Slow Monster rebuild

[350TSS]

I started to think about the tank mould and quickly realised I had a problem, when making the pattern I had assumed that the filler bolted through the visible tank top surface. Stupid really as I only had to open the filler cap to see how it worked. The filler cap has no connection with the outer surface of the tank but rather is bolted to a recessed enclosure about 15mm below the surface. This would be impossible to incorporate into my tank pattern as it now sits.
I considered manufacturing a new plate to bolt to the top surface but this would have involved accurately cross drilling the surface plate to take the hinge pin for the cap itself.
I would also have to make up the neck that the cap locates into and seals against and this would have to be at the right height viz a viz the tank surface or the cap would not sit flush or more importantly seal. Looking at the cap itself there a number of critical dimensions measured from the tank surface, depth of mounting lugs, point of engagement of the filler cap in the neck, compressed depth of the sealing ring, depth of lip for engagement of locking latch. Manufacturing a new plate to hold the filler cap was not going to end well.
I therefore had to find a way of manufacturing the recess that I could bond into the tank after the top skin had been manufactured but before the tank base was also bonded to the tank top surface.
Scouring the garage for something suitable to make a mould from I came across a pot I keep all my chuck keys in which was exactly the same diameter as the filler cap plate.

I re-cycled some 3mm polypropylene from one of the belt cover moulds and I now have a reasonable facsimile of the original steel tank recess with a nice big flange to bond into the new CF tank when it gets made.

I cut the polypropylene with a jigsaw with a fine toothed metal cutting blade in. The polypropylene was melting with the passage of the blade then re-forming behind the blade so I had to go round each circle about 3 times before they parted company.

[Mr Gazza]

Originally Posted by 350TSS

This would be impossible to incorporate into my tank pattern as it now sits.

Not so.

You could make a male version of the recess on your lathe, from a piece of MDF of appropriate thickness.
This would then need to be shaped to the gentle contour of the inside of the mould, where it sits.
It could be highly finished in vitro as it were. You could then hold it in place on the bolted up mould halves with a couple of small screws from the outside. (don't forget to remove these before release!)
Then apply a small radius of plasticine round the joint.
Plasticine is great stuff for adding radii and fiddly bits inside finished moulds. Composite suppliers sell the stuff cheaply for that purpose. You can also get dumbbells to form radii of different radius
These are usually made in stainless steel and are literally just balls of differing diameter connected in pairs by a rod. They make a good enough finish on soft plasticine to pass on the finished moulding... Maybe with just a quick compounding?

You could still add internal radii on any of your existing moulds this way to aid release.

Just found an image for you and was reminded that these are used for pressing in wax fillets...Wax fillets of different radii are also available from your composite supplier..

Obviously plasticine and wax fillets are one use only and need to be cleaned off and re applied each time the mould is prepared.

[350TSS]

I will obviously still have to make the filler neck with the correct position for the locking latch, I will machine this from aluminium bar 60mm dia and bond it into the new recess

[350TSS]

I picked up some titanium rear sprocket nuts on e bay. These were "seconds" with very slight defects, hardly noticeable and certainly not affecting serviceability , they were about 1/2 to 2/3rds the price of perfect ones and will save another 24g of un-sprung weight.

They will be drilled for lock wiring.

[utopia]

Originally Posted by 350TSS

I picked up some titanium rear sprocket nuts on e bay.

Er .. I hesitate to mention it but .. the Dymags use bolts to mount the sprocket.
They're low-headed hex socket bolts too (thus giving about 4mm clearance on the swingarm), so probably hard to find in titanium.
To date, I've left the std bolts in. They rotate on a very small radius anyway, so they add very little inertia/gyro effect.
Nevertheless, I'd be interested to hear of any titanium replacements that you can find.

