E: Engine Comet Mongrel

vibrac

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A note on belly pans
having researched the ACU rules for the new twin racer it says that the belly pan should be large enough to contain the contents of the sump. Note of course that they were thinking Jap stuff with engine oil storage not 75 year old engines on bikes with oil tanks. Now I guess the contents of a Vincent sump is that compartment tucked away at the back of the crankcase waiting to be sucked back to the tank so thats what 60cc? 120cc?
Whatever it means a small belly pan and thats important because the smaller the pan the better you can tuck the exhausts away. And just have your arguments ready for the scrutineer.
 

Cyborg

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On another note, Oil in the belly pan, standard pump?

Not sure if I understand the question, but in this case, the belly pan was more about filling up some of the space under the engine. That may make me sound more like a cake decorator than an assembler of odd motorcycle bits. The space under the engine was a result of rule #1 for this project, which is use whatever is already in inventory. Rule 2 was if I didn’t already have it, then make it. 2 came with a caveat that if I couldn’t make it, or it was ridiculously labour intensive then I could dip into the sporran. Anyway.. back to the space. The frame came from a Honda GL500 Silverwing (because I already had it along with the appropriate paperwork). It’s engine was used as a stress member, so there was a convenient mount that could be used without too much drama. The frame was set up in the mill and with minor machining the stock Vincent mount would bolt right up. Anyway, in using the stock location, the motor sits up higher than it normally would than if I was using a UFM or featherbed. Not that high if you compare it to some of the GP bikes of today, but thought it would look better with a belly pan. Some days, I’m not so sure. The oil tank ( back several pages) mounts as shown in the photo. After slaving away making it, I think the bike looks better without it and the oil tank should have gone in the tail section. You get a better view of all the monkey motion going on in the rear suspension. I’m using a standard pump and assume it wouldn’t object to pushing the return oil a little farther if the tank was in the tail.
The red thing in the photo isn’t the tank, it’s the plug for making the mold.
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1EA4AE4A-A7C1-4423-B359-76DEC1FEDCD0.jpeg
 

Bill Thomas

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Looks good to me, I think it's only because the oil tank is a different colour.
I spent years trying to make my Special look right, With a white Fi glass front mudguard,
Then one day I painted it black and to me it all came together. Cheers Bill.
 

Cyborg

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That photo doesn’t show what is bugging me. When the actual tank and seat are sitting where they will be mounted, the top of the oil tank looks like it is at an odd angle. Without CAD, which is completely out of my wheelhouse, I couldn’t have figured that out until things were assembled. The oil tank was made to fit the opening and the fuel tank was also made to fit the unusual choice of frame. While obsessing about the angle of the oil tank might make me sound a little light in the loafers, I wanted this thing to have a reasonable look to it from a styling point of view. (I’ve probably ranted about this before) Styling while still having some sort of nod to function..... unlike a lot of the current “cafe racers” out there that are strictly chasing a look without regard for function or safety for that matter. Hindsight being 20/20, it would have been wiser to build a frame from scratch and jump through the hoops to get the necessary paperwork. The GL is shaft drive and had some of that horrid stamped steel, so it took a bit of surgery. When adding tubing, it would have been nice to run the forward ones from the swingarm pivot to the steering head, but the timing cover was a bit of an obstacle. I don’t have any concerns about strength as the (engine stress member) frame didn’t have tubes there to start with. The backbone consists of 3 tubes with lots of gussets, so should be able to contain the Comet’s hp and withstand whatever forces are generated by the oddball disc brakes and scrawny tires.
Stock frame on the left.
Ps.. I have thought about painting or powder coating the oil tank black.
6D07B388-80D9-4284-9130-1BBDDB77E227.jpeg0ED7047A-47FE-4CB6-B07F-D75BAE3EDECE.jpeg83E6A892-726D-4CB0-BA67-A701B09B3D43.jpeg
 
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Bill Thomas

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VOC Member
I am the same, It has to look right to me,
I have changed my Special so many times, Fairings, Exhausts, Carbs, Seats, Brakes, Etc.
I even put the Comet engine in there once, That was the worst looking Bike I have ever built !.
The trouble is, What I like today, Might not be what I like tomorrow.
At the moment, I think the world of my 560, Just love looking at it, Just wish the engine would start !!.
But with me it has been a life time Hobby.
Cheers Bill.
 

Cyborg

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VOC Member
Will the tank touch your leg and overheat it there?
Doesn’t really come in contact. The seating position and width of the fuel tank more less keeps the leg away, although I haven’t sat on the thing with everything completely assembled in its final form. Not expecting it to be any worse than a Pre OIF Triumph or BSA etc.
Also... given the Comet ( in it’s current state) barely generates enough HP to pull the skin off a rice pudding, I wonder if it will generate enough heat to get the alloy tank to the uncomfortable level.
In that photo, the oil tank isn’t mounted, just sitting in there. When bolted in, the top of the tank slants inward slightly. Combine that with my inability to ride for any great length of time in one go, I “should” be ok?
 
