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Author Topic: HMS Lundon  (Read 18507 times)

SwedishProjectBuilder

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Re: HMS Lundon
« Reply #25 on: March 19, 2013, 10:33:16 PM »



I was sure I had ordered 4mm diameter pipes, but they needed some improvement.

Some drilling

Fixing edges




Still havent got rid of the paper that is left from glueing..

Still not sure how to construct the fitting for the push-rods that will make the rudders move.

I was kind of in a rush, therefor some bad pictures..




Forward ballasttank, pretty much done. Not entirely done, will make a small cut in the disc, where the engine support will be inserted to make the engine not roll. Bad explanation, sorry for that, hopefully wont take long until I can show a picture.





Small question:
I need help locating an electric engine for propulsion, 12-15V approximately, and as short as possible within reasonable price range. Preferably geared down to 4000-5000rpm.
Reasonable price, 15-30.
I know that the type I've used for the ballasttanks are suitable, but is there any shorter ones?
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Subculture

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Re: HMS Lundon
« Reply #26 on: March 20, 2013, 11:26:47 AM »

Sure about that RPM? I'd have thought 2-3000 RPM top whack for a boat that size, maybe less, depending on the propeller diameter and pitch.

Blower motor out of a car heater will run all day long direct drive on 12 volts- no gearbox required, and it looks like you have the buoyancy to support the weight of a can like that.

SwedishProjectBuilder

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Re: HMS Lundon
« Reply #27 on: March 20, 2013, 11:49:18 AM »

Sure about that RPM? I'd have thought 2-3000 RPM top whack for a boat that size, maybe less, depending on the propeller diameter and pitch.

Blower motor out of a car heater will run all day long direct drive on 12 volts- no gearbox required, and it looks like you have the buoyancy to support the weight of a can like that.


No Iam not sure about that RPM, unfortunately my knowledge about propeller rpm it limited..
I will use a 7-blade, brass, prop with a diameter of approximately 70mm. Pitch, not sure.


Thank you for the suggestion, will take a look at it.
Cheers
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Subculture

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Re: HMS Lundon
« Reply #28 on: March 20, 2013, 12:22:32 PM »

There are a lot of factors governing propeller RPM, Diameter and pitch of prop,  blade number and area.


However we can dial in roughly what we want if we at least know the diameter and pitch.


We know the diameter is 70mm. Optimal pitch is generally between about 1-1.3 times the diameter for electric powered craft. So working to the upper end of that 1.3 times the diameter is 91mm for pitch.


Converting that to imperial measurement gives 3.6". Assuming 25% slip we use the following formula for a 3000RPM shaft speed 3.6x3000RPM/1408= 7.6mph or a tad over 12kmh. I doubt you want that sort of speed, and it will take a lot of watts to push your boat along.


I would aim for 1500-2000RPM shaft speed.







SwedishProjectBuilder

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Re: HMS Lundon
« Reply #29 on: March 20, 2013, 08:22:16 PM »

Ohh, very nice!
Thanks for the help, Subculture very valuable information!


Cheers!

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Davy1

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Re: HMS Lundon
« Reply #30 on: March 21, 2013, 10:29:18 AM »

Just to help answer your question about motors and minimising motor length. This photo (if it appears - some time since I posted a photo on here. ok2 )
This shows the method I used on my British R class. The motor shaft points towards the bow. The reduction gears (if you want - notched drive belts used here.) give the necessary 3 to 1 reduction.
This arrangement drives a big sub (about 6 feet long) at a very good speed. (The originals were also fast!)
The shaft seal is rather hidden in the photo but is Simmering type seal. Worked very well for many years now.
David
 
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Davy1

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Re: HMS Lundon
« Reply #31 on: March 21, 2013, 10:29:44 AM »

Just to help answer your question about motors and minimising motor length. This photo (if it appears - some time since I posted a photo on here. ok2 )
This shows the method I used on my British R class. The motor shaft points towards the bow. The reduction gears (if you want - notched drive belts used here.) give the necessary 3 to 1 reduction.
This arrangement drives a big sub (about 6 feet long) at a very good speed. (The originals were also fast!)
The shaft seal is rather hidden in the photo but is Simmering type seal. Worked very well for many years now.
David
Sorry about posting it twice. The photo posting method worked too well!
 
