F: Frame Series ‘D’ Rear Bodywork mounting to Series ‘C’ Comet

[davidd]

Craig,

You can do that. The tub is a little wide at the front without the side panels closing it back down, but that should not be a big problem. The single rear brake on the D is operated by a cable. No rear fender or brackets are necessary. The difficult part will be the hinge arrangement at the top front of the tub which attaches to the UFM. Someway, the hinge has to mount to the RFM. The tub frame has two top tubes that each have a small tube attached at 90 degrees. A spindle pokes through the end, then through the UFM, and then the remaining tube on the tub to make a hinge.

The bottom mount is a robust slotted tube that slots on to a longer pivot bolt. The end nuts, when tightened, turn into a counterbore on the tube that locks the bottom in place.

David

 

[craig]

I am concerned about the dual rear brake C system. Can I mount the existing C Comet brake arms in the low position and still hook them up?
Major mod needed here for rear brakes?



I wanted to retain the Comet rear fender front section, remove lifting handle, relocate rear brake light switch, Fab an upper mount and lower mount, relocate horn, take off rear stand, take off rear fender flap............bolt this D tail on, wire as needed, and go!
Maybe add Hill center stand.



Thank you all for help in this project.
Cheers
Craig

 

[vibrac]

You can easily remove one brake drum from a Comet then its just a case of one cable to the rear drum with the sprocket. An alternate is use a sprocket carrier and have one drum like a D twin but on the off side.
I would just forget the cross shaft gubbins and RH drum
Our Comet Racer never had two drums on the rear

 

[craig]

So about these upper and lower mounts differing from a twin.
You think a simple bracket will allow this?
maybe this new bracket triangulated to the sidecar/horn RFM lower tube?

What about the C rear spring boxes interfering with this bracket or tail section?

Will the lower mount (swing arm pivot) be moved forward on a Comet? Causing this D tail to droop down at the rear?

 

[davidd]

Craig,

So about these upper and lower mounts differing from a twin.
You think a simple bracket will allow this?
maybe this new bracket triangulated to the sidecar/horn RFM lower tube?

Starting with the hardest mod first, I would recommend taking the frame out of the tub and once it is modified, refitting the tub to the frame. The swing arm pivot on the Comet is 1/2" forward and 1" up or higher on the Comet than it is on the twin. It could be that you could add an extra free standing pivot to the Comet just to be the lower mount. It is difficult to say without the pieces at hand. Also, the pivot needs to be fairly robust as the entire tub is cantilevered off the swing arm pivot and the top mount. The top is in tension and the swing arm pivot is in compression and has to take all the weight of the riders, tub and gear.

If you look at the Victor photo you can see how much higher the swing arm pivot is. In the photo of the tub for the twin the pivot is at the bottom of the glass and on the Victor it is up much higher.

As for the upper mount, if you remove the frame and modify it you can use it on any of the existing upper tubes. The seat tube may do. I have slotted the sidecar tube and moved the damper and spring boxes down there, so if the height is closer to the second tube down you could do that. Additionally, you can do something like the Reg Bolton mode to bolt to the UFM and move the seat and/or suspension back from the UFM.

I do not know about the twin brake rods because the D RFM does not have the means to mount them so I am not sure about the clearances. However, I would think they would work as is. I don't think the rear guard will fit in the space between the wheel and the tub. As for the brake switch, the stock D brake switch on the balance beam is far safer for all Vincent riders.

Personally, I would separate the frame and the tub as mentioned. It will allow you to modify the frame to fit the way you want, including the seat height and you can put the tub on and trim it to fit well on the bike.

David

 

[craig]

I went out , took the Comet rear stand off , rolled the left rear brake arm to the low position, and hooked up the rod mechanics to see what happens. Not sure about doing this on the right side of the Comet yet.

I want the D series fiberglass, steel tub/frame transferable between a Comet/Rapide/Shadow....so that is my goal.
I need bracketry for the Comet to allow this ....so I may have to move the tub an inch (maybe ½") to the rear on the Comet and come up with top tube and bottom studs.

 

[craig]

Will a D solid rear axle simply replace a C solid rear axle?

 

[craig]

More thoughtless ideas.
Hasn't anyone done this D tail on a C Comet?

 

[Comet Rider]

Craig,
Try sending a message to Calle in Sweden. He has an enclosed big bore Comet

 

[timetraveller]

Note that the three tubes at the rear of the 'C' UFM are not all the same length and you cannot just put a straight plate against them. You will need packers or to chop the UFM about.