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Old 10-19-2011, 01:23 PM   #1
CosentinoEngineering OP
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Some advice required?

Well, here it goes.....

The purpose of this thread is to give design/engineering advice to those in need of it for bike modification projects. As you can see on my 'Lots of Assembly Required' thread I'm a degreed engineer with a decent amount of experience with motorcycle design and a lot of experience being a garage hack!

I'm opening this thread to provide advice to those who are adventurous enough to start hacking on their own bike but need some technical assistance from time to time. It is not a general all questions answered thread but more for construction techniques, material recommendations, design philosophy. Questions like 'what is the best tire to use?', 'how do I install heated grips?, 'What is the correct tire inflation pressure?' are not suitable for this thread and I likely wouldn't be able to provide a better answer than the vendor you buy the parts from. Questions like 'What material should I use for a custom subframe?', 'Why is a long swingarm good?', and such are and hopefully I will be able to help your project move along a bit faster.

Now for the disclaimer: This is the internet and regardless of the advice I give you modifying your vehicle is a potentially dangerous hobby that can lead to serious injury or death. Any modifications you undertake are done at your own risk.

Tweaking season is now open.


Chris
http://moto2-usa.blogspot.com/
Lots of Assembly Required
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Old 10-19-2011, 03:31 PM   #2
sakurama
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This is just a quick endorsement of Chris - he's the man!

I've been a teammate and friend for over 15 years now and the help, advice and insight that he's offered has been absolutely invaluable. I encouraged Chris to start this thread since it's basically what he's been doing for me since I've known him. What end mill is best for aluminum? What speed should I turn with a carbide insert if my part is 3" in diameter? If I put a smaller front wheel on my bike do I lose or gain trail? These are all good questions for him.

Chris is not just a CAD jockey but a true, grease under the nails mechanic and ace fabricator. He knows more about building and fabrication than anyone I know and he's even worked on stuff for NASA. He can weld, machine (manual and CNC) and knows everything about what makes a motorcycle handle.

I'm lucky as he's been my teacher as I've learned to weld, mill, design and fabricate my own projects. I hope you hit him up with all manner of technical questions and I look forward to watching this thread. Consider him your resident "Prof. Motorcycle".

Gregor
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Old 10-19-2011, 10:37 PM   #3
jwalters
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I have a question! I have a 1985 RZ350 that has gone through a bit of transformation. The idea was to put modern suspension and tires/rims on the street legal RZ350 2-stroke. I fitted R1 USD forks, R6 rear shock, R6 radiator, FZ600 swing arm and an SV650 rear rim/GS500 cush drive.

Replacing the old parts with modern aluminum and composites, was a 25 lbs reduction in weight. But the main reason for doing this, was being able to run modern street tires and modern suspension bits on a mid 80's street legal two stroke.

To the question: I have to make some spacers for the rear rim, but not sure how to center the rim relative to the frame. Should the rear rim be centered relative to the steering stem, subframe, swing arm, or by weight distribution? Theoretically, I think there should be even weight on either side of the bike when the bike is standing straight up and down but I'm curious how others do this.

I don't have any recent pictures of it, but here are a couple shots from early in the build. (BTW, I have a spacer on it now, that's a bit off center. Even so, this bike is a BLAST to ride, soooo light!)


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jwalters screwed with this post 10-20-2011 at 12:01 AM
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Old 10-20-2011, 12:02 AM   #4
Donkey Hotey
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What is the airspeed velocity of an unladen swallow?
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Old 10-20-2011, 12:17 AM   #5
PeterW
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Quote:
Originally Posted by Donkey Hotey View Post
What is the airspeed velocity of an unladen swallow?
http://style.org/unladenswallow/

Never built a frame in my life, so feel free to shoot me down in flames.

The wheels and steering stem need to be inline. If not the bike is going to handle badly.
Weight central is ideal, but the rider can correct for that (even if he does walk a bit lopsided after long rides) - wheels and steering out of line, nothing you can do about it while on the bike.

