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Author Topic: Hamina Class Missile Boat 1:28 Scale  (Read 53556 times)

Martin [Admin]

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #175 on: February 07, 2010, 10:02:22 PM »


Model bellows look very untidy and terribly out of scale on most model boats Harrison and they look terrible after a
while with all the gunk they collect from the lake. I like the Robart ones, with your skills, I'd wager you could do
much better than bellows
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tonyH

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #176 on: February 07, 2010, 11:08:57 PM »

Very true what Martin wrote. Have you got the space on the transom to reverse the bellows and have them on the inside?

Or could you use Bowden cables through greased polythene tube for the steering?

Tony
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #177 on: February 07, 2010, 11:42:07 PM »

Hi Tony,

yes, these look great.. I guess petrolium jelly sits nicely in the grooves..
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #178 on: February 15, 2010, 09:55:12 AM »

Does anyone know the length and width of the Robart spars, also the hole size for the fixed part?
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #179 on: March 20, 2010, 11:28:07 AM »

Well, it's been more than a month since I have been able to do anything on the boat  :((

Work has been quite demanding of my time.

I'vce ordered a set of Robart spar thingys to measure off and hopefully I'll be able to model them in to the design over the next week, if I get some time away from work that is.

I'm still aiming for a hull water test run this summer...
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colin-stevens

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #180 on: March 20, 2010, 03:48:07 PM »

subtech do a nice line in water proof seals for control rods. basically a turned brass cylinder with a o ring inside. work for subs, very tidy.
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hollowhornbear

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #181 on: April 23, 2010, 11:49:47 AM »

any news, hows it going or not?
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #182 on: April 23, 2010, 12:24:24 PM »

Hi,

I look at the gun on my desk every morning and I can't wait to get back on to getting the hull finished, I'm quite bogged down with work at the moment but things are looking a bit cleared towards the middle of next month.

I have some waterjet cutting that needs doing pretty soon so I will try an coinside that with having the hull bulkhead designs ready for cutting.

Thanks for keeping track of my build
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #183 on: April 29, 2010, 03:16:22 PM »

It does feel good to get back on to the build, I would very much like to see some sea trials of the hull this summer.

Thanks to Martin for the info on the 'Watertight Output Bushings' so Robart call them... Whats wrong with 'Plastic Pushrods' or 'Plastic Bellows', anyway, only Robart knew what I was talking about and I've got some on the way... The chap did say that he wasn't sure if they still made them before finding some... So I purchased twice as many as I needed just in case...

Lucky for me he had a ruler there and got all the important measurements, I've used the photo for the rest so it's not slowing things down.
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #184 on: April 29, 2010, 03:36:52 PM »

The Bushings are mounted in place, all I now need to do is work out how I am going to orientate the servos.
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #185 on: May 01, 2010, 11:22:00 AM »

I've just finished all the inside servo mounts and linkages which I'm quite happy about, I should be able to print the servo rod profile on to a piece of paper and bend them pretty precisely.

Once I've done the outside linkages, I'll move on to the deck and fixing points for all the other stuff which will need to be mounted inside.
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derekwarner

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #186 on: May 01, 2010, 11:52:24 AM »

Harrison... I have watched in awe for many months with your CAD-CAM drawing skills  :-))

However I do not understand how you plan to achieve the many linkage alignments that have been shown in perfect symmetry & defined lengths without provision for adjustment in each connecting rod in their respective longitudinal plane ........

It is the pitch of the threadform & the non consistant starting point of the thread that creates this issue.......Derek
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Derek Warner

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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #187 on: May 01, 2010, 11:58:47 AM »

Hi Derek,

All the rods are threaded, I've not shown this to reduce the demand on the PC. There needs to be very little requirement for adjustment as the accuracy of the cut parts will be less then 0.1mm.

I am able to move parts around which are mated to others, I've not been able to show this in pictures but when one part is moved the parts mated also behave exactly as they would in real life. This is called physical dynamics, I can also simulate gravity and perform fluid simulations which may be useful later when I start to model the hull.
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #188 on: May 01, 2010, 01:27:22 PM »

I've just finished all the outer linkages, there really isn't much space between the hull mounting and the control points to play around with. Definitely not enough space to have to ball socketsback to back, which is a bit disappointing.

I'm hoping that there will be enough adjustment on the inner threaded robs to take up and free movement outside, this isn't really an issue on the bucket control as I will only be using forwards and reverse in farmost position and then using the drive to vary thrust as required for meanovering.

The linkages my need to be revised if they are unable to handle the force of the water from the drives, I expect that some real world testing will be in order.

