Topic: project 71 cb750 with 330 wheel convertion

[333]

I don't see any spring.  Not yet, at least.  But it still won't work.  You roll on the gas, the chain pulls from the jack shaft on the wheel sprocket.  The slack happens as the chain comes off the jack shaft to go back to the wheel sprocket.  This is where a tensioner needs to be, where the slack is.  And I don't see the tubing interfering with the chain.  Looks close, but it looks to me that it'll clear it.

[edbikerii]

It is a tensioner.  Here's the builder's quote:

Looks like the chain has a small sprocket to allow chain to roll over yes?

yes that is the tensioner..

[Industrial Cafe]

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

it's the bar coming off the jack shaft up to a pivot point on the swingarm itself, then out of that comes the arm with the baby sprocket.
   The jack shaft is about 2.5-3 inches further back from the main swing arm pivot, which tells me the whole assembly has the ability to move.


If 631girl (who needs to change his screen name by the way)  would satisfy our curiosity that would be great!

[sangyo soichiro]

The two quotes below (by 333 and IC) contradict each other.  Again, it's hard to see the pictures, but I think Industrial Cafe is correct that the main swing arm pivot is not the same as that of the drive-sprocket-linkage-thing-that's-driven-by-the-transmission--thingy (is that what everyone is calling the "jackshaft" by the way?).

Except that the jack shaft is at the pivot point of the entire swing arm. 

  The jack shaft is about 2.5-3 inches further back from the main swing arm pivot....

[Industrial Cafe]

yeah that's a jackshaft

[Syscrush]

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.

No, it's your use of the word "power".  The only way that "power coming from the drive sprocket is going to go to that little sprocket instead of the wheel", is if there's a brake (or other significant source of friction) on the idler sprocket.  Running the chain up over that idler won't dissipate power, although it will exert a downward force as you note.  Power is the rate of work done over time, and work is force applied through a distance.  I don't see that downward force moving that idler far enough to actually sap any appreciable amount of power.

The idler appears to be part of a tensioning system, although it's not a simple spring-loaded setup like you could use if it was on the bottom run of the chain instead of the top.  If IC is correct that the linkage causes the tensioner to rise as the suspension compresses, then I guess it is effectively spring-loaded - the spring would be the rear suspension.

[mlinder]

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.

No, it's your use of the word "power".  The only way that "power coming from the drive sprocket is going to go to that little sprocket instead of the wheel", is if there's a brake (or other significant source of friction) on the idler sprocket.  Running the chain up over that idler won't dissipate power, although it will exert a downward force as you note.  Power is the rate of work done over time, and work is force applied through a distance.  I don't see that downward force moving that idler far enough to actually sap any appreciable amount of power.

The idler appears to be part of a tensioning system, although it's not a simple spring-loaded setup like you could use if it was on the bottom run of the chain instead of the top.  If IC is correct that the linkage causes the tensioner to rise as the suspension compresses, then I guess it is effectively spring-loaded - the spring would be the rear suspension.

No.

[mark]

I'm looking at this picture and here's what I see...

(1)the jackshaft appears to be behind the swingarm pivot point and mounted to the swingarm... therefore raising/lowering the bike will not affect the tension of the rear chain loop. It would, however affect the front chain loop.

(2)the idler/tensioner arm appears to be clamped to the swingarm with a large bolt. It looks like friction is keeping it in position.

(3)as power is applied, I see the idler/tensioner arm being forced down - allowing the rear chain loop to contact the top of the swingarm.

but I've been wrong before.

 

[ohiocaferacer]

631girl......welcome to the site....and thank you for bringing some thinking outside the box, back into this forum!!!

On a side note........this thread is exactly one of the reason I have stopped visiting this site...to much drama and BS....and not enough innovation or new interesting info. I used to enjoy visiting this site to see all the new and interesting ideas some people were coming up with, in regards to our vintage Honda's....then it seemed everyone was doing the same old thing.....another sportbike front end....or another cafe project. Dont get me wrong......I enjoyed those.....but show something new or improved or different...not the same thing done over again and again. Hell......go throw one of those truck beds on the rear of that CB750 with some big ole 22's out back....with hydraulics......not my thing.....but hell it would be something different(interesting) and might even have some fab details I could use in one of my future projects. In the mean time......this build has spiked my interest and i'll be checking back to see some updates.....and hope this forum takes a turn for the better.

