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Author Topic: Mobile Marine Models FT-X - BUILD  (Read 7746 times)

F4TCT

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Mobile Marine Models FT-X - BUILD
« on: July 02, 2017, 03:01:31 pm »

Hi all,

The build is hosted on my website but thought I would also list the build here.

I've had this tug for just over 3 years now, having waited over a year for it and despite being told 6 weeks from time of order! I have recently purchased a small 2nd hand lathe which has allowed the build to progress somewhat.

I have taken great inspiration from C-10, a member on the tug forum who has also built the FT-X. Many thanks to him for his excellent build.

The build progress shown, is how it is; mistakes and general worts n all.


Dan
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F4TCT

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Re: Mobile Marine Models FT-X
« Reply #1 on: July 02, 2017, 03:06:58 pm »

The bottle on the rear deck or seen in the photos is a big 5 Litre one to show size comparison.



The bow thruster itself has a diameter of 30mm. These were installed during construction of the boat by MMM.









These are the drive motors. The are best run on 24volts and appear to be similar to ones used on mobility scooters. Plenty of torque which is what a tug needs.



Some of the the other running gear. The prop shafts themselves are a solid 8mm (which again is unusual - given the biggest is normally 6mm) all made by MMM. The kort nozzles are 90mm diameter.



The props are casted by the prop shop and are a small fortune (100 for the pair). Prop shop props are generally known as the best on the market.


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F4TCT

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Re: Mobile Marine Models FT-X
« Reply #2 on: July 02, 2017, 03:13:07 pm »

The first job was to install the running gear. An age was spent carefully marking out where holes should be made. You cant really rely on the shape of the hull itself as for example, on the inside, the thickness varies only slightly but could throw the kort out - hence the little jig assembled to keep both korts on the same vertical and horizontal plane so to speak..





The assembly was glued into place with 2 hour epoxy and left to set overnight. The kort assembly was then fibre glassed into place for extra security. At this stage they would have to be cut out of they needed to be removed - measure lots of times and cut once!



Couplings are needed to connect the shaft of the motor to the prop shaft which turns the prop. Getting 8mm couplings in the model world is seemingly impossible, given the largest is 6mm for the standard m6 shafts which you see on large lifeboats etc. MMM make their own safety couplings which is essentially a piece of hose, some turned brass and these are connected with 1mm dia brass rod. The idea is that if the prop were to become fowled, then the coupling would break instead of the motor receiving a lot of stall currant. I absolutely cannot stand them, however its proven very difficult to get hold of commercially available ones and so these will have to do.



The FT-X really is best used with 90mm korts, however the bottom of the nozzle sticks well below the keel. This doesn't make sense to me and whilst the korts would need a big knock to hurt them, I felt it best to try and eliminate the issue by deepening the keel. This was done by rough cutting some 3/4" solid oak into shape and then scribing the outline. This was then cut down further and fettled with a sander. Fibre glass filler was used to secure the oak to the keel and once set, normal car body filler was used to fill in the gaps to achieve a nice finish.





And finally all smooth with a quick coat of Halford's primer to show any hi/low areas.



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F4TCT

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Re: Mobile Marine Models FT-X - BUILD
« Reply #3 on: July 02, 2017, 03:22:22 pm »

Ok so this is where things start to get serious. Annoyingly I feel the shafts are a little to short as the motors and mount practically sit on the bottom of the hull with no apparent easy solution to secure them. A belt drive could be used (as i had to in my other tug) however I have slippage issues and its generally not very good. The shafts should be as close to the same horizontal plane as the waterline is, however its simply not possible in this boat without radical work. The angle of the shafts affect attitude of the boat in the water under a lot of power. I found some right angle brackets laying around and decided this would be the way forward. I chocked the motor assembly (which must weigh 7-8kg) so the shafts are in line and marked out drilling holes. M4 nuts and bolts were used to secure the angled mounts to the motor mount.



When satisfied everything was perfect, the fibreglass filler was applied under and other the brackets to secure them to the hull.





