Belly tank help

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scooner car
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Belly tank help

Post by scooner car » Sun Nov 29, 2009 3:37 pm

I am keen on building a belly tank,similar to John Lynch&Alan Fountain
I was wondering if there is a fiberglass mould out there for the body,a good web site/book that i can get onto for idears for chassis&syspension etc
Many thanks
Scott

David Leikvold
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tank

Post by David Leikvold » Sun Nov 29, 2009 5:16 pm

Scott, you could start by looking at the build diary for the Spirit of Sunshine lakester that Dr Goggles and the Reverend Hedgash built over the last few years. It's on the Landracing.com website somewhere and also in a modified form on this forum too, I just can't remember where. Their tank was a wing tank off a Canberra bomber and while it is very snug in there it all fits and works well. I sat in it at Speedweek this year, for once I was glad I had short legs! First time out it went 160+mph with a very standard Commodore V6. If you wanted to go slightly bigger you could always build your own tank in fibreglass. It's not as hard as you might think and it means you have more control over the dimensions and fit of all the components too. Smaller is better of course, less skin friction and such, but everything has to fit somehow. If you're looking for a lot of inspiration in one place I would suggest you go find a modern Formula Ford and see how they package up everything. There are plenty of websites and books out there that will give you good details about openwheelers of any type. That will give you a wealth of ideas that could be useful for a lakester. Good hunting.
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Rob
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Post by Rob » Sun Nov 29, 2009 5:32 pm

G'day Scott,

There are a few guys with P-38 tank moulds in the states and I have heard a few rumours about one in Oz but nothing concrete.

Alan Fountain uses a tank he sourced in the US, it's from a B-52 and given the number of aircraft of that type they have/had, should be plentiful in the scrap yards near Tuscon.

Your absolute best bet is to attend an event, talk to the people, check out the vehicles and take as many photos as you can.

Cheers,
Rob
I owe, I owe, so off to work I go.

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Dr Goggles
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P38's

Post by Dr Goggles » Sun Nov 29, 2009 8:22 pm

Go to the H.A.M.B or landracing.com and look for Elmo Rodge, he makes them, or PM me I have his email, nice bloke.

And just for the interest check out this tank...v.nice build, go to post 55

http://www.jalopyjournal.com/forum/show ... ost4609707

Dr G
...few understand what I'm trying to do , but they vastly outnumber those who understand why..

grumm441
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Pot Belly tank

Post by grumm441 » Tue Dec 01, 2009 6:43 pm

They make it
I make it work

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T-34
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Post by T-34 » Wed Dec 02, 2009 10:47 am

Been looking into this a little myself

Rod and race have a couple of different types - http://www.rodnrace.com/c99/p-38-Belly-Tank-WW-ll-Drop-Tank-Shell-Mark-ll-Drop-Tank-Shells.htm

http://www.p38-droptank.com is another supplier supplying P38 type shells, The guy's name is Wayne Yeats - and the specs on the tanks are as follows.

Length-------12' 6"
Diameter----36"
Spacing at 1' increments:

0 / 1-18.5" / 2-25.5" / 3-31.0" / 4-34.5" / 5-35.5" / 6-35.5" / 7-34.0" / 8-30.5" / 9-25.0" / 10-18.0" / 11-12.5" / 12-7.5" / 12.5-0"

PM me if you want Waynes email address. The shells can be 'stacked' in multiples to save on shipping.

Prices are $1100 for the rodnrace shell and $2k for Waynes one.
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Raging Bull
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Post by Raging Bull » Wed Dec 02, 2009 9:52 pm

Hi to all,

Maybe a good thread for me to jump in and introduce myself...

I'm Victor from Yanchep in Western Australia and have been coming back on and off to this forum reading over the last year or more and arrived at a decision recently to make my next scratch built race car a bellytanker which I hope to debut at the 2011 event and am planning to come check join in2010.

So to anyone who may be interested in placing an order jointly for an extra tank or two which will help us all with freight costs then perhaps we can work something out jointly?

I like the p-38 shape as it's wide enough in the center for both - my shoulders (ohh okay, hehee and my waistline) and the engine I have in mind to use which will be a V-configuration and am just researching engine dimensions now for the main two contending engine options....

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Instantaneous center of torque rotation

Post by Raging Bull » Wed Dec 02, 2009 10:14 pm

Does anyone have any thoughts on this idea about the rear suspension of the car Dr Goggles linked to....

The suspension on that car has a very short torque arm compared to what would seem the more "traditional" setups that run longish radius rods and therfore transfer the torque reaction further up towards the C of G...

This therefore means that under power the shorter torque arm set up would be more reactionary and provide more traction under acceleration but also more unloading and loss of traction under deceleration....

So can this perhaps lead to an instability? Say maybe when backing off to correct excessive wheelspin?

Does effectively linking both sides to compress and rebound together make this this design a bit "skatey"?

I've experimented with this idea on other race cars but don't know how it would affect in these circumstances.

Has anyone tried this suspension that can comment?

David Leikvold
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Post by David Leikvold » Sat Dec 05, 2009 11:27 am

Haven't tried it so I'm just guessing, surmising, hypothesising. I don't think there'd be much adverse reaction from backing off because of wheelspin. If the car had previously been accelerating very hard from a low speed and then broke into wheelspin, thus stopping the acceleration, the suspension would have already settled forward/back up into a steady state again so the reaction, whatever it was, would have happened already. At higher speeds the force of acceleration is much less so any reaction would also be much less.

