Cafe Racer Thread

[Ro Co]

Wow! I like it. I assume it CR500 powered? What hp are you shooting for?

[motion]

Originally Posted by Schumi

little bike update from me, comments appreciated from this group of fine motorcycle connoisseurs we have here:
I haven't worked much on my track bike lately but I am starting the manufacturing of some of the small frame components and put in the order for all the titanium hardware. All the component design is done except for the monocoque bodywork and radiator head tank and bleeder tube. Still a good amount of CAD and analysis to do on the monocoque section before I have moulds made.

B.O.M. is essentially done and so I have a very accurate prediction of the final weight of the bike. As it sits, with oil and water but without fuel, It should be 196 lbs +/- about 2 lbs.

The upper body design is still slightly being tweaker as I said, but it was far enough along to do some rendering/sketching, so here is the 'artist's conception' of the final bike, directly based off the CAD:



Now the hard part begins... and step 1 is I move everything out of my Hermosa Beach beach house and into a proper shop....

I totally dig your enthusiasm and this kind of project in general.... but, I don't see how you can keep this thing sub 200 lbs. The Japanese factories, with all their wizardry and money, could only keep production RS250Rs and TZ250s to about 220lbs. And that's dry weight. I'm assuming you have a CR500 motor in there, which is really an ancient, heavy motor. Unless their are replacement cases and head available that are significantly lighter? Also, a 500 single 2-T motor is going to be hella buzzy, and won't last long on tracks with very long straights.

Comments?

[motion]

And, is that a carb I see? Why not FI?

[Schumi]

Originally Posted by motion

I totally dig your enthusiasm and this kind of project in general.... but, I don't see how you can keep this thing sub 200 lbs. The Japanese factories, with all their wizardry and money, could only keep production RS250Rs and TZ250s to about 220lbs. And that's dry weight. I'm assuming you have a CR500 motor in there, which is really an ancient, heavy motor. Unless their are replacement cases and head available that are significantly lighter? Also, a 500 single 2-T motor is going to be hella buzzy, and won't last long on tracks with very long straights.

Comments?

So.. you're totally right about tradition bikes and their processes not being about to get weights that low. I have a bit more help though... my work as an engineer revolves around structures, specifically finite element optimization of both metals (typically high strength aluminum alloys and titanium) and composites (typically carbon fiber).

Every nut, bolt, spacer, etc has been either measured or calculated and mass is tracked in a BOM. I have most of the parts actually physically here too to scale accurately to check against CAD measurements.

This bike uses a pretty standard main twin spar frame construction mainly because I didn't want to spend too much time there, but outside that it is all rather interesting stuff. Every bolt on the bike has been run through a calculation spreadsheet of mine to determine sizing- some fasteners have been replaced with HS6082 or 7075 AL bolts, many are 6AL4V titanium. Axles are 7050T651 AL for the front and 6AL4V for the rear. Their internal profiles being iteratively optimized in simulation for strength and stiffness targets. The rear sets are made from anadvanced Lithium-Aluminum alloy which is several percent less-dense than 6061 but about 9% higher in elastic modulus, so I am able to achieve the foot peg stiffness I want while using less material that seen on average.

Handlebars are carbon fiber. cooling ducting is carbon fiber. The carbon seat support doubles are the radiator support and partially the exit ducting to the radiator, under the seat. It is integral to the monocoque body/tail. In this way, lots of mass is saved by not having to have multiple structures doing different things.

The motor has been worked over to remove any extras. Titanium studs, titanium nuts. The kickstart and kickstart gears (heavy gears!) have been removed and a plastic spacer fitted to where they were, since this bike will only be started by a portable starter.

The cooling system uses thin AL hard line in most places to save weight over rubber hose and is very small- this is a time trials bike, so it is only designed to run a few laps at a time. Enough to hear the tires and brakes to set time.

The rear brake disc is Carbon/SiC. The rear brake caliper bracket is titanium, also another part that was material optimized via an iterative optimization code.

A lot of other things.

