Designing an 8 port as a bit of fun...

General Chat with an emphasis on BMC Minis & Other iconic cars of the 1960's. Includes information on MK1 Action days.
Post Reply
Trog
Posts: 25
Joined: Tue Mar 10, 2015 1:12 am

Re: Designing an 8 port as a bit of fun...

Post by Trog »

Chapter 3 "Rozzer is having a problem with his differential" Part 1

With a prototype head I was able to dry build the engine in the car and start to develop the complete package of the engine bay:
01 package.jpg
02 package.jpg
04 package.jpg
The exhaust was “off the shelf” so not a problem (Though I still need one if anyone happens to have one lying around!!!), however the inlet manifold would be a whole different story. I would also need to design a thermostat housing and package things like the oil cooler, coil pack, and fuel pressure regulator. I also wanted to add expansion and recovery tanks to the cooling system. Finally, I would need to add all the sensors and wiring for the EFI system.
The EFI system I am using is a Megasquirt, primarily because a colleague at work had one he had bought but not used. It is a sequential firing system so I will need a multiple coil pack and a cam position sensor as well as the other sensors injectors and other malarkey.
The thermostat housing was the first thing to be designed, this was always going to be a casting. Initially this was the same height as the mini head and used a mini spacer for the heater take off. However, as I worked through the hose fitting, I realised I needed to rotate the top housing about 20 degrees and the spacer no longer aligned properly. So, I made a tall housing that included the heater outlet. This also allowed me to add bosses for the water temperature sensors and fan switch.
Thermo Housing.jpg
07 Built.JPG
3D printing made this whole process so much easier, the speed of design, iteration, and re-design was awesome! You can also see the oil cooler position in this image, I used an RSP Cooper cooler after much research! But that’s another story.
Finally, I made a radiator mounting bracket and called that job done! Hose is standard Cooper, the thermostat housing is in a slightly different position, but the hose still works, though I do need a new one!
You do not have the required permissions to view the files attached to this post.

Trog
Posts: 25
Joined: Tue Mar 10, 2015 1:12 am

Re: Designing an 8 port as a bit of fun...

Post by Trog »

Chapter 3 "Rozzer is having a problem with his differential" Part 2

Next was the inlet manifold. I can’t tell you how many hours I spent on this. A lot of this was “old school” engineering; making mock-ups from carboard, plastic pipe, even foam pipe insulation, experimenting with all sorts of packages. The images are of early CAD work to help with feasibility, sadly I have no pictures of the actual mock-ups!
Plenums.jpg
The main problem was trying to get the inlet runners as long as possible. Ideally 12 to 18 inches (in old speak). The “up and over” worked well though it drove the injectors into the manifold, but it would require a modified bonnet so was unacceptable. With a forward plenum chamber the issue was finding space for the throttle body and air filter as the long run pushed the plenum down and then the alternator pushed it towards the right of the car.

This iteration process slowly brought me to a design where the plenum was above the alternator with a central inlet underneath which turned 90 degrees to the right to put the Throttle body above the starter motor. This did make the runners shorter than I hoped but it packaged well under the hood and allowed enough room for the throttle body (off an MGF) and air filter. On an aside I used the K&N filter area calculator, the filter you will see on the images is about 200% of the surface area!
010.JPG
Even with this extra space The HVAC duct was in the way! I was reluctant to remove this completely, so I made a new one out of glass fibre that gave me the extra couple of inches required
HVAC.jpg
You do not have the required permissions to view the files attached to this post.

Trog
Posts: 25
Joined: Tue Mar 10, 2015 1:12 am

Re: Designing an 8 port as a bit of fun...

Post by Trog »

Chapter 3 "Rozzer is having a problem with his differential" Part 3

Once I had the final package solution, I had to change that into a viable design. I will show you the steps now, but this actually went on concurrently with the next few chapter(s) where I will cover casting and machining the head. (I have no idea how many chapters there will be, I’m making this up as I go along.)

The manifold, as shown above, is a single piece. How could I make this? If it is too hard to make do I split it into an assembly and if so, how many parts and where do I make the split. Finally, how do I make all the separate parts.

Looking at a single part, well I could cast it but that’s one big casting and once made leaves no room for modification etc.. So, no not a casting. What about a fabrication? Well it could made from Aluminium but as I can’t weld or fabricate aluminium (my steel welding ain’t so good either!) that would be expensive but would at least be modifiable. FRP is an option, but would take a lot of work, I have never made anything that large before. So, a single piece seemed to be out of the question.
The most common way to split the system is into a plenum chamber and inlet tracts so this is the direction I chose. I decided on a split line between the two parts, keeping all of the plenum volume in one part. Much CAD and prototyping helped me to get a shape for the plenum chamber: As a general rule the plenum chamber should be about the same volume as the engine displacement for a normally aspirated 4 stroke engine. This is actually quite small and a hard target to achieve!

Initially I was going to make 4 short cast inlets Joined by a laser cut backplate. 4 velocity stacks would smooth the airflow. However, it became apparent that a single casting would be cheaper and easier to make so that was the final direction I took. One of the drivers for the multi part inlet was to aid assembly and plug changes however during the development I realised that the easiest way to get to the plugs was to remove the complete inlet assembly rather than disassembly parts of it! Yes, it’s a bit tricky to do but with all the limitations I had to work around some compromises seemed inevitable. The way I have mitigated this is to use Iridium plugs that last about 100,000 km.! I am thinking I don’t mind removing the manifold every 10 years to change the plugs!

