Jul 11, 2007, 12:15 PM
USA'd ex Brit
Back.. In California
Joined Aug 2006
5,783 Posts
Quote:
 Originally Posted by Brooks Measuring pull with a rubberband and ruler is not as straightforward as measuing pull with a metal spring balance (fisherman's scale). Whereas the spring constant (cm of spring extention / oz of pull) is relativly stable wrt load, the rubberband constant is not. Eg. if 1 oz. pulls the spring out 1 cm, 2 oz. would pull the spring out 2 cm. But a rubberband would behave differently, eg. for my rubberband 1 oz. = 1 cm of stretch, 2 oz.= 4 cm, 4 oz. = 16 cm of stretch. As the pull increases, a rubberband stretches more and more. This is because the cross sectional area of a rubberband decreases as weight is added. With less area to take the stress, the band elongates more. A steel spring does the same, but to a much lesser degree (although this is one reason why spring balances are not legal for selling food). All this means in practice is that you need to calibrate your rubberband with several different known weights, hopefully weights in the vicinity of the tug's actual bollard pull. I measured 3 known weights, and used my calculator's built-in linear regression program to figure out the appropriate rubberband K factor for each pondside measurement. The K was a pretty good fit to a straight line, so you could just graph the data, and skip the math, if you wanted. Some bollard pull results for my vac u tug with standard motor, Phil Pace's 4 blade prop, 6cell NiCd battery : Without lead weight 3.2-3.8 oz. With lead weight 4.2-5.4 oz. Phil's results, for comparison 4.5 oz. If your bitts can stand it, a running start generates much more pull...
Or you could just buy a digital fishermans scale from WalMart..

Tigger (standard Springer) pulls 1lb 8oz, Scoot (straight Kort nozzle) pulls 2lb 12oz, (tapered Kort nozzle) 2lb 14oz... Mustang Sally (proposed Springer) should easily break the 3 - 3 1/2lb barrier..

A 'running start' is a 'no no' as it will probably result in the Bitts being pulled from the deck of your tug.. or barge.. You wont see a real tug doing that!.
 Jul 11, 2007, 12:32 PM Damp and Dizzy member Bozeman, Montana, United States Joined Aug 2003 3,541 Posts With your big pull capacities, you could start a new Springer event: Salvage of sunken ship/barge/treasure. A line would run from the sunken object up to a pully suspended from a large buoy (large enough to support the sunken object if it were hauled off the bottom). The salvage line would have a small buoy attached to the end. A Springer would engage the end of the line, and try to pull the treasure to the surface. The large buoy would probably need an anchor to keep it in place while the Springer tugged away on the salvage line. Or maybe it could be a team event, with a 2nd Springer holding the large buoy in place until the treasure emerged, then helping the 1st Springer to manuver the whole gaggle to shore. A 6 pack of suitable beverages might make a good treasure to rescue :-). I only mentioned the running start in case the value of the casulty was sufficient to risk damage to the model tug. One of the key mental steps one has to take in salvage is the shift from "retrieve the casulty just like it was" to "get it back anyway you can, broken if necessary". Whether a broken tug is acceptable is a judgement call, of course. Last edited by Brooks; Jul 11, 2007 at 12:40 PM.
Jul 11, 2007, 01:17 PM
**NOT GUILTY**
Millbrook, Alabama
Joined Jun 2004
6,491 Posts
Quote:
 Originally Posted by toesup A 'running start' is a 'no no' as it will probably result in the Bitts being pulled from the deck of your tug.. or barge.. You wont see a real tug doing that!.
That will not be a problem with my set up...as the tow line is not actually connected to the bollard, rather only lays on top of it then goes straight down a tube and is looped around the metal servo clevis rod that is in a hard wood block on the bottom of the glass deck. I feel pretty sure I can run at full speed and snap that line all day long with out ill effects to the tug. I built it that strong.

Now a normal tug is another matter all together.

