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350TSS · 08-08-2019, 07:41 PM

Last two days I spent tidying up the external finish of the tank and the fly-screen, laborious and dull work (and reading) – nothing photogenic.

I carefully trimmed the tank top to better match the base and considered further my idea of a ledge to act as a gasket face. This will not work as the mould for the ledge was taken from the bottom of the tank base and the top of the tank base does not match it sufficiently well. There is a lot of mileage/ hours yet in successfully marrying tank top to tank bottom.

I also cut the hole for the filler insert and dummy fitted it and realised that I had miscalculated on the insert’s depth or rather I applied additional laminations to the top surface rather than the bottom – it was too shallow so the filler arrangement would be about 4 to 6mm proud of the tank top. To alleviate this I laid down 4 reinforcing laminates on the inside of the tank top around the filler hole but I have no way of knowing whether this will be too little or too much until the resin sets and then it is too late as it will be virtually impossible to evenly sand down any excess. The aluminium filler arrangement complete with hole for the filler neck was installed in the insert which I must now to bond to the tank top . I think there are two chances at the end of this process of the filler cap being both a) flush with the tank top across its circumference and b) straight i.e. - slim and none.

Yesterday I spent a couple of hours pondering how to make the front fork retention arrangement for attachment of the front of the seat. The bridge on the frame under which the fork is due to locate is approximately level, the frame tubes behind the bridge rises at c 35 degrees and the bottom of the seat base rises in the opposite direction at c 20 degrees. My datum for measuring it is a piece of fresh air at the mid-point between the frame rails about 55mm below the bottom of the slightly variable height seat base about 45 mm behind the lower most rear edge of the bridge. I had 2 goes at making it in “Oasis” foam with the idea that I would just encapsulate it in CF but to get the section I would need I think the rear suspension rocker will impinge upon that space also my chain oiler reservoir is partially in the way.
I obviously want to make the mounting as light as possible (no point in making a CF seat if you are going to lumber it with a boat anchor for a mounting arrangement) so steel tube was initially rejected and aluminium plate 3 or 4mm thick considered. The point where the seat base is parallel to the underside of the bridge is about 175 to 200mm distant from the bridge so even aluminium plate will be quite heavy and quite a lot of leverage will be applied to the mounting bolts so I think I need more section than 4mm for it to be stiff enough to adequately retain the front of the seat, There will be pads resting on the frame rail (rubber) about where the main weight will be applied to the seat. I would also rather make it from one sheet with the fork tangs cut out so that both tangs engage at the same angle and any bending in the manufacture of the plate plate is common to both tangs.
I considered a plate with say 6 to 8mm folds on each side to provide the sectional stiffness but if the folds are present on either side the plate cannot be bent. If it is a straight folded sheet it will need to be at least 300mm long to marry with the seat base underside where it is parallel with the bridge and have sufficient depth of surface contact so that the attachment bolts spread the load – it would be too heavy and the 3 or 4 retaining bolts would be directly under my bum.

The best way to do it with the tools and skills I have (no aluminium welding) has exercised both brain cells for a good few hours and no clear resolution is in sight. But this is exactly why I love project bikes rather than bolting together somebody else’s idea of how to do it.

08-08-2019, 07:41 PM	#968
350TSS Too much time on my hands member Join Date: Jan 2013 Location: Shipbourne Bike: M900 Posts: 1,419	Last two days I spent tidying up the external finish of the tank and the fly-screen, laborious and dull work (and reading) – nothing photogenic. I carefully trimmed the tank top to better match the base and considered further my idea of a ledge to act as a gasket face. This will not work as the mould for the ledge was taken from the bottom of the tank base and the top of the tank base does not match it sufficiently well. There is a lot of mileage/ hours yet in successfully marrying tank top to tank bottom. I also cut the hole for the filler insert and dummy fitted it and realised that I had miscalculated on the insert’s depth or rather I applied additional laminations to the top surface rather than the bottom – it was too shallow so the filler arrangement would be about 4 to 6mm proud of the tank top. To alleviate this I laid down 4 reinforcing laminates on the inside of the tank top around the filler hole but I have no way of knowing whether this will be too little or too much until the resin sets and then it is too late as it will be virtually impossible to evenly sand down any excess. The aluminium filler arrangement complete with hole for the filler neck was installed in the insert which I must now to bond to the tank top . I think there are two chances at the end of this process of the filler cap being both a) flush with the tank top across its circumference and b) straight i.e. - slim and none. Yesterday I spent a couple of hours pondering how to make the front fork retention arrangement for attachment of the front of the seat. The bridge on the frame under which the fork is due to locate is approximately level, the frame tubes behind the bridge rises at c 35 degrees and the bottom of the seat base rises in the opposite direction at c 20 degrees. My datum for measuring it is a piece of fresh air at the mid-point between the frame rails about 55mm below the bottom of the slightly variable height seat base about 45 mm behind the lower most rear edge of the bridge. I had 2 goes at making it in “Oasis” foam with the idea that I would just encapsulate it in CF but to get the section I would need I think the rear suspension rocker will impinge upon that space also my chain oiler reservoir is partially in the way. I obviously want to make the mounting as light as possible (no point in making a CF seat if you are going to lumber it with a boat anchor for a mounting arrangement) so steel tube was initially rejected and aluminium plate 3 or 4mm thick considered. The point where the seat base is parallel to the underside of the bridge is about 175 to 200mm distant from the bridge so even aluminium plate will be quite heavy and quite a lot of leverage will be applied to the mounting bolts so I think I need more section than 4mm for it to be stiff enough to adequately retain the front of the seat, There will be pads resting on the frame rail (rubber) about where the main weight will be applied to the seat. I would also rather make it from one sheet with the fork tangs cut out so that both tangs engage at the same angle and any bending in the manufacture of the plate plate is common to both tangs. I considered a plate with say 6 to 8mm folds on each side to provide the sectional stiffness but if the folds are present on either side the plate cannot be bent. If it is a straight folded sheet it will need to be at least 300mm long to marry with the seat base underside where it is parallel with the bridge and have sufficient depth of surface contact so that the attachment bolts spread the load – it would be too heavy and the 3 or 4 retaining bolts would be directly under my bum. The best way to do it with the tools and skills I have (no aluminium welding) has exercised both brain cells for a good few hours and no clear resolution is in sight. But this is exactly why I love project bikes rather than bolting together somebody else’s idea of how to do it.