Keep us posted...great work.

[Industrial Cafe]

For me it's not the build that's the problem, it's the builder, he started off with a #$%*ty additude and ....I've said it too many times, won't explain anything in detail. how are we to understand the setup when he won't talk?

[Raul CB750K1]

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?

If you weighed 160 lbs, would you be able to lift 170 lbs with the use of a pulley? Think about it and you will understand why part of the force goes to put the sprocket down

[Roach Carver]

I wish we could all clear out and let this guy have his post back. Some newer/ older forum members jumped down his throat under pretenses that his engineering was faulty and he was not safe, yadda yadda. who do you think you are. I dont care if your an engineer ( I would like to see your diploma BTW if you are). Let the guy build what he wants. dont like it?, then go away. like ohio said, things have become stagnant around here lately and it is this kind of bs that has caused us to lose some good contributors. The one thing I hate about forums like this is it allows the weak to pretend that they are tough. No consequence for shooting your mouth off. the things that are said here would very likely NEVER be said to this guys face.

[Glenn Stauffer]

I wish we could all clear out and let this guy have his post back. Some newer/ older forum members jumped down his throat under pretenses that his engineering was faulty and he was not safe, yadda yadda. who do you think you are. I dont care if your an engineer ( I would like to see your diploma BTW if you are). Let the guy build what he wants. dont like it?, then go away. like ohio said, things have become stagnant around here lately and it is this kind of bs that has caused us to lose some good contributors. The one thing I hate about forums like this is it allows the weak to pretend that they are tough. No consequence for shooting your mouth off. the things that are said here would very likely NEVER be said to this guys face.

I'm in complete agreement with you, 71cb750.  Whatever drives people to explode all over a thread like this is beyond my understanding.  If the original poster wants this thread back, I'll be more than happy to help dig out the good stuff from these 13 pages of posts.

[Syscrush]

If you weighed 160 lbs, would you be able to lift 170 lbs with the use of a pulley? Think about it and you will understand why part of the force goes to put the sprocket down

Pulleys can multiply or divide force, but can't change power.

If that idler doesn't move up and down, then it doesn't disspate any power other than the friction of the idler spinning on its shaft.  Even if it does move up and down, it won't disspiate significant power.

[sangyo soichiro]

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.

No, it's your use of the word "power".  The only way that "power coming from the drive sprocket is going to go to that little sprocket instead of the wheel", is if there's a brake (or other significant source of friction) on the idler sprocket.  Running the chain up over that idler won't dissipate power, although it will exert a downward force as you note.  Power is the rate of work done over time, and work is force applied through a distance.  I don't see that downward force moving that idler far enough to actually sap any appreciable amount of power.

The idler appears to be part of a tensioning system, although it's not a simple spring-loaded setup like you could use if it was on the bottom run of the chain instead of the top.  If IC is correct that the linkage causes the tensioner to rise as the suspension compresses, then I guess it is effectively spring-loaded - the spring would be the rear suspension.

That downward force would increase the friction through that sprocket though.  Remember, friction equals the coefficient of friction multiplied by the normal force.  The normal force (downward force) could get pretty high. 

There is a certain amount of horsepower generated at the crankshaft.  That horsepower must then be transferred to the rear wheel.  Through every frictional connection, there are losses of power.  In other words, power is dissipated through these type of connections.  Maybe my use of the word "lot" can be disputed, but my use of the word "power" is okay I think. 

[754]

I tend to agree with Ind Cafe.

The OP comes on here saying, they are asking for help.

 THEN when anyone challenges the way it is built, there is no explanation, they want help, yet wont proveide any details on what/how they are doing.

 Although they actually started a post on here about how much oil the motor takes, it took DAYS to reply where they were putting it, but still no explanation.. Unless maybe propane botle (2 pictured) is explanetory. like where are the lines, how do you check it, etc.. would be helpful.

 Looks to me like most of the rear assembly is off a Busa, then grafted to a 750, but not yet in usable tested form. This is either exciting to the readers, or boring, depending on your personal views.

 It would be a PLUS to the forum, if a new member comes along, with something new, and can actually take the time to field questions, and explain things..

