Reply
 
Thread Tools Display Modes
 
Old 12-22-2011, 03:05 PM   #1
Mini-Skoolie
 
Join Date: Dec 2011
Posts: 10
another couple of water tank questions

1. I'm putting in a freshwater 180L tank under the deck of my housetruck. I've had a look at a few different mounting systems and am thinking of using two pieces of angle-iron across the bottom of the tank, and 8mm bolts up through each end of the angle iron to the deck rails on the truck. Just wondering if the 8mm bolts will be strong enough or should I get something that is rated for the load? Is two bars enough? The tank is 595mm across and 910mm long (angle iron would be going across the 595).

2. for the greywater tank (no sewerage) is it ok to run the pipe from the sinks to the tank so they go up and down. I can attach very easily to the bottom of the wooden deck, but will need to dip down under the deck rail once or twice. The inlet on the tank will still be well below the outlets of the sinks. I guess this means there will be water sitting in the pipes, which is not good, but I do have a hepvo valve below the sinks to stop smell coming back up.
kouka2 is offline   Reply With Quote
Old 12-22-2011, 06:56 PM   #2
wtd
Bus Nut
 
wtd's Avatar
 
Join Date: Jun 2005
Location: California City, CA
Posts: 267
Year: 1982
Coachwork: Thomas TransitLiner
Re: another couple of water tank questions

#1 -
I guess you're thinking something like this -

The lowest grade of threaded rod has a yield strength of about 36,000 psi (permanently deforms) and a tensile strength of about 60,000 psi (breaks).
Your 8mm is about 5/16", so I'll leave you to work out the aritmetic.
The rule of thumb for nuts is that thread engagement of 80% of bolt diameter is sufficient to cause the bolt to fail in tension before the threads strip.
Whether the angle bar you use is strong enough, it depends of course on the size of the bar. You didn't mention this in your post. 2 bars would probably be strong enough, but the tank is much happier if it's supported continuously around it's perimeter and it's absolutely ecstatic when supported over it's entire bottom.
If you suspend it with threaded rod don't forget something to prevent lateral motion in both directions.

#2 -
True about the standing water, but you wind up with the 'stranded solids' problem, when the water stops in the pipe everything that was suspended in it falls to the bottom of the pipe. Same way when a pipe is pitched too steep, the water 'outruns' the solids and leaves then behind in the pipe, crud dries in the pipe and sooner or later a clog. That'a why there's minimum as well as maximum fall on a pipe.
Probably wouldn't mean much in a gray water pipe, just thought I'd mention it.

Tom
__________________
The Rolling Motel Room
Where DIY meets WTF
wtd is offline   Reply With Quote
Old 12-22-2011, 09:15 PM   #3
Mini-Skoolie
 
Join Date: Dec 2011
Posts: 10
Re: another couple of water tank questions

Yeah similar to that, but with the angle iron up the other way (an upside down L), and across the bottom of the tank further in rather than on the edge. The angle iron is 40mm x 40mm. I only have two bits, but I have some other, lighter angle iron I could use in the middle as well, or possibly on the ends to prevent movement (but that would have to be screwed into the deck rather than bolts to the deck rails)... I had thought that the flatness of the tank top against the deck rails, tension on the rods and the weight of the tank would prevent lateral movement.

I got some 11mm threaded rod today. I also have two long bolts which are 12mm. I didn't follow your maths at all sorry, can you please spell that out?

My biggest limiting factor is that all the engineers are closed for a couple of weeks, so it would be hard to buy something else and get it cut now. I need to be on the road in a couple of weeks, but won't drive unless I have something safe.


Sounds like I will have to rethink the greywater pipe install, thanks for the heads up.
kouka2 is offline   Reply With Quote
Old 12-22-2011, 09:40 PM   #4
wtd
Bus Nut
 
wtd's Avatar
 
Join Date: Jun 2005
Location: California City, CA
Posts: 267
Year: 1982
Coachwork: Thomas TransitLiner
Re: another couple of water tank questions

Sounds like you've got enough good stuff to work.
The angle bar's plenty. I'd get a piece of plywood under the tank tho' as soon as practicable. Over the long haul the bottom will sag and be liable to fail. Also the plywood will prevent the angle bars from rubbing holes in the bottom of the tank.
The 8mm bolts will hold about 9,000 pounds each before they 'stretch', so they're plenty. Use the 12mm bolts if you want but they're overkill - might want to save 'em for when you need 'em.
The plan to bolt it up tight to the truck frame is just the ticket to prevent lateral motion - put something between the truck frame and the tank to prevent abrasion of the tank - some weatherstripping, sponge rubber or something like that - old garden hose would work fine.

