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E: Engine Comet Mongrel


vibrac

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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.85BAF949-5C27-4F81-851B-9ED16737651E.jpeg1EA4AE4A-A7C1-4423-B359-76DEC1FEDCD0.jpeg
 

Bill Thomas

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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
 
Last edited:

Bill Thomas

Well Known and Active Website User
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

Well Known and Active Website User
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?
 
Last edited:

MartynG

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
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?
 

MartynG

Well Known and Active Website User
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

PIC 06.jpg
 

davidd

Well Known and Active Website User
VOC Member
I was chatting with Maurice Candy in the paddock of Road America once and his Manx was sitting there. I noticed that his frame was not painted and asked him if it rusted. He said "no, it always seems to get plenty of oil". He said he did not paint it so he can see cracks. Not practical on a street bike, but I have found many cracked frames by cleaning them and seeing the cracks in the paint (all were racers). It is one of the reasons that I keep the bike clean. It is easier to spot cracks.

David
 

Cyborg

Well Known and Active Website User
VOC Member
Just for the record David, I did take a stab at making an aluminum fuel tank to be used with a fibreglass cover. The first 2/3 went “ok”, but was turning out to be too labour intensive. As previously mentioned it just got to the point where I wanted a tank, so I could move on. Using a lighter gauge would have helped with the forming of compound curves, but then I’d have to up my game with the TIG welding. I seem to be able to sort out torch angle, arc length, amperage, pedal control, gas coverage, etc, but I still haven’t been able to feed the filler rod properly. Ok for short runs, but can’t advance the rod through my hand without bashing it into the tungsten.... then have to do the walk of shame over to the grinder. Tried a TIG pen, but not any better.. maybe with more practice. Often thought about a small variable speed motor to feed or help feed the rod.

As I ‘m currently indisposed and have time on my hands to post things.....
I don’t have any decent photos of my frame jig, but it is more or less a traditional setup. Some advantages and some shortcomings. I found this article from Tony Foale. The table he is using probably cost a kings ransom when new, but one could make something accurate enough for the job. Always interesting to see how someone else skins the cat.

 

vibrac

Well Known and Active Website User
VOC Member
Here is a Tony Foal frame I got for a song at an auction I had for a year or so it was intended for a Honda 4 engine it has some similarities to Egli. It had no providence or V5 so not easy to put on road
Tony Foal was in US when I tried to contact him
1574967524181.png
 

davidd

Well Known and Active Website User
VOC Member
I think the best way to train your hand to feed is to do it while sitting on the sofa watching tv. Keep doing it until you think you have it. Then try it with a glove on.

That is a nice article. I think the things that are important in a jig is to have everything adjustable to level. I used a table that I was able to buy. I put adjustable feet on it to level it and it is reasonably smooth.
DSCN1549.jpg
I use the right side of the jig to make the RFM and the top to make the UFM. The 2" x6" for the UFM was squared on all sides on the milling machine and I put centerlines on almost everything. The UFM portion is bolted onto the two legs which were welded to the table square. This allowed me to level the fore and aft on the UFM portion and to also remove it from the jig.
DSCN2193.jpg
I can remove it and set it on the welding table for easier tacking. Once it is tacked, I can toss it in the car are take it to my welder.
DSCN2157.jpg
I have one of these on the table and one here on the UFM jig.

The stuff Tony has is tens of thousands of dollars, which is not a surprise. His fish mouthing is expensive also. I got a Balleigh, which I considered very expensive, but it really does the job and It is one of the few tools I have that did a better job than I expected.
Egli Jig 2016 32.jpg

David
 

Cyborg

Well Known and Active Website User
VOC Member
Nice jig you have there. The Balleigh looks slick. I had a look at a couple and see they have one that uses an abrasive belt which is interesting.
Tried practicing feeding rod a couple of times while sitting in front of the tube, but keep forgetting to do it. Probably need to attach some rods to the remote. Didn’t think of practicing first without the glove, will give that a try. Main issue seems to be that although I can go through proper motions I find it difficult to do it for any length of time and also very difficult to keep the filler going straight into the puddle without stuffing it into the tungsten every once in a while. Also difficult doing everything all at once. Like a one man band.
 

davidd

Well Known and Active Website User
VOC Member
I hope that you are using lanthanated tungsten. Grinding the thoriated tungsten is not considered a healthy habit.

I do not "grip" and move the rod in my hand. I just move my hand closer. This often causes more stops to re grip, but that is what I do. I don't think of the tungsten as being that close to the rod. It tends to melt before the rod gets too near due to the heat surrounding the tungsten. It does mean that I am moving the rod a lot more as I am poking it in and out of the weld area, but it doesn't seem to need a lot of motion to keep the rod cool.

Make sure your vision is good. I have helped several folks who have just had too hard a time seeing the weld even with my Jackson TrueSight, which helps most old guys.

David
 

Cyborg

Well Known and Active Website User
VOC Member
I use lanthanated , but still wear a mask when grinding... on an old repurposed sewing machine motor with a diamond wheel attached. It’s set up and dedicated strictly for tungsten. The wear on the wheel reflects my somewhat spastic arc length and filler feed.
I try and move the arc back slightly and then dip the rod into the puddle to melt it, all the while trying to keep the semi molten end of the rod etc within the argon shielding. I find it slightly bizarre how little it takes to contaminate the weld. Maybe my decision to learn how to TIG on AC (aluminum) first was the wrong move. So much to deal with and the aluminum tends to be there one second and gone the next. Any oxide or crud remaining after prepping the weld will find its way into the puddle and then it starts to look like a dog turd. Even something minor on the backside will bob to the surface... seems that’s an unwritten rule. It was just this past April that I switched it over to DC to weld the flange onto the intake manifold (stainless steel). I couldn’t believe the difference in the arc. Like opium compared to crystal meth. When I ran a test pass, I kept checking the amperage to see if something was amiss. The oil tank literally had about 6 ft of welding and this is what it looks like. If I could master the filler feed, then it look better. I suppose it’s a bit of a vanity thing, because in reality, penetration is fine and there’s no hot cracking. At the end of the day it holds oil. The top of the welding table is an old range hood with two 2 speed fans. I bought a better helmet along with a cheater lens. My eyesight is actually pretty good considering, but the lens makes a world of difference.
BD127A89-4452-4BB5-80E4-1304BAB02135.jpegF3E60AA7-EEF4-40CC-8A6D-24A4CD182EDF.jpeg
 

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