Captain Slick
 Jul 11, 2007, 01:25 PM **NOT GUILTY** Millbrook, Alabama Joined Jun 2004 6,491 Posts (I'm sure this has been done) An ole fashioned TUG-O-WAR would be fun! Pick teams of tugs to share in the war just like humans do. Captain Slick
 Jul 11, 2007, 01:38 PM no wings any more, just dust! stoke on trent Joined Oct 2004 8,052 Posts that would be fun hoggy, or perhaps a sumo style push-out
Jul 11, 2007, 06:27 PM
USA'd ex Brit
Back.. In California
Joined Aug 2006
5,783 Posts
Quote:
 Originally Posted by Hoghappy An ole fashioned TUG-O-WAR would be fun! Pick teams of tugs to share in the war just like humans do.
Quote:
 Originally Posted by Ghost 2501 that would be fun hoggy, or perhaps a sumo style push-out
Its been done guys...
http://media.putfile.com/Scoot-the-Springer
 Jul 12, 2007, 09:30 AM Registered User McAlester Joined Nov 2004 1,370 Posts Hmm. If you hadn't sealed that rear deck, she'da had you sunk! - 'Doc
 Jul 12, 2007, 09:56 AM **NOT GUILTY** Millbrook, Alabama Joined Jun 2004 6,491 Posts Cool Video... ...but...that sure was a short tow rope...lol What I have in mind is a group of boats on one side, pulling off against another group at the other end of the main rope...all at the same time. They could be bow to stern, but I think side by side, all tied to the end of the main tow line that maybe has a loop in the end to tie several tug boat tow lines to, is my vision. A true team sporting event. Choose whatever method to pick the teams, but at random would be cool or club VS club? No real limit to the number of tugs pulling at the same time in this event. Captain Slick
 Jul 12, 2007, 01:46 PM Registered User SoAl Joined Mar 2007 247 Posts Tug 'o War That sounds like the prelude to a grate how to class... "Now that we have recovered all of our boats and drained the water from them, lets dry them out and oil everything" LOL Scott
 Jul 12, 2007, 10:16 PM Old wreck in Milwaukee United States, WI, West Allis Joined May 2007 3,893 Posts This is a happy coincidence. I was looking at a digital fish scale at K Mart last Saturday with this very thing in mind. I was thinking about mounting it to a 2x4 or a snow fence post with a pulley near the base. The towline would pull down on the scale and the towline would pass through the pulley to run horizontally out to the tug. Anyone see a flaw in this plan? I am converting one of my old tugs from a single Graupner/Marx Z drive to twin screw conventional. The one z drive barely moved the boat. I'm hoping the twin props will give it some muscle. I hope the measuring rig will give some reliable data.
Jul 12, 2007, 10:16 PM
USA'd ex Brit
Back.. In California
Joined Aug 2006
5,783 Posts
Quote:
 Originally Posted by RhumbLine That sounds like the prelude to a grate how to class... "Now that we have recovered all of our boats and drained the water from them, lets dry them out and oil everything" LOL Scott
No water ingress was reported in either Templeton OR Scoot during the making of that motion picture...
Jul 12, 2007, 10:22 PM
USA'd ex Brit
Back.. In California
Joined Aug 2006
5,783 Posts
Quote:
 Originally Posted by Prins Willem ..I was looking at a digital fish scale at K Mart last Saturday with this very thing in mind. I was thinking about mounting it to a 2x4 or a snow fence post with a pulley near the base. The towline would pull down on the scale and the towline would pass through the pulley to run horizontally out to the tug. Anyone see a flaw in this plan?
I just tie my scale off to the nearest immovable object (..ok, a sun lounger ) and pull away...
 Jul 12, 2007, 10:52 PM Registered User Monterey Bay California Joined Feb 2004 14,166 Posts I hope you are sitting on the sun lounger, Toes!!! I know Scoot could drag one of those, "unattended", right into the pool!!!
Jul 13, 2007, 07:34 AM
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Millbrook, Alabama
Joined Jun 2004
6,491 Posts
Quote:
 Originally Posted by Prins Willem This is a happy coincidence. I was looking at a digital fish scale at K Mart last Saturday with this very thing in mind. I was thinking about mounting it to a 2x4 or a snow fence post with a pulley near the base. The towline would pull down on the scale and the towline would pass through the pulley to run horizontally out to the tug. Anyone see a flaw in this plan?
I'm not a rocket scientist, but wouldn't the pully increase the pull power thereby giving you a false reading? I'm thinking a direct hookup would be more accurate.

Captain Slick