LA Class Scratch build using arduino and pistons

**ccontrol** · 02-26-2017, 04:44 PM

Bravo John, I look forward to keeping up with this build.

**johnredearth** · 03-03-2017, 04:59 PM

Los Angeles Update:
This is happening part time, unfortunately I have to work, and unfortunately my family does deserve time. I haven’t even broken the news to my wife that another sub is happening. She feigns disinterest, no that is wrong, she IS disinterested, but it is the time that is the issue. At the same time we are starting up a new business in another area.. OK, enough of my personal stuff.
I use ‘dive in to submarines’ on facebook, as place to bounce ideas. One of the issues was that of how big the motor would have to be for this sub. The prop is 80 ml across, with seven blades. So I threw some ideas at the crew and one gave me the idea to use a brushless motor direct drive. Needless to say, I am on board with this, and bought a Multistar Elite 3508-268KV High Voltage Endurance Motor. It is not tested yet, but the issue is going to be mounting it, as it is an outrunner and will have to be secured from the base (back). Not a problem really but I will get to that when I get to it.
So I started with the prop this week. I have a jig for making props but it extends to 6 blades only, and I considered making the prop six bladed, but honestly after going to all that trouble I think it should be 7, and it such a prominent feature of the sub. So I used a metal cut off wheel in my bench saw, a sheet of 1.2ml brass, and cut seven blocks of brass for each prop. Then I used the bench saw to set the cut for the base of each blade and make another cut to remove the vast amount of waste, and then set to the grinder, and ground one down to the right shape. This became the template for the other seven. I am at the point now of getting the file and possibly using the belt sander, to start to put the aerofoil shape into the blades.
This is an interesting point. I have always done this with props and generally ground the ‘lip’ of the blade down to a knife edge, or nearly so. It clearly gives the blades better efficiency and by putting an aerofoil shape in the dynamics are so much better. However this is a seven bladed, 80ml prop, and I am going to sharpen these blades. Honestly it will be like having a scythe behind the boat. Ducks legs, childrens’ fingers, shins, fish, all watch out. Who needs torpedos? I just have to back into another boat and machine a hole through it. Anyway, that is a task for today.
The real work this week was with arduino, and it is finished.
Each stage of the build of this ‘sketch,’ which is the techo name for ‘code’ in Arduino speak was an achievement. I started with a basic piece of code that received the signal from three channels of the RX, and tested it all using the serial monitor, which I use all the time to make sure I know what is happening in the code. Once that was working I saved it, then saved it as the next step and gradually built the code up step by step. It is like climbing a mountain. Each step is secured before moving on, and yes, twice I have to go back to the previous set up and start again.
I haggled with Adafruit until someone gave me some lovely code that allowed me to get readings for the three sensors. (That is where we were up to).
I then added instructions to run two pistons and added the second one. Not hard, I just had to rename all the piston instructions spiston (stern piston) and then create functions called bpiston, and duplicate the arguments. Done, and saved.
Then I added another channel from the RX called trim, which is attached to a knob on the Tx. This became the channel to control the trim. The next step was to write instructions to make this command move both pistons in the same direction together, thus moving the air inside the sub toward the bow or stern, giving for and aft trim. Done
Then I used the ‘routine’ channel to create the actual dive and surface routines. This means that on ‘surface,’ the bow piston starts first, followed by the stern, in order to get ‘bows up’ on surfacing. As this boat is ‘bows up’ when on the surface, I use the same to dive but this is just to get the hull level. I know all this will need to be adjusted when the boat is built but that is just changing a number in the code. Currently they have a 2 second lead. To do this I also had to borrow from some ‘old’ code I have that added a delay without using the ‘delay’ function so as not to stuff up everything else. Done and saved!
When diving, using the routine, the pistons withdraw to the sweetspot that I recorded through the use of the snapshot on the Tx. Have I covered that?
OK, when I use the controls to get the pistons to the point where the boat is at neutral buoyancy, perfectly trimmed, I flick the snapshot switch. This takes a snapshot of the positions of the pistons, and the pressure from the pressure gauge. I did something new here in that I want this ‘snapshot’ to be remembered, so I researched and added some code to make sure it is recorded in the little hard drive on the arduino so that when I go to the lake next time, the settings will be remembered. This is in fact the real breakthrough of this coding! The boat will remember the sweetspot each time I go to the lake. I can then do some final adjustments for the ‘day,’ then snapshot it again.
The final stage was to add the ‘bow’ servo. This is the servo that is on the sail on this boat, or would be a bow servo in another boat. This is only controlled by the arduino. When the snapshot switch is thrown the other way, from neutral into ‘auto,’ and the servo will adjust to keep the boat at the pressure that is being read from the gauge and the snapshot. The coding for this was pretty easy. For those of you with a background in this, I had previously used a PID algorithm to control the depth keeping, (and the auto course control on my surface boats). I now use a much simpler method which takes up much less arduino energy. Also, when the auto is turned off, the servo centres and then is disconnected.
With it all l working, I videoed it in action and this can be found on my website blog. I also have the code and the circuit diagram on that page. Everything to do with arduino is open source!
So I now have the complete system set up for the new boat. I just now need to get this hull finished to the point of being useable, and build the scythe!
BTW, the blog, pics and video are here

