new fuel tank

[Bob_Rich]

HI  

Am sorting out my 1969  Lotus 7 S3  and fuel related problems but examination of the fuel tank  ( Serk steel  unit fitted in 1971 ) it is really badly corroded

so am fitting new one. It is aluminium and it arrived today  from Redline and while it look like key dimensions will tie up OK it is of a different cross section

Could someone post me a picture  of a non injection tank fitted in a standard live axel 7 Please??  It would help me with task where  I suspect will be some fettling required

thanks in advance Bob 

[Wrightpayne]

I’d perhaps give Arch Motors a call to check you have the correct tank - they probably made the one you have.

Whilst Redline are undoubtedly experts on our cars, Arch know all the nuances of the early chassis and what is needed to renovate / upgrade them to later designed components.

You may have the right tank and they are also best placed to advise on fettling bracketry to fit it.

I helped Tazio modernise an early 80s Caterham live axle crossflow and that tank had gone the same way, not helped by sitting in a garage for 20+ years unused! 

[Bob_Rich]

Hi  Wrightpayne

I know Bruce at Arch quite well --lats time I rebuilt my 7 he did the chassis/body for me as well as suspensionsn parts and the reat=r axel strong thing plate

I ordered all the parts from Chris at Redline unfortunately he was short in his stock of the fuel tank strap kit (30T022A). While it is on back order I thought it would be possible to make something to complete the installation.  The kit came with two very long M6 by 300mm bolts which  suggests to me that it is quite different to  the way my old tank was secured.   The tank fits in the space OK  But I think  if I could see a picture of the alloy tank installation  I could fabricate the necessary part my self--hence the request for a picture. Chris is going the send me the part when he gets them in  so I guess I will have to wait--its a nuisance as the weather is good !! ah well

[Gridgway]

I have been exactly here with my 80s short cockpit resto.  The old steel tank was rusted solid, so I got a new ally tank.

The steel straps that go round the old tank do not fit the new one.  It is intended to be fitted with the long studs holding an angle piece that goes along the top leading edge of the tank.  The tabs to bolt to at the bracketry that goes around the bottom of the tank are in the wrong place to bolt to - as well as being rather thin and not strong enough.

It needs chassis welding really, but I solved it by making plates to bolt to the tabs and using two long studs each side to hold the lateral retaining angle piece.  All very hard to describe.

Thought I had taken some decent pics, but can't find any.  Whereabouts are you Bob?  I'm in Epsom.  If you could see it in person it would make sense.  Or I could perhaps take pics or do a vid for you.

[Bob_Rich]

Thanks Gridgeway

 

  If I understand you you are suggesting that even with the standard alloy tank accessories I may need some fettling?  It seems the final parts from Redline are some time  off.  two pictures   one above and one below  should be enough for me to get the idea.  If you could do that I would be very grateful. what is obvious,  and what you have discovered , as have I is that the alloy tank cross section is quite different to the steel one. I am sure if I saw how it is supposed to go I could fettle something.  Got a lot on this week but would like to move the  seven up the list as the weather is good !!

I am in just south of Chelmsford in Essex.  I have friends who live near Epsom and when we see them it is about  a tad over 100  miles--I think  photo's  would be better option

Thanks for the offer of info   much appreciated

 

Bob

[Gridgway]

It's a pretty simple mod, but certainly non-standard!  I'll work out how to get some pics over the next day or so.  Hopefully I can get the boot floor out with the roll bar in place as that will make the pics simplest, but otherwise I will go from underneath!

[Bob_Rich]

Hi  Again

 

Thanks  for this  certainly  pictures from underneath and the forward facing side of the tank should be possible from underneath as well. Probably don't have to take the boot floor out just lift it a tad and should be able to get a phone camera shot.  I modified the boot floor to  into two pieces so I could remove it without taking the roll over bar out as  I have an electric fuel pump Facet unit with a filter so the get at that I need to get the boot floor out.

Anyway thank for going to the trouble

cheers 

Bob

[Gridgway]

Right I'll try to explain this.  Photos are tricky, but I have two.

The basic principle is that there is an angle piece that sits on the top front edge of the tank.  Then a long stud goes down each side from a hole in each end of the angle piece to a tab welded to the rectangle basket that the tank sits in.

However in the old chassis set up for the steel tank with straps there isn't a suitable tab.  There are though two tabs each side.  I made up a thin plate to bolt to those two tabs each side.  Then I used #two studs each side bolted to the front and rear of the plate I had made making a triangle each side.  Happily the cross angle piece has two holes in each end which gave me the idea.

Here are the pics.  This one is looking up from underneath the tank to show the plate bolted to the tabs (inner holes) and the studs going up to top of the tank (outer holes).    The rear of the tab is bent to make it perpendicular to the stud.

Then this pic shows more of the side of the tank showing the two studs going up to the angle cross-piece.  Hope it makes some sense!!

The problem with just using the long bolt supplied is that on its own, the front tab is too far forward and pulls the tank forward and over (if that makes sense).  The supplied bolt is not long enough to go to the rear tab.  It might have worked with just a single longer stud to the rear tab, but I like over-engineering and one tab on its own felt a little on the flimsy side to me.