 I am not saying that a few on here did not jump all over this new poster, but rather than answer questions, they would respond with things like, well if you ever built something like this you would understand, or, you are just upset cause you cant build anything like it...kind of answer.. simple explanation would have changed the whole scenario..

 Terry, I can take criticism, on anything I build. I am willing to explain it, or  describe the working of it. The brace was not my invention, and there are many in use. If anyone comes to visit, the chassis is sitting here, feel free to start twisting the front end, if you can. My intention was to offer up something I knew, gratis to the membership, ie help out & share something with the forum members.. if there was interest. Now that I could use the work, my attitude has changed.

[Industrial Cafe]

http://forums.sohc4.net/index.php?topic=64243.0

nice and "ridiculous free"   ...doubt we'll get anywhere with it though.

[Syscrush]

No, it's your use of the word "power".  The only way that "power coming from the drive sprocket is going to go to that little sprocket instead of the wheel", is if there's a brake (or other significant source of friction) on the idler sprocket.

That downward force would increase the friction through that sprocket though.  Remember, friction equals the coefficient of friction multiplied by the normal force.  The normal force (downward force) could get pretty high. 

There is a certain amount of horsepower generated at the crankshaft.  That horsepower must then be transferred to the rear wheel.  Through every frictional connection, there are losses of power.  In other words, power is dissipated through these type of connections.  Maybe my use of the word "lot" can be disputed, but my use of the word "power" is okay I think. 

We are in agreement that friction is the only mechanism for the idler to reduce the power to the drive wheel.  And we probably agree that the loss would be less if the idler was on the lower run of the chain, where the tension is lower.

Well, under steady-state running friction would be the only loss, but under acceleration, the moment of inertia of that little sprocket would have an effect, too.

I very much doubt that the losses associated with either the friction or angular momentum of that idler would be measurable.  But I could be wrong.  Assuming that it's running on decent sealed bearings, the frictional loss of that idler should be less than the diff between a freshly cleaned & lubed chain vs. one that's due for cleaning & a lube job.

[mlinder]

No, it's your use of the word "power".  The only way that "power coming from the drive sprocket is going to go to that little sprocket instead of the wheel", is if there's a brake (or other significant source of friction) on the idler sprocket.

That downward force would increase the friction through that sprocket though.  Remember, friction equals the coefficient of friction multiplied by the normal force.  The normal force (downward force) could get pretty high. 

There is a certain amount of horsepower generated at the crankshaft.  That horsepower must then be transferred to the rear wheel.  Through every frictional connection, there are losses of power.  In other words, power is dissipated through these type of connections.  Maybe my use of the word "lot" can be disputed, but my use of the word "power" is okay I think. 

We are in agreement that friction is the only mechanism for the idler to reduce the power to the drive wheel.  And we probably agree that the loss would be less if the idler was on the lower run of the chain, where the tension is lower.

Well, under steady-state running friction would be the only loss, but under acceleration, the moment of inertia of that little sprocket would have an effect, too.

I very much doubt that the losses associated with either the friction or angular momentum of that idler would be measurable.  But I could be wrong.  Assuming that it's running on decent sealed bearings, the frictional loss of that idler should be less than the diff between a freshly cleaned & lubed chain vs. one that's due for cleaning & a lube job.

Very measurable. The amount would depend on the angle of drive sprocket to 'tensioner', but there's math for this, and it's measurable.
I'll let Soichiro do the math for you. It's not just friction.

[sangyo soichiro]

Well, under steady-state running friction would be the only loss, but under acceleration, the moment of inertia of that little sprocket would have an effect, too.

I'm glad you pointed that out.  

I'm in the process of souping up my engine as we speak.  One of the things I'm trying to do is to cleverly remove mass from all the rotating parts so as to reduce the moment of inertia as much as reasonably possible.  

(Also polishing the gear teeth to reduce the frictional losses.)  

No, it's your use of the word "power".  The only way that "power coming from the drive sprocket is going to go to that little sprocket instead of the wheel", is if there's a brake (or other significant source of friction) on the idler sprocket.

That downward force would increase the friction through that sprocket though.  Remember, friction equals the coefficient of friction multiplied by the normal force.  The normal force (downward force) could get pretty high.  