Cheers

**salmon** · 03-03-2017, 06:54 PM

Are you willing to post the code you used here?

I did R/C boat racing years ago and use to sharpen my props to a razor sharp edge. One cold day, I was adjusting something with the boat in my lap, when I went to pick it up, the blade sliced through the jeans and into my flesh. I notice on the props I have bought for my subs, the edge is not all that sharp or in some cases, it is just rounded off edged with no foil built in.

**Guest** · 03-03-2017, 09:16 PM

Press in a replacement shaft in the multistar motor so that the shaft exits at the other side, then you can mount it like a conventional can motor.

**Ralph --- SSBN 598** · 03-03-2017, 09:20 PM

I do not know if a sharp edged propeller is better than a rounded off edge.

I did study the Wright brother's build of their airplanes.
They made a water tank that they could put various items in and see the water flow around and over these items.
The water had some sort of particles in it to show turbulence.
Contrary to what I would have thought, the rounds edge was not the best shape to reduce turbulence.
It turned out from their testing that a square strut with rounded corners disturbed the flow less than the others.
They tested for strut and framing issues and not as much for airfoil shapes.

Airplane propellers have a rounded leading edge and may have a sharp trailing edge.
The idea is to displace a lot of water or air at the leading edge and then have two surfaces. One that is straight or con caved to give the shortest distance for medium travel. The other side is convex to make the medium travel farther and faster to create a low pressure area which pulls the propeller towards the low presser.

A sharp edge trying to split the medium instead of pushing it away and around the edge can create harmonics. (not necessarily good for propulsion. very noisy)

Something I remember from my early years.

**johnredearth** · 03-04-2017, 05:56 AM

Hey thanks for that. You have solved a problem I have not even started to address. Cheers

John

**johnredearth** · 03-04-2017, 06:01 AM

Hi Ralph

I have just made the seven props and I have put an aerofoil section on them, and it does leave sharp leading edge. Each blade looks reminds me of a scene from Jurassic park. And Salmon, if you go to my blog on the web page you can link to the project page and the circuit diagram and code is all there. The thing about arduino is that it is open source! John