I'm guessing that you're using a plastic tank of some sort, you didn't mention. If you're using a metal tank forget the abrasion stuff.

Tom
__________________
The Rolling Motel Room
Where DIY meets WTF
wtd is offline   Reply With Quote
Old 12-23-2011, 11:55 AM   #5
wtd
Bus Nut
 
wtd's Avatar
 
Join Date: Jun 2005
Location: California City, CA
Posts: 267
Year: 1982
Coachwork: Thomas TransitLiner
Re: another couple of water tank questions

Quote:
Originally Posted by Iceni John
Your 180 liter tank will hold about 170 kg of water when full, or about 200 kg complete with supports and framework. Factor in at least twice this weight to allow for dynamic forces, such as driving over a bumpy road, and you're talking about almost half a tonne. This is why you must make any tank supports as strong as possible. Now think what would happen if one of your under-tank cross-supports broke, or one of the hangers gave way - would the tank still be secure?

I put my two fresh water tanks in last year, and I'm in the process right now of installing my black and gray tanks. Each fresh tank holds 110 US gallons (about 450 liters), so that's up to a ton of dynamic load each. For this reason I hung each tank from ten lengths of 1/2" (12.7 mm) threaded rod, with double nuts top and bottom (and Nylok on the bottom). Each tank sits on a full-length frame of 1.5 x 3" (38 x 75 mm) Mil-spec angle steel that sits on five cross supports of heavy channel steel, and to counteract any bowing out when full all four sides and the bottom are sheathed in 1/2" plywood. To absolutely prevent any lateral movement the tanks are located by the frame rail on one side, a structural cross-member in the front, and on the other side and the rear I made a lip of the same angle steel that is massively screwed and bolted to the bus floor and frame. In other words, the tanks aren't going anywhere! This means that the hangers need do only that - they do not need to take care of any lateral forces whatsoever. The tanks are completely restrained in all six directions of possible movement. After I filled both fresh tanks I took my bus for a drive, and there was absolutely no movement or settling at all.

Tank supports are one area where more is better. If in doubt, make it stronger. Imagine how Isambard Kingdom Brunel would have made them if he were converting a bus!

Good luck, John
Gee, why not a set of wheels on the bottom of the tank too, just in case all that wasted material doesn't give way?
A rose is beautiful, 1000 roses isn't a thousand times more beautiful.
Tom
__________________
The Rolling Motel Room
Where DIY meets WTF
wtd is offline   Reply With Quote
Old 12-23-2011, 12:15 PM   #6
Bus Geek
 
lornaschinske's Avatar
 
Join Date: Jun 2004
Location: Roswell, NM
Posts: 3,587
Year: 1986
Coachwork: BlueBird
Chassis: 40 ft All American FE
Engine: 8.2LTA Fuel Pincher DD V8
Rated Cap: 89
Re: another couple of water tank questions

Don't forget to protect the top of the tank from abrasion as well. We held our slightly off the rails in the floor with foam insulation pieces and shot Great Foam around them to "glue" them in place.
__________________
This post is my opinion. It is not intended to influence anyone's judgment nor do I advocate anyone do what I propose.
Fulltime since 2006
The goal of life is living in agreement with nature. Zeno (335BC-264BC)
https://lorndavi.wordpress.com/blog/
https://i570.photobucket.com/albums/s...ps0340a6ff.jpg
lornaschinske is offline   Reply With Quote
Old 12-23-2011, 03:17 PM   #7
Mini-Skoolie
 
Join Date: Dec 2011
Posts: 10
Re: another couple of water tank questions

The tank is gavlanised steel. It's second-hand and has come off a house bus. I have a piece of 9mm ply I can put between the tank and the angle iron at the bottom. Would I still need some protection from abrasion at the top? The place where the tank meets the deck rail is a welded join, slightly raised, which means it will be taking the tension on those 4 or 6 points. Would it be useful to put a piece of ply on top too?

John, my top priority is to not have the tank come off while driving down the highway Second priority is to be legal (although I doubt that the authorities here in NZ will have a problem with what I am doing), and third is to have a functional water system.