The aft part of the prop shaft requires fixing to the hull to ensure there is no vibration. MMM supply a white metal casting for this, however at first I didn't want to use it. Instead I wanted to make my own A-Frame which would in theory provide more lateral support, but with the awkward sizes of shaft casing used versus the sizes of brass tube available, I struggled to get something which would slide over the shaft. I wasn't prepared to braise the bare shaft onto some flat sheet brass - which would then be bent to form a V shape and secure inside the hull, due to the temperatures involved and how the temperature affects the brass. A standard blow torch with normal propane will melt brass of this thickness quite easily and taking the brass to red hot which is when the braising rod is introduced to join the surfaces, its metallurgical structure changes making it very easy to bend.I decided to just go with the white metal fitting for ease. It had roughly 0.5mm play over the shaft which allowed me to use metal epoxy to secure it to the shaft using a rotation of shaft method to ensure the epoxy was spread inside. Once dry and solid, some PVA was used to dress the seam and blend all in together.





Holes where then drilled into the hull along the centre line of each prop where the support bracket would stick through. This was then fibre glassed to the bottom of the hull along with the shafts themselves.



The opening was then filled with car body filler, sanded and then given a quick coat of red.



The external part of the shafts can be secured using normal car body filler, the insides were secured using fibreglass as this makes for easier sanding. The area was given a quick paint and a few blotches were present which were then dealt with by some squadron green.



Annoyingly the props seem to hang roughly 1mm off centre - not a lot but when the kort turns over the prop, they practically touch which is not good. Luckily it only seems to be a vertical issues rather than horizontal and so the issue can be resolved by simply using a washer or two to space the kort lower.



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F4TCT

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Re: Mobile Marine Models FT-X - BUILD
« Reply #4 on: July 02, 2017, 03:27:51 pm »

Whilst I decide upon other options for the boat and design an electrical bus system, I set my mind to the wheelhouse, one of the feature points of the model when complete.As you see, this is the bog standard moulding for the wheelhouse - which is fine, however it makes life difficult to detail it.



The idea is to have a fully lit interior with all the usual electrical panels etc. The wheelhouse therefore has to be a modular type of system which simply fits together and I for one cannot be bothered to fiddle around with plasticard trying to make it fit. Im getting into Autocad and basic 3d modelling to help with boat boats. 3D Printing is the next step. I set about designing a decent and accurate looking wheelhouse in google sketchup.













The panels were then placed into turbocad (an easier version of autocad). They need to be orientated to the 'top' plane which then allows for them to be laser cut or water jetted which is the plan. At this stage, the vendor in which I plan to use for the cutting, seemingly cannot see the drawings on his software (yet i've sent things to him before and its been fine).





There's still an awful lot to think about - working radars, working nav mast lights on separate circuits for different towing lengths etc, interior lighting, exterior lighting, crew figures (got a really neat idea for this one) internal 3d parts such as the captains chairs, all wiring must be hidden or what is shown, must be scale.Anyway, we will pick up the wheelhouse parts at a later stage of the build.

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Re: Mobile Marine Models FT-X - BUILD
« Reply #5 on: July 02, 2017, 03:45:23 pm »

I did last night turn my attention to the winches. Tugs generally have 2 main winches - one fore and one aft. There is no off the shelf solution for a working tug winch so sadly they will have to be built from scratch.I have never built one before but it does add severe complication to the build in the way of physically cutting the materials.The main construction consists of 3mm, 2mm brass sheet aswell as bearings, pulleys, belts and 8mm thick brass rod.The brass rod will need to be turned on a suitable laithe - some thing i don't have, The brass sheet needs to be cut into exact circles and other shapes - again I don't have the gear, Thirdly the bearings need to be installed but i have no clear way to secure them...The pulley and belt will be connected to a geared motor directly under the deck which in turn will be controller with a speed controller, probably on a second remote control handset.









This is the simplest solution I could come up with and should be more than robust enough to class as a working winch.

Most of the boat, certainly all below the waterline has been sanded down, filled where necessary and washed off. This can be painted when I get myself to Halfords and get some filler primer. I need some acrylic matt/flat clearcoat lacquer in a large rattle can if anyone can suggest where i can get one from. The halfords stuff is a shiny finish and would rather have a matt anti-foul.

Annoyingly there has been a slight oversight, mostly because i'm stupid (see my footer) - It seems the shafts are around 3mm to far aft which then makes removing the kort nozzles impossible.

