Author Topic: Let's go roadracing...continuing saga (Read 187270 times)

bwaller · « **Reply #500 on:** April 28, 2013, 06:32:53 am »

Well it's a horizontal graph where many are vertical but the power deliver is quite linear. Some will say too much so for a race engine, and not enough burst on top but I tell myself it's easier for an old fart to ride.

Kemp · « **Reply #501 on:** April 28, 2013, 06:54:16 am »

Not that I know anything about dyno graphs but I'm wondering about the very squiggly line of the HP curve from 8500 to top, could that due to valve spring harmonics?

turboguzzi · « **Reply #502 on:** April 28, 2013, 09:36:24 am »

super cool brent, guess its once again proof that the smaller sohcs are really stranlged at the valve seat cross section... should be fun this year, eh?

BTW, first race of the season here and got today my first ever class win. and i have to add: it's an undeserved one, but a win is a win, no?

top guy Toschi (ex Italian supertwins champ in the 90's) crashed after four turns, second fastest guy had a LiPo battery break down after three laps. I managed to finish the race in one piece with a wrapped/overheated front disc and severe right arm pump....

here i am (999 far left) with my buddies Carlo (506) , who rides this year a Pantah twin instead of his old CB500/4 and got a second in 500 and Piero (514) who won the 500 class with his sohc

sorry for the light hijack..

bwaller · « **Reply #503 on:** April 28, 2013, 10:29:45 am »

Very well done TG, I bet that feels good. When does the "big single" come out?

Kemp I wish Rick was here to answer correctly but as Mike mentioned before there was no smoothing control of that graph. I'm talking out my ass but when he changed the screen to focus on that specific rpm range the line did appear smoother.

hrcscott · « **Reply #504 on:** April 29, 2013, 03:44:12 pm »

Perfect...just #!$*%% Perfect...I can see a lot of second places in my future

Nice work Brent...stuff like this will keep you as my personal build consultant

cheers and congrats,
Scott

bwaller · « **Reply #505 on:** May 14, 2013, 07:20:29 pm »

I raced with the USCRA at NHMS, Laconia NH on Monday. First outing and it was cold. 49 (9C)degrees until noon then blasted up to 52 (11C)! Cold tires+cold track = lack of adhesion. After the back end broke free a few times in practise I was apprehensive to push it.

It was a good day though, a 2nd & 3rd, then the rear sprocket let go after the start of the third race. That's repairable so could have been much worse. The rear wheel didn't lock up and put me on my head, plus the twenty guys behind made it past without running me over.

I may have video later.

Syscrush · « **Reply #506 on:** May 14, 2013, 07:24:46 pm »

Wow. I don't think I've ever seen that mode of failure before. What causes that?

bwaller · « **Reply #507 on:** May 14, 2013, 07:53:25 pm »

It's a bit of a long story Syscrush, but I wasn't happy with the sprocket mount after installing the new swingarm and re-aligning the wheel. It meant having to move that sprocket away from the hub center to align. I have a new design in the works.

Some pics here. (thanks Tim)

http://aphillips66.smugmug.com/Motorcycles/USCRA-Vintage-GP-May-2013/29411533_C8V4RN#!i=2510900066&k=5w7wsHC&lb=1&s=A

scottly · « **Reply #508 on:** May 14, 2013, 08:09:26 pm »

Are the sprocket mounting studs part of a cush drive? Any pics of what the sprocket looked like before the failure?

Tintop · « **Reply #509 on:** May 14, 2013, 08:14:17 pm »

Glad to hear you & the bike are OK. So the sprocket mounting parts sucks, but how did the new swingarm feel??

RAFster122s · « **Reply #510 on:** May 14, 2013, 09:14:58 pm »

Wow, that is a scary failure. Glad no one got hurt.

David

bwaller · « **Reply #511 on:** May 15, 2013, 04:24:42 am »

Brian, I think the true test of a stiffer arm will be on the throttle out of faster corners. This will be tough for me to distinquish because as a result of installing the new arm I discovered my rear wheel was out of alignment. T12 at Loudon is a hard throttle left hander onto the front straight & the bike was much more predictable than last year. Arm or alignment or both....can't say. I always felt it tougher to get through T2 & 4@ Mosport, unable to pick the fast line. Hopefully this year will be different.

scottly, it's a CB350 twin rear hub. There are four cush bushings in the hub. The wheel mis-alignment is embarrasing but surely wasn't anything obvious. (These stock frames are anything but straight. I should have built a jig in the beginning when I first noticed oddities!) There is a steel sleeve cast into the hub that the original steel 530 sprocket rides on, held in position by a circlip. My sprocket is "outboard" of this position now so I'll machine an aluminum "offset" spacer that better supports the sprocket. This will eliminate any side loading of the sprocket which I believe caused the failure.