 

 

[Bob_Rich]

Hi  

Thanks for the pictures and the explanation.  I think I can see what is intended !  I get the impression that the basic car chassis/frame on my 7 does not have the brackets to bolt to. The steel tank was firmly against the rear chassis  tube  whereas your first picture shows a distinct gap.  Anyway am busy at the moment as  summer holiday season is bringing other things to do ! (grandson etc )  so I will get onto the early next week- - might send send you a picture to show what I am thinking of doing

Thanks for the help

 

cheers

Bob 

[Gridgway]

If you want, post a picture of the basket that the tank sits in (with the tank not in situ).  Then we can see.

[Bob_Rich]

hi again Gridgeway

Got a quiet morning !! so 

I  have attached a picture of what I think is required is a small bracket at A  and B I think 

then an angle piece across the front of the tank  takes the long bolts to secure the  tank

I may also keep the original straps , tweaked, as a belt and braces sort of approach

But In saying this I think you have secured your tank at the rear ?

anyway thank for help very grateful

Bob

[OldAndrewE]

What's wrong with just using the original straps, reshaped as necessary?

[Gridgway]

I'm fairly sure that they are not long enough.  But given what Bob has got is different from mine, my suggestion was going to be too get some appropriate steel strap and make pieces to lengthen those in there.

I'd also test fit the new tank to make sure it fits and can be secured as there's no rear lateral support.  Also the side supports don't look parallel, but that must be a camera issue 

[Wrightpayne]

I asked Tazio about his ally tank swap and he just re-fashioned the existing straps.

[Bob_Rich]

thanks for all the interesting comments.

the tank does fit ok in the space where the old steel tank was.   But I don't think the new tank is square it is slightly out in that it does not sit squarely in the two brackets that the tank sits on. But I think it can be secured in OK when some rubber is put in to avoid ally to steel contact. I am assuming that the fixings in the chassis are square  as they we done by Arch  on their jigs when I had the chassis  rebuilt for my last rebuild in 2006--not done many miles since  ~5000.

what seems to me to be different is that the two very long M6 bolts provided suggest  a very different  method of securing the tank.  Also the ally tank will likely be more flexible that the old steel tank?   so that the holding force of the existing straps could  result in the tank walls yielding such a way that the tank could start to move and get the steel chaffing on the ally 

Anyway will try to make up some  clamp system using a piece of  angle when I get back on the task if the full clamp kit has not arrived by then.

cheers and thanks 

Bob

[Bob_Rich]

Hi all

 

Just a final (I hope) post on fitting the alloy tank to my S3 seven.  The attached picture shows the tank in situ. Basically my seven being a very early model with a steel tank  appears to have a different layout to the later Caterham based unit.  The new tank is a similar length  but its base is around 20mm shorter ( front to back) so there is potential for the tank to slide back and forth.  I lined the two seating points with right angled UPVC sections made from a bit of guttering and then lined it further with 25mm by 1.6mm sheet rubber.  The existing steel straps (25mm by 1mm ) were carefully measured and re-formed  over steel sections   to fit the tank nice and snug but did not bend the the straps around/on the tank. To brace the tank  I made two braces up that were trapped with the straps at the tank front and secured with M4 bolt sets to the steel section that hold the rear boot floor.  The braces were made up with 50mm 16swg ally sheet with a  12mm 1.6mm square section ally tube pop riveted on to  50mm sheet part . The tank was lined with 50mm 1.6mm rubber under the straps to soften  the force on the tank by the steel straps and to avoid ally/steel contact.  A meter check shows the tank is electrically isolated and so the tank was grounded to the OV of the rear lights  with the lead going to the M5 bush on the tank.

It seem to be OK . It is held firmly and doesn't leak and filled it with 15 litres of 97 grade E5 fuel.  The facet fuel pump need a longer  fuel hose from the tank outlet to the  pump filter on the inlet. The fuel pump was checked out again no leaks and delivers around I litre/minute into a container positioned by the front  carb so all seems OK.  Also I need to sort a fuel gauge system. The AC Delco gauge is still OK but sender  is horrible corroded and now doesn't work so I may need a new gauge and sender as the AC Delco sender is not now available.

Anyway now need to get back on the car and find out why it won't start -- Iguess that may be another post.

thanks all for comments and assistance 

cheers  Bob

[Gridgway]

On the topic of senders, mine was all rusted up and had to be replaced.  All that's available now are the generic ones with the float arm in two bits that you have to cut to length, solder together and bend accordingly.  As there is a baffle in the tank the float arm can't be very long. It's extremely hard to know how to get the right length and shape as you can's see it in the tank (obviously).

I made a full scale mockup of that section of the tank using foamboard so I could sort it out.  Seems to work ok.  You'd need to check that the generic sender available is compatible with your gauge.  I still have the mockup in the shed if pics of it are any use.  Or if I could get it to you you could use it. 

[Gridgway]

on the engine starting problem, happy to help there!  

[Bob_Rich]

hi gridgway

Speedy cables have declined to repair it- no reason given.  I have stripped it down and I am considering a repair myself but before I do I need a chat with a chemist friend on th issue of various bits submerged in petrol. I an going to start a three about the car not starting

cheers and thanks for help.

 

Bob

[jbcollier]

Yeah, the new tanks are not a drop in fitment in early Sevens.  I shimmed mine with a length of wood to get it to sit right.  Rubber on all the contact points as well.

I did another mod as I was tired of the tank being a pain to fill.  I fit a large fitting and ran a hose from the far corner of the tank to the fill pipe.  Now there is no more spitting back.