These are things that OEM bike makers just can't do due to cost limitations (Titanium and specialty AL alloys do not come cheap) and design time or manufacturing limitations- often times designing parts to be lighter could be done but they lack the time to exercise such detailed simulation work, or they are limited by production lines and tooling costs (tooling up ways to mass produce carbon monocoques is not cheap, let alone to material cost to make each body). I'm hired by companies to solve just these problems- balancing materials development, structures optimization, and mass production tooling and piece prices. Thankfully for this project I am only building currently 1 of these, with a potential for maybe 2 more once the first is completed. I'm not tracking my own costs. I don't really want to think about it.

Anyways. back to the motor. CR500 is an old motor, but it is surprising well designed- it is one of the tightest shrunk-wrapped cases i've seen a a 'big' single. The entire motor stock out of a 1991 CR500 weighs if I recall correctly (without pulling up my mass tracking sheet).. about 29kg. With my rework that is down to about 26kg. It has been bored slightly larger and will run a lot higher compression and with computerized ignition, port timing changes, some exotic fuel... and a lot of other details I expect to push around 80HP from it without getting to crazy. There are some who build them for over 100HP but with bigger bores and more work than I am willing to do at first. Maybe later. My main reason for going with a CR500 motor was... I had one laying around when I started this project and I just thought "hm why not". They are easy to rebuild and parts are cheap and I will be melting a lot of internals. The other engine I was considering using was a Aprilia SXV-550, which weighs about 33kg stock and can put out something like 75HP. I could have probably got that engine to a similar power-to-weight ratio but it would have been more expensive and the exhaust and intake more weight and more challenging.

It won't be all that fast compared to, say, my MV F4. But it will be a lot quicker on the twisties.

196 lbs (88kg) is light but it could be lighter- I am using RS250 Cup aluminum wheels- because I think they are dead sexy and I have had a love for that wheel design for decades- but they aren't super light. A set of carbon wheels made to fit (the wheels are skinnier than superbike wheels- due to the low weight/power, the rear is only a 4.5" wide rim vs. 6" for most big bikes) would cut another 3kg or so - 6.6 lbs.

[Schumi]

Also the hugger is to keep the tire from throwing rocks into the radiator core, which is right in front of it unprotected under the seat. Maybe that actually isn't an issue, but I dunno, I have seen how sticky race tires get and even if it doesn't happen on track, when you are riding the bike into the pits I have seen lots of marbles get picked up and thrown by race rubber.

It is actually Carbon/Kevlar and is only 2-3 layers thick, depending on the area. It's not a pound of two... it's about 200 grams

[Schumi]

And the vibration from it being such a rowdy single- I have thought about that, I know it will probably make the bike impossible to enjoy. But I had this engine in a CR500 supermoto before and rode it on the street a while and.. I lived with it.

Also, The engine is being built for making power higher in the RPM band and on the supermoto the real bad vibration through the seat and bars was really in the 3000-5000 rpm area. I plan on spending all my time with this bike between 6000-8250. Where the frame excites/damps frequencies on this new frame though... I haven't explored. We'll see....

[Flieger]

Schumi, you are my new hero.

[mepstein]

Found two moto Morini 350's in a storage unit that my employe put away 26 years ago. One ran before storage, one didn't, I'm working on restoring the one with the missing engine. It's a scavenger hunt right now for parts.

[Schumi]

Originally Posted by peteremsley

Wow. That some fancy materials. out Pieroboning Pierobon...

Wow! I cannot believe I have never seen/heard of this company before. I love that. I am not much of a Duc guy, but one day I want to build a bike with Ducati air cooled 900.

Did some quick searching, that bike is their 'F042'- based on a 2V 1100 making 95HP. They claim the dry weight is 139 kg! That is light, but yeah.. not super light. Most of that extra is engine... I'm sure that 1100, while a sweet sounding machine, is a good 45kg+. Still nothing beats two strokes in power-to-wight. Lots of weight advantage to not having big heads or camshafts or cam chains. And those air cooled Ducs have to have some pretty heavy cylinder castings and a lot of oil volume to soak up heat.