My similar sized steel diesel tank sits in two brackets mounted horizontally, off the chassis. It does have some friction protection on the top straps. They wrap around the body and attach to the brackets at the bottom with two 10mm bolts. I guess the main difference is that the brackets are super solid, and the whole thing will have been certified by an engineer.
kouka2 is offline   Reply With Quote
Old 12-23-2011, 03:56 PM   #8
wtd
Bus Nut
 
wtd's Avatar
 
Join Date: Jun 2005
Location: California City, CA
Posts: 267
Year: 1982
Coachwork: Thomas TransitLiner
Re: another couple of water tank questions

Quote:
Would I still need some protection from abrasion at the top? The place where the tank meets the deck rail is a welded join, slightly raised, which means it will be taking the tension on those 4 or 6 points. Would it be useful to put a piece of ply on top too?
Abrasion protection would be good on top - the ply on top would be perfect.

John -
Quote:
Roses may be pretty, but a strong piece of engineering is prettier!
That's just my point - there's no 'engineering' in there - just some arbitrary decisions about what you thought was 'strong enough' and then some assembly.
Why 1/2" bolts - why not 3/4"?
Why 1 1/2" x 3" angle bar - why not 6"x6".
Why 5 supports - why not 6?
etc. etc.
None of these is based on any 'engineering' - just your decision that these were 'strong enough'.
Always when I see this it reminds me of when we used to build tobacco barns when I was a kid. Made 'em outta HUGE timbers, took forever to put one up, just like they'd been building them for as far back as anyone could remember. They'd last a coupl;a hundred years - we had ones around that had.
After some time in engineering school I thought back on those and realized that with that material and manpower you could have built 6 barns in half as much time that would last just as long.
Engineering creates a solution that's appropriate to the problem - no more, no less. That's the beauty of engineering.

Tom
__________________
The Rolling Motel Room
Where DIY meets WTF
wtd is offline   Reply With Quote
Old 12-23-2011, 05:11 PM   #9
Bus Crazy
 
Join Date: Mar 2011
Location: Oregon/Philippines
Posts: 1,660
Re: another couple of water tank questions

welding might be a good idea
__________________
Jesus Christ... Conversion in progress.
chev49 is offline   Reply With Quote
Old 12-23-2011, 05:42 PM   #10
wtd
Bus Nut
 
wtd's Avatar
 
Join Date: Jun 2005
Location: California City, CA
Posts: 267
Year: 1982
Coachwork: Thomas TransitLiner
Re: another couple of water tank questions

Quote:
Originally Posted by Iceni John
The reason I overbuild (sic) is because I like the end result, pure and simple
The only reason you need, just don't confuse your prediliction for overbuilding with good engineering practice, or any engineering for that matter. It's actually throwing materials at a problem until you're satisfied with what it looks like.

Merry Christmas to you as well !


Quote:
Originally Posted by chev49
welding might be a good idea
.
Suggestions were made to the OP based on the materials that OP had on hand or were available to him.

Tom
__________________
The Rolling Motel Room
Where DIY meets WTF
wtd is offline   Reply With Quote
Old 12-23-2011, 08:58 PM   #11
Skoolie
 
Join Date: Jan 2009
Posts: 143
Send a message via ICQ to mightybus
Re: another couple of water tank questions

I design above ground long term spent nuclear fuel rod storage buildings. Ask me a question.
mightybus is offline   Reply With Quote
Old 12-26-2011, 01:42 PM   #12
wtd
Bus Nut
 
wtd's Avatar
 
Join Date: Jun 2005
Location: California City, CA
Posts: 267
Year: 1982
Coachwork: Thomas TransitLiner
Re: another couple of water tank questions

Just fiddlin' around and actually calc'd the parts OP is using -

In inches and pounds, but, well, just call me an Ugly American - only the comparisons are needed and they can by anything, as long as they're the same -

Using 1-1/2"x1-1/2"x1/8" angle (don't know the thickness of OP's angle) and 24" lengths -
Bending stress on the iron is about 5300 psi. The strength of A36 steel - about the most common around, propbably similar to what OP has, is 36,000 psi - so there's about a 7 times safety factor. Seems like plenty, if you tank's getting more than this you'll probably be more worried about finding a doctor than about what happened to your tank.
Just for a 'quick check', NFPA 1192 specifies that propane tank mounts must be able to sustain a force of 8 times the full tanks weight in any direction, so we're comfortably in the safety ballpark.