The plenum is made from GRP; I made a 3D print of the inside of the plenum, I then overlaid it woven glass mat before adding 2 steel reinforced flanges and then a final few layers of woven mat. Once finished the 3D print was broken up and removed.
001.jpg
002.jpg
Finally, I was able to find places for the coil pack and fuel pressure regulator. These look a bit snug to the brake master cylinder but have sufficient clearance to ensure that they will not contact due to engine movement

On the dry build images there is a grey bracket that runs across the front of the engine under the plenum. There is a pin on this which locates onto the plenum. The function of this is to support the inlet system that is cantilevered off the head. While the weight is not too great; during driving the vibrations and potential resonations could cause a failure, especially of the GRP. This pin that locates onto a rubber bushed hole will absorb these. You will see this sort of design on a number of production cars. I have also found that it makes assembling the manifold a lot easier, once located onto the pin the manifold stays put while you put the 8 bolts in!

Enough I hear you cry, I will leave the chapter there!!!
You do not have the required permissions to view the files attached to this post.

User avatar
Exminiman
Posts: 625
Joined: Tue Jan 17, 2017 8:59 am

Re: Designing an 8 port as a bit of fun...

Post by Exminiman »

Just interested to know why; “I need to maintain a minimum wall thickness of 6 mm“
Was it based on original specs or calculations ?
Keep up the post going Trog, favinating stuff :D

Fanfaniracing
Posts: 411
Joined: Sun Feb 19, 2012 12:11 pm

Re: Designing an 8 port as a bit of fun...

Post by Fanfaniracing »

WOW!!! :shock:

Absolutely fantastic!!!

User avatar
mk1
Site Admin
Posts: 14306
Joined: Thu Jun 24, 2010 11:30 am
Location: Sunning myself on my top secret tropical island.
Contact:

Re: Designing an 8 port as a bit of fun...

Post by mk1 »

This thread just gets better & better!

Thank you very much for taking the time to share your adventure with us.

You make it all sound so easy :)

The use of the 3D printer seems to be an absolute god send, not only are you able to mock the various components up in prototype form to see any issues that may have been overlooked, although there seem to be impressively very few of those, but you can also print your own formers and patterns for production work. This must really speed things up too.

As a matter of interest, how long did it take to print the head prototype?

On another note, I have have no idea what FRP is, I assume Something Re-enforced Plastic, what's the Something?

I look forward to reading the next exciting episode.
Mark F
Forum founder, backer & only admin for nearly 20 years.
I Must be f*&%^g mad

User avatar
Pandora
Posts: 2498
Joined: Thu Jun 24, 2010 8:01 pm
Location: Dunfermline, Fife

Re: Designing an 8 port as a bit of fun...

Post by Pandora »

I think it's Fibre Reinforced Plastic (GRP to us)

I have a love-hate with 3D printers. We have loads of them at work and the student's quite honestly couldn't get by with out them, but I see a lot of things being made on them that quite honestly could be made in minutes in the workshop using bandsaws, sanders etc and doing so would benefit the creative design process. The same is true of lasers for cutting sheet materials.

I fear a lot of traditional skills and knowledge of the development process are being lost.

However, projects like this show exactly how the technology SHOULD be used, and where it's real value lies.

It's fascinating stuff, and full credit to you. 99.99999% of folks who have ideas like this never even see the drawing board, let alone built!

Al

Dearg1275
Posts: 773
Joined: Mon May 11, 2015 4:16 pm
Location: Scotland

Re: Designing an 8 port as a bit of fun...

Post by Dearg1275 »

My mind is truly boggled. Inspiring stuff!

D

Trog
Posts: 25
Joined: Tue Mar 10, 2015 1:12 am

Re: Designing an 8 port as a bit of fun...

Post by Trog »

Exminiman wrote:Just interested to know why; “I need to maintain a minimum wall thickness of 6 mm“
Was it based on original specs or calculations ?
Keep up the post going Trog, favinating stuff :D
A "genaral" rule for cast iron, allows for some core movement and still have enough gap left for the iron to flow through.

Trog
Posts: 25
Joined: Tue Mar 10, 2015 1:12 am

Re: Designing an 8 port as a bit of fun...

Post by Trog »

mk1 wrote:This thread just gets better & better!

Thank you very much for taking the time to share your adventure with us.

You make it all sound so easy :)

The use of the 3D printer seems to be an absolute god send, not only are you able to mock the various components up in prototype form to see any issues that may have been overlooked, although there seem to be impressively very few of those, but you can also print your own formers and patterns for production work. This must really speed things up too.

As a matter of interest, how long did it take to print the head prototype?

On another note, I have have no idea what FRP is, I assume Something Re-enforced Plastic, what's the Something?

I look forward to reading the next exciting episode.
Glad you are enjoying it

It was not as easy as it sounds! But is was as fun!

Not sure how long it took to print the head, I did it in slices of about 12 -15 mm as any bigger and it would warp. I would say 2 weeks, but not printing 24/7! Yes the printer was the one tool above all others that made this possible!

FRP Fibre reinforced plastic, also know as GRP, or fibre glass! (though technically it could include Carbon or Kevlar fibres...)

Post Reply