Topic: Vintage sidecar rebuild - new video

[Tintop]

It was my P2 vintage sidecar Sam.

I think the problem with the chair brake is two fold.  First issue is it's working too well, and I can't limit the pressure to it enough to get the balance right with the front brake now.  This has only come to light now because of the extra speed we're now carrying.  The shift linkage now works, and being able to get the up & down shifts has improved straight line speeds, and allowed me to carry more into the corners.  As well the carb jetting improvements have allowed me to get on the gas sooner, and more controlled in the corners.  The total result is we're going much faster everywhere, and what worked (chair brake) before isn't now.  Probably because I'm going deeper with more speed, and getting later (& harder) on the brake.  Just have to make adjustments to the new reality.  It's a good problem to have.

[Sam Green Racing]

I was thinking more on the vibration problem Brian.

Sam.

[Tintop]

I was thinking more on the vibration problem Brian.

Sam.

Engine vibration at the high rpm's we're running is definitely part of the mix Sam.  Being a 360 parallel twin means it's going to be a shaker.  Certainly a likely cause of the coil & tach mount failures (vibration induced metal fatigue).  The fairing brace had been repaired before, and failed at the same point, so that's a design issue.  I also wasn't aware that we were locking up the chair wheel before this.  From what I was told this past weekend, we were smoking it going into the turn at the end of the straight (hence the erratic handling).  That being the case it will be nicely flat spotted, and adding huge vibration.  It will need a new tire for the next race.

[FuZZie]

Not sure what I'm suppose to send back.

All body work is getting removed / frame will be getting a complete crack check / chair wheel will get stripped to the spindle, and get a new tire (old flat spotted now ), and brake modified.  Some engine work to do re the clutch, and starter gear.

Don't press your luck, either go over it top to bottom or send it back!

Perhaps Douggie is thinking F2 Brian.    If it was the Yam, what have you changed since your last outing that could have caused these problems?

Sam.

Yea guys sorry MY BAD, I though tintop was pushing that loaner.   

[Sam Green Racing]

Don't feel off put Douggie, I thought it was the F2 as well when I read it. 

[bear]

I'm assuming your chair brake is linked to your rear brake Brian.
If so you don't have any bias adjustment?

Cheers,
Brian

[scottly]

If I recall correctly the chair brake is a drum brake?

[Tintop]

I'm assuming your chair brake is linked to your rear brake Brian.
If so you don't have any bias adjustment?

Cheers,
Brian

The chair brake (Mini drum) is linked to the front Brian, rear is separate.  That's the way it was built, and raced before I got it.  There is a hydraulic bias adjuster between them (front & chair).  Didn't have this issue last year, but finding the extra speed, and having to brake that much harder has uncovered the problem.  Re-plumbing it so the rear and chair are linked (with bias adjuster) could be done.  However I don't really use the rear now, so it would require a new learning curve, and getting use to new handling traits under braking.  If it would settle it down so it braked hard & straight (like it did when I was slower I'd make the change for the next race weekend in July.  That way I'd get some practice before Mosport, and its high speed/heavy braking turns.
Plan to unload everything tomorrow, and get it up on stands. 

[scottly]

Is the rear brake a disc, or a drum?

[bear]

I'm assuming your chair brake is linked to your rear brake Brian.
If so you don't have any bias adjustment?

Cheers,
Brian

The chair brake (Mini drum) is linked to the front Brian, rear is separate.  That's the way it was built, and raced before I got it.  There is a hydraulic bias adjuster between them (front & chair).  Didn't have this issue last year, but finding the extra speed, and having to brake that much harder has uncovered the problem.  Re-plumbing it so the rear and chair are linked (with bias adjuster) could be done.  However I don't really use the rear now, so it would require a new learning curve, and getting use to new handling traits under braking.  If it would settle it down so it braked hard & straight (like it did when I was slower I'd make the change for the next race weekend in July.  That way I'd get some practice before Mosport, and its high speed/heavy braking turns.
Plan to unload everything tomorrow, and get it up on stands. 

It's pretty well unheard of to have the chair linked to the front down here Brian.
Your right, the front brake does nearly all the work so it's pretty unusual to have the chair linked to it because of the big load variation on the chair wheel.
How are the other bikes you race with set up?

Cheers,
Brian

[Tintop]

It's the chair wheel load variations, combined with the harder braking from the increased speed, that are causing my problems now.

Quite a few have a similar set-up to mine Brian.  That said, they all came from the same builder.  He'd build one, race it for a season, and then sell it on and build another.  Some others (different builder) only run a front and rear brake, no chair.  Most of those are running a drum rear.

I've gone through the rules again, and there doesn't seem to be any restriction on linking, just what components you can use.  So with that in mind I'm going to look at changing mine to linked rear & chair with a bias adjuster between.

[bear]

[quote author=Tintop link=topic=102875.msg1388198#msg1388198 date=1370382569
I've gone through the rules again, and there doesn't seem to be any restriction on linking, just what components you can use.  So with that in mind I'm going to look at changing mine to linked rear & chair with a bias adjuster between.
[/quote]

I think it would be well worth the effort Brian.
I've found that the linked chair to rear setup helps to settle the bike more than anything.

Cheers,
Brian

[scottly]

Wouldn't having a brake on the chair have a steering effect? The rig will pull to the chair side whenever the brake is applied. Anyone ever use "steering brakes" on a dune buggy, or tractor, for that matter? You can nearly pivot the machine around the braked wheel. Trouble with a hack is the chair wheel is unloaded when you want it to go that way, and is loaded when you don't want to go that way.. 

