Curved Inlet

[retired2]

Bernard, thanks for the verification.

I've just made a couple of small modifications to the inlet so I can make better use of the materials I have to hand for making the plugs. Getting closer to some actual construction and the 2mm polycarbonate sheet should be arriving later this week. All the toolpaths are now complete and, barring any unscheduled shopping trips, I can start machining tomorrow.

Mike,

Bernard is correct, I suggested making the rectangular end of the round to rectangular transition 10% larger.  However, let me qualify that statement.  The HVAC industry is the source of that recommendation.  Whether it is applicable here or not is uncertain, but my thoughts are it can do no harm.

[Mike F]

Thanks Retired, that gives me the go ahead to start machining tomorrow  ;D Really looking forward to seeing how it performs in my system.

[Latham]

Having just finished a (non-curved) round to rectangular fiberless inlet using the lost foam method, I'll be very curious to see how you construct yours.

L

[Mike F]

Latham; As I have access to a CNC milling/routing machine that I made some time ago, making a curved inlet was always going to be relatively easy. The way I have decided to make it was to do a male mould or plug so that the internal walls of the inlet would be smooth. This means I have to make the inlet in two halves and then join them - no big deal when working with composites. I have just finished machining the plugs and have attached photos. These had to be made in two pieces each as the overall depth was greater than my machine could cope with. The photos show one half already glued together and the other still in two pieces. They are also posed in their finished state to give an impression of the size. This is designed for 100mm ducting.

Cheers,

Mike

[Latham]

Mike:

Good grief, you set a high bar. Makes my mold plug look like a baling wire/duct tape contraption.  :'(

Please keep posting.

L

[Mike F]

Good grief, you set a high bar.

Yes, unfortunately, I am a bit anal when it comes to making things but, I have always said that it takes very little extra time to do things accurately than to do a half hearted attempt. As I have said previously, if I was to make a lash-up I would never get round to making a proper job - unlike many on this forum. Before I get flamed, I must also add that I am in admiration of those people who can assemble working models very quickly, by whatever means and, if it were not for people like that and this forum, I would have no starting point and nothing would ever get built. In the end, we all work slightly differently and as long as everyone contributes, the end result and the progress will be so much better and quicker.

Now we need to see some photos of your finished build. My thoughts were with you when you were dissolving the foam with the acetone. I have made plenty of things that way and it can be soooo messy with liquid styrene everywhere and if you let the solution dry, it takes some getting rid of - makes a pretty good varnish though :)

Cheers,

Mike

[Latham]

Mike:

Dissolving the foam wasn't too big of a mess. I screwed a piece of plywood to the dowel. Set the whole thinig on the same large garbage bag I'd used to cover the lathe. I was a bit concerened the goo would disolve the garbage bag but it didn't. At least when you dissolve the foam, you don't end up with much mass.

I'll certainly upload build photos when I've got them. There's another project or two stacked in front of this top hat.

L

[Mike F]

Bit of an update - no fibreglass laid up yet but the plugs are now lacquered, rubbed down, polished and have the release agent on them. Just need to add the false base and ends before the glassing starts. I have also managed to machine the MDF top, bottom and entry mount, get those  lacquered and rubbed down and also laser cut the polycarbonate to the right shape. Attached is a photo of the almost completed body of the separator.

Still have to make the small floor for the inlet air where the two radii meet and do the machining for the bell mouth. After the reminder about the air straighteners, I also need to fabricate those.

Shouldn't be too long now before I can give it a whirl, so to speak :)

Mike

[Mike F]

Some more progress. Managed to get the plugs laid up last night and released this afternoon. I am very pleased with the outcome and the two shells just need trimming before joining them. They have a pretty good finish on the inside so shouldn't trip up the air flow too much.

The polycarbonate is giving me a bit of a headache where the two ends are joined. I think I have a solution and will post here if it works out okay. I am glad I went with the recommendation of using polycarbonate as I know for sure that had I used acrylic, it would not have withstood the abuse this has already taken!

Cheers,

Mike

[Latham]

Great looking pieces.

I'm wonderng how you got the cloth to lay on your plugs. It doesn't look like they were vacuum bagged. Did you use a mat cloth?

Thanks,

L

p.s. I've got my seperator up and running. It works great. I need to put a coat of poly on the outside and then I'll post a pic or two on a new thread.

[Mike F]

Hi Latham; No, they weren't vac bagged though I had considered it. The glass was laid on in just one piece, although there were three layers. The plugs were first gel coated and left to go tacky before the first, thin, 50g cloth was applied. The second layer was one of 600g glass cloth and the final layer was one of 75g glass cloth. The secret of getting the glass around compound curves is to use twill weave. A standard, plain weave cloth just would never go round the complex shape but the twill weave allows the warp and weft to move and the material can be coaxed and persuaded round relatively easily. All three layers of glass were applied in one operation with the flanges having an extra layer of 600g to beef them up.

I am hoping to get the flanges trimmed and the two shells joined this evening - all being well. I have just drawn up the bell mouth plug and am currently doing the toolpaths. I have decided that the bell mouth will be easier to manufacture by glassing it straight onto the ducting. The plug will be made to accept the duct then the plug and the end of the ducting will be glassed over. I'll post some pictures of the procedure.

Mike

[Latham]

Interesting, I'v never used a twill weave fabric. Had to Google it. I bias cut some strips to lay over my 90º edges and still struggled with that.

Thanks,

L

[Mike F]

Yes, twill is great for going round compound curves.

Didn't get the shells joined this evening but got the outlet plug made instead :) Still have to rub it down and lacquer it before laying it up but, it's another job out of the way.

[phil (admin)]

Wow, some of these builds are way over the top!

Love watching the progress.

[retired2]

Wow, some of these builds are way over the top!

Love watching the progress.

Wait till I get my 3D printer!!