There is a certain amount of horsepower generated at the crankshaft.  That horsepower must then be transferred to the rear wheel.  Through every frictional connection, there are losses of power.  In other words, power is dissipated through these type of connections.  Maybe my use of the word "lot" can be disputed, but my use of the word "power" is okay I think.  

We are in agreement that friction is the only mechanism for the idler to reduce the power to the drive wheel.  And we probably agree that the loss would be less if the idler was on the lower run of the chain, where the tension is lower.

Well, under steady-state running friction would be the only loss, but under acceleration, the moment of inertia of that little sprocket would have an effect, too.

I very much doubt that the losses associated with either the friction or angular momentum of that idler would be measurable.  But I could be wrong.  Assuming that it's running on decent sealed bearings, the frictional loss of that idler should be less than the diff between a freshly cleaned & lubed chain vs. one that's due for cleaning & a lube job.

Very measurable. The amount would depend on the angle of drive sprocket to 'tensioner', but there's math for this, and it's measurable.
I'll let Soichiro do the math for you. It's not just friction.

I suppose we could do a rough calculation, but I think Syscrush was suggesting that the losses would be so small that it would amount to the difference in frictional loss between a clean and dirty chain.  My own personal hunch is that there might be more loss of hp - not just through that little sprocket, but through the entire configuration.  Guessing here, but maybe as much as a few hp loss.  Just guessing though.


Edit:  But as edbikerii pointed out, maximizing the rear wheel hp is not the goal of this build....

[seaweb11]

I'm no engineer so I won't comment on this rear assembly, it is interesting.
I am also not a photoshop expert so I won't comment on that either.

Here are a few pics that have not been shown that could assist those that are looking at the build from a "how did it come together" point of view.

[Terry in Australia]

I tend to agree with Ind Cafe.


 Terry, I can take criticism, on anything I build. I am willing to explain it, or  describe the working of it. The brace was not my invention, and there are many in use. If anyone comes to visit, the chassis is sitting here, feel free to start twisting the front end, if you can. My intention was to offer up something I knew, gratis to the membership, ie help out & share something with the forum members.. if there was interest. Now that I could use the work, my attitude has changed.

Bullsh1t VFrank, you posted a rough drawing of the brace, and everyone ignored it, then you got prissy because they ignored it, and continued to waffle on about it. You never posted a pic of it on your bike, with an OEM fender and caliper/s fitted, because apart from your refusal to ever post any pics, it just wouldn't fly.

I agree that it is not your design, I've seen several similar over the years in steel, but it was your suggestion that anyone could make it in thick aluminum plate and round bar in your garage with a minimum of tools, which of course, is rubbish. So stop talking craap, put your money where your mouth is, and either put up, or shut up. Cheers, Terry.

[Mdub]

I think what everybody is missing is that when the suspension is aired up, the whole swingarm drops to lift the bike.
The little sprocket goes with it, and the chain is tightened and doesn't touch the sprocket anymore.
The only thing the little sprocket does is keep the chain from scatching the swing arm when the bike is 'slammed' (aired down)
on the ground.
The little sprocket is NOT part of the drive train in the riding position.



[/quote]

[mlinder]

I think what everybody is missing is that when the suspension is aired up, the whole swingarm drops to lift the bike.
The little sprocket goes with it, and the chain is tightened and doesn't touch the sprocket anymore.
The only thing the little sprocket does is keep the chain from scatching the swing arm when the bike is 'slammed' (aired down)
on the ground.
The little sprocket is NOT part of the drive train in the riding position.

Don't think so. Appears to me that the geometry there will have contact on the 'extra' sprocket pretty much all the time.

[Mdub]

[/quote]


Don't think so. Appears to me that the geometry there will have contact on the 'extra' sprocket pretty much all the time.
[/quote]

Can you tell me why you don't think so with a logical explanation?
The little sprocket is attached to the swing arm and pivots with it.
If you draw a straight line between the top of the front sprocket and the top of the rear sprocket,
it is easy to see that the little sprocket will clear that straight line when the suspension is raised
(swing arm rotated down).
This is not rocket science, it is geometry 101.
I'm sure he is getting a kick out of the fact that all of these experts can't see the obvious.
In the engineering field, we call that "Paralysis through analysyis"