Description
Dear All
I've just about finished the CAD for my new fury tank for my IRS fury.
I've designed the tank to fill the transmission with about an inch clearance to the prop shaft. My reasons to do this were:
fuel tank and inch round your prop shaft, wouldn't be my choice...
- keep it at the back (even in the event of a rear end shunt, it may still split but at least its further away from you)
- find ways to lower the mass, even if it means having two separate tanks down the rear corners, with a T connecting the outlets up
- aluminium (stainless will be heavy, reduced mass, no rusting. ok it will still corrode but not the same way) and more baffles
- injection won't make any difference to this, so good luck 
is yours different to this one?
looks nice and low?
[Edited on 3/12/12 by blakep82]
Hi Blakep82
The fury tank (at least mine) used to sit higher and was the most far back thing on the car - totally the wrong place for that mass.
Ali is an option, but I can't weld that myself.
I was also thinking of using the tank as a buck for a mold for a carbon fibre tank instead. I'd definitely get the weight down that way, and
there are plenty of tank sealing kits so the fuel doesn't harm the CF/kevlar.
With regards to the prop - it doesn't wrap around, but sits about 1-2" lower than the tank. I'll also put a prop-catcher in there as
well. The fury has ally panels between me and the tank and nothing between the tank and the ground. there's little difference between a split
tank hitting the ally panels at the back of the seat, and a split tank hitting the transmission tunnel sides.
[Edited on 3/12/12 by FuryRebuild]
If the prop lets go and starts to flail around in the tunnel, will the tank survive?
ETA: Ah, we cross posted You have a prop catcher.
[Edited on 3/12/12 by scudderfish]
it will with stainless - very tough.
I don't hear of props going often, but will be putting a prop-catcher in anyway.
quote:
Originally posted by FuryRebuild
it will with stainless - very tough.
I don't hear of props going often, but will be putting a prop-catcher in anyway.
does anyone know anyone who's lost a prop? I've had this prop for years and it's taken a lot without issue. It's also rated for loads of torque and one that i bought from Fisher when I originally went for the car.
I lost a prop in mine, but then if you look at the pictures in my archive you can see that I lost quite a lot more. The damage from the prop was not
too serious, but I would not want that anywhere near the tank,...
As a wild idea, are you planning on having any passengers? You can see where that question is leading too,.... 
hth
Hi Howard
I seem to remember replying in your thread offering commiserations after that one - you did a proper job. I lost it at harewood and snapped a wheel
off, as well as the standard radiator damage and a lot of other carnage as well.
I think with a trusted prop and prop-catchers in there I'll be safe.
I do occasionally have passengers, but putting the tank there wouldn't pass scrutineering - the tank must be able to drain to the ground rather
than be in the passenger compartment. The new ECU and PDM will be going infront of the seat under the passenger's knees anyway.
I know of 1 that let go
I have put steel plate on the inside of my tunnel where the front UJ is
Prop catcher is a good idea
when you say scrutineering, is it for racing? If so, how about replacing the floor on the passenger side with the fuel cell, I know it might sound
scary but in most tin tops the rear seat is formed by the fuel tank.
If you are racing just how much fuel do you need? If you do need more to make it viable on the road, how about 2 tanks, long range in the back that
feeds the one in that is the passenger seat?
just some random thoughts,..
and yes thank you for the commiserations, all I need now is the time to finish off the wiring, and put the bonnet clips on and then she'll be
ready for an MOT,... too long on axle stands really!
My friend broke a prop and has a scar on his leg to prove it. I think its usually homemade/unbalanced ones that fail. Properly made it should be fine,
but with 2 well fitted prop catchers its definately fine.
Just to add the other common failure path is sprocket nut coming loose.
[Edited on 3/12/12 by JoelP]
I had one fail
did have a very highly tuned pinto fitted thou!!!
this was bought from a well known Kitcar supply and was balanced.....
[Edited on 3/12/12 by gavin174]
Yes propshafts do go walkabout in the days gone bye an important part of doing any RWD service wass checking the coupling bolts are tight and
the condition of the UJs, also you have to consider where the prop ends after a frontal impact. The other aspect is maintenance anything that
reduces access to other units or makes a removing the component difficult or impossible isn't the way to go.
All design should follow the KIS principle Keep It Simple, you seem to have the desire to make everything as complex as possible, if there
is no real gain why suffer the pain, just because a thing can be done doesn’t make it a good idea.
quote:
Originally posted by FuryRebuild
does anyone know anyone who's lost a prop? I've had this prop for years and it's taken a lot without issue. It's also rated for loads of torque and one that i bought from Fisher when I originally went for the car.
quote:
Originally posted by gavin174
I had one fail
did have a very highly tuned pinto fitted thou!!!
this was bought from a well known Kitcar supply and was balanced.....