This adds further complication when trying to paint the bloody things, never mind.

Electronics in the way of speed controllers and power boards have been ordered. Still got a lot of working out in regards to weights, sizes of batteries before they can be ordered. They are going to be atleast 9KG each and I need two + even more ballast aft.



I managed to get along to halfords and picked up some etch primer, 2 cans of red primer and some lacquer.Etch primer is mainly used for metal, although it will work on GRP. Its certainly better than normal primer anyhow. The boat was given a coat which was allowed to dry.



The spraying of the red primer could begin. This shows what one can covers, there were a couple of coats.





The next area was sprayed, so in total, 2 large cans of red primer (each 500ml) have gone onto the hull.









Not exactly the work of Van Gogh... but does the job.

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F4TCT

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Re: Mobile Marine Models FT-X - BUILD
« Reply #6 on: July 02, 2017, 03:51:25 pm »

Just like a well written story, the moment the spray can emptied itself, the post man delivered the electronics.ACTion electronics was run by Dave Milbourn until a few years ago when he sold it to the component shop. Both are a great people who pride themselves on top service. Products could be sent as a kit form where the buyer could solder everything together for that extra feeling of accomplishment or they would normally be supplied as per below... Not shown is another model of speed controller which is for the bow thrusters. ACTion do not make a suitable model to control them in the manner needed.What we essentially have here are 4 speed controllers (they alter the power to the motors depending on where your throttle control its on the transmitter) and 2 servo morphs. These allow a servo to be controlled and tuned to the users requirement. For example, the amount the servo turns can be controlled, different amounts on left and right and also the speed of the servo. Very useful for my kort nozzles as they need to be tuned to not hit the shaft! 2 of the speed controllers are big ones for the main drive motors, and the other 2 are for the 12v system which will power the 2 winches.



Excellent instructions are included and are available for download also...



I have used ACTion gear in all of my models, however my main gripe with the products is the need to cut out your own protective box. I meant to sue Dave a while ago for the vast array of injuries I have sustained over the years in simply making a hole in some plastic, but never got round to it. I have almost drilled into my testicle once (don't ask) - yes those nasty sort of injuries... Plus the sheer amount of black swarf which is produced gets everywhere.





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Re: Mobile Marine Models FT-X - BUILD
« Reply #7 on: July 02, 2017, 04:00:58 pm »

I have just came back to this project after a rather long break (raising a family and buying a flight simulator and re-decorating 2 houses etc etc). The tug has been in storage and has unfortunately suffered some damage. I also realised I had made a slight error in respect of the positioning of the korts. My idea was to make the korts removable for whatever reason but they catch on the aft end of the shafts. There is no way to solve this other than to somehow remove the korts and start again. Its either the korts or the shafts.... I don't fancy doing the latter as this will no doubt impact space inside the tug for batteries etc.



Here's the damage. I don't believe the knock given to the kort was particularly excessive which worries me a little. I think the shaft could have been burried deeper in the resin cast.





I remember at this stage I really had to start making decisions in regard to internal fit out. I did however have a shopping list with links saved and I set about ordering the necessary bits from component shop, always an excellent service with them. One thing I wanted to do previously but never could frankly be bothered is to remove the baseboard which came with the tug. I will replace this with a bigger version in order to cope with the heavy batteries and aid in the mounting of the motors.



Well the delivery having finally arrived, mostly consisting of small electrical items although now we have the batteries, this will be a great help in order to plan the internals a little better. I did remember weighing this tug down in the bath and the batteries should make a very nice job of this. The tug will have to be transported minus the batteries as its heavy enough as it is...



And the batteries in a little more detail...



I then turned my attention to removing the mistakes and anything else which was going to get in my way. Firstly the board in which the bow thruster motors sit on was removed.





I then started on the korts. I was petrified of going through the main bulk of the hull with the cutter. Luckily I didn't and I will remove the excess GRP with a sander and get it back to a nice flat level ready for the new replacements which have just been ordered from Mobile Marine Models.





Sanding still yet to take place.



I managed to peel most of the kort assembly off with a flat screwdriver and by making small slices using the cutter.