Cheers
Pete

PeterW screwed with this post 10-20-2011 at 12:24 AM
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Old 10-20-2011, 02:04 AM   #6
sakurama
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Quote:
Originally Posted by jwalters View Post
I have a question! Should the rear rim be centered relative to the steering stem, subframe, swing arm, or by weight distribution?
Cool bike and good question. Curious what Chris has to say. I know my BMW and a lot of older boxers actually didn't have the wheels in line due to the driveshaft.
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Old 10-20-2011, 08:27 AM   #7
Captain Beardylocks
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word. I'll be tempted to ask a zillion things, but I'll do my best to make sure only the really tricky problems (or the really, really stupid ones) show up here.
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Old 10-20-2011, 10:32 AM   #8
CosentinoEngineering OP
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african or european?


Chris
http://moto2-usa.blogspot.com/
Chip in and help!
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Old 10-20-2011, 11:15 AM   #9
CosentinoEngineering OP
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RZ350 question

Cool bike, its hard to beat the water cooled 2 strokes for light weight and performance. I did something similar in my early days on a 1980 kz1000. It was still a big heavy pig but handled a lot better!

I just used the following alignment technique on an old Dunstall Norton frame that was twisted and the resulting bike handles excellently and tracks straight.

I like to use the steering head as the first point of reference. Since this is where the turning process is initiated it is crucial that everything is properly oriented with respect to the steering axis. The first step is to ensure your swingarm pivot axis is perpendicular to the steering axis. I do this by bolting the swingarm pivot in place and fixturing the frame on a flat surface and shimming it until the swingarm pivot is as close to vertical as you can manage. You then bolt a set of tapered cones and a ground shaft (same things used on some manual wheel balancers) into the steering head bearing cups and use a scribe or height gauge to see if the ground shaft is parallel to the flat surface the frame is on. If it is great, if not get out a long bar and start carefully bending the frame until it is.

Getting a good bending technique is essential to making small changes and not see-sawing around the point you actually want. What you want to do is feel for the yield of the material and be able to sneak up on it without going too far. The procedure is to slowly apply force and feel for a change in resistance which is the yield point. Any bending before the yield point is elastic bending and the structure will return to its original shape when the force is removed. This type of bending feels like pushing against a spring. Bending after the yield point is what produces permanent changes. To sense the yield point you need to apply force slowly and the yield point is when you feel the structure seem to relax a little bit without you having reduced the force. I recommend practice with scrap tubing. It is a subtle change but once you feel it you'll know it.

Back to alignment. Once the swingarm pivot is square to the steering axis you can start bolting parts into the chassis. I install the forks and front wheel without spacers. If you are using modern stuff the steering stem likely has a thru hole which is very convenient. I have a ground shaft with a pointed end and turn up plastic bushings for a tight fit that allow me to use this center hole as an alignment reference. Slide the bushings and shaft in and adjust the wheel until the pointer is pointing at the middle of the tire. Then measure the side gaps and make spacers as needed. Always double check after the final spacers are installed and the front axle is properly tightened. Now you know the front tire and its contact patch is centered on the steering axis and the swingarm pivot is square to it. Check brake caliper to disc clearance as this may have changed and you don't want the rotors rubbing on the calipers.

Now check the swingarm to see if the rear axle is parallel to the swingarm pivot axis. I assemble the axle without the wheel and pivot race/shaft into the swingarm and shim it on a flat surface so that the swingarm pivot is parallel to the table surface. Check to see if the rear axle is parallel to the table. If not bend one or both arms until it is. Don't worry about the chain adjuster direction, that can be done next.

Now assemble the swingarm into the frame and the rear wheel into the swingarm with no spacers. The goal is to line the rear wheel up with the front wheel. There are various techniques to do this: string, straight edges, laser alignment, etc. Sometimes it is nice to do this with no tires installed so you can work directly from the tire bead mounting surfaces. Once the rear wheel is in line with the front: measure, make spacers, install, then do a final check. Don't forget to double check the chain run and make sure both sprockets are aligned. For what its worth any misalignment only means worn chains and lost horsepower........