**johnredearth** · 03-09-2017, 05:47 AM

First the prop. I used the belt sander to start the process of developing an aerofoil section on the back of each blade, and then continued with a file. Being an ‘old’ fitter and turner, I feel very comfortable with a file. I worked on the aerofoil and then polished them up. The next part that I usually do with props is to bend a concave into the opposite face, but this time I have 7 straight slots in the hub, and decided to leave this part out. Instead I used the dremmel cutting wheel to cut the bases off the blades, and then the belt sander again to get each blade fitting neatly into the hub. I put it together and here is the result. It is 80mm across and quite a monster. I soldered it up with silver solder.
Then it was on to do the ‘drive’ train. I used the same methodology I used in the Nautilus to develop the connecting system to make a direct drive from the brushless motor onto the drive shaft.
What I did more successfully this time was to work through on the white board everything I needed to make. When I started building I then used the lathe to do the similar parts, and did all the drilling at once etc etc which reduced production time dramatically. Just a little planning...
The process involves making two pieces of brass (square to fit in the lathe), and screwing them together and drilling through the centre of both. Then fitting the motor to one side and screwing it on. I needed to reverse the motor to do this as it is an outrunner and fitted a longer 4mm shaft. That was not so easy as it was a tight fit, and I used my vice to press in the new shaft. The other side of the plate is then bored out in the lathe to fit to a brass rod (OD 16 mm) that I bored out to fit the shaft and connector. The far end of this has a 5.5 ml outlet. The stainless drive shaft is 5 ml, so this end is designed to be the seal. I drilled two holes vertically into the end and threaded them with 3 ml thread. I needed some ‘meat’ to do this. I stuffed it up first time so had to do it twice. Pic Then parted off a bit of the end to be the cap, and bored out a space for a little o ring that fits nicely to the shaft. Screw it together and low and behold you have an easy and cheap seal. I use these in both my boats and I have never even had to change the o’rings years later. (maybe I should)
Then I made a coupler that will join the shaft where I cut it (I have to do that to avoid removing the prop to remove the shaft). I also made a bush for the end of the shaft where it goes out of the hull, and a plastic bush to sit inside it.
Then I made the direct couple. I drilled a 5ml hole into a small piece of brass rod and silver soldered it onto the shaft. Then i put the shaft into the lathe, aligned it perfectly and shaved the outside of the brass rod to make it line up nicely with the shaft, and then drilled a 4mm hole into it for the motor shaft. (trying to make it before soldering will end in tears. The soldering process will be hit and miss)
Next the end cap. I have a tried and true method of making these and it took about half an hour. I tested it with the o’ring and a piece of acrylic tube and it was perfect first time. (Using about 15% compression) Then bored a hole in the centre to take the shaft housing. This brushless motor will take no space at all, and the next step is to start building the structures to hold two servo’s, get the holes sorted and to put two bolts into the end cap so that I can bolt it onto some heavy brass that will lock it into the hull. My thought is that the speed controller and the self leveller will also go in here. All the wires that will be needed to go to the unit will be a nine wire ‘band’ using coloured wire from the electronics shop, for the two servos and the speed controller, and two power wires to go to the speed controller.
Arduino
I am not sure I covered this, but last week I finished the coding. This week I made a couple of pin changes to it to fit with the use of a little ‘Nano’ instead of the bulky ‘Uno’, completed the circuit diagram, and loaded them onto my web page for general use. Click here. Then I created a new video which goes for about half an hour which includes how I built the code from the ground up. Please look if you are a wonk. If not, I refer you to my video ‘arduino for boats 1’ before you start. I mean it! Seeing this without prep is a sure fire way to be put off!
Hull
Then I got to work with the filler. I absent mindedly bought ‘builders filler’ from the local hardware shop. I tried it and it is really not the right type for this work and had to get the real stuff, ‘car filler’ from an auto shop. Then came some elbow grease sanding down the filler and re-sanding and I am about to fill the little holes and low spots and then use some very light sand paper to get it close to finish.

Once again, my blog with pics is here.

**johnredearth** · 03-17-2017, 05:47 PM

I have been working on the drive train, which includes the seven bladed prop, the prop shaft, the end bush, the seal running into the stern end cap for the motor room, the connection and connectors for the motor, a structure to hold the servos, a place for the self levelling device and the speed controller and exit slots for the nine radio wires. (6 for two servos, and 3 for the speed controller) and two larger exits for the power wires. Plus some bolts so that I have a method of fixing it and removing it as needed.

While I am doing this I am making videos of the build for the web site. It is fun as I am multitasking, going from job to job, and then when ready, adding material to movies but splitting it between subjects. So we have the hull build, the drive train, the prop, the planes, the Sail and the arduino stuff.

But then came a disaster. A WTF stupid disaster. I have been working on the hull, sanding the bow and stern sections and getting them better and better. I used my hand sander (for car panel work) to get the overall smoothing of the hull and then applied a new layer of filler and reduced the grain on the sander to 150. After a good smooth out I sprayed with grey primer and sanded with 400 grit to get the 150 grit scratches out and thought that, ‘it is where I want it.’ Not finished but then I only want the hull to be rough so that I can start on the internal workings. The finishing process will be last.

So with enthusiasm I prepared to gut it lengthwise and produce a top hatch. I have done this before with success, so chose to ‘rip’ a piece of timber the exact thickness of the hull, and screw it to the top of the sub hull. This becomes a solid guide to use against the rip saw fence. Then I measured the depth of the cut, and where to start and finish it on the rip saw table. (I never video these moments. I like to show how I do things but the idea of someone using a rip saw table unprepared and cutting off fingers is something I do not want to be responsible for!)

So I made the cuts length wise, pulled it off and put it onto the bench and realised my huge mistake. I had ripped from the base and not the top, thus making the hatch very deep. Then came my second mistake as I should have just re ripped and filled the ‘wrong slot’ but instead I used the hand saw to cut the section out, and cut through the foam within. I realised at once this was no good. The base would not be strong enough and would twist and bend over time.