The cutter I used was one of these. It cuts using essentially vibrations and comes with many different sized cutters and shapes. Very very useful and I fail to see how this job could have been done without it.



In regard to the korts themselves, I was only going to order one replacement but then remembered I needed the whole mounting assembly anyway so I ordered a pair. Just aswell really as I found damage on the other kort. They are both currently set aside while the epoxy dries having assembled them.

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tugboyben

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Re: Mobile Marine Models FT-X - BUILD
« Reply #8 on: July 02, 2017, 04:01:49 pm »

Great work
I like the bow thruster idea Have you been able to test it out


Jason
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F4TCT

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Re: Mobile Marine Models FT-X - BUILD
« Reply #9 on: July 02, 2017, 04:08:06 pm »

I decided to start on the baseboard on which the batteries will sit. A rough template was made up out of cardboard and then trasnsfered to some 12mm MDF and cut out.



I'm thinking something like this for the layout. Obviously I will have another battery on the left side. Its pretty much as I drew this out over a year ago. Getting the shafts lined up correctly again has been a bit of a pain and infact I might start again in regard placement of the mounts. I think there is a slight twist on the way I have installed the motors.





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Re: Mobile Marine Models FT-X - BUILD
« Reply #10 on: July 02, 2017, 04:17:13 pm »

Ok some more positive progress and news atleast.
Today I met up with my friend Mike Pendlebury who's actually building my 1/12th Trent Lifeboat. They guys an absolute genius. I mentioned the issues I've been having with line up of the running gear and we got the tug on the bench and had an in depth look. My forward motor mounts were fine however some adjustment was needed on the angle at which they were presented. The MDF board was first glued to the base of the hull.
The motor mounts were in the wrong position previously so new holes were made in order to be able to sit the mounts onto the MDF board. They were then screwed and fibreglassed in place.
During the previous few days of going to Mike's, I was browsing Mobile Marine Models website and noticed I did infact have the 'Kort Eze' shafts. The chunky bit on the end of the shaft is designed to come off in order to remove the kort nozzles themselves. We were puzzled at how they came off but after a phone call to Bryan at MMM, he very helpfully sent us an email containing the instructions (which I never was given when I got the tug). It's a simple job of getting a suitably size spanner which fits over the main shaft tube but not the chunky bit and hitting it with a hammer.
The Kort Eze then came away with very little issue.
And a closeup of the Kort Eze.
If you remember the jig I made using bits of wood and clamps at the start of the build, well we essentially re-created this on Mike's workbench in order to line up the korts. This time a reference could be taken from the end of the shaft tube as the Kort Eze had been removed. It was then fairly easy to work out if the korts would be able to be removed. We opted to use the existing holes I made in the hull however the gap between the front of the kort and the end of the shaft tube was a little larger than what it should be however its a small compromise. Atleast there's plenty of room to get the things out should I need to.
And with the Kort Eze loosely pushed on...
We carefully reset the jig to ensure both korts had the same angle and spacing between the internal surface and the props. The supports were tacked into place with superglue and then fibre glassed in when we knew it was correct.
So what went wrong?Well, firstly one prop shaft tube is around 1-2mm forward of the other one. This could be down to a small difference in the shaft length however its not an issue - anymore!Secondly, the hull shape is not entirely symmetrical on each side thus throwing measurements out slightly.Thirdly, the castings of the kort nozzles are simply not right or consistent. It's very much a case of luck to get the shaft perfectly perpendicular to the rest of the nozzle during assembly. The internal surfaces of the nozzles are seemingly not uniform given when they turn, they still catch on the props despite them being perfectly centered. As a result, some time will have to be taken to sand off a considerable amount of material in order to stop this. More on that in another update.On the whole a very productive day which now will allow me to progress with the build.Next steps are to fettle the korts, repaint were necessary, install korts and oil up the shafts and running gear and finally start on electrics.
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F4TCT

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Re: Mobile Marine Models FT-X - BUILD
« Reply #11 on: July 02, 2017, 04:23:30 pm »