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SwedishProjectBuilder

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Re: HMS Lundon
« Reply #32 on: March 21, 2013, 11:51:37 AM »

That all looks really good.
Maybe I will use the "belt-version", seems to be a very nice solution. I too will use one or two simmerings to seal the prop-shaft, they will be located in the smaller part of the brass pipe.

The problem I have is that I want to maximize the size of my ballasttanks. You see, the rods pushing/pulling the pistons in the tanks, cant go besides each other when in fully submerged position. If I have the shortest possible main engine I can move the rear-ballasttank further back and thereby I wont be needed to "optimize" the tanks (cutting the pipes and cutting the piston-rods).


Salvaged these from the old submarine. Will cut 2 of the 3 "arms" on each one of them.
Will be have to drill up bigger holes, but rather that then to make them smaller  :}
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SwedishProjectBuilder

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Re: HMS Lundon
« Reply #33 on: March 22, 2013, 10:30:10 PM »

Good evening everyone!
Is there any one who have found simmerrings for 6mm shafts for sale online?
I've tried to get in contact with a few companies, Trelleborg for example, but not successful yet..
Thanks in advance,
Cheers
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Subculture

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Re: HMS Lundon
« Reply #34 on: March 23, 2013, 11:01:15 AM »

These guys are good for miniature oil seals

http://simplybearings.co.uk/shop/Seals-All+Oil+Seals/c19_4463/index.html

Simmerring is Freudenberg/Simrit trade name for  oil seals. A lot of other companies selling these. if you want a genuine Simmerring, then norbert bruggen sells them in one off quantities, and BSL brammer in the Uk distribute them, but will only want to do business if you order a bunch of them ( eg. 25 or more).

Another alternative that works very well is to use an o-ring with a compression gland. Usually silicone o-rings are used, as they are soft and much more resistant to heat from any friction that might develop.

6mm shaft sounds rather big, 4 or perhaps 5mm would be more appropriate.

SwedishProjectBuilder

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Re: HMS Lundon
« Reply #35 on: March 26, 2013, 10:31:00 PM »

Thanks for the help!
Have now ordered 2 seal rings for the prop shaft.
Had some time to work the past weekend, some progress but also some set backs..
The brass outlets from the tanks are not as "watertight" as I first thought. Either I will make an epoxi solution or I'll have to remake them. (will try the epoxi solution first)
I accidentally broke the rod for one of the pistons.. Had not made the "trenches" for the O-rings deep enough and therefor the O-rings provided an awful a lot of friction which in the end (when I tried to take the piston out) resolved in the rod breaking.
Good news is that I have all figured out how to solve the problems and how to "fix it".
Oh, and the pushrods for the rudders are soon done. The servos is in place and all I need is some new linkages from engel-modellbau.
Also tried out the ballasttank motors, works excellent together with the gears and piston rods (except when the rods break)


unfortunatley I was so mad that I forgot to take pictures...
Will give you an update the next week.


Cheers
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Davy1

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Re: HMS Lundon
« Reply #36 on: March 27, 2013, 09:40:17 AM »

Sorry to see that you broke a threaded rod - a lot of force involved in piston tanks!
You may find that if the piston tank has not been moved for some days it is particularly stiff and it may be worth moving the gears by hand for a few mm, just to free it. (Lubricating the cylinder does not seem to be any help with this problem.)
If you are still having problems after you have increased the size of  the "trenches" you may consider:
- Removing one O ring (2 is a little over engineered, perhaps.)
-Replacing the O rings with the softer silicone O rings (usually red in colour)
Keep up the good work!
David
 
 
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Subculture

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Re: HMS Lundon
« Reply #37 on: March 27, 2013, 05:33:57 PM »

Recommendation is no more than 10% squish on o-rings for dynamic movement. perhaps the inside finish of the cylinder is a little wavy, and too low tolerance to enable 10% squish? If so you may need to look for a better piece of tube, or consider cup seals like Engel tanks. They are very large tanks you have built there.