**johnredearth** · 03-17-2017, 05:49 PM

Then I finished it all by applying some petrol and watched the foam disappear, leaving a very impressive bow and stern shell. (I don’t video this either for self immolation reasons)
In moments like these there is always time to reflect, consider why the hell you started this project, and maybe, just maybe , how to do this better.

So the idea was this: I went to the car store and bought a tub of car body filler which is impregnated with fibreglass. This stuff is really really tough. Then I went home and cut 40 ml strips off the base of the upper hatch. Then I got on the lathe and turned down two plastic discs that would be a neat internal fit into the hull. This latter idea is also going to be the method I will use to assist with aligning the top and improving the fit.

I may mention here my ‘ripping’ process always give me one problem. A three mil slot that needs to be filled in some way. On my other boats I have made a 3 mm acrylic shell that I have glued to the base, but now I have two slots in this hull. So I need a method that fixes this issue at the same time.

So I put the ‘reduced’ top hatch in place, packed it to fit, and carefully marked on the hull where it came down to at each corner. Then I got the hot glue gun out and hot glued the 40 ml strips in edge to edge, but made them fit perfectly to the marks so they will mate with the top hatch without the need of a gap filling process. In fact, it looks really good! This of course left a 6 mm gap at the bottom, three quarters down the hull. I then I mixed up some fibre glass filler and layered it onto the internal joints which were previously only hot glued. When it had hardened I put the disks in place and they lined up the lower strips nicely and tacked them along the length of the sub using the filler. Now I have a six mil space to fill, three quarters down the hull, which I then did with ordinary car body filler.

The idea will be to get the disks, and gut them so that they become round shells. Drill a hole vertically into the sides where the hatch meets, glue them into the lower hull and then cut through the top parts, and use brass plugs as locaters to fit in the holes, fit them and then glue the top down onto them. Perfect hatch locators, hull strengtheners and possible the mechanism for holding the WTC in place.

All this because of a mistake. I fact this may be a good approach for the future! I am an upbeat person. I think there is always a way out! Maybe I shouldn’t have mentioned the WTF moment, but then these things happen.
BTW, I have now been purchasing off ebay the outstanding parts I need for this build and my account, not including batteries and radio, is still under $500 aus.

Blog with pics http://www.scratchbuildwithjohn.com/...rine-update-5/

**johnredearth** · 03-25-2017, 12:00 AM

I am now concentrating on the motor room. I have already built into the end cap, the seal and housing for the seal of the prop shaft and a very efficient (space wise) mounting plate for the motor. I made some brackets, bolted them to the end cap, bent them to the shape of the hull and using the fire glass filler, glued the whole assembly into the hull, ensuring it was nicely lined up. (The bolts obviously meaning it is now removable). The prop shaft line up was helped by the disks I have previously made as I could ensure that the motor shaft is right in the middle of the boat. (Pic in blog) Unfortunately in doing so I mucked up the horizontal alignment in that the holes I had made for the servo arms were now out of whack. I moved one of them and filled the other hole. (Another WTF moment.. I must be trying to do this just too fast).

But, it’s all good, lined up and looking nice. I used piece of 6mm acrylic and bent a piece (after heating) to the shape of the inner end cap and screwed and glued it in place. Then added a removable shelf behind the motor for the servos. The servo arms and the holes in the end cap are now a real treat. Line up perfectly.

So now the attention turns to the planes and rudder. I decided to get to the lathe and make some small parts to assist with the inner configuration. I am referring here to the fact that the planes and rudder fulcrums run right through the prop shaft. I have sorted how I am going to fix this, but not the detail so I made some little sleeves out of round brass, drilled it through to fit the 1/8 inch brass rod that will be the shaft, and then turned down the inner part of it so that I have got room for a decent grub screw in the top, and yet it is not too thick in the middle for filing. I should also say here that when I made the planes and rudder I set the fulcrums up to be 10mm unaligned, to reduce the trauma of the conflict a little!

I have a good way of making these planes. Firstly I cut two rectangular pieces out of 6 mm acrylic on the rips saw which will fit the profile of the whole plane, and also rip a shallow cut lengthwise which is the fulcrum of the planes. Then I glued them together with acrylic glue, which actually welds it now into a 12mm block. Then its off the belt sander to get the outline shape right, and then to grind the aerofoil into them.