Moving forward... I've not really accomplished a great amount to be honest but have instead been taking care of some smaller jobs in between the time I have free.Firstly with the korts now sorted, I decided to give the tug a bath... I wanted to see how much ballast is actually needed to drop the boat onto the waterline... I installed the spare (broken) kort while the paint was curing on my other new one.
The motors are now installed in the tug and will be staying there. They help the ballast but not a great deal. The stern:
The bow, And yes... water level is below the bow thruster port...
er... yes it just about fits in the bath. Please excuse the horrendous black tiles, they were there when I moved in. The batteries were then placed into the rough area they will be located and positioned to equally balance the tug in the roll.
Results... Well the waterline at the bow now sits just below the bow thruster port and the stern has lifted even higher as expected. I have some lead weights I put in as a laugh, possibly in the region of 20-30kg aswell as all of the electronics and motors for the winches and she still needed more. I need a way to be able to remove weight from the stern without using the read deck hatch as I have plans for this. I feel I may have to compromise somewhere on her ride height here. I guess it depends on the mission, she can sit high but this may incur instability issues etc. I'll wait and see what the sea trials bring.
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F4TCT

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Re: Mobile Marine Models FT-X - BUILD
« Reply #12 on: July 02, 2017, 04:29:19 pm »

I mentioned the korts a little earlier. During my time at Mike's, I realised we didn't fully screw the shafts back into the motor couplings. I did this and tried the korts over the props and they now seem fine. There's one small area on one which looks a little bit too close to the blade - proving what I said earlier. Anyway, I use a flap wheel on the kort and ground the affected area down.



This was then repainted. While the korts were off, I decided to spray up the anodes in Mr Hobby's aluminium. I first had to mask them off. I used the lighter tack frog tape as a test, having only used it for house decorating.



And the finished result...



I have spent the evening just before this update doing some small soldering jobs on the motors. Standard Tamiya connectors are used here. Port side its under normal polarity for motor direction and Starboard is reversed and so to make things easier, the wires were reversed on the plugs so everything is normal upto the female connector.





Having just installed a new utility room set of units, I have plenty of cardboard packaging left over. I decided to get one with making a stand for the tug. I normally hate this task to be honest. The hull shape is pretty simple on the FT-X and so I tried laying the boat on its side and simply scribing the shape onto some cardboard.






This will then be transferred to some 5mm MDF type material (off cut from a kitchen unit back) and cut out. This will then be shaped to fit and then used and stored as a template in order to make the stand out of some bulkier material.
I managed to quickly build a stand just before Christmas.
It will atleast keep the boat relatively level but most importantly, stable.
Not had a great amount of time to work on the boat since I built the stand, but today I decided to press on with installing other parts of the battery compartment.
The next pressing matter is the design and installation of the electrical system. I'm not very good at imagining how this is going to look and this is what I have been thinking about for months. I think its time to just get on with it and do the best I can. I want it to be neat and reliable.
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Re: Mobile Marine Models FT-X - BUILD
« Reply #13 on: July 02, 2017, 04:42:01 pm »

I decided to utilise the space in the bow to mount some major components. The first stage was to find the shape using card in order to use this as a template for some more MDF at a later stage.



Unlike any of my other builds, I want to make the components sectional in the way that I can literally unscrew a shelf full of speed controllers etc, hence the need for so many tamiya connectors.



In other news, I today have ordered the pulleys and belts from Motionco. These are for the bow thrusters, having decided where they will sit in the bow. More on this in a future update.


The shelf for some of the electronics was made from 6mm MDF.



A support for the shelf was also cut and fibre glassed to the inside of the bow.



The hardest bit for me was deciding upon the layout of the electronics. Historically i've always tried to make them look as neat as possible but it's always somehow got out of hand and started to look like spaghetti. To explain what components are being used here:The black things at the back are speed controllers, They are ACTion Electronics P98's. One for each motor which will be controlled via a single throttle input. There really is no need to tank steer this thing with bow thrusters and movable korts.


The fuse board is an ACTion P102. It essentially has three different circuits on there which are all fused. This adds a great level of protection and fault tolerance. Group one is the left green socket. Group two is number two and three sockets from the left and finally group 3 are sockets four and five. If say the port motor fuse blew (for example the prop was fouled on something, the instant it is brought to a halt will cause a current surge. If the current is more than the designated fuse then it blows to protect the speed controllers etc. It then allows the boat to limp home on the other motor.