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Martyn Goodwin

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That photo doesn’t show what is bugging me. When the actual tank and seat are sitting where they will be mounted, the top of the oil tank looks like it is at an odd angle. Without CAD, which is completely out of my wheelhouse, I couldn’t have figured that out until things were assembled. The oil tank was made to fit the opening and the fuel tank was also made to fit the unusual choice of frame. While obsessing about the angle of the oil tank might make me sound a little light in the loafers, I wanted this thing to have a reasonable look to it from a styling point of view. (I’ve probably ranted about this before) Styling while still having some sort of nod to function..... unlike a lot of the current “cafe racers” out there that are strictly chasing a look without regard for function or safety for that matter. Hindsight being 20/20, it would have been wiser to build a frame from scratch and jump through the hoops to get the necessary paperwork. The GL is shaft drive and had some of that horrid stamped steel, so it took a bit of surgery. When adding tubing, it would have been nice to run the forward ones from the swingarm pivot to the steering head, but the timing cover was a bit of an obstacle. I don’t have any concerns about strength as the (engine stress member) frame didn’t have tubes there to start with. The backbone consists of 3 tubes with lots of gussets, so should be able to contain the Comet’s hp and withstand whatever forces are generated by the oddball disc brakes and scrawny tires.
Stock frame on the left.
Ps.. I have thought about painting or powder coating the oil tank black.
View attachment 30591View attachment 30592View attachment 30593
Powder coating is great for outdoor furniture and the like. Has NO PLACE on a bike - see the next edition of OVR out in a few days time - a letter to the editor from Gibraltar
 

Cyborg

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VOC Member
Powder coating is great for outdoor furniture and the like. Has NO PLACE on a bike - see the next edition of OVR out in a few days time - a letter to the editor from Gibraltar
I half expected you might show up, but thought it would be to give me a digital kick in the stones for slagging the Comet’s HP.
Although I am sympathetic to your cause, I don’t totally agree. I would never powder coat a frame, especially one that was prone to cracking or one that I had monkeyed with. This one was sprayed with a relatively thin coat of epoxy primer followed by a thin coat of epoxy gloss black, so if anything untoward starts to happen it will immediately telegraph through to the surface. Normally my powder coating is reserved for brackets etc. I suppose having said that you could accuse me of hypocrisy because, although the oil tank will have rubber mounts there is always the possibility of stress cracks and repairing it with TIG would mean removal of the powder coating. I do have the rather nasty stuff to remove powder coating, but suspect I would have to use the same stuff on the epoxy... and it really stinks. In any event, if the fuel tank ends up being black, then it would make sense to paint the oil tank with the same epoxy. The belly pan is a different story. Being it is not near anything painted, I don’t think it will matter if the shade or gloss is slightly different. Thinking that powder coating will stand up better against the road rash/blast from the front tire.
On a side note... having gone to the trouble of making them out of aluminum, it seems a shame to coat them with anything.
Is there something else I’m missing with the powder coating?
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
I half expected you might show up, but thought it would be to give me a digital kick in the stones for slagging the Comet’s HP.
Although I am sympathetic to your cause, I don’t totally agree. I would never powder coat a frame, especially one that was prone to cracking or one that I had monkeyed with. This one was sprayed with a relatively thin coat of epoxy primer followed by a thin coat of epoxy gloss black, so if anything untoward starts to happen it will immediately telegraph through to the surface. Normally my powder coating is reserved for brackets etc. I suppose having said that you could accuse me of hypocrisy because, although the oil tank will have rubber mounts there is always the possibility of stress cracks and repairing it with TIG would mean removal of the powder coating. I do have the rather nasty stuff to remove powder coating, but suspect I would have to use the same stuff on the epoxy... and it really stinks. In any event, if the fuel tank ends up being black, then it would make sense to paint the oil tank with the same epoxy. The belly pan is a different story. Being it is not near anything painted, I don’t think it will matter if the shade or gloss is slightly different. Thinking that powder coating will stand up better against the road rash/blast from the front tire.
On a side note... having gone to the trouble of making them out of aluminum, it seems a shame to coat them with anything.
Is there something else I’m missing with the powder coating?
No you have nailed it. Powder coating has some elasticity so, as you pointed out, if there is a crack developing under the powder coat you will not know about it till the base material fails totally - and in a bike , especially a race bike, such a failure - without any pre-warning could be horrible to experience. Here is a photo submitted to OVR by one of my readers letter to the editor that will be in the December edition. Apparently nothing was suspected till total and catastrophic failure.

Martyn

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