That said, that is a bike you could ride all day long and then ride home too. An I bet the power delivery is like butter. What a beauty.

[motion]

Originally Posted by Schumi

So.. you're totally right about tradition bikes and their processes not being about to get weights that low. I have a bit more help though... my work as an engineer revolves around structures, specifically finite element optimization of both metals (typically high strength aluminum alloys and titanium) and composites (typically carbon fiber).

Every nut, bolt, spacer, etc has been either measured or calculated and mass is tracked in a BOM. I have most of the parts actually physically here too to scale accurately to check against CAD measurements.

This bike uses a pretty standard main twin spar frame construction mainly because I didn't want to spend too much time there, but outside that it is all rather interesting stuff. Every bolt on the bike has been run through a calculation spreadsheet of mine to determine sizing- some fasteners have been replaced with HS6082 or 7075 AL bolts, many are 6AL4V titanium. Axles are 7050T651 AL for the front and 6AL4V for the rear. Their internal profiles being iteratively optimized in simulation for strength and stiffness targets. The rear sets are made from anadvanced Lithium-Aluminum alloy which is several percent less-dense than 6061 but about 9% higher in elastic modulus, so I am able to achieve the foot peg stiffness I want while using less material that seen on average.

Handlebars are carbon fiber. cooling ducting is carbon fiber. The carbon seat support doubles are the radiator support and partially the exit ducting to the radiator, under the seat. It is integral to the monocoque body/tail. In this way, lots of mass is saved by not having to have multiple structures doing different things.

The motor has been worked over to remove any extras. Titanium studs, titanium nuts. The kickstart and kickstart gears (heavy gears!) have been removed and a plastic spacer fitted to where they were, since this bike will only be started by a portable starter.

The cooling system uses thin AL hard line in most places to save weight over rubber hose and is very small- this is a time trials bike, so it is only designed to run a few laps at a time. Enough to hear the tires and brakes to set time.

The rear brake disc is Carbon/SiC. The rear brake caliper bracket is titanium, also another part that was material optimized via an iterative optimization code.

A lot of other things.

These are things that OEM bike makers just can't do due to cost limitations (Titanium and specialty AL alloys do not come cheap) and design time or manufacturing limitations- often times designing parts to be lighter could be done but they lack the time to exercise such detailed simulation work, or they are limited by production lines and tooling costs (tooling up ways to mass produce carbon monocoques is not cheap, let alone to material cost to make each body). I'm hired by companies to solve just these problems- balancing materials development, structures optimization, and mass production tooling and piece prices. Thankfully for this project I am only building currently 1 of these, with a potential for maybe 2 more once the first is completed. I'm not tracking my own costs. I don't really want to think about it.

Anyways. back to the motor. CR500 is an old motor, but it is surprising well designed- it is one of the tightest shrunk-wrapped cases i've seen a a 'big' single. The entire motor stock out of a 1991 CR500 weighs if I recall correctly (without pulling up my mass tracking sheet).. about 29kg. With my rework that is down to about 26kg. It has been bored slightly larger and will run a lot higher compression and with computerized ignition, port timing changes, some exotic fuel... and a lot of other details I expect to push around 80HP from it without getting to crazy. There are some who build them for over 100HP but with bigger bores and more work than I am willing to do at first. Maybe later. My main reason for going with a CR500 motor was... I had one laying around when I started this project and I just thought "hm why not". They are easy to rebuild and parts are cheap and I will be melting a lot of internals. The other engine I was considering using was a Aprilia SXV-550, which weighs about 33kg stock and can put out something like 75HP. I could have probably got that engine to a similar power-to-weight ratio but it would have been more expensive and the exhaust and intake more weight and more challenging.

It won't be all that fast compared to, say, my MV F4. But it will be a lot quicker on the twisties.

196 lbs (88kg) is light but it could be lighter- I am using RS250 Cup aluminum wheels- because I think they are dead sexy and I have had a love for that wheel design for decades- but they aren't super light. A set of carbon wheels made to fit (the wheels are skinnier than superbike wheels- due to the low weight/power, the rear is only a 4.5" wide rim vs. 6" for most big bikes) would cut another 3kg or so - 6.6 lbs.

