E: Engine Comet Mongrel

[eglijim]

Thanks to you and Bob. I was hoping to get the WB down close to that point and I could get quite close, depending on if I use progressive linkage. No doubt just a shock would be simpler and take up less space if configured like a Vincent RFM. It will likely end up that way as the hours are piling up. I know an ex Honda factory fellow, who left to start his own business selling/rebuilding suspension for MX and road race bikes. He has agreed to help illuminate the path and has quite a good sense of humour. Anyway, according to my bride, we're off to someplace warm...

Just for the record and as the WB could be an issue for you, my Slater/ Cheney Egli is 57" and the bears racer is 58" but this is adjustable as it has eccentric head races and adjustable fork yokes. In addition , we had an optional shorter swinging arm in steel. Measured with the rear wheel in the middle of its range.

 

[Cyborg]

Just for the record and as the WB could be an issue for you, my Slater/ Cheney Egli is 57" and the bears racer is 58" but this is adjustable as it has eccentric head races and adjustable fork yokes. In addition , we had an optional shorter swinging arm in steel. Measured with the rear wheel in the middle of its range.

The frame jig that I am using allows me to have the yoke/tubes/axle in place and I had made up a template that represents the location of the front fender so I can check clearance under full compression. With the motor sitting on a hydraulic lift, I was able to determine how far forward I could mount the engine. The swing arm is in its own jig and ready to be temporary tacked together. Once that's done, it can be offered up to the frame/engine assembly so I can figure out what the wheelbase will be and sort out suspension mounting points. I haven't made the final cuts on the swing arm, so once I measure everything up, I'll cut the tack welds, cut the arms to length and add the chain adjusters/bracing/shock mount etc. I have the swing arm pivot point fixed in the frame jig. There is a laser mounted in the head stock and another laser in a jig hanging from the front axle..... a magnetic angle indicator is attached as well. The lasers will indicate changes in trail as I'm farting around locating the frame/swingarm pivot points. The front yoke assembly is bolted to a mill table (X Y axis) which is in turn bolted to my Rube Goldberg jig, so I can play with W/B, rake, trail etc.. Sounds good on paper.... we'll see how the pudding turns out.

 

[eglijim]

The frame jig that I am using allows me to have the yoke/tubes/axle in place and I had made up a template that represents the location of the front fender so I can check clearance under full compression. With the motor sitting on a hydraulic lift, I was able to determine how far forward I could mount the engine. The swing arm is in its own jig and ready to be temporary tacked together. Once that's done, it can be offered up to the frame/engine assembly so I can figure out what the wheelbase will be and sort out suspension mounting points. I haven't made the final cuts on the swing arm, so once I measure everything up, I'll cut the tack welds, cut the arms to length and add the chain adjusters/bracing/shock mount etc. I have the swing arm pivot point fixed in the frame jig. There is a laser mounted in the head stock and another laser in a jig hanging from the front axle..... a magnetic angle indicator is attached as well. The lasers will indicate changes in trail as I'm farting around locating the frame/swingarm pivot points. The front yoke assembly is bolted to a mill table (X Y axis) which is in turn bolted to my Rube Goldberg jig, so I can play with W/B, rake, trail etc.. Sounds good on paper.... we'll see how the pudding turns out.

Sounds as though you have covered the bases which could cause build problems downstream. As i think i said previously, the reason for the built in adjustability with the bears chassis was a belt and braces approach to permit tinkering with the handling if required(or it was a dog). Don't know if you intend a frame rail from the headstock to swinging arm area but we tacked on an abutment here on the bears for the steering damper. The Egli's fixed abutment we have fixed to the front (milled aluminium) head bracket.