And finally the Electronize FR15HVR-AN is another speed controller which is responsible for the bow thrusters. It was explained by the manufacturers of the tug that if a standard speed controller was used in the normal way, then the sheer of the thrust off them in tests could flip the tug over. This is because the tubes come out of the bottom of the tug and the sucking and pushing combination massively upsets the tug. The only way round this was to use a specific type of speed controller wired so that there was constant positive current to the motors and the blue and yellow wires which were typically both connected to a single motor to determine forwards and backwards operation were instead used as switching negatives. The wiring is shown below.







And underneath the shelf the wires are connected using choc blocks. The two female connectors will plug into each respective male connector.



A preview of how the shelf is looking.



A On/Off switch was added and soldered in on the underside of the shelf. This will switch power on the main drive of the tug, essentially everything shown above.



Meanwhile the BEC wires were coiled up under the shelf also as they are not needed. The BEC is the Battery Eliminator Circuit. It will spit out 5 volts to power the radio reciever instead of having to use its own dedicated 5 volt battery. The ends will be insulated when I get some small enough heat shrink.



And the Switch on the topside.



Some cables were made up to connect the speed controllers to the motors.





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Re: Mobile Marine Models FT-X - BUILD
« Reply #14 on: July 02, 2017, 05:04:21 pm »

In other news, the motionco pulleys arrived.




The 6mm bore pulleys attached to the motor shafts with no issues.



Connecting the pulleys to the thruster shafts was a different story. The shafts have an M5 thread on the end however the next smallest bore I could get was 3mm. Therefore I planned on drilling out the bore and tapping it myself. I found a spare of adjustable plumbing grips to have the same locking thread as the pulley making it a secure holding to combat the torque of drilling.





Sadly, the drilling seemed to be very problematic as all I have is a hand drill. The drill itself is good, however the issue I feel is me keeping the thing straight. This is were a pillar drill would be very useful. I do plan to get one as soon as I sort my outbuilding/workshop out. A lathe and milling machine is on the cards also.

The bow thrusters were mounted on some 6mm MDF. This would allow me to position the motors to gain the correct tension on the belt and then finalise the position with a screw.



At the end of the last update, I was stuck with threading the pulleys which attach onto the prop shafts. I mentioned my issue on a model forum on which I am a member and Trevor kindly offered to bore and tap the pulleys for me. I got them back a few days after sending and so the motors could be installed.





The main prop shafts were oiled and finally installed in the tug. The kort-eze was then tapped back on and thus completing the main drive. The motors were ran out of water for around an hour on low speed with plenty of lubrication added. This allowed me to experiment with the various programs on the speed controllers. No pics as there wasn't much to see. As part of the previous process, the korts themselves were installed. They came with some resin arms which would normally connect via a rod to the servo. These weren't needed and so they were set on fire in the garden....... for a very good reason... They contain a brass sleeve in the middle which would act as a secondary securing device for the korts.




I intended from the start of the build to use pulleys for the kort system. The main kort shaft is 8mm dia and the only pulleys which I could get for this were these larger type, again from motionco.



I obviously also needed a pulley for the servo. I found them quite hard to find but I tracked down some brass servo fittings which featured a 6mm bore in the middle. This combined with some 6mm brass rod and the bore reducers which I ordered with the pulleys should give me a way to mount the pulleys.





The brass rod was forced into the bore reducer with a vice.



And finally the pulley was attached to the kort shaft.



The next stage was to build a suitable and secure mount for the servos and put the servos in the correct place to achieve the correct tension! The bottom line is I managed to do it first time, somehow! It all just seemed to work and the tensions are perfect. I essentially started with two bits of MDF and I secured one servo directly to it and slipped the belt on and held this under tension. I then propped up the two bits of MDF with servo attached and very carefully place the other servo on the 'frame' and again slipped the belt on. I gained the tension needed while still placing tension on the already fixed servo... when they felt right, I clamped the loose servo with my fingers and drilled directly into the MDF and secured it. The whole procedure was repeated with the two secure servos, to check the belt tension. It was perfect.The assembly frame was cut down tom size and this picture shows the setup hanging in tension.