Bolts OP is using have a yield strength of about 9000 lbs, supporting 100 pounds each - well in the 'safety zone'.

Deflection at the center of the bar will be about 0.001" with a full tank. About 1/3 the thickness of common typing paper.

Tom
__________________
The Rolling Motel Room
Where DIY meets WTF
wtd is offline   Reply With Quote
Old 12-28-2011, 10:19 AM   #13
Skoolie
 
freakn's Avatar
 
Join Date: Dec 2010
Location: Southeast British Columbia
Posts: 106
Year: 2003
Coachwork: Bluebird
Chassis: International
Engine: DT466E
Rated Cap: 72
Re: another couple of water tank questions

Personally I would go with the 12mm bolt if possible. Look at the fuel tanks in most north american vehicles. They usually range from 80 to 130 litres, I have never seen one held in with 5/16" bolts. More often than not they are 7/16" (11mm) or larger. When you consider the thread depth on a 5/16 (8mm) bolt, is there even a 1/4" of steel left? Think about it, we use 1/2" grade 8 bolts to hold a 5000 lb hitch on your truck according to the math I'm seeing here, 5/16" bolts would be fine. We have to remember that tensile ratings are done in a lab with perfect conditions. They don't take into account the amount of corrosion a bolt will see (most bus seats are held down with 5/16" bolts, how many of those broke from being rusted thin?) Also if a bolt is over tightened when installed it will stretch, which also causes it to be thinner and weaker than spec. When it comes to hanging tanks, you can't go wrong using a bigger better bolt. Plus you have piece of mind...my 2cents
__________________
Living the dream in the Kootenays
freakn is offline   Reply With Quote
Old 12-28-2011, 11:14 AM   #14
wtd
Bus Nut
 
wtd's Avatar
 
Join Date: Jun 2005
Location: California City, CA
Posts: 267
Year: 1982
Coachwork: Thomas TransitLiner
Re: another couple of water tank questions

In every example you gave above the bolt is designed to resist failure in shear, not in tension.
Bolting a tank up tight between an angle bar and the truck frame puts the bolt almost completely in tension.
They're different.
Larger bolts are called for in every application that you mentioned, it's just that none of those applications are the same as OP's.

Quote:
When you consider the thread depth on a 5/16 (8mm) bolt, is there even a 1/4" of steel left?
The bolt strength is given for the size of bolt - you don't make 'adjustments' like that.

Just me, a bolt holding less than 10% of it's yield strength is fine with me, not sure how much more 'safety' you'd want than that - why not 3/4" bolts - lots 'safer'.

To each his own tho', just wanted to show OP the conditions and let him decide.

Tom
__________________
The Rolling Motel Room
Where DIY meets WTF
wtd is offline   Reply With Quote
Old 01-03-2012, 01:43 AM   #15
Bus Nut
 
Join Date: Jul 2010
Location: Elk Plain, WA.
Posts: 513
Year: 1993
Coachwork: Genesis
Chassis: International
Engine: DTA360
Rated Cap: 16
Re: another couple of water tank questions

Have any of you looked at a 30 year old camp trailer??? One that's been used a lot with good sized holding tanks under it??? Pretty simple mounting under them... Just sayin'...
dirtygoat is offline   Reply With Quote
Old 01-03-2012, 04:47 AM   #16
Bus Crazy
 
Join Date: Mar 2011
Location: Oregon/Philippines
Posts: 1,660
Re: another couple of water tank questions

some of them have really large ones.... ive scrapped 5 for parts this last year and the 81 monico i am not quite done with has a 70 gal grey tank..
__________________
Jesus Christ... Conversion in progress.
chev49 is offline   Reply With Quote
Old 01-10-2012, 02:28 AM   #17
Mini-Skoolie
 
Join Date: Dec 2011
Posts: 10
Re: another couple of water tank questions

Thanks everyone, that's been very helpful. I thought I'd replied already but it's disappeared. Tom, that's great with those final calculations, cheers.

We decided to sandwich with ply and use the materials mentioned earlier.

I have another couple of questions

- I don't have any easy way to vent the greywater tank above the truck (no black water). Can I just put a small 1/2" vent in the top of the tank? The tank is a 200L plastic barrel, so I was just going to screw it in. The outlet hose for emptying is around 45mm diameter. I gather there are two issues here: smell, and equalising pressure for emptying. Does the vent need to be open when the tank is not being emptied (i.e. when tank is being 'filled' from kitchen or bathroom)? I'm using a hepvo valve under the sink and 45 then 50mm hose to the tank.

