Best way to mount Manx seat to Slimline frame?

Is there a standard way to mount a Manx solo seat to a Slimline frame? I just got my Manx seat (UK made, fibreglass base) and there are four threaded mounting holes on the bottom, which line up with nothing on the frame.



Norton Race Parts sells a flat alloy plate that fits under the entire seat base and clamps to the frame tubes at the front and mounts by spacers to those two weird square seat mount tabs on the top shocker mount lugs. This pic shows the bottom of it with clamps that go round the frame at the front etc.


Is this really necessary, or can I do the usual and cobble up some bits of flat bar in an inverted C shape running from one top shocker bolt to the other, and same again from the stock oil tank and battery box lugs further forward on the frame? The fibreglass or plastic seat base is a bit thin and flexible though, so does it need a flat plate like the NRP one to support it? I can make up such an alloy plate with a bit of work. But is it overkill? I do have the frame cross brace stud and spacers so figure a rubber pad on that will help support the seat base.

Or is there a better way of doing it?

And is there supposed to be that gap of about an inch above the top shock mount and the seat like in the below pic, or do I need to drop that rear fender down half to maybe one inch?


I built this bike about 35 years ago and recently dragged it out of the shed after a 30 year hiatus so getting back into Featherbed mode.

Pic of the seat base showing the four holes that line up with absolutely nothing...
(Please disregard the gawdawful wiring. That's they way we did things in 1985 when I built it in my kitchen.)

Why don't you make 2 brackets one each side of the bottom of the seat and mount on the top shocks like the Commando's set up. When I built my 850 Featherbed I ran it with a interstate seat just had to remove the seat brackets and reinstall where it needed to fit the Featherbed frame, not a hard job to do and 2 simple brackets I be doing the same on my Slimline frame.

ashman said:

Why don't you make 2 brackets one each side of the bottom of the seat and mount on the top shocks like the Commando's set up. When I built my 850 Featherbed I ran it with a interstate seat just had to remove the seat brackets and reinstall where it needed to fit the Featherbed frame, not a hard job to do and 2 simple brackets I be doing the same on my Slimline frame.

Click to expand...

That or something like it was my first thought. But a) the fibreglass seat base seems very thin and flexible, not solid pressed steel like the Commando. So that seems to be why some people use an alloy plate under it. But is it necessary? I don't know.
And b) the top shockie mounts line up some inches behind the rearward bolt holes in the seat in the hump area so the Commando type brackets have nothing to bolt on to, unless once again we are back to something like the flat alloy plate extending back from the bolt holes.
It sure would be nice to have the Commando style quick detach feature to lift the seat off for maintenance etc, especially if I end up with a small battery in the hump. Seems like i am forever charging or changing battery in one bike or another. Bane of my existence... So whichever way I go with it, will look at using slots rather than holes on the mountings to facilitate lifting it off. Good idea. Thanks.

Occy Straps !



Just Kidding , use No. 8 wire .

Er . . .

Theres some things like this , but the right hand sides bent up 45 degrees , 3/4 the way around . AND its flat right down most of the way
in back of it , too , with a 45 kink out , at the end ( far Rt. ) BUT these'd only be o.k. if it were PINNED elsewhere , for locationaliseation .

And the silly 16 G ? tin things just hold it down on the pins . Perhaps . Seeing what youve got in it , 3/8 in. coach bolts should do .

------------------------

look more like this ,


with the bottom longer , folded back on itself , the Rt. Angle - attach there to seat . IF you see what I mean , Pins locate it , these onto frame - clip over . Q.D.

IF your frames got seat hinge pins , Id do a custom bracket from sheet , cut back to a inch or so strip , with Rt. angles & bends etc .

Looks like its got bits of metal for the holes , where yours are ! .



Adda .


these are of some significance , for that , std. on that frame .



ARGGHHH > !



Some've gotta longer tin bracket , fwd . with one found hole . 3/4 steel strip .

You've forgotten your medications again, haven't you Matthew!

How does YOUR seat not fall off . ? we prefer them not to . isit a ES2 F'bed ?

Hows the turps , up there ? .

Matt Spencer said:

How does YOUR seat not fall off . ? we prefer them not to . isit a ES2 F'bed ?

Hows the turps , up there ? .

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Yep - I'll post a couple of pics when I have time

I would try to reinforce the seat a bit first, then fit the brackets /hinges. 4 mounting points in a rough rectangle to take the rider’s weight. Or possibly sliding fit from rear, with vertical securing allen screw at front centre.

It is common practice when fitting a race seat to many bikes, to put a thin sheet of aluminium under it to tie it to the mounting points. I would not make machined clamps to hold it - do it LIGHT, but firm. THe four mounting holes in the seat would probably sit nicely above spacers on an alunimium sheet
If you fit the sheet to the frame, then take it off and drill the holes for the seat screws, you will probably be OK
That sheet in the photo looks a bit wrong. I would not do it like that, although there might not he many holding points on a slimeline frame.