The servos were given a more secure mount with nuts and bolts.





The supports were screwed onto the frame.



The whole setup was then secured to the tug hull with fibreglass filler. It was allowed to harden and then the frame with servos was removed.



I am using servo-morphs again from ACTion Electronics in-line with the servos in order to control their rotation speed and maximum throws so they don't hit and bang on the prop shaft. I wanted a place to locate these close to the servos and decided to make a separate mount which sits on top of the servo frame. Some 6mm MDF was cut to shape and securing screws drilled.



I checked and re-checked the clearance to lift the shelf which servo-morphs attached. I then secured the servo-morph boxes with superglue.



The servo leads themselves were then routed and tidied up by securing them to the servo itself.





The servo-morphs were then installed in their boxes and wires routed.



The setup was then installed in the tug. The frame holding the servos goes in first, then the shelf holding the servo-morphs is installed and the two wires connected. The belts can then be slid into place. This makes for a very easy and compact setup which can easily be removed.



I then put the tug back in the bath as I couldn't resist giving the motors a run in water. I weighted the stern down and the leaking began once again. I couldn't believe it. I dried the tug off and gave the kort brackets an over coat of normal car body filler in the hope this would stem any leaks. I have yet to test the repair but the picture above shows the difference of colour in filler.The next issue I found is that in testing, the BEC on the main board (Battery Eliminator Circuit) which pumps out 5 volts and is designed to power a radio receiver, struggled to cope with one servo alone, never mind two with a respective servo-morph. I then decided to use two separate BEC modules of which two models exist. One pumps out 5 volts, but its input voltage is limited to 12 volts. The other pumps out 6 volts, handles upto 1.5 amps and the input voltage can be anything upto 36 volts I believe. I have opted for the for latter model and they are on order. This will allow me to power the servos off a separate power bus therefore bypassing the receiver. The servo-morphs will still be connected to the receiver but only by the white or command wire. I still need a 12volt battery in which to run the lighting circuit off and may end up using that as servo power also, however the bigger model allows me to do as I please.

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F4TCT

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Re: Mobile Marine Models FT-X - BUILD
« Reply #15 on: July 02, 2017, 05:12:54 pm »

Time for another update, albeit a fairly small one. I've not had much time to work on the tug due to other commitments.Picking up from the previous update, the system was tested and I began to notice small issues. The servos we very glitchy and would simply not sit still, the RX powering them simply overheated (I expected this) and I wasn't really happy with the rigidity of the setup. I contacted Dave Milbourn, the former owner of ACTion Electronics. Daves a genius and he set about thinking of a new way to atleast power the system. He also suggested I swap the servos to a more known brand such as Hitec.Dave came up with the following electrical layout:



I had previously ordered some plastic pulleys from a robotics website, however they didn't fit on the old servos. As they were a Hitec fit to start with, they simply dropped onto the new servos. I also removed the brass collar (which had been set fire to previously) and turned the large alloy pulley upside down and secured it that way. There was a small height difference of around 4mm which was fixed by using some 4mm MDF as shims glued onto the servo frame supports.



I decided to move the servos a little closer to the main kort pulley, this also meant a new set of belts. I also made a new servo frame, using the old as a template. You can see one of the shims I spoke about in this photo.



This shows the harness Dave made.



I now have two options for power. I can run the system off a 6v BEC which is turn is powered off a 12v battery. Alternatively I can use a dedicated 6v battery which a switch harness on. The use of a powerboard in the first instance is fine, as the lighting circuit on this tug will be 12v, using 12v LED's.Upon testing the system, it certainly feels a lot more rigid and there's hardly any glitching. The small amount there is can be attributed to incorrect trim settings on the transmitter.

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T33cno

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Re: Mobile Marine Models FT-X - BUILD
« Reply #16 on: July 02, 2017, 08:45:13 pm »

A good days work just reposting alone  :-)
Thanks for sharing it is great to see and the photos make it real  :-))
I delayed posting so not to interrupt your flow  8)


My only dislike is the use of MDF which IMHO lets down terrific work .