I think they chose the short arms to maintain some triangulation in the suspension so that the diff didn't walk sideways. If they went longer with the arms the angle would decrease, even as the body got wider and rigidity and lateral stability would be lost. In theory what they've got would work but only if the chassis where the arms bolt on was well braced, which it isn't, particularly as they've chosen to run without radius rods located out near the wheels. If those close together pickup points can flex the car would be very hard to keep in a straight line. I think the car would be a real handful over one wheel bumps.

If it was mine I'd probably run radius rods and a V shaped bar over the top of the diff (two pickup points on the chassis at the same point as the radius rods and the point of the V on top of the diff centre. That would give good triangulation and stop the diff moving anywhere but straight up and down. That's the setup we've used on Trevor's streamliner. For a little better drag reduction the outer radius rods could be made with streamlined CrMo tube. The axle tubes would also benefit from being covered with an airfoil section. The other potential difficulty I see with their design is that there is no provision for body roll. Any roll would require bending of components and with the shocks so close together they don't have much leverage to fight it.
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snap

Post by David Leikvold » Sun Dec 06, 2009 10:02 am

And something I didn't think of yesterday, the weakest points in that arrangement, and thus the most likely to fail, are the two rod ends. Expect them to crack through the tread roots when the car tortures them with body roll and one wheel bumps.
I know there isn't much body roll in salt racing but consider this: Every one wheel bump over the less than perfect salt at Bonneville or over the silt at El Mirage will have the diff twisting those rod ends ever so slightly. Even scraped salt is still a series of tiny hollows surrounded by pressure ridges. That fine vibration the salt induces in the car is of no concern to most cars but every single one of those tiny up and down cycles is working on those rod ends one wheel at a time. I have no idea how long even top quality rod ends would last (how long is a piece of string?) but if they don't change them very frequently one will eventually fail without warning, one side of the diff will suddenly come loose and the car will be destroyed in a heart beat.
If anyone is thinking about copying this design I would certainly recommend that they don't.
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scooner car
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Post by scooner car » Sun Dec 06, 2009 10:15 am

Thanks everyone for there input
I think i will get some drawings from a B52 tank&use a CAD program to draw up a plan of sketeton(to make a mould from).Get a joinery company to cut it out on a CNC from custom wood.Then get a fiberglass mould made.
I am looking at using a Nissan VH45&twin turboing it
Dont know about a trans,maybe 2x shortened 3 speeds joined together???
With the diff does it need to have full floating hubs???like a truck diff
Thanks
Scott

David Leikvold
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shape

Post by David Leikvold » Sun Dec 06, 2009 12:46 pm

Scott, if you have trouble finding dimensions for the B52 tank you could always use the ones recently posted for the P38 tank and just scale them up a bit. Don't forget that the original intention of any belly tank was to carry as much liquid as possible with as little aerodynamic drag as possible. That isn't exactly the same thing we are wanting. I don't see any real benefit in keeping the cross section of the tank circular all the way along the car, that is just wasting frontal area and increasing drag.
By all means keep the tear drop shape overall but don't make the tank any wider than it actually needs to be, so in other words, don't make any part of the body wider than the engine or the driver. The cross section in the middle of the car should be a vertically oriented ellipse, preferably with a flat bottom under the driver's seat. Al Fountain's car is the original shape because the engine is very wide, whereas your VH45 is a much narrower engine.

It wouldn't be impossible to build the plug for the mould yourself. Just cut the semi-circular cross section stations from custom wood, mount them securely on a central spine on a full length base plate and then run thin strips of custom wood in one piece from front to back screwed to each station. They will naturally follow the curves you want. Sand them back to circular (rather than ribbed like an airship) and they can then be glassed up and smoothed to form the finished semi-circular plug. Then you just have to make two body panels from the mould. If you were to run a flat bottom section you could make up a filler piece to put in the mould so the second part came out the finished shape. The two piece body would also give you easy access to work on the car. If you then cut the top half into three pieces, i.e. nose, canopy and engine cover you could, with some more thought and a bit of fibreglass work then attach all three pieces without needing any external fasteners. Neater is always better.
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Post by Rob » Sun Dec 06, 2009 2:34 pm

I was always led to believe that the large P-38 tank was 13' 6"?

I'm sure Alan Fountain would measure his (B52) tank for you if needs be.

Cheers,
Rob
I owe, I owe, so off to work I go.

scooner car
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Post by scooner car » Sun Dec 06, 2009 7:04 pm

Hi Dave
I was going to get round discs cut out of custom wood,with a round hole in the middle
i was then going to glue these discs onto a dowl or tube
then tack on some thin wire ribs&then plaster cast over the ribs
this will be the exact size of the belly tank
the make a mold off this

David Leikvold
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half

Post by David Leikvold » Sun Dec 06, 2009 7:31 pm

Scott, if you did the semi-circular method you'd only use half the materials and only have half the work to do. No point making it harder than it needs to be.And the mould halves for a full circle plug would be virtually identical anyway.

Rob, maybe the P38 had more than one size belly tank. I don't know but perhaps they had a few different options so that there was always a usable tank where they were stationed. Mind you, an extra foot of length wouldn't add much volume unless the diameter increased accordingly. Any WW11 aviation historians out there who could help?
Good, Fast, Cheap, pick any two!

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