Swamp Thing 3 Drivetrain Research

Here are some links to get you guys headed in the right direction. The basic setup of the drivetrain is that of a tandem bike. The wikipedia article is good because it explains all of the bicycle terminology, in case you aren't familiar with it.


http://en.wikipedia.org/wiki/Tandem_bike#Tandem_specific_components

http://www.motoredbikes.com/showthread.php?t=23511


This was the idea from last year, when they didn't have variable pitch. I don't think all of that is necessary, since we are definitely doing variable pitch this year.

What do you guys think of this: A single gear bicycle drive train. Then we'd need a bevel gear to change the direction of motion by 90 degrees. so put the bevel gear on the end that the wheel is attached to. and then have a shaft going to the propeller. with variable pitch.

Brian recommends these cranks

http://store.somafab.com/sumecr.html

That seems like it would be the simplest thing to do. I'm assuming there's not a problem with the chains slipping underwater?

Last year, they did not have a problem with the chain, although we might need to have more tension than you would need in the air.

we'd still need to choose a gear ratio, but yeah that seems pretty simple.

Drive train: Here are some issues we need to figure out with the drive train. Some of these things need to wait on the propeller.

1. What gear ratio should we have? Should we have double gear reduction?
-last year we had 7/1 gear ratio. Most teams at the competition had 3/1 and some had 4/1.

2. How are we going to mount the drive train for the sub?


3. How are we going to keep the pilot's feet in the pedals?
-use old scuba fins and cut the fins off
-Scott's idea with the rowing machine pedals

4. Should we waterproof the gear box? How would we couple the linear actuator to the waterproof gearbox? Run a conduit?

I was just looking up bevel gears and on one of the websites I was looking on they said the optimum ratios were between 1:1 and up to 6:1. Most manufactured 1:1, 1.5:1, 2:1 and 3:1 ratios in an array of materials and sizes.

cool. thanks, Don! I asked Brian (Blue) what gear ratio the bevel gear had last year and he didn't specifically say. He said 2:1 and 3:1. They're at the house. Tim and I took it apart, so we can check it out next time we are there.

holy crap, you guys have to check out this video. It's how the drivetrain of a pedal kayak works.

http://www.nativewatercraft.com/media/videos/propel/ult_multi_propel.cfm

Ok a couple of things... issues with the drive train in the previous years were alignment, which caused chains to slip. If the d-train is constructed correctly then we wont run into the slipping issue we had in the past.

To construct it correctly I wanted to resort purchasing sealed bottom brackets for the cranks that had completely aluminum parts for corrosion. To ensure this bracket would be installed correctly my idea was to take an over sized aluminum/stainless tube and thread the inside to accommodate the bottom bracket. then welding this piece to the drive-trains center (whichever way that is).

The bevel gear used in the last sub was 1:1.

The gear ratio used in the last sub was close to 7:1. the problem we had was improper distribution with buoyancy (aka massive computer box for servo on the driver side of the drive train) this caused a moment and caused the sub to roll as forward motion was achieved.

mounting should be rather easy. you just need to incorporate it into your design...whether is something that goes top to bottom or whathave you.

To be honest my main concern would be how to to dive a control rod to move the variable pitch mechanism. This should be priority number 1 and all other design considerations should be tailored to fit the variable pitch mechanism.

Hey, thank you so much for you input!

I don't understand what you are talking about in your last sentence. You lost me at "dive a control rod" lol

*drive a control rod* the mechanism for Variable Pitch

drive train parts (recommended by Brian Green)

pedals:
http://store.somafab.com/sohetrpe.html

clips:
http://store.somafab.com/mkshalfclips.html

chain:
http://store.somafab.com/kmcstch.html

bottom bracket - $43.99!!!!
http://store.somafab.com/irdqbjissqta.html

chain tensioner
http://www.mcmaster.com/#tensioners/=bnv8gg

sample chains to try to figure out size
http://www.mcmaster.com/#about-roller-chain/=bnvahc

tapered roller bearing (1" bore) such as

http://www.amazon.com/BCA-Bearings-LM48548-Bower-Brng/dp/B000BZNAPQ


flange mounted bearings
on reidsupply.com (look for info in the dropbox)

"marine" tapered roller bearings. idk if they have the correct bore size. looks like this is an OEM part for some boat. I'll call tomorrow and find out.

http://baldknobmarina.com/eshopprod_cat_5665-47915-48762_product_754283.DL_HIGH_SPEED_TAPERED_ROLLER_.htm - they said they didn't have SS gears and recommended I try some place down the street in IL

https://www.discountmarinesource.com/p-30312-sierra-tapered-roller-bearing-18-1162.aspx - couldn't find a phone number to call

http://www.iboats.com/Tapered-Roller-Bearing-Sierra/dm/view_id.172111?cm_mmc=Google+Shopping - lady was really helpful. Their bearings are marine grade, which means they are meant to be in constant contact with water. She gave me the number for the manufacturer so I can ask if they have any in the size we need. Sierra 800-648-3976 extension 3. Unfortunately the guy at that phone number was very unhelpful

http://www.go2marine.com/product.do?no=82264F&WT.mc_id=gb1&utm_source=googlebase&utm_medium=productfeed&utm_campaign=googleshopping - unhelpful. he said that bearings are meant to be submerged in oil so they aren't corrosion resistant.

http://www.marineengine.com/newparts/part_search.php?part_num=18-1162 - the guy was really nice, but said he couldn't get the specs for his marine tapered roller bearings over the phone. I would have to contact the manufacturer (ie sierra, the douchebags I just called), but mercury marine might be good..

Mercury marine said that "marine" bearings are not corrosion resistant.... wtf!