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andyn

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #189 on: May 01, 2010, 01:37:33 PM »

I think the linkages will be fine, but I'm more worried about whether you'll get the range of movement on the bucket you need.
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #190 on: May 01, 2010, 01:47:44 PM »

I think you may be right about the movement, perhaps a larger servo horn is required for bucket control.

Steering movement seems to be perfect so there should be maximum torque available.
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #191 on: May 01, 2010, 01:50:35 PM »

It may even be the case that there isn't enough bucket movement due to the length of the Robart bushing....
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derekwarner

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #192 on: May 01, 2010, 02:19:24 PM »

Thanks Harrison......my apologies  :embarrassed: ......I did not explain my question clearly

1. if I could assume you are using typical DUBRO type components
2. if I could assume the chosen size for thread form is 2-56 UN.....

Then we look further.......2-56 UN thread form is 0.072"diameter x 0.0125"pitch

3. accordingly to have two 2-56 thread forms cut into two individual component rods could @ a worst case = 0.025"...or 25 thou per linkage joint out of symmetry

Would this lead you to have six individual servo functions each with the potential of 0.025" imbalance & resultant chatter?....Derek  >:-o
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Derek Warner

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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #193 on: May 01, 2010, 02:28:47 PM »

I think you've missed out the servo gear movement  :}

I'm not sending it to Mars, I expect the MG995's to have more than enough power to keep sufficient tension on the linkages to ensure the only noticeable movement or chatter will be within the servo gearing.

As long as all the main hardware components are in place, I am sure that there will be room for any refinements that may be required after testing.
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derekwarner

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #194 on: May 01, 2010, 02:48:25 PM »

Harrison......I am not really qualified to offer further comment  {:-{, however our member FLJ.....may take the challenge & offer a professional comment based upon the fundamentals of accuracy in multiple mechanics when coupled/linked directly to electronics........Derek  :-))
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Derek Warner

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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #195 on: May 01, 2010, 02:59:35 PM »

I'm not entirely sure what you mean by "coupled/linked directly to electronics", there will be a limitation on the resolution of the ADC within the microcontroller inside the servo reading the feedback potentiometer. This will restrict the number of points or degrees of movement.
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #196 on: May 01, 2010, 03:06:13 PM »

It may be a good idea to present any suggestions in a way which can be clearly understood by all potential veiwers of this build, so as not to loose thier interest.
 
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #197 on: May 01, 2010, 03:15:39 PM »

Here are a couple of pictures of the boat as it currently looks (without the Mini MK111).
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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #198 on: May 04, 2010, 09:24:20 AM »

I've had to add a couple millimeters to the height of the aft most bulkhead as there is only just enough space between the hull and the deck for the control servos.

To keep the flat deck profile, I have had to add decreasing heights to each bulkhead leading up to the bow.. A very time consuming process due to the method in which the bulkhead profiles have been created (from cuts in the solid hull), it was also very boring.

I spent a good part of yesterday trying to figure out exactly how to fix the superstructure to the hull bulkheads and deck, it needs to be strong but I would really like to get the hull fabricated and start some testing.

Something else which sprung to mind, was having some 'D' link type holes sticking up from the deck at four points so that carry handles can be attached with  clips, this will also be very good for storing the boat up out of the way and strapping it down to the bike trailer which I intend to get for it.

I expect that I could add them to two of the bulkheads before and after the main superstructure and they would protrude form the deck, this then brough me on to the idea of having similar type fixings for the superstructure. I could put a good watertight connector on the deck undernear where the structure would sit and it could connect to the bus which (if you've been following the build) is a common control bus providing power and control to all systems with an unlimited potential for expension (well, 65,335 possible addresses).

I'm still unsure exactly how the deck will be secured, as it is 1800mm long it will need to be split up in to sections. This is not ideal, as sealent will be required at each join. Access panels are also something to consider, I was thinking that I should use the same type of system that seals the deck.

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Harrison

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Re: Hamina Class Missile Boat 1:28 Scale
« Reply #199 on: May 04, 2010, 11:10:19 AM »

I think that ten fixing points should be sufficient for the superstructure, as the line where the hull meets superstructure is perfect I would like to avoid anything other than a finished an painted mate. This will of course mean that it will not be removable at a later date, but as this is also the case for the hull and bulkheads I don't see too much of an issue.

I'm going to put some additional holes under the main carry holes so as to sandwich the bulkhead between two stainless 'D' plates which I will have cut, this will then take all the ware from the carry hooks.
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