Topic: project 71 cb750 with 330 wheel convertion

[Industrial Cafe]

I was going to reference your fork conversion thread as how it should be done. Guess I just did  

http://forums.sohc4.net/index.php?topic=63784.msg696183

Good stuff

Did you cast that rake and lathe the handle yourself? Got pics? What sandpaper did you use?

I used a billet handle spun down on a JET 13" x 40" Belt Drive Bench Lathe, cut sheet metal for the tines,
and sanded with 320, 400, 600, 1500, and maas metal polish.  no pics, as the rake doesn't actually exist.

that link to the unknown members page should help him out at least with hanging it off the frame, his front end doesn't look finished yet either.
I couldn't find the link for that air setup, but I did find this overpriced junk-
http://www.tobefast.com/trickyair-busa-front-air-forks-pr-4469.html

the one I saw was different, it had modified fork caps that were basically just short fat cylinders and he removed the plastic spring spacer.

[333]

First post in this mess, but here goes.

The tensioner is on the wrong side.  The top. where the motor is pulling on the wheel sprocket is where the most tension is, and therefore needs no tensioner.  On the bottom, where there IS slack in the chain is where the tensioner is needed.

[kslrr]

First post in this mess, but here goes.

The tensioner is on the wrong side.  The top. where the motor is pulling on the wheel sprocket is where the most tension is, and therefore needs no tensioner.  On the bottom, where there IS slack in the chain is where the tensioner is needed.

What he is doing is not so much of a tensioner, but rather to direct the chain over the top of the swing-arm.  If you look at his early pics, you can see how the alignment of the sprockets cause the chain to hit the swing-arm.  Also, I don't think there is any spring to his tensioner.  I do agree that a non-toothed whell would be better.

[333]

But the mechanical advantage goes to the chain.  The way it is set up, the moment the chain tightens, that arm will twist on it's mounting point and allow the chain to hit.  Think of it this way.  Sure you can hold a 15lb bowling ball with one hand against your body, but try to hold it with your arm straight out to the side.  That sprocket needs a solid 90 degree bracket directly under the chain.

[kslrr]

But the mechanical advantage goes to the chain.  The way it is set up, the moment the chain tightens, that arm will twist on it's mounting point and allow the chain to hit.  Think of it this way.  Sure you can hold a 15lb bowling ball with one hand against your body, but try to hold it with your arm straight out to the side.  That sprocket needs a solid 90 degree bracket directly under the chain.

You are right about that.  I'm sure he'll figure it out since he is realy in a "try it and see what happens" mode.  Maybe he'll include a locking pin once the chain is where he want's it.

[Industrial Cafe]

you may be correct 333, I think it's more animated than stationary, look at the hinged point... I think it moves
also, I'm worried about the jack shaft only having a strong fixed point on one side.

[sangyo soichiro]

First post in this mess, but here goes.

The tensioner is on the wrong side.  The top. where the motor is pulling on the wheel sprocket is where the most tension is, and therefore needs no tensioner.  On the bottom, where there IS slack in the chain is where the tensioner is needed.

This is a great point.  And as far as performance goes, a lot of the power coming from the drive sprocket is going to go to that little sprocket instead of the wheel where it ideally should go.

I've been distracted by the pissing match that I totally neglected the engineering of the bike.  Good thing folks like 333 are paying attention.

[bgfootball67]

Correct me if I am wrong, but most of the slack in the chain will be eliminated when air is added to the rear shock and it is at ride heidth.  The other tensioner is used to help eliminate chain slap.  I have seen this set up on both the top and bottom of the swing arm on custom v-twins.  You can use a dirt bike set up to eliminate the slack, they work 100 times better than a skate board wheel (ask me how I know, different rubber compound)...

I asked quite a bit ago about him being worried about the power loss by running a jack shaft.  Every time I have seen someone use the jack shaft on a build they have plenty of horsepower to spare (Busa, big inch V-twin), he said he was not worried.

No disrespect Spanner & a few others, but if you made some of the comments on one of my threads like this one, I would have told you to go F yourself too.  JMHO....

[Industrial Cafe]

with a rake?

edit: I'd like to add, with all this jibber jabber I don't think the OP will ever find the real questions and concerns in the thread.

yes I am guilty of posting nonsense too.

[mystic_1]

I mentioned the problem with the tensioner being up top, back on page.... er don't even remember now. 

But trust me, the post exists

So, 631, is the tensioner actually a tensioner or just an stationary idler?

mystic_1

[Syscrush]

This is a great point.  And as far as performance goes, a lot of the power coming from the drive sprocket is going to go to that little sprocket instead of the wheel where it ideally should go.