I would try to cobble up a short cross-plate that would mount rigidly to the seat base, then extend forward the inch or so necessary to engage the two prongs that hold the stock seat.
At the rear, I would do something like the 2nd picture of post #6. Then make a matching strap to rigidly fix to the seat having vertical prongs to engage the holes in the cross brace (post #6).
Then a tab ar the hump rear for a Dzus fastener.
Overall, it is a modified Atlas/Dommie arrangement.

Good luck and tell us how it worked out.

Slick

Yep . In the First Photo , it looks like the aft holes , one each side , Might ? - get the ones on the cross bracket .Are the seat holes threaded ?

IF there were the rear facing prong or prongs to mate at the front , Push on there - drop & fasten - two bolts up Under rear . with dexterous fingers .



Over Center catches are dime a dozen .

Re First order .



Relieved BOLT ENDS for underseat Installation might stop the air being blue .
USUALLY theyre rounded Cnr Ends . And Use SHORT ones , Reqd. Length + 50 % maybe .

THESE you usually purloin from scrap yards -- holding Car Seats to the seat runner rails .
Seeing theyre both seats , and underhand , we can see why they use' em .



You could use ( ford ) FALCON seat bolts . If you werein Aussie .

Thanks all. Well it looks like there are as many ways to mount a Manx seat as there are Manx seats and no universally accepted "proper" way. So in the end I have made up an alloy plate something like I posted in the first post, but without the clamps at the front. My seat base is so thin it needs the extra support of the 3mm alloy plate. Mounted it to some standoffs rising from the original Atlas seat brackets on the top shock mounts at the rear, and by an angle bracket from the plate down to to the original Atlas tool tray mounting tabs at the middle. (With the Manx tank, the "prongs" are way up under the tank by 4" or so.). Front of the seat rests on the frame, on rubber strips etc. or maybe some spare Manx tank mount rubbers. The cross-bolt between the two subframe loops also supports the weight of the plate, after the lugs were cut down. Whole thing is designed to lift off with the removal or possibly just loosening of the two bolts in the former tool tray mounting tabs.
Will get it finished off tomorrow and post pics.

That sounds like a good solution. Perhaps you can use Dzus fasteners in the tool tray holes to make it quick detachable.

Slick

That's a good idea. I have a mate who is an aircraft engineer and those guys have all kinds of trick fasteners like that that so will have a scrounge around in his shed.

HopperXL said:

Thanks all. Well it looks like there are as many ways to mount a Manx seat as there are Manx seats and no universally accepted "proper" way. So in the end I have made up an alloy plate something like I posted in the first post, but without the clamps at the front. My seat base is so thin it needs the extra support of the 3mm alloy plate. Mounted it to some standoffs rising from the original Atlas seat brackets on the top shock mounts at the rear, and by an angle bracket from the plate down to to the original Atlas tool tray mounting tabs at the middle. (With the Manx tank, the "prongs" are way up under the tank by 4" or so.). Front of the seat rests on the frame, on rubber strips etc. or maybe some spare Manx tank mount rubbers. The cross-bolt between the two subframe loops also supports the weight of the plate, after the lugs were cut down. Whole thing is designed to lift off with the removal or possibly just loosening of the two bolts in the former tool tray mounting tabs.
Will get it finished off tomorrow and post pics.

Click to expand...

A few pics to go with this earlier post of mine:
The 3mm alloy plate mounted to the frame.


But first the alloy plate, and the angle bracket are attached to the seat base.


Plate sits at the front on extra tank rubbers, and in the middle on the angle bracket going down to the Atlas tool tray mounting tabs.


And at the back it sits on two standouts from the top shock mounting L bracket the Atlas seat attached to. I have made this adjustable at the moment until I get the tank delivered and set up the exact final seat position.



Overall, looking good:


That angle bracket going to the tool tray mounts has since been painted black to make it blend in with the frame. Next job is to install the generator-end-mount regulator and get rid of that mess of wiring under the seat.

Thanks for all the tips and input,guys.

That all looks good and nicely done..

Slick

Looks like a regular Narly/Horton factory over there! Would love to see some more pics of the projects.

t ingermanson said:

Looks like a regular Narly/Horton factory over there! Would love to see some more pics of the projects.

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The one in the background is the Narley. A Harley 45 Flathead engine out of a Servicar Trike. "How to make your Norton go slower". Although they will pull their 100mph with a bit of breathing on them, so a legitimate Ton Up Boys mount. And Harley had the 750 Flathead racers doing 149.9mph at Daytona in 1969, so faster than a Manx has been officially timed, I believe. A mate and I built it years ago just for a bit of fun and because my dad was an old time Harley Flathead racer and always wanted to put one in a Featherbed bed with four speed foot shift but never had access to the parts to do it in Tasmania in the 1940s. Few pics of the bike and one of the old man on his 1942 WLA beach racer. I have the timing slips somewhere from when he cracked 102mph on it on the beach.