[350TSS]

Mr Gazza
The impossibility was to do with the way in which the pattern was made with a 9mm ply skeleton and dense foam under a skinning of body filler. There was no way I could break through the surface and cut out a recess without compromising the overall pattern.
Those round balls and rods look useful what are they called as I would like to buy some

Utopia - Not my dymags they have studs and nuts - mine were for an S4 not an M900 although I specified a 520 chain and sprockets

[350TSS]

Utopia I am now worried I have a clearance problem on the SA , but it can wait until I install the SA and rear wheel - better to be forewarned though

[utopia]

Originally Posted by 350TSS

Utopia - Not my dymags they have studs and nuts - mine were for an S4 not an M900 although I specified a 520 chain and sprockets

Originally Posted by 350TSS

Utopia I am now worried I have a clearance problem on the SA , but it can wait until I install the SA and rear wheel - better to be forewarned though

Hmmm ... I would have thought the rear wheel would be the same for both an S4 and an M900, both having the double sided swingarm.
(and just in case you were wondering, despite my bike being a 750, it has an M900 ally swingarm and wider, M900 rear wheel).
I suppose they may have changed the design, but I would be a little surprised at that.
Anyway, sorry to be the harbinger of worry.
I've just measured my bike and I have about 12mm clearance between the outer face of the sprocket and the inner face of the swingarm, if that helps.
That's on the original, Talon sprocket as supplied by Dymag, but my replacement Renthall looks to be the same (I had wondered if it was slightly counterbored, but no).

[Mr Gazza]

We always called them dumbbells in the trade, but I see them referred to as fillet rubbers and fillet balls here.. https://www.ecfibreglasssupplies.co....uct/wax-fillet .. Other suppliers are available.

Regardless of how you made your mouldtool for the tank, it is still easier to make an insert in the mould for the filler recess. It would have been difficult to split the mould over the recess and an untidy way to mould it with the flash line down the middle. With the recess as a separate component it will be far easier to release. Provided you remember to very gently taper the sides.
I think you will be better off machining an accurate part for this, rather than hoping that the filler will fit the Brownie bites carton. Certainly on an injection model, the filler has a peripheral O-ring that takes no prisoners when you go to fit it. and then there is a surface rubber seal which is equally precise in it's requirements to fit.

All you need is an accurate stepped disc, you can measure and add the internal radii in wax/plasticine after fixing it in the mould... those will become external radii on the moulding... Obviously.

Alternatively, you can buy "flush" fillers which actually mount to a surface (and so are slightly raised in reality) you would just need to drill a hole for the filler neck.

Fairly sure my Renthal sprocket is counterbored for the (Alloy) flange nuts.

[350TSS]

Thanks guys,
The carbie monster tank does not have a seal, the filler cap assembly simply drops into a recess in the tank and bolts to the bottom surface of the recess, so no worries about accuracy and machining grooves for "o" rings etc.
I agree that splitting the tank through the middle of the recess would be a) difficult and b) likely to lead to flash lines. The precise positioning of the mould splitting for the top surface of the tank is still "fluid", current thinking is to split it front to back rather than down the middle with the widest point of the frame the reference point at the base of the tank and the highest point of the expansion blister (as per 900SS tank) at the top.

I bought the dumb bells of e bay for £25 delivered , wish I'd known about them a few months ago, thanks anyway Mr Gazza.
As to rear wheel /sprocket/swinging arm/chain alignment I will check this when it gets put together but I cannot foresee it being a massive issue as the Chain alignment with the swinging arm is fixed , the only concern is the position of the surface the sprocket bolts to on the wheel relative to the inside of the swinging arm.

[350TSS]

After my usual 3 -4 hours fibre-glassing, I thought I would try to tidy up the filler cap, the gold painted lid was pitted and the outer ring with the machined grooves was corroded/stained. Twenty minutes with a wire brush on the outer ring and it looked worse than before I started, so, I decided to get rid of the grooves. Half an hour with a file and they were gone but there was some collateral damage on the lid so that got treated to 240 wet and dry.
Here are the before and after pictures, I am leaning towards not painting the lid but rather treating it to progressively finer wet and dry and 10 minutes on the buffer.
fallout frank horrigan
fallout ian

[Darkness]

Just be careful to keep that Elefant safe: they’re a protected species you know!