For adjusting chain tension it is nice to have a fixture or good ruler to measure from axle center to swingarm pivot center on each side to make sure the rear wheel is pointing towards the steering axis.

None of this mentioned weight imbalances. I don't think many bikes are off balance enough to have to compensate in wheel alignment. A slight shift of rider position, usually subconsciously, is enough to compensate for even the worst imbalances.

You would be surprised on how big a misalignment can be tolerated with no serious side effects at street pace. This is how BMW got away with having the wheels out of line on a production bike. The rear was offset but still pointing straight ahead so the affect was not to have unwanted rear wheel 'steering' inputs. I must say that I think this is sloppy engineering of the worst kind and am surprised it came from the Germans.

Even though you can get away with reasonably large misalignments you _will_ notice a difference switching to a properly aligned motorcycle.

Hope it helped.


Chris
http://moto2-usa.blogspot.com/
Chip in and help!
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CosentinoEngineering screwed with this post 10-20-2011 at 07:25 PM
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Old 10-20-2011, 03:42 PM   #10
MODNROD
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strength vs weight

I have a 1987 Vmax (yay, the crowd roars......a bit).
It's a lot like the bike world equivalent of a 426 Max Wedge Superstocker. Turns are approached with a certain amount of trepidation, but in an excited way, a bit like "Heehee, which way will she go this time?" Braking is best done after the old girl has stopped.......eventually. Get the big old girl in a straight line and pull the pin though, and it bucks and bellows and wobbles its way down the chute with little control and a huge grin! Question time:
I know the usual practise for these things is a fork brace, frame brace, and swingarm bracing to reduce the fun.
1. Fork brace - will filling the standard die-cast Ally mudguard piece with hard-setting resin work as well as a 1/2" thick billet piece? The resin is really light.....
2. Frame brace - Would using hi-strength/lo-elastomer Polyurethane engine mount bushings strengthen the frame without having to resort to big chunks of railway track across my bloody lovely V4? Bushes are light......
3. Swingarm brace - This I need, now. Without Vboost, 90rwhp, cool. With Vboost, 110rwhp, not cool, very wallowy and a gentle shimmy all the way to 1/2 track on the 1/4. With my 4-1, 120rwhp, very uncool, the wallowing makes the tyre buzz up. I plan on 160-200rwhp, you see my dilemma. I was going to get a 1" CM tube, bend to follow the swingarm profile, then stitch weld to it. I thought it would have more strength than the usual triangulated affairs, along with less weight (no joining tubes to the arm). Would this work, or is the triangulated monstrosity the way to go for reducing wheel axle deflection (up and down)?

Thanks Chris, have a lovely day!
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MODNROD screwed with this post 10-20-2011 at 03:47 PM
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Old 10-20-2011, 04:05 PM   #11
jwalters
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THANK YOU!

I've never printed out an advrider post before now....

Quote:
Originally Posted by thecosman View Post
Cool bike, its hard to beat the water cooled 2 strokes for light weight and performance. I did something similar in my early days on a 1980 kz1000. It was still a big heavy pig but handled a lot better!

I just used the following alignment technique on an old Dunstall Norton frame that was twisted and the resulting bike handles excellently and tracks straight.

I like to use the steering head as the first point of reference. Since this is where the turning process is initiated it is crucial that everything is properly oriented with respect to the steering axis. The first step is to ensure your swingarm pivot axis is perpendicular to the steering axis. I do this by bolting the swingarm pivot in place and fixturing the frame on a flat surface and shimming it until the swingarm pivot is as close to vertical as you can manage. You then bolt a set of tapered cones and a ground shaft (same things used on some manual wheel balancers) into the steering head bearing cups and use a scribe or height gauge to see if the ground shaft is parallel to the flat surface the frame is on. If it is great, if not get out a long bar and start carefully bending the frame until it is.