In my line of work, we use a lot of pneumatic motors. These were traditionally constructed from cast iron, with nitrile rubber cup seals, and lubricated periodically with a mineral based oil. Despite frequent maintenance, they were often a source of problems, especially as they aged. A few years ago, the motors were re-engineered, with mainly aluminium construction, and Teflon (PTFE) coated cylinders. These have proved to be exceedingly reliable and need zero maintenance over their lifetime (which is considerable). I've seen companies that offer the coating surface, but I don't think they deal with the small quantities modellers want. Shame as it would make an ideal tube for piston tanks, with the teflon coating being self lubricating, waterproof and hard wearing, and the aluminium tube providing a nice concentric bore for the seal.

SwedishProjectBuilder

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Re: HMS Lundon
« Reply #38 on: April 02, 2013, 11:55:26 AM »


The teflon I find very interesting, will try to have a word with the teacher I had in an previous course I took, construction materials.
They are very large tanks you have built there.


Well, I've designed the submarine to be easily upgradeable in the future. I have big plans, turret mounted camera, long-disctance capacity etc.
Anyone have any suggestions about where to order a suitable brass-prop. except Engel-modelbau and Cornwallmodelboats?


Cheers
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Subculture

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Re: HMS Lundon
« Reply #39 on: April 02, 2013, 02:38:50 PM »

Prop shop make lovely investment cast props. not cheap, but lovely things.

http://www.prop-shop.co.uk

Davy1

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Re: HMS Lundon
« Reply #40 on: April 03, 2013, 09:49:59 AM »

With your evident metalwork and lathe skills, why not try making your own props?
You are not talking about a scale prop here (I don't think?) and you will save yourself a lot of money - for more partying!
The basic method is not difficult. A short section of brass rod in a lathe, drilled and tapped for a grub screw perhaps. (Or you can just soft solder it onto a brass prop shaft. With a hacksaw cut 3 or 4 slots at about 45 degrees. (Use the lathe chuck to get equal spacing's. ) 
Cut the blades from sheet brass (About 1mm sheet. Use tin snips or an old pair of scissors.)
Soft solder  or hard solder (better) the blades fitted in the slots.
Clean up and bend the outer blades to a flatter pitch (turn it by hand in the lathe chuck.)
I have used this method several times for Edwardian and Victorian props which are not available from a catalogue. Probably not the most efficient props but "model" props are never very efficient anyway.
You can also adjust the pitch easily to suit your motor/ desired speed etc.
David

 
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Davy1

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Re: HMS Lundon
« Reply #41 on: April 03, 2013, 09:50:26 AM »

Forgot to say that hard solder is better for the blades not least because you can then reheat the prop to re-anneal the brass blades if they start to get hard to bend.
David


 
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SwedishProjectBuilder

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Re: HMS Lundon
« Reply #42 on: April 06, 2013, 09:25:49 PM »

Thank you for the tip David!
Will probably buy the propeller though.. Would like to make one in the future, but till then I'll buy one.
Next update wont be until next weekend. Due to lots of other stuff, also still waiting on a delivery.


Cheers
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Davy1

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Re: HMS Lundon
« Reply #43 on: April 08, 2013, 02:23:21 PM »

Actually, some time after I had posted, I saw that you wanted a 7 bladed modern submarine prop!
That would be a very tall order to make. Best to buy that one commercially!
 