The next step is to use a nice piece of brass rod (1/8th in this case) and a snug piece of brass sleeve. I drill through the hull with a drill of ‘rod’ size and put the rod through and work it until it is square. Hot glue is a good idea to hold it in place. Then I took the hydroplane and used the profile of the hull to mark onto it the centre which is to be removed, cut it out, and now we have two matching hydroplanes, port and starboard. Then drill out the fulcrum slot with rod thickness drill and slip them onto the shaft and grind the planes till they fit snugly to the hull. Once they are fitting I use a set square, and marking opposite to the fulcrum, mark where the planes will be cut so that I have a ‘stub’ which will be glued to the hull.

Then I use a drill that fits the outer sleeve, and drill partway into the planes, past the spot they will be cut, and also open out the hole in the hull. Then I cut the planes along the cut off line, in this case by hand using a fret saw) and then start assembly. I have already turned down my little linkage for the centre of the hull which looks a little like a dog bone. It is drilled out to fit the rod. So then, taking two pieces of sleeve, and the dog bone, the stubs of the planes and the rod, I glue the whole lot in, in ensuring the rod and the dog bone turns freely, but the stub and the sleeve is glued in. The sleeve protrudes out of the stubs, and will fit into the planes. In this process I use a long piece of rod and make the final adjustments to ensure the planes will be square (bow stern, topside and keel).

Then I have generally drilled and tapped a grub screw into the planes alongside where the shaft will travel to enable a fixing once I am happy with it, and then slide the planes onto the assembly and check out the movements, fit and slide.

The next step is to work on the dog bone to make it miss the prop shaft. I have done this by silver soldering onto the middle of the dog bone a piece of rectangular brass, and then putting the assembly into the vice and using a round file, filing through the dog bone to get a clearance for where the shaft will go. This is a process of trial and error but eventually I get a nice c section with a perfectly lined up top and bottom. I then solder (using ordinary solder) a ball joint for the servo arm at an opportune place, and then drill and tap two grub screw holes in the top of the dog bone. Phew!

Then it is off the fit and file and fix. In doing this I used apiece of brass and silver soldered in the end of an allen key to get better reach onto the grub screws, attached a servo arm rod, the cup for the servo arm and eventually got it working. Tried out adding the prop shaft and ‘oila,’ the first set were in. (In this case, I started with the rudders, as they are the ones that are further back in the hull (Remember the 10 mm off centre fulcrum)

Then it was off to tod exactly the same with the hydroplanes. Then it was off to connect the arms to the servos. In doing so II cut the servo linage arms and fitted a couple of sleeves with grub screws so I can remove parts easily, and also make fine adjustments to the length of the arms.

I have now made a very nice intro as I have finally worked out what I and doing here!

Also if you click here for the blog you will see the pics of the build.