No pics of original, but this was my previous set-up

simon#42 · « **Reply #512 on:** May 15, 2013, 10:23:18 am »

why bother with a cush drive at all ? extra weight and complication and it will always move a bit out of line . dont worry about chain life a modern chain will do a season on a tz750 without a cush drive . its a race bike brent not an engineering project !

MRieck · « **Reply #513 on:** May 15, 2013, 10:48:22 am »

Quote from: simon#42 on May 15, 2013, 10:23:18 am

why bother with a cush drive at all ? extra weight and complication and it will always move a bit out of line . dont worry about chain life a modern chain will do a season on a tz750 without a cush drive . its a race bike brent not an engineering project !

I thought the two were inseparable Simon?

bwaller · « **Reply #514 on:** May 15, 2013, 12:14:42 pm »

I had this hub when I built the bike Simon and it saved me 1lb compared to stock. Big deal I know, I can easily find something much lighter and will this off-season. For now I'll make an adaptor and put this nuissance behind me.

simon#42 · « **Reply #515 on:** May 15, 2013, 03:09:17 pm »

you could be right mike ! but the less moving bits you have on the bike the less there is to break .

brent saving one pound is always worth the effort , thats one pound that you dont have to accelerate and decelerate 10 times a lap .

back in the early 90's i ran a 250 aprilia , it was a great bike but chewed up gearboxes at an alarming rate . after about five i spoke to them to see why it was happening . no problem they said we have a modified part that will solve it and it only costs 750 quid [ well it was actually about 50 million lira or something like that ] . was quite surprised when the modified part turned out to be a rear wheel with no cush drive !

bwaller · « **Reply #516 on:** May 15, 2013, 03:24:52 pm »

Hah! That's quite a gearbox fix. I'll keep it in mind though.

turboguzzi · « **Reply #517 on:** May 15, 2013, 04:07:54 pm »

after you heard the story about the engine less line of superbike homologation replicas aprilia put up in the factory for the FIM stewards, you'll believe anything really

always thought that cush drives help G/B teeth actually, not chain life, but intuition doesnt always work, does it.
was reading about how welding/canceling the cush drive in clutch baskets too solves rattling at idle without any ill effects. you learn something new everyday,

FunJimmy · « **Reply #518 on:** May 15, 2013, 08:03:34 pm »

Must have missed this due to our local Provincial election.
That's a crazy failure Brent. Glad you escaped a catastrophic incident.
I’d ditch the cush drive too. Good luck on the next race day.

bwaller · « **Reply #519 on:** May 20, 2013, 12:31:25 pm »

Here's a vid from laconia. The guy that gets by & wins is on a Ducati 851. After the morning fiasco the races were shortened to six laps so it's not too long.

# 273 New Hampshire Motor Speedway

MRieck · « **Reply #520 on:** May 20, 2013, 04:29:39 pm »

Pretty nice Brent.

No shame when going up against much larger displacement. Maybe TG will buy into the intake seat boring.

Tintop · « **Reply #521 on:** May 20, 2013, 07:17:33 pm »

Well done bw. Very nice work through the traffic.

See you @ Shanny. Is your son's bike ready??

bwaller · « **Reply #522 on:** May 20, 2013, 08:23:25 pm »

His engine is finally together tonight, new swingarm needs a little machining, then fork rebuild, fiberglassing, waiting for parts. By hook or by crook my new sprocket carrier will be finished this week. We're doing a trackday Monday...hopefully. Why the hell does everything always come down to the wire?

FunJimmy · « **Reply #523 on:** May 20, 2013, 08:40:22 pm »

Nice race Brent. The bike seems very well sorted.

RAFster122s · « **Reply #524 on:** May 20, 2013, 09:04:50 pm »

Great video Brent. Your bike has beastly amounts of power and you have consistent and good starts. Some nice passing during the race. The guy on the Duc was really losing time on the corners whereas you were eating up any power advantage he might have on the straights in the corners. Either he was too timid in the corners or you ride much harder than he does...surely it isn't a question of braking, as you were braking later but not killing your cornering speed. Sometimes slower is faster as they say...

The IOM superbike race Mike recently posted in another thread shows how ballsy road racing is/can be...

News:

Author Topic: Let's go roadracing...continuing saga (Read 187270 times)