[bear]

Wouldn't having a brake on the chair have a steering effect? The rig will pull to the chair side whenever the brake is applied. Anyone ever use "steering brakes" on a dune buggy, or tractor, for that matter? You can nearly pivot the machine around the braked wheel. Trouble with a hack is the chair wheel is unloaded when you want it to go that way, and is loaded when you don't want to go that way.. 

You would think so Scot but the chair wheel does not sit at a pivot point on most chairs.
Nor does it carry a lot of weight, other than through the middle of a right hander.
Not a place you would expect to be braking real hard.
Because most chair wheels are positioned much closer the rear of a bike, if they are balanced properly they help to steady or balance the bike rather than offer a massive amount of extra braking.

Cheers
Brian

GO THE MIGHTY BLUES

[Tintop]

Last season when I came hard on the brakes the rig stopped up dead straight.  I'd agree with Brian's assessment that the chair brake only acts to help balance the bike under braking.

I'm of the opinion now that the redo of the seat shifted weight backwards, the refreshed engine was more power, and there's more top end speed with the improved shifter.  The effect is we're going much faster into braking zones, and because I'm braking harder the chair wheel is now locking.  Looked at what needs to be done to reconfigure the brakes.  Only issue will be does the rear master have enough volume to handle both?  Re-plumbing the lines shouldn't be a big deal.

[bear]

  Only issue will be does the rear master have enough volume to handle both?  Re-plumbing the lines shouldn't be a big deal.

Only one way to find out Brian, suck it and see.
We usually do our initial set up on stands in the workshop.
By applying just enough pressure to the rear brake peddle to lock up the rear wheel.
Then adjust the bias so that the chair wheel will still turn with some effort.

While we are on the subject of brakes, do you have any issues with front brake fade now your giving them a bit more of a work out?

Cheers,
Brian

[bear]

  Only issue will be does the rear master have enough volume to handle both?  Re-plumbing the lines shouldn't be a big deal.

Only one way to find out Brian, suck it and see.
We usually do our initial set up on stands in the workshop.
By applying just enough pressure to the rear brake peddle to lock up the rear wheel.
Then adjust the bias so that the chair wheel will still turn with some effort.

While we are on the subject of brakes, do you have any issues with front brake fade now your giving them a bit more of a work out?

Cheers,
Brian

[Tintop]

The front has been holding up OK Brian.  However the real test would be at Mosport.

However brakes are no longer a top priority.  After removing the body work to clean things up & check for cracks, I noticed the two main tubes running across the frame didn't look quite right.  Think the frame is bent.   I've been in contact with the builder to find out if this is the way it's suppose to be, or.......  Not sure if it can be straightened, or would require replacement of the tubes.  With only 4 week to go, either way making the next race is in serious doubt.

[Tintop]

So consensus is the frame is tweaked.  Both main tubes that run across the frame have a bend in them.  Causing the bike section to have more lean than it should.  It can be fixed, but would require a complete tear down.  Decided there isn't enough time before the next race to do that.  I've started the change to linking the rear & chair brakes.  Just need to fab up a new hard line to connect the rear master to the bias adjuster.  The shifter shaft seal is leaking so that will get replaced.  Also going to see if I can get a bearing, or bushing installed in the cover to support the shifter shaft.  Repaired the cracked coil mount, and trying to decide the best way to remount the tach.  Think that the extra vibration is coming from a flat spotted chair tire, so that will also be replaced.

[FuZZie]

So consensus is the frame is tweaked.  Both main tubes that run across the frame have a bend in them.  Causing the bike section to have more lean than it should.  It can be fixed, but would require a complete tear down.  Decided there isn't enough time before the next race to do that.

I'd be inclined to think that is the main culprit to your problems, would need to be only a fraction out to cause problems with the third wheel.
But I understand the time frame issue. 

[Tintop]

Actually the frame issue has little to do with the chair brake.  Was watching the F1 chairs @ Donnington and they were locking the chair wheel in left's when it started to float.

The 'sag' is affecting how the other wheels sit on the pavement.  Good for lefts, not so good for rights.  Now that I know what's happening I'll just have to keep that in mind, and change my turn-in points & lines to suit.  There's about 6 weeks between the next race and Mosport, so a possibility to fix it then.

[scottly]

Actually the frame issue has little to do with the chair brake.  Was watching the F1 chairs @ Donnington and they were locking the chair wheel in left's when it started to float.

Either ditch the chair brake altogether, or fit an inertial proportioning valve to limit the brake pressure to the chair brake in left turns. This type of valve was used on mid-70's VW bus's to help prevent the rear wheels from locking in sudden stops. If fitted sideways, one could be used to prevent the chair wheel from locking and grinding flat spots into the tread. I still can't see how a chair brake can do anything but try to steer the rig to the left?

[Sam Green Racing]

Actually the frame issue has little to do with the chair brake.  Was watching the F1 chairs @ Donnington and they were locking the chair wheel in left's when it started to float.

I still can't see how a chair brake can do anything but try to steer the rig to the left?

That makes sense Scott when one considers that the chair itself is trying to do that in the first place.

Sam.

[bear]

Actually the frame issue has little to do with the chair brake.  Was watching the F1 chairs @ Donnington and they were locking the chair wheel in left's when it started to float.

I still can't see how a chair brake can do anything but try to steer the rig to the left?

That makes sense Scott when one considers that the chair itself is trying to do that in the first place.

Sam.

Arrrr..............
The dark art of sidecars. It,s a worry isn't it gentlemen.

Cheers,
Brian

[Sam Green Racing]

Brian, my first real motorcycle was a BSA 650 Gold Flash with a transporter body sidecar, I used it to transport my scrambler/motocross bike. It was a bit of a handfull for a 120lb youngster with no muscles.

Sam.