Wow.  What are the physics like in the world you inhabit?

[Industrial Cafe]

very physical.

[coldright]

This is a great point.  And as far as performance goes, a lot of the power coming from the drive sprocket is going to go to that little sprocket instead of the wheel where it ideally should go.

Wow.  What are the physics like in the world you inhabit?

You're asking Soichiro this question?  Wow is right.

[sangyo soichiro]

This is a great point.  And as far as performance goes, a lot of the power coming from the drive sprocket is going to go to that little sprocket instead of the wheel where it ideally should go.

Wow.  What are the physics like in the world you inhabit?

Look at the photo.  There are three sprockets (EDIT:  Actually five sprockets... .  Ideally you'd want the chain straight on the top (consider the motion of the system).  The way it is now, the chain will exert a downward force on the center sprocket.  It's a wasted force that could have been applied to the rear wheel.  Plus frictional forces from that center doohickey...

So which part of what I said are you teasing me about; was it my use of the word "lot"?  Just curious.

[Zaipai]

This is a great point.  And as far as performance goes, a lot of the power coming from the drive sprocket is going to go to that little sprocket instead of the wheel where it ideally should go.

Wow.  What are the physics like in the world you inhabit?

Look at the photo.  There are three sprockets.  Ideally you'd want the chain straight on the top (consider the motion of the system).  The way it is now, the chain will exert a downward force on the center sprocket.  It's a wasted force that could have been applied to the rear wheel.  Plus frictional forces from that center doohickey...

So which part of what I said are you teasing me about; was it my use of the word "lot"?  Just curious.

So is the bike lowed in this picture? And if it is would the chain not straighten up when it gets to riding height? Just wondering...

[Terry in Australia]

Well it's nice to see that the OP is back (and I'm sorry that his GF isn't coming back) and with the exception of Spanny, everyone's playing nice again.

There's nothing wrong with pointing out that one man's fabricating skills are rubbish, part of the problem with todays society is that a lot of folk think they're really good at something just because their family/friends don't want to hurt their feeling so they lie about how crap they really are, (take a look at the American Idol audition rejects, for example)  but I saw the nasty side of a few folks here who I thought were nice people, and that surprised me.

Anyway, welcome back mate, and I hope you make that thing work as good as it (almost) looks. No one here that I know of has achieved that huge tire look on a CB750, so if you make it work, you'll be up there with the great innovators on this site. You might even be able to do some "kits" for other like minded members, and make some bucks. Cheers, Terry.

[sangyo soichiro]

So is the bike lowed in this picture? And if it is would the chain not straighten up when it gets to riding height? Just wondering...

It looks lowered judging by the looks of the "shock".  But then what happens when you hit a bump in the road and that little sprocket wants to stretch that chain...?  (Seriously.  Something's going to break.)

By the way, is that shock/suspension a pneumatic cylinder?  It looks like it.  How is that going to work?  Air is pretty "squishy," and the diameter looks fairly small.

[333]

Except that the jack shaft is at the pivot point of the entire swing arm.  So regardless of the angle of the swing arm, the chain won't tighten OR loosen.

[333]

This is a great point.  And as far as performance goes, a lot of the power coming from the drive sprocket is going to go to that little sprocket instead of the wheel where it ideally should go.

Wow.  What are the physics like in the world you inhabit?

Don't ask.  It will involve a conveyor belt.

[edbikerii]

Forgive me if I'm wrong, but I don't think the builder's goal here is actually to get the maximum horsepower to the ground.

Frankly, I think "the look" of the fat-ass tire is the goal, no?

I mean, we all know that those fat-ass tires don't exactly improve handling, right?

Besides, what are we talking about on this bike, maybe 60 HP tops?

Not that that should stop any of the discussion here, as it is very interesting.

[Industrial Cafe]

Except that the jack shaft is at the pivot point of the entire swing arm.  So regardless of the angle of the swing arm, the chain won't tighten OR loosen.

exactly why I want him to post a video of it in action, even if it's lifted by a floor jack.

[sangyo soichiro]

Except that the jack shaft is at the pivot point of the entire swing arm.  So regardless of the angle of the swing arm, the chain won't tighten OR loosen.

Well, I'll admit that I'm having a hard time seeing exactly what's going on in these pictures. 

[Industrial Cafe]

doesn't it look like the sprocket in the middle moves up and down opposite the suspension?

[333]

Where do you see any lever or whatever that does that?  It doesn't even have a spring on it.

[edbikerii]

I thought it was spring loaded to serve as a tensioner. 

doesn't it look like the sprocket in the middle moves up and down opposite the suspension?