[350TSS]

Today I have mostly been making ……………………………..swarf.
The fuel filler neck to be slightly more accurate from a 60mm long billet of 2.5” round bar to a c4mm wall tube with an ID of variously 45mm and 43mm. The fuel filler neck will be bonded permanently into the tank filler recess.

I made it a bit more complicated by deciding to make provision for a re-moveable mesh stainless steel filter. I found a supplier of the mesh on fleabay who offered various grades as follows:
Mesh Count Description Nominal
Aperture (mm) Wire Diameter Open Area (%) Weight kg/m²
4 Heavy 5.45 0.9mm (20 SWG) 74 1.61
8 Varroa 2.47 0.71mm (22 SWG) 60 2.00
10 Coarse 1.98 0.56mm (24 SWG) 61 1.51
20 Medium 0.915 355µm (28 SWG) 52 1.25
30 Insect Screen 0.567 280µm (32 SWG) 45 1.17
40 Vivarium Vent 0.411 224µm (34 SWG) 42 1.00
60 Papermaking 0.263 160µm (37 SWG) 39 0.76
80 Fine 0.178 140µm (39 SWG) 31 0.78
120 Filter 0.122 90µm (43 SWG) 33 0.48
200 Super Fine 0.075 53µm (47 SWG) 34 0.28
400 Metal Silk 0.035 28µm (49 SWG) 31 0.16

I opted for the 40 grade being a compromise between stopping rubbish (but not water) getting into the tank and not choking the filling process too much so that the petrol delivery pump does not sense the back pressure and auto stop. With only a 42% open area of the mesh the effective size of the hole at the bottom will have to be c2.4 times the surface area of the internal diameter of the neck. The neck can only be 60mm deep because on the original tank the space between the filler recess and the bottom of the tank is that big, the original air box is a massive intrusion into the tank capacity. My tank design is deeper but I have no way currently of measuring by how much so I decided to opt for the original Monster tank dimension. The limited original depth of the filler neck obviously restricts your ability to meet that ratio.
Thinking about it as I write I could probably have got away with the 60 grade mesh, however the mesh was only £2.99 for a 150mm x 150mm sheet so I could easily buy the finer mesh when I have some experience of the tank filling without auto stopping the petrol delivery pump.
The design I have come up with I think nearly makes that 2.4 ratio but still allows the mesh filter to be attached to the neck and be capable of removal for cleaning.
Water ingress is by far the most likely contaminator of the fuel and this will be alleviated by using a British bike style fuel tap (with reserve tap and with right angle exit hole also with mesh filter on the dual entry ports) threaded into an aluminium boss which will be bonded into the tank. This boss will have a “ditch” to trap any remaining water. Finally the original plastic circular filter will sit between the tank and the vacuum pump.
The tank will be vented via a boss on the blister on the top of the tank connected to non-return valve as per a 900SS. The original Monster tank also I think has a vent in the filler recess connected via internal pipework to a drain pipe that exits from the tank near the petrol outlet pipe and is connected to a drain tube and thence to atmosphere/road. I am reluctant to include this complication as it is another potential place where leaks can occur but you may convince me otherwise.
I did a check on the rear sprocket stud/swinging arm potential clash and I think the picture taken from directly above shows that there will be clearance, not much but a few mm as the spindle boss which is/will be bearing on the swinging arm clearly protrudes further than the sprocket studs. Chain alignment will obviously be checked on assembly.

image hoster

[350TSS]

Sorry the table above did not come out when posted but you can follow the numbers from the first line of the mesh details.
Darkness: I can confirm no elephants were harmed in the making of this bike - in fact a number have been preserved in Albie's monster rebuild

[Darkness]

Originally Posted by 350TSS

Darkness: I can confirm no elephants were harmed in the making of this bike - in fact a number have been preserved in Albie's monster rebuild