OK, you've obviously done your homework

I am totally digging the project. The engine is the sticking point for me. Have you considered a modified Aprilia RS250 (Suzuki VJ22) motor? With ignition, heads, race fuel, and a big bore kit, you can go all the way to 100hp. Stock is about 58HP to the rear wheel with pump gas, so I would think 75HP would be readily attainable. I'm thinking the engine weight would be pretty light? I have a couple engines on my bench if you need me to weigh one.

[Jeff Higgins]

Absolutely awesome project, Mike. Just out of curiosity, which CAD and FEA softwares are you using? I'm a CATIA V5 user myself.

[patz]

Originally Posted by mepstein

Found two moto Morini 350's in a storage unit that my employe put away 26 years ago. One ran before storage, one didn't, I'm working on restoring the one with the missing engine. It's a scavenger hunt right now for parts.

Love Morini's I have a one in my moped. Would like to get one of their super bikes....

[Schumi]

Originally Posted by motion

I am totally digging the project. The engine is the sticking point for me. Have you considered a modified Aprilia RS250 (Suzuki VJ22) motor? With ignition, heads, race fuel, and a big bore kit, you can go all the way to 100hp. Stock is about 58HP to the rear wheel with pump gas, so I would think 75HP would be readily attainable. I'm thinking the engine weight would be pretty light? I have a couple engines on my bench if you need me to weigh one.

While the CR wasn't free it was damn close, and modding it for big power is damn cheap. I may get wild with different fuels. I won't feel bad when I melt the top end every 4 laps. I could never do that with a VJ twin, I am sure parts for them are getting more and more expensive by the day.

I want to do a VJ/RS project in the future for sure, the RS250 bikes were my first exposure to two stroke road racers in person and were an inspiration for this project. One of the main benefits to the monocoque tank/tail structure is technically I could re-use the entire upper body section on other bike frames, and so one day doing this on an RS250 frame and swingarm is a goal. If you could get me what a VJ22 motor weighs, with noting whatever accessories or fluids it contains, I'd really like that info. I'm moving to France at the end of this year and setting up a small shop, and plan on getting my hands on a side project bike to work in addition while this RC500 project continues.

The RGV's can weigh about 125kg I believe, less on a diet... and that is 1990's materials and technology. Would love to ride one. Love the sound.


Higgins- I use CATIA for CAD. For analysis work, I primarily use various solvers of the Altair Hyperworks suite.

[Schumi]

Actually I remembered what I told myself I was going to acquire next already.... it's along the lines of:



SEX.

[motion]

Originally Posted by Schumi

While the CR wasn't free it was damn close, and modding it for big power is damn cheap. I may get wild with different fuels. I won't feel bad when I melt the top end every 4 laps. I could never do that with a VJ twin, I am sure parts for them are getting more and more expensive by the day.

I want to do a VJ/RS project in the future for sure, the RS250 bikes were my first exposure to two stroke road racers in person and were an inspiration for this project. One of the main benefits to the monocoque tank/tail structure is technically I could re-use the entire upper body section on other bike frames, and so one day doing this on an RS250 frame and swingarm is a goal. If you could get me what a VJ22 motor weighs, with noting whatever accessories or fluids it contains, I'd really like that info. I'm moving to France at the end of this year and setting up a small shop, and plan on getting my hands on a side project bike to work in addition while this RC500 project continues.

The RGV's can weigh about 125kg I believe, less on a diet... and that is 1990's materials and technology. Would love to ride one. Love the sound.


Higgins- I use CATIA for CAD. For analysis work, I primarily use various solvers of the Altair Hyperworks suite.

I'll try to get it weighed this week. Are you a French national? Why moving to France? What area? I ask because Mrs. Motion and I will be snooping around Provence this fall for a place.

[patz]

My Morini powered ride with new seat I fabbed up.

[javadog]

Interesting project (Mike's CR500 special).