 

[Cyborg]

I was able to jam the frame into the mill and cut two slots into an existing mount and bolt in a unmodified later style Vincent head mount. There will be two frame tubes that attach from just behind that mount and then head back to the swingarm pivot point. They will have to have a slight bend so the right hand one will clear the timing chest. They don't attach directly to the steering head, but are close and the area has lots of gusseting. I have no concerns about rigidity, but curious about final weight even though it's meant to be a road bike/cake decorating exercise. The only real adjustability once done will be the normal things and a bit of rear ride height adjustment assuming I go ahead with the current plan to use the rear shock, linkage/rocker etc. from a Ducati Monster. That won't be finalized until I'm back in the garage and test fit everything. I'm not anticipating any show stoppers, but.......

Ps. I have another triple tree, so can add some trail if necessary.

 

[eglijim]

I was able to jam the frame into the mill and cut two slots into an existing mount and bolt in a unmodified later style Vincent head mount. There will be two frame tubes that attach from just behind that mount and then head back to the swingarm pivot point. They will have to have a slight bend so the right hand one will clear the timing chest. They don't attach directly to the steering head, but are close and the area has lots of gusseting. I have no concerns about rigidity, but curious about final weight even though it's meant to be a road bike/cake decorating exercise. The only real adjustability once done will be the normal things and a bit of rear ride height adjustment assuming I go ahead with the current plan to use the rear shock, linkage/rocker etc. from a Ducati Monster. That won't be finalized until I'm back in the garage and test fit everything. I'm not anticipating any show stoppers, but.......

Ps. I have another triple tree, so can add some trail if necessary.

Have a complete 600 Monster in the garage if you need any measures.

 

[Cyborg]

What year is your Monster? For rear suspension, does it have that fork mounted on the swingarm that connects to the rocker, then to the shock and so on....?

 

[eglijim]

What year is your Monster? For rear suspension, does it have that fork mounted on the swingarm that connects to the rocker, then to the shock and so on....?

Earlyish carb model 1998, will send pic later if you want ?.

 

[Cyborg]

I think I will be ok with measurements. I have the Monster frame/swingarm etc, so I know where the shock and fork mounts need to be welded onto my swingarm. With the fork and top of the shock mounted to the rocker, I can determine where the rocker shaft support has to be welded in. The only measurements I might need are the the distance centre to centre between your motor mounts and the centre of the swing arm spindle. I don't have the Ducati cases, so don't have the exact location of Ducati swingarm spindle. Hope that makes sense. Moving the location of my rocker spindle to ease installation may not matter, but I won't know for sure until I'm back in the shop and have had a chance to stare at it for a while. I don't think moving it back or forward a few degrees will change the geometry in a negative way. I'm CAD challenged and my artistic skills stink, so best to have the parts in front of me before I impose upon you.

 

[eglijim]

I think I will be ok with measurements. I have the Monster frame/swingarm etc, so I know where the shock and fork mounts need to be welded onto my swingarm. With the fork and top of the shock mounted to the rocker, I can determine where the rocker shaft support has to be welded in. The only measurements I might need are the the distance centre to centre between your motor mounts and the centre of the swing arm spindle. I don't have the Ducati cases, so don't have the exact location of Ducati swingarm spindle. Hope that makes sense. Moving the location of my rocker spindle to ease installation may not matter, but I won't know for sure until I'm back in the shop and have had a chance to stare at it for a while. I don't think moving it back or forward a few degrees will change the geometry in a negative way. I'm CAD challenged and my artistic skills stink, so best to have the parts in front of me before I impose upon you.

Think I know what you are after having had another look, the s/a centre is 10.3cm below (and fractionally behind a vertical drawn from the rear engine mount) and 35cm from the "front" mount at the cylinder base. The latter number should be close but not guaranteed as had to eyeball the line over the engine case.

 

[Cyborg]

Thanks that will do. There is nothing impeding the location of the rocker pivot, so with those measurements I can locate it so it will replicate the Ducati position. I'm operating under the assumption that I will have to buy a new spring for the shock, but the dampening should be ok. The front forks are early 80's Honda vintage with anti dive. They are as new, but, no point on spending gobs of money on a trick shock if the forks are "just ok".