[Edited on 3/12/12 by gavin174]
Tim Hoverds RGB Fury broke the shaft and went up in smoke as a result. Someone on here had his break on his almost new MK (?) and go up i smoke. Pif on here had his go and it grabbed the wiring loom, ripping it all out... several othersas well.
going back to the tank design for a moment.....
whould it not be easier to make it in 2 parts and pipe them together ?
quote:
Originally posted by mcerd1
going back to the tank design for a moment.....
whould it not be easier to make it in 2 parts and pipe them together ?
I did think about two tanks, but when nearly all the work is in the CAD rather than anything else. From now on it's just a bit of welding.
And to the comment "making it complicated for the fun of it" the plan is all about packaging and placement of mass. i get to move
significant amounts of mass down and central reducing polar moment of intertia and making the car turn in better and be more controllable if the back
decides to step out.
And I thought my fuel tank was 'out there.'
I now see myself as a relative conformist. For the record, I'm not sure that the risk/reward balance is right with your design.
ETA: I'm trying to balance my mass and aid traction by placing the tank right over the axle. I know that there are big compromised involved but
that's car design for you.
[Edited on 4/12/12 by TimC]
Hi TimC
Can you elaborate?
quote:
Originally posted by FuryRebuild
Hi TimC
Can you elaborate?
Mine's of that concept - the plan is to just go into the transmission tunnel as well.
Hi
What volume is that design then? It looks huge..
The Striker chassis is very similar to the fury and I must admit that I can see how you could use the space below the prop for a tank, I reckon's
that it would be something like 60cm long, about 18cm wide and up to 10cm high or around 10 litres of space available, not enough?
Given you've got IRS so the props not going to move, with some very good prop catcher's (you're meant to have these for scruitineering
BTW) I can see how this could work, although I would want the bottom of the tank to be very solid myself..
Certianly that's more than enough capacity for speed events
Out of interest, given it's interesting shape how would you know what amount was in it, without resorting to the 'empty to nothing and fill
with exactly what's needed' method?
The Striker in my archive started out with the tank in the same position as you had, what we did was remove that and after moving the passenger seat
40mm forward we then put a section into the alloy bulkhead and installed an 10 Litre alloy stockcar tank ( vertical type) in the resulting space
(i.e. behind the bulkhead and in front of the rear, live, axle - bottom of tank is directly above the rear tube of the chassis so well out of harms
way, access to filler is by raisng the rear deck cover)
It's about 25cm x 10cm and 35cm tall, and you can check the level with a marked stick..
It did make a noticable difference to on the limit handling though, so you're on the right track!
Hi Jim
The tank gives about 30L of fuel, and I have an ATL probe fuel level sender and matched gauge to measure the levels. I'm going to do some
track-days and some long-distance cruising but probably not compete now. However, that doesn't mean the right things shouldn't be done -
scrutineering has rules for a reason. I found that with my pinto engine, i would get about 13mpg on a cruise, and am going for a 215bhp duratec this
time, so again I expect heroic fuel economy
I did lose it at the raggedy limit at harewood and span it into the armco, probably not going much quicker than I did on the previous lap. What I
remember is that first circuit it was quick but I had all the traction I needed. Second circuit I was in the armco. It put the car out of action for a
whilse.
In this incarnation I'm looking to reduce mass and move what I can lower down. Hence rewiring the car as well. I'm going to modern projector
headlights and led rear lights, solid-state relays, a power distribution module (making my own) and mil-spec connectors and high quality wire.
Shifting weight closer to the centre will make it less likely to break away, but when it does you'll get less warning and it will rotate faster.
Hi
Where it was really noticable was on a S bend, like the ones at Loton for example
When you wanted to switch from a quick left to a quick right, very quickly, you would get it trying to wag it's ar5e as about 10kgs of fuel -
that had been at the very left hand end of a long thin horizontal tank right across the very back of the car - suddenly all moved to the other end!
Could have probably improved it with lots of baffles or lots of foam - but it also made one worry less about going off backwards when the first thing
into the scenery after a layer of fibreglass wasn't an old mini van tank
Hi
I fitted a smallish 17L tank behind the passenger seat in my Locost and tried it out in a 2 hour endurance race at Kyalami raceway here in SA this
past weekend. My best lap was almost a second faster than my previous best at Kyalami, so an "inboard" tank do seem to make a good
difference.
quote:
Originally posted by scudderfish
Shifting weight closer to the centre will make it less likely to break away, but when it does you'll get less warning and it will rotate faster.
I disagree.
When the car starts to go with a high polar moment of inertia (think of a 1kg weight on the end of a 1m stick, and you're holding the
non-weighted end and waggling it) once you have that weight moving, you have high inertia and stopping it moving (as in correcting it when it starts
to go wrong) is more difficult. What's more, you're correcting it with inputs from the front, trying to affect strange forces acting at the
back. This again fiddles with chassis dynamics.
Reducing the polar moment of inertia means turning in is easier, the car is more stable and if it goes, it requires less energy to correct it.
What's more, your rear tyres don't have the lateral forces pushing them out which means you reach the same limit of friction at a higher
speed.