David
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SwedishProjectBuilder

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Re: HMS Lundon
« Reply #44 on: April 24, 2013, 09:54:15 PM »

The slightly bigger sister ship has "unfortunately" stolen quite a lot of time and therefor not much have been done the last month...


I have received a few parts for the rudders and also the main-engine. But as for now the submarine will be on hold for a few more weeks...
cheers
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SwedishProjectBuilder

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Re: HMS Lundon
« Reply #45 on: November 01, 2013, 10:47:59 AM »

Hello,


Finally my interest for the submarine has come back!
With new knowledge and courage, the project will carry on.
To begin with:
New pistons will be manufactured with deeper seal cuts and stronger fixation to the threaded rod, the tanks will be shortened by a few cm each to make extra room for the rudder-servos and the molding of the aft will begin.


I'm glad to be back in business!
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SwedishProjectBuilder

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Re: HMS Lundon
« Reply #46 on: November 12, 2013, 11:36:52 PM »













The servos is not fastened yet, either small screws will be used or they will simply be glued onto one of the "discs". I do prefer the screws but will it hold, remains yet to be seen..



The main-engine will be moved further to the aft, about 1-2cm will be gained.
And the mount will probably be re-made into something a bit better looking.






Next up will be the renovation of the broken piston, I have decided to use the old pistons and instead remake the mounting to the geared rod.
This time much more strong and reliable.
What i did realize, after undergoing a semester in solidmechanics, was that the mount I had made, by drilling a hole in the rod, severely damaged the rod. (quite obvious when you think about it, but it didnt made me worried at the time...)


Cheers
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SwedishProjectBuilder

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Re: HMS Lundon
« Reply #47 on: November 15, 2013, 12:15:24 AM »

So, the broken piston is now fixed, picture coming soon.
Also, the tanks are sealed and actually work.
Slight issue though, as for now (with the current aft engine mount) the tanks only can take in 0,6 liters each.
And I would like to be able to have 1 liter in each. For every cm i can gain it will give 0,0252 liters. Roughly 15cm/tank extra will be needed.
Either I buy myself a longer pvc-pipe and extend the sub. Or I could remake one piston with two rods to make them go besides the other pistons rod. Which would require 1 more gear.
Because making another solution for the rudder rods is just not an option at the moment and neither is relocating the aft engine. (which at maximum would give me 15cm).

As for now though, I will simply put that issue to the side and focus on making the the sub watertight and begin the crafting of the hull.
*EDIT*
When thinking about it, 1,2 liters isn't that bad after all. Or am I wrong? I suppose it depends on where I would like the waterline to be... {:-{
Cheers
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Davy1

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Re: HMS Lundon
« Reply #48 on: November 15, 2013, 08:53:42 AM »

Yes, you are right 1.2 l isn't too bad. I am not that sure of the size of the sub but for most subs that you can carry easily, that could well be enough.

As you say it depends on the waterline. Also if you keep the displacement (i.e volume) of the superstructure down that will help.

So probably best to go with what you have.

Inserting extra sections is usually the sign of a desperate engineer!

David
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SwedishProjectBuilder

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Re: HMS Lundon
« Reply #49 on: November 15, 2013, 10:05:43 AM »

So probably best to go with what you have.

Inserting extra sections is usually the sign of a desperate engineer!

David
Hehe %%
Thanks for the response, somewhat more comfortable about cutting the tanks and rods now  :-)


The floating capacity of the sub is roughly 12 liters. An additional 0.5-1 liter can be added combined with the aft and stern, which gives me the possibility to put an additional 1kg ballast as far below the waterline as possible to lower the center of mass.


As you mentioned, the superstructure must be as light as possible, especially the one above the waterline.


The repaired piston. I added one more disc above a circular ring(?) fixed to the rod. The ring is fixed to the piston with a small pin, which can be seen in one of the holes.
In the background, epoxy, lots of it. "not for structural purposes".. %)

Cheers

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