- does it matter where I put the water pump in relation to everything else? Closer to the tank or the kitchen tap? Closer to the califont? It's a sureflow 10L/m

- we're going to lag the freshwater pipes (12mm garden hose, it's not for drinking water), and before winter I will need to do something with the pump, but what about the fittings? I got told today that the small metal ball valve I was using needed frost protection (it has a plastic part inside). But will the other fittings be ok? They're a mix of brass and plastic. A hard frost here would be -10C (that's -14F?)
kouka2 is offline   Reply With Quote
Old 01-10-2012, 02:44 AM   #18
Bus Crazy
 
Join Date: Mar 2011
Location: Oregon/Philippines
Posts: 1,660
Re: another couple of water tank questions

the grey water tank or tanks all need to be vented, but dont need large vents to function so 1/2 inch or 3/4 is overkill, but they have to always be vented and above the level of the tank by quite a bit. I have two of them (out of my 5) that have 1/4 inch vents.
the pump goes after the fresh water tank, and newer ones have a check valve built in. the pump can go just before the split for the hot water heaters and your cold supply for the shower, etc. its location doesn't matter a great deal as long as it constantly gets water from the bottom of the fresh tank. fresh water supplies should be inside the bus unless of course they are in an insulated compartment, and one can always have a small duct from the furnace to the compartment if desired.

you can look up the plumbing diagram in archives for proper fresh water diagram, just make sure you have a check valve either in or after the fresh water pump, and one in the city water hose connection for when you are hooked up to city water. The check valve at the pump is there not to allow the city water to fill your fresh water tanks and flood everything.
__________________
Jesus Christ... Conversion in progress.
chev49 is offline   Reply With Quote
Old 01-10-2012, 03:02 AM   #19
Mini-Skoolie
 
Join Date: Dec 2011
Posts: 10
Re: another couple of water tank questions

What's a check valve? The freshwater tank is outside. I'm not so worried about it and the frost (just the things that will break as opposed to freeze like the pump or the califont), but will probably look at some insulation at some point. The freshwater tank has a vent/overflow, and fills from the side of the tank. I don't have a system for using mains pressure water direct.

I'm pretty clear about the plumbing diagram, just wasn't sure if it mattered if the pump was at the tank end or the tap end. At the tank end would be better in my case in terms of access and noise. I'm thinking of building it into a small box. Any guidelines on how much insulation it needs? Does it need air around it inside a box or can I wrap it in insul blanket?

With the greywater, what happens if I have a short vent? How short is short?
kouka2 is offline   Reply With Quote
Old 01-10-2012, 09:14 AM   #20
Bus Crazy
 
Join Date: Mar 2011
Location: Oregon/Philippines
Posts: 1,660
Re: another couple of water tank questions

a check valve only lets the water flow one way.. in the fresh water tank pump, it is designed to not let water flow back into the fresh water tank. The plumbing diagrams may or may not show this check valve in the system. So always install the pump in the direction of the water flow. I have 3 of them, and two of them have a arrow on the pump head.

the electric pumps are pretty quiet, and i don't see any need for additional sound insulation, but they need securely mounted. I use flexible line on each side also, and secure those back about 6 inches from the pump also. If water tank is undernieth the bus, then it should be well insulated, or heat tape.

Most vents that i have seen for fresh water go at least a couple of feet above the level of the bus, (or to the water inlet panel) They also serve as an indicator that the tank is full, so mounting these small tubes where you can observe the end is a good idea.
__________________
Jesus Christ... Conversion in progress.
chev49 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
68 Bluebird--couple questions jepopp GM | Chevrolet Drivetrain 0 01-13-2014 03:07 PM
New (to me) Shuttle Bus - IA - couple of questions Stuff Titles, Insurance, Registration and Money Matters 0 04-28-2010 09:40 AM
Intro and a couple questions RVBUS Conversion General Discussions 1 07-29-2009 08:22 AM
A couple of misc. bus questions timbuk Everything Else | General Skoolie Discussions 1 04-12-2008 01:06 PM
Plumbing/Fresh water tank questions Branden Plumbing, Water and Waste 6 04-19-2005 03:30 PM

» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 06:18 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
×