bloke in the early days of high end custom car audio in the USA
was best know by the name fishman because at diffrent times he had fish tanks with
eather live and plastic fish just like you said large lol

[Cruisecontrol]

The burning question is; Why?
What is there to see that is worth the drama?

[TurboKat]

If you have to ask...

[Cruisecontrol]

Polycarbonate sidewalls on the tyres next?

[Deano]

If you had 10mm thick glass does it have to be hardened?

I use poly carb on the window covers and they withstand oil no probs but petrol really fucks it up by the look of it

[latheboy]

The burning question is; Why?
What is there to see that is worth the drama?
TK is right....

I spent 20 hours machining the thing so I want to show off the work involved..

[latheboy]

I'm talking to a glass guy and waiting to hear what he reckons..

[TonyOW31]

Can't cut hardened glass with a waterjet, it shatters it...

Can cut normal glass though, then get it hardened.


Sandblaster ya reckon Gamma.... Might talk to some people

Didn't know that, the last stuff I had waterjet cut was toughened glass for the viewing port of an industrial oven, came out really nice.

[latheboy]

I just got a quote for Laminated glass watercut for $80

Not bad i reckon.

[TonyOW31]

I just got a quote for Laminated glass watercut for $80

Not bad i reckon.

Bargain, thing I like about that is if you give them a dxf, it will be +/- .15. no fucking round when it comes to fitting.

[latheboy]

The biggest problem i've come across with laser cutters is knowing which side of the line on the DXF they cut to.
This is what changes the size of the part.

[Redmohawk]

Nice off to the water jet cutters

[TonyOW31]

The biggest problem i've come across with laser cutters is knowing which side of the line on the DXF they cut to.
This is what changes the size of the part.

I realised that when I first started using them, so now I always give them a dimensioned drawing along with the dxf, removes any ambiguity.

[latheboy]

I realised that when I first started using them, so now I always give them a dimensioned drawing along with the dxf, removes any ambiguity.

Yep, same...

Or tell them which side of the line i want it cut on.

[Gix11]

Interesting. I always thought DXF files were cut on the outside. I'll have to keep that in mind when supplying them. Cheers.

[TonyOW31]

Interesting. I always thought DXF files were cut on the outside. I'll have to keep that in mind when supplying them. Cheers.

They have to offset the cut by the value of the kerf, laser and waterjet are quite small, whereas plasma and oxy cutting is quite large, especially in thick materials.

[Gix11]

Guess it makes sense when you get to that precision. I usually only supply for engraving / etching / cutting of logos etc, so precision is not really an issue.