One suggestion... 6Al4V has been tried for axles by some serious racers and nobody liked it. I imagine 7050 would be even less suited. Steel is still the favored material for axles in the higher classes of 2-wheeled racing. Large diameter, thin wall, but steel...

I'd be curious what piston/porting/pipe you end up with and who you end up having do the porting work and pipe building. I'm planning a CR500 motard and would like to move a chunk of the power from the midrange to above 6000.

JR

[Schumi]

My wife is from Bretagne and we are moving back to closer to where she is from to look into some real estate renovation projects. I'm semi-retired and just looking for a new journey, living abroad seems like fun, and I need somewhere where real estate is cheap enough so I can outfit a proper workshop. France fits that bill.

As far as axles on the bikes go- Steel is used on the big bikes because they have forks and hubs designed for giant diameters. As you go up in diameter it makes sense to use a high strength, thin walled tube versus something else because it is so easy to get the stiffness you need, and steel is simple because fatigue is ignored and is one less thing to worry about. Also, real race bikes require frequent tire changes where damaging threads is a very real issue, so steel makes a good choice as the nuts/end bolts can be spun down quick and take large variances in torque while producing safe clamping loads without fear of cross threading or yielding AL threads ... or on titanium, galling between the Ti and steel nut/bolts
.
The rear axle on the wheel I am using needs to be 20mm, which is small- the stock Rs250 uses a simple low alloy steel axle. 6AL4V has a yield of at least 850 MPa or more, which will easily match the steel original for strength at a reducting in stiffness of about 50%, which, in my type of rear swingarm design, isn't much of a matter. Fatigue is also not an issue with titanium. There is no mathematical reason it cannot be used, it is often not used for race bikes due to cost and difficultly to machine- extremely difficult to machine with a good finish, and finish is key as the axles fit into bearing bores.

7050 Al is a more fatigue resistant 7-series similar to 7075. Increased copper content gives the increased fatigue life, at cost of slight decrease in corrosion performance IIRC. Again, the design is tailored to the application. The front axle is 25mm and the steel design to fit the original forks (GSX-R forks in this case) was semi-hollow. The Aluminum design needs to be solid most of the way through to keep stresses around the step-down into the bearings low enough to allow for it to have suitable fatigue life (and I'm using some pretty harsh street impact numbers driving those fatigue cases, which it really shouldn't see on a race track ever.) Even with the mostly solid design, the aluminum saves 240 gram over the OEM steel design, at the slight disadvantaged of reduced stiffness. However, with the ridiculously light curb weight of this bike, the stiffness requirements need not be as high as wheel loading is so much lower on track than a big sportbike. I am running very very stiff forks for such a light bike which carry a substantial about of my required CP stiffness in the total front end.

It's easy to move power on a two stroke to different areas of the band- by raising/lowering the ports you are effectively changing the timing, like advancing/retarding a camshaft does to intake/exhaust valves in a four. Putting extra thickness in the base gasket raises the jug, and then taking that extra off the head takes the head back to where it should be- this, along with a pipe tuned for it, raises the power band. This is really needed on supermotos due to the smaller rear tire vs. the stock dirtbike tire lowers the final gearing, and so a standard CR500 engine at 6000RPM in 5th gear with a super moto tire on the rear and a 15/45 sprocket combo will only do about 70mph.

[javadog]

You may be okay on the axles, it depends on how hard you ride the bike. People have been trying them on lightweight race bikes for 40+ years and the fast guys always hated them. You might ponder using a lighter set of forks than the GSX-R ones, which are fairly heavy for a bike of that weight.

I used to have a ti front axle for a slightly older set of GSX-R forks but I peddled it to a Canadian that never rides his bikes (or finished them, for that matter. I guess the one thing leads to the other....)

I know all about tuning 2-strokes and I'd rather buy a motor than build one. It's always easier to build a motor that someone has had success with, than to figure it out for the first time. I've researched CR500 tuners. Most tune the motors for motocross use, so they are not suitable for my needs. If you run across a guy that's built one for roadracing, let me know.

JR

[widebody911]

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