3D Printed Parts

[madjak]

I'd probably still have a metal base plate, but then have a two part plenum where the top half is removable. I think that makes it easier to build anyway. I like the idea of the metal base as you can mount the trumpets through the ali and get a solid mount. If mounting through a plastic base it would compress, maybe crack from vibrations. There is a really interesting air box design where the air flows past the top or bottom of the air box and through slots located at each trumpet into the main chamber. So you get even flow of air to each cylinder rather than a drop of pressure as you get to the rear cylinder.

Anyway I'll have a think about it and see if I get time to draw up a better design. I really need to get some accurate measurements of the engine bay so i can figure out the space and angles I have to work with.

Rick

[sailaholic]

Hey rick, have a look at my Mazdaspeed itb box in the link.

viewtopic.php?f=57&t=48599&start=120#wrap

It's fiberglass and mounts straight to the throttle bodies with the velocity stacks clamping it down.

You can't see it in the photo but the bottom rear corner is dishing inwards to clear the proportion valve etc.

Fitting the trumpets is a MAJOR pain in the ass and requires a triple jointed forearm a half length spanner and plenty of time.


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[gslender]

Rick, was wondering if you can provide some basic advice on how the 3D drawing tools work.

Assuming I wanted to create an empty box with a 5 sides (1 side up is open), do I start out with 5 box rectangles where the width of the rectangle is the mm thickness of the material, and I bring them all together in the x,y,z planes to make a 5 sided box?

... or do I start with a 6 sided rectangle box, and define the material type to be mm thick and delete/remove one of the sides of the box?

I'm just a little unsure how it is commonly approached.

G

[madjak]

3D modelling method can be approached different ways and the best way is dependant on several steps later on. If you choose the wrong way to start with you'll end up getting yourself stuck later. For these surfaces I start with 2D CAD lines and extrude or sweep curves along them. Working with curved surfaces in 3D is very tricky as it's very hard to match curves in multiple directions. Rhino is good because it has some simple to use tools that will match curved surfaces to others.

If you want, I'll record a video tutorial showing how I model something in Rhino. I'm not sure how useful it will be but it might show the methodology better than I can explain.

Sailaholic, that Mazdaspeed intake is remarkably similar to the one I quickly modelled. I think I have some good ideas on how to build it with a better design but I need to figure out throttle body geometry and space. Do you think there is any real demand for a new airbox? What is wrong with the mazdaspeed one you linked?

Rick

[gslender]

Sailaholic, that Mazdaspeed intake is remarkably similar to the one I quickly modeled. I think I have some good ideas on how to build it with a better design but I need to figure out throttle body geometry and space. Do you think there is any real demand for a new airbox? What is wrong with the mazdaspeed one you linked?

There should be some demand for a Jenvey ITB compatible airbox. There is nothing available on the market that fits in the limited space of the MX5 and even with moving a few things out of the way like have (brake bias and clutch reservoir) I still could not get either the pipercross or jenvey parts to fit.

That's why I'm modelling something in Balsa and intend to get it made / fabricated.

The box I've made allows me to clear a few things and anything within that space (curved or not) would be adequate.

I should be able to design something Visio and then hopefully transfer the 2D dimensions into a 3D object - at least from a reference perspective.

G

[sailaholic]

My biggest problem with the existing airbox is that it is set up to cross the front of the engine to the stock filter box which I don't want to do.

The second problem is while it fits nicely in the space id like to fit longer velocity stacks if I could create more space.


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[madjak]

Just sketch out some cross sections, top view, side view and put some dimensions on it and send it to me. I can model it quick enough.

If there are a few people interested I suppose I could look at making them. It's a big undertaking though and I'm going to busy soon fitting a new engine. First stage is to model it, print a prototype and see if it fits. I'm happy to take it that far if you want.

What length trumpets are you looking for? I'm just printing a test one now.

The airbox should probably end with the throttle body flange. Then you can take the air intake wherever you like from there.

[gslender]

Just sketch out some cross sections, top view, side view and put some dimensions on it and send it to me. I can model it quick enough.

If there are a few people interested I suppose I could look at making them. It's a big undertaking though and I'm going to busy soon fitting a new engine. First stage is to model it, print a prototype and see if it fits. I'm happy to take it that far if you want.

Sounds good. I'll have a crack at that as I'm good with Visio and can get it looking fairly close to what I want.