Part II bring it on
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Stavros

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Re: Mobile Marine Models FT-X - BUILD
« Reply #17 on: July 02, 2017, 09:51:33 pm »

Can not agree more with you T33cno and another thing I hate with a passion is those choccy block connectors they will most definatly cause major problems in time to come....Either solder the wires together or use some decent connectors




Dave
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Re: Mobile Marine Models FT-X - BUILD
« Reply #18 on: July 03, 2017, 07:09:25 am »


Hi.
The last tug I built used motors with 8mm shafts, like yourself I'm not a fan of those couplings and I got in contact with SHG who made some up for me I think they were around 8-9 each if they are still going they are worth a call.
Dave B
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F4TCT

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Re: Mobile Marine Models FT-X - BUILD
« Reply #19 on: July 03, 2017, 08:06:41 am »

Thanks for the advice folks, I'll try and implement your suggestions over time.


I noticed some nasty noises coming out of the lathe and took the cover off to find the drive belt in quite a state. I have a new one on order which will arrive tomorrow.


I was wondering whats the best way to go about changing it?








Dan
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T33cno

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Re: Mobile Marine Models FT-X - BUILD
« Reply #20 on: July 03, 2017, 08:30:22 am »

I found the problem with MMM couplings is the gas pipe he uses to link the brass parts. As it came off a drum it resists being straight and causes vibration.
I used powerflex couplings from Steve at model boats bits dot com


http://www.modelboatbits.com/COUPLINGS/


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Re: Mobile Marine Models FT-X - BUILD
« Reply #21 on: July 03, 2017, 08:43:01 am »

Hi Andy, I've just measured the length on my MMM couplings and they are 80mm long.


I note on the website they are 52mm long.


I'm certainly not moving motors at this stage and so the solution my be to turn some brass in an effort to fill the gap.


I will order a set and have a play around.


From my early testing with the current setup, I'm not getting that much vibration, if any at all. however things do change.


Dan



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Re: Mobile Marine Models FT-X - BUILD
« Reply #22 on: July 03, 2017, 09:40:53 am »

To replace the drive belt, undo the retaining screws on the 2 intermediate gears, pull them off, slacking the motor mounting screws to give you some slack, remove damaged belt, replace belt and tension up......belt should have approx 5mm slack movement along its longest length, replace gears and away you go.
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Re: Mobile Marine Models FT-X - BUILD
« Reply #23 on: July 03, 2017, 09:47:24 am »

Cheers  :-))



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Re: Mobile Marine Models FT-X - BUILD
« Reply #24 on: July 05, 2017, 05:52:11 pm »

The new belt arrived and it was fitted to the lathe and only took about 5 minutes. A lot of worry over nothing. Runs even better now.





I did previously turn the so far 10,  rear deck hatch securing nuts last week. Today I drilled and tapped them to M4.








The lathe is a god send for simple tapping operations also. Using the tap wrench along with a live centre, keeps the thread arrow straight. I have ordered a spring loaded tap centre thing which I will mount in the drill chuck for future tapping.





The nuts were turned from 10mm dia. brass rod. The thinner sections have been turned down to 6.5mm to allow the brass tube to slide over. The tube will be made into the rear deck rails.


The finished nuts...











Over the weekend while waiting for the new lathe belt, I spent a lot of time lining up and measuring the rear deck hatch.


The main challenge was to ensure the hatch sat evenly between the rear bulwarks and so the securing nuts would sit evenly between the edge of the hatch and the raised area of the hatch.








There's just enough space for the 10mm dia. nut.








The holes in the hatch were all drilled and then the hatch used as a guide for the holes to be drilled into the deck.


I drilled one at a time and secured each hole with a temporary bolt while the other holes to be drilled, were marked.





The test bolts are 40mm long and this is were I'm unsure of which method to secure the bolts, will be used.


I dropped John a message who built 'Big Bertha' and mentioned in the first post of this thread, as this is an aspect of his build that I'm going to copy. I asked about how he secured the bolts and he simply screwed the bolts from the bottom of the deck and secured them with very thin superglue which was allowed to wick down the thread.





My idea was to secure the bolts in a length of 10mm thick wood and then secure that to the underside of the deck. I feel this method will be a lot more rigid, secure and prevent damage from knocks etc. The superglue trick can still be used to watertight the bolts. Stainless bolts will be used.










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