Boat Motor Carrier

1998 Ford Transit chassis. Thinking of using two 50X75 (5mm)steel angles bolted to the provided captured nuts under the chassis and through the 50mm face of the angles. From rearmost bolt to end of angle will be 800mm. Intend welding 75X3mm RHS steel between rearmost ends of the angles on the 75mm faces. On top of this will be an aluminium tray approx 100X50X50 by about 2Mtrs for the scooter which weighs 100kgs. Later I intend to weld a 75X4steel RHS about 150mm long central under the 75X3mm RHS running forward and aft to take a removable towing tongue and ball. Intention is a small boat and trailer. Downward force on the ball would be less than 40 Kgs.

Ok,

I'll give you the basic approach, but you would really need to tell me which arm of the steel angle is vertical and how exactly the angle is attached to the chassis (how many bolts, what's their spacing, what diameter, etc) since I don't know the chassis well enough to tell from your description.

Basically,
Stress = M/Z where M is bending moment and Z is the section modulus of the angle iron in the vertical direction. You can get a table of Z for various shapes from a steel supplier or calculate it (see a text book).

For the scooter, M = 0.8 Meters * 100kg Spread that over the two angles and you have a first cut.

Next, assume you need a minimum factor of safety of 4, so multiply the calculated stress by at least 4 to ensure the structure is strong enough.

Next, realize that the load on this carrier will be dynamic (ie: it bounces up and down as the truck does). This implies 2 things. First, you need to account for the additional load caused by accellerations ( assuming 1/2 G is probably reasonable). Second, the structure will be subject to fatigue. If the scooter is only carried occaisionally, fatigue will probably not be a problem, but if the scooter were to be carried every day for years, then you need to take fatigue into account. You can get an S/N curve for the steel you will be using to do this. (S = Stress, N = Number of cycles).

Assuming this structure is attached to the truck with 2 bolts through each angle iron, the moment is acting around the rearmost bolt and being resisted by the foremost bolt. The load on that bolt is the total moment calculated above divided by the distance between the bolts. The shear strenght of the bolt must be greater than this force (including the factor of safety). Also the single rearmost bolt must be capable of taking the shear due to the weight of the scooter.
To give you an idea, assume you were to use a 3/8 inch bolt.
Area = PI * r^2 = 3.24 * (3/16)^2 = 0.115 sq inches. The weight of the scooter is 100kg = 220 pounds. So the shear stress on the aftermost bolt would be 220 pounds/.115 sq inches = 1913 psi. With a factor of safety of 4 that would be a stress of 7652 psi. The yield strength of steel in shear is in the order of 11000 psi.

That's the basic approach. Make the long leg of the angle iron vertical, and have fun.

My gut instinct without running numbers is that the sizes you mention are in the right ball park. So do some calculations, and then take a look at some of the products being offered on the market. One thing you will notice is that a lot of the products out there will be based on square tubing rather than angles. Both square tubing and I beams are inherently stronger than an angle iron just due to their shape.

2007-12-28 18:14:11 by willgray7

MOTOR TORPEDO BOATS MANEUVER OFF PANAMA CANAL [ETC.] - National Archives and Records Administration 1943 - ARC 38945, LI 208-UN-38 - DVD Copied by ...

I adopted this kitty 3 days ago and everything was normal until today. He was trying to wake me up as usual and everything was normal too but once I woke up and played with it, he started making noises like a purrrring noise so i thought it was normal. But the purring noise kept going for like 30 minutes now... just like a sort of silent motor boat... It seems the noise is coming from the throat, not the stomach. He is currently playing with a ball and everything seems normal except for that noise. So I googled this weird problem and found a few things. Can anyone else evaluate the problem ? Should I wait it out or take it to a vet? I currently don't have a carrier.

-Thanks
Well I went out for a bit and came back and he stopped making that noise. He breathes normally. I guess my cat loves to purr for a really long time. Thanks for your help guys.

Purring does come from the throat, they use their voicebox.

Don't worry, mine purrs like a motorboat too, and he's completely healthy
It's just the way your cat is.

2010-01-13 06:40:13 by Young

FEATURES - Weight Capacity: 130 lbs - Weight: 18 lb - Durable 1" steel tube frame - Synthetic mounting block resists gas & oil and will last longer than wood - Ergonomic handles - Comes with holding strap - Great for maintenance or storage of your outboard motor - Easy ASSEMBLY
Shipping prices listed are for the Lower 48 Continental U.S. States only.
Service, maintain, and store your boat motor on an outboard motor carrier. The OMC-130 motor cart holds up to 130 lbs or motors up to 30 hp. It includes an integrated gas can rack with strap for holding your boats gas can and motor at the same time.