What length trumpets are you looking for? I'm just printing a test one now.

I don't need any trumpets - I've already got 40mm and they seem to provide enough torque as they are. Others are suggesting longer, but you need more airbox space and I think 50mm is already probably as much as you can fit given you have limited space around that entire area.

The airbox should probably end with the throttle body flange. Then you can take the air intake wherever you like from there.

Yep. The Jenvey boxes have a 76mm / 3" flange that was probably calculated based on the 4 ITBs at 45mm each considering that a 2L engine (the size suitable for these sized ITBs) would only be able to suck in so much air volume.

G

[madjak]

With the Jenvey ITBs, I think this would be easier with the shorter throttle bodies. For some reason all the mx5 kits come with the 118mm throttle bodies and 40mm trumpets. Why not use the 90mm throttle bodies which gives nearly 30mm more clearance. You'd need longer trumpets at around 70mm to match the same intake length of the standard 118mm throttle bodies. The extra room would allow you to bend the trumpets to get the longer length if you require it, say 90 or 120mm ones.

Also, the firewall end can have an odd shape to fit around the obstacles that can't be moved. As long as the trumpets can fit inside.

Here is the trumpet print at 67% (about 1 hour left).

20140919_154846_sm.jpg

If it works I'll post it off to Magpie next week and see if it fits! Though really because the bell sticks out, it will probably still protrude around 90mm but that's at much higher point than if it came out straight so hopefully it will clear.

[Gladiator]

This is very cool. I imagine it would be exciting watching your product "grow".


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[gslender]

It took me a while, but here is the PDF of the intake box I've made in balsa that fits with the ITBs and all the dimensions correct etc.

Would it be much effort to create something similar in 3D printing and would it be strong enough? And, or if not, can you get it made other ways?

intake box itb.pdf

[madjak]

It took me a while, but here is the PDF of the intake box I've made in balsa that fits with the ITBs and all the dimensions correct etc.

Would it be much effort to create something similar in 3D printing and would it be strong enough? And, or if not, can you get it made other ways?

intake box itb.pdf

A square box is probably not ideal to print due to stress on the corners and bowing of the flat surfaces. I think I'd radius all corners by around 10mm just to make it stronger. With plastic, the weakest parts are the flat surfaces with curved surfaces typically being much stronger. Also I'd make the plastic a bit thicker with a honeycomb interior for strength.

My other main concern with this is bolting the plastic straight on to the throttle bodies which will be hot. I think I'd prefer to see something in between the two, such as a metal plate. Even though this would transfer heat too, as the air flows over the surface, it will be cooled. This would mean a 3 part form. A plate that mounts onto the ITBs, so you can mount trumpets etc. Then a plastic body that would clip onto or bolt to the back plate. And then a lid.

I can certainly print this structure no problems, though it would need to be in multiple parts due to the size of the printer. Basically there would be two end pieces (one for the intake flange and end, the other on cutting through on the diagonal end surface. Then the main body would be printed in two parts, complete with holes. The lid would be printed also in two parts, though this could be aluminium. The aluminum plate could be trapesoidal, with the plastic slotting down on each end. Would probably only need to be fixed in the middle on the top and bottom? (can you get there?) Alternatively just fix the back plate to the box first, then bolt it on with the trumpets basically as if it was solid plastic.

Btw, shouldn't the intake be angled down 5-10 degrees? Makes it easier to clear the bonnet, though I suppose on ITBs this point is lower in the engine bay.

I'll have a look at it next week for you. I'll also record my modelling session so you can see how it was built.

Rick

[madjak]

here are a few photos of a prototype curved trumpet for the Jenveys.

20140925_171857.jpg

20140925_171912.jpg

The first print in white failed. A bolt fell out of the printer head and it rotated a bit. You can see the offset line in the model, so I'm reprinting again in pretty orange! The mess on the trumpet face is a temporary support structure that will break off fairly easily and clean up fine with some sand paper. I have to print these in two pieces due to the geometry causing overhangs that the printing would fail on.

The new orange part has a little recess flange that will join the two parts together (hopefully) and allow it to rotate. The trick with this is getting the correct tolerances so it's not to tight. These parts print quickly at around 1 hour each.

[gslender]

An hour each! That's quick?

[madjak]

The air box will be around 40 hours at least I estimate, so a few hours is quick. The plastic layers are printed at 0.2mm so your airbox at 400mm or so will be 2000 layers of plastic.