**johnredearth** · 04-01-2017, 05:48 AM

So progressing with the linkage I now connected them through the rear of the end cap directly to the planes and manually had them working. The ‘dog bone’ connectors work very well but were hard to get into place in the narrow stern. I found I needed to make an allen key extension for the grub screws and I can tell you that once installed, these ‘dog bones’ will not be removed except for necessity.
The hydro dog bone hit the side of the hull (whee the ball connector was). I ended up using my dremmel drum sander to cut into the side, and in doing so went right through. This is not such a disaster as it seems as it is ‘under’ the stern hydroplane, helps me to see where the fit the dog bones more easily, and can easily be covered if necessary. All good and now there is complete freedom of movement.
I then connected the servos to the receiver and for the first time discovered where the ‘centre’ was and had them working nicely. Once the relative positions were established I super glued the 1/8th shafts into place into the rudders and hydros, and tested again. There is not too much of an issue here as the couplings on the servo arms give some adjustment.
As always, getting to the fitting and detail part of such complex systems as hydros, props, servos, levers, and then making it water tight is not an easy process. There are lots of corrections to go though. What I thought would be a few hours turned into a day of fiddling and adjusting.
Then came the motor. I connected this up with a solid connector for direct drive, wired up the speed controller It was very exciting to get it running! But, I found an unacceptable amount of vibration. This lead to a lot of fiddling. I realised I had forgotten something I learned using this technique for the Nautilus. Namely that when the shaft is silver soldered into the brass rod, where it will connect to the motor, the next step is to place the shaft in the lathe, line it up perfectly and give the outside of the rod a light cut. Once this is done I needed to open the jaws, line up on the machined brass rod before drilling as there is too much flex if I do this from simply clamping onto the shaft. So with that done, the vibration slowed, but not completely. I then found my prop shaft was not as straight as I wanted, and then used the lathe to centre it and then used the dial indicator to find the run out. That was fiddly.
There is still some vibration, but not much. This however became a problem for the next step as I decided to add the self levelling device to the motor room. The device wandered when connected and I am sure it is to do with the vibration so I removed it and it will go in the control room when it is built. On its own it works very nicely and as always you have to adjust it to match the movement of the servo.
I also found the ESC was only ‘one way’ as it was designed for heli’s. The instructions showed that it should do forward and reverse so I emailed support and Hobby King, to get the unwelcome news that it won’t do anything but forward and I need another ESC. Mmm. I do find the instructions for escs and motors a bit opaque! At least I found the mistake and have ordered another that will do what I need.
Once this was done, I finished the motor room shell. I cut a pieced of acrylic tube down to minimum size (there is a reason for keeping this small) and then used my mandrel to machine a piece of acrylic for the end of the room and glued them using acrylic glue. After drying I tested it for water tightness and it was fantastic. I moved on and then fitted to o ring to the motor room, unbolted it from the boat, added the rubber boots for the servo controls and, with a full bucket of water, completed the first pressure test. Amazingly, it showed all the wires and their outlets were completely water tight, but there is a pinhole leak in a rubber boot. Once again, annoying but I will leave for now.
Then for the first time I ran the whole thing from within the sealed motor room. Very nice and very satisfying.
I am now going away to Germany for three weeks. My plans amongst others is to use some of the time to develop my videos and also possibly to visit Engel, the Mercedes of submarining.

click here for blog

**johnredearth** · 04-07-2017, 05:45 PM

On holidays at the moment, which does not give me any more time to work on my boat, but I am able at least to put some videos together. This is a nice video on the discovered method if you haven’t seen it before.

**johnredearth** · 04-14-2017, 10:37 AM

So I am still on holidays but that has not prevented me from thinking, which is one of the great benefits of this hobby. So many things can be redesigned in the head, during boring lunches with in laws and while waiting for them to start speaking English. (Don’t tell them that)
What I have had time to do though is to compile several videos for the website and to better plan the video titles, subjects and labels. I uploaded 8 or so new videos on the build to date.
Most interestingly I decided to change my main game plan. The arduino code for the sub is already done, but I realise now that I can add a compass to the boat. I really enjoy my surface boats having a compass and it is not hard to add to the code. This means I can run the sub, in this case, to a place on the lake, direct it onto a specific course and then to turn on auto, and it holds this course. I know how to do this and it will take a bit of recoding but not much. The idea of holding a course submerged is quite enticing. This will require the addition of a compass ($8).
The second change I want to make is that of ‘shorting’ out the connections on the self levelling device keeping it turned off until I flick the ‘auto’ switch. It makes sense to do it and so why not. It will require the addition of one more relay. ($2.00)
Secondly I have now decided to rethink the WTC. I have decided to make two new ‘couplers’ which can be glued to the ends of a central tube which will enable the attachment and removal of the two piston units. They will be attached by o’rings. This will require some careful measurement of the central unit to ensure it will hold the two lipo batteries, and also a tray onto which the electronic parts can be placed. Also, the 6mm spindles from the pistons will need to move through this arrangement when the pistons are in diving mode. The piston tube lengths will be calculated by adding the central cylinder, to the two piston gear box segments, and also the motor room. In general we want 25-35% of the total space provided for ballast, which will give me the length of the piston tubes in total.
The new idea here however is to make two plastic discs of 132 mm which will fit snugly inside the hull of the boat. These will then have a 100mm cavity machined into them, but not through them, that will snugly hold the ends of the pistons. The plastic will of course need water and air breather holes. The discs will have three uses.
• To make up a unit in which the discs can be bolted together using a long threaded rod, thus holding the WTC together to enable the management of pressure and to ensure the WTC does not ‘pop’ apart when the pressure builds up
• To enable a fastening system (yet to be designed) so that the whole unit can be slotted into place in the bottom of the boat, and held there.
• To allow for a screw on system to hold the top of the boat nicely in place.
A bloody fantastic idea, that I am sure someone has already come up with, as is always the case.
For the blog with pics and links view here.

LA Class Scratch build using arduino and pistons

LA Class Scratch build using arduino and pistons

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