Getting a good bending technique is essential to making small changes and not see-sawing around the point you actually want. What you want to do is feel for the yield of the material and be able to sneak up on it without going too far. The procedure is to slowly apply force and feel for a change in resistance which is the yield point. Any bending before the yield point is elastic bending and the structure will return to its original shape when the force is removed. this type of bending feels like pushing against a spring. Bending after the yield point is what produces permanent changes. To sense the yield point you need to apply force slowly and the yield point is when you feel the structure seem to relax a little bit without you having reduced the force. I recommend practice with scrap tubing. It is a subtle change but once you feel it you'll know it.

Back to alignment. Once the swingarm pivot is square to the steering axis you can start bolting parts into the chassis. I install the forks and front wheel without spacers. If you are using modern stuff the steering stem likely has a thru hole which is very convenient. I have a ground shaft with a pointed end and turn up plastic bushings for a tight fit that allow me to use this center hole as an alignment reference. Slide the bushings and shaft in and adjust the wheel until the pointer is pointing at the middle of the tire. Then measure the side gaps and make spacers as needed. Always double check after the final spacers are installed and the front axle is properly tightened. Now you know the front tire and its contact patch is centered on the steering axis and the swingarm pivot is square to it. Check brake caliper to disc clearance as this may have changed and you don't want the rotors rubbing on the calipers.

Now check the swingarm to see if the rear axle is parallel to the swingarm pivot axis. I assemble the axle without the wheel and pivot race/shaft into the swingarm and shim it on a flat surface so that the swingarm pivot is parallel to the table surface. Check to see if the rear axle is parallel to the table. If not bend one or both arms until it is. Don't worry about the chain adjuster direction, that can be done next.

Now assemble the swingarm into the frame and the rear wheel into the swingarm with no spacers. The goal is to line the rear wheel up with the front wheel. There are various techniques to do this: string, straight edges, laser alignment, etc. Sometimes it is nice to do this with no tires installed so you can work directly from the tire bead mounting surfaces. Once the rear wheel is in line with the front: measure, make spacers, install, then do a final check. Don't forget to double check the chain run and make sure both sprockets are aligned. For what its worth any misalignment only means worn chains and lost horsepower........

For adjusting chain tension it is nice to have a fixture or good ruler to measure from axle center to swingarm pivot center on each side to make sure the rear wheel is not pointing towards the steering axis.

None of this mentioned weight imbalances. I don't think many bikes are off balance enough to have to compensate in wheel alignment. A slight shift of rider position, usually subconsciously, is enough to compensate for even the worst imbalances.

You would be surprised on how big a misalignment can be tolerated with no serious side effects at street pace. This is how BMW got away with having the wheels out of line on a production bike. The rear was offset but still pointing straight ahead so the affect was not to have unwanted rear wheel 'steering' inputs. I must say that I think this is sloppy engineering of the worst kind and am surprised it came from the Germans.

Even though you can get away with reasonably large misalignments you _will_ notice a difference switching to a properly aligned motorcycle.

Hope it helped.


Chris
http://moto2-usa.blogspot.com/
Chip in and help!
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Old 10-20-2011, 06:01 PM   #12
Donkey Hotey
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Quote:
Originally Posted by thecosman View Post
african or european?
We found the real engineer!

Story:
About five years ago, we get a new manager and he's holding his first staff meeting. It's his first time as a manager and he's nervous. He goes though a bunch of stuff, then tells us a little about his background.

Finally, he says, "Does anybody have anything they want to ask me?" Nothing.

"Really, I don't mind the tough questions, I'm an open book."

So I ask, "What is the airspeed velocity of an unladen swallow?"

He looks at me incredulously and says, "What the hell does that have to do with anything?"

One of the other engineers says, "He failed the test!" and about five of us started laughing. He took it in good spirit. I guess he was a Trekkie.
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Old 10-20-2011, 06:35 PM   #13
RecycledRS
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Best alignment description I've heard!
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Old 10-20-2011, 07:27 PM   #14
CosentinoEngineering OP
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>>We found the real engineer!

Just don't ask me what my favorite color is, I always screw that one up. Classic movie making if there ever was such a thing....


Chris
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Old 10-20-2011, 07:27 PM   #15
CosentinoEngineering OP
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>>floor sweeper?

Let me get out my sweeping compound.......


Chris
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