I would argue that if you're losing it at higher speed, you're going to have more of a controlled drift rather than a whip. One of the
nicest cars I ever drove for this was an original wedge-shaped MR2 - you could drive it on your right foot as well as the steering wheel.
If you take a look at how race cars are packaged, lots and lots of effort goes in getting the mass down, the centre of gravity low and the polar
moment of inertia down. There's never a massive weight hanging out behind the rear wheels. The most rearward part is the last bit of the
transaxle and the wing pushing down on the chassis.
I was at a practice session at Harewood and a chap with a very successful sevenesque kept losing it (he was regularly placed in the top 5, so somewhat
good a driver). He took off his rear mounted spare wheel and was suddenly right back on the pace. that wheel and tire would weigh more or less the
same as a tank and some fuel. It's an extreme example (as in well back) but illustrates the point.
So, still doing the tank. Thinking of using the tank as a mold and making a carbon fibre jobby instead - less mass again.
quote:
Originally posted by sebastiaan
quote:
Originally posted by scudderfish
Shifting weight closer to the centre will make it less likely to break away, but when it does you'll get less warning and it will rotate faster.
Exactly! a lower polar moment of interia will help the car to turn easier, but it will be much harder to correct when it all stsrts to go wrong... I'd go for a properly baffled (non-sloshing...) rear and low mounted tank if I were you.
One last note: making the car easier to turn means the initial oversteer will develop easier as well. In a way, you are removing interia from the
system, making everything happen quicker. Good for ultimate laptimes (hence the racecar packaging) IF you can handle it. I for one cannot ;-)
On the CF tank, remember that steel / Ali yields before rupturing and CF will not. Sorry to be a bit negative about this, but I would not make the
tank out of CF for that simple reason. CF with a fuel bag, maybe.
But, in the end, it is your car of course. And I admire the amount of thought and fabrication skill that is going into your (re)build.
Hi Sebastian
Firstly I'm enjoying this debate; it's good that topics can be challenged and kicked about and I do value everyone's input and thanks
for your measured and patient explanation. I'd sooner put an idea out there and either get it confirmed, refined or culled.
that is a point you have about over-rotating it, and I expect it's going to be a major effort to learn to drive the car again, especially with
all the suspension changes I'm making - part of the setup will be the measured circle g-force tests.
When hill-climbing I used to run a setup designed for chuckability - some of the 12ft 90 degree corners are like slotting it into a back-lane, and I
used to get entry speeds into the first corner at harewood of 60mph. I have seen the evo boys go in way quicker than that
I've also gone for a good anti-roll bar setup so I can soften my springs (and changing from spax to gaz dampers) so it should now manage roll the
correct way and will be less twitchy on the larger circuits.
On the subject of tanks that is a great observation, and not one that had crossed my mind. I will have to go away and think about that very carefully.
I may just go for metal. Ali would be good for weight, but I can't weld that at home - I'd have to offset the price of someone tigging it
for me vs tigging the steel myself. Saying that I've been rigorous with removing weight, so may have to part with a few sheckels more to get the
weight. Once the ali has oxidized then I won't need to worry about any further corrosion.
What everybody tends to forget with fuel tanks is fatigue, mass X of fuel sloshing around in the tank causes the surfaces of the tank to flex
and it is not unknown for the seams to crack. Years ago an after market tank supplier ran into big trouble with a replacement tank for FX4 taxis
which split along the seam, many members who have been around here for a while will also remember the sad saga of the plastic tank man.
A fuel tank should have as few seams as possible and the folds should have very generous corner radi.
Thanks BritishTrident.
Bend-radii are at 3mm - I spoke with my cutter/press-brake people and this is the minimum radius they've recommended for stainless. it's
less for mild and i don't know what it is for aluminum.
I can push a different global bend radius through the cad to change this; it may mean the odd alignment needs resetting but the s/w will let me set
alignment per bend for this (as in radius starts at the material edge, or finishes at the edge).
I have tried as much as possible to reduce the number of welds, and have measured all the folding options to keep the welding down but at the same
time needed to be sure it was theoretically buildable.
what happened with the plastic tanks? i've not heard of that.
I would use at least 13mm radius as an absolute minimum , most commercially tanks you will find have radi > 20mm.
^^ flex in the tank was one of my concerns about your 'T' shaped tank idea
depending on how it was mounted to the chassis there could be quite alot of stress on the inside corners of the T.
the chassis might be alot stffer than the tank, but that doesn't mean it won't flex at all...
Hi
Don't concentrate to hard on getting the mass too low and forward in the car. Remember that you need weight transfer to add front end grip during
cornering. The lower you place all the weight and further forwards it is the less weight transfer you will have. Also it will exaggerate the fact that
the one mass you can not move your body which is offset to one side, this will only add to more unevenness weight transfer. Personally from dealing
with a few Furys and strikers i would concentrate on getting the loading more even across the rear axle and then play with weight transfer control to
the front during cornering IE Damper control in compression and rebound in particular.
My 2p
Cheers Matt