ESE's works engine tuner

[TZ350]

The back squating, appears to be a manifestation of center of gravity shifting backwards, thus removing weight from the front wheel...???
Sorry, I´m not getting it.

Sorry, I hadn't realy thought about it and should have explained that the squating compresses both the front and back suspension. I think the bike basically hinges in the middle at the swing arm pivot and the whole bike squats down. I will try and get a video clip of it next time its on the dyno and then we can see for sure whats happining.

[Buckets4Me]

for those fans of TT3D close to the edge

[bucketracer]

... the squating compresses both the front and back suspension. I will try and get a video clip of it next time its on the dyno ...

Its possible that the front suspension is compressed as a reaction to the bike driving the dyno drum around.

[Yow Ling]

Instead of shortening the frame to redistribute the weight , why not move the fuel forward you could put it up by the steering stem just inside the frame rails that would move 2 or 3 kg forward, maybe but the battery in there as well, adjust the bars so you have more rider forward, motor can stay where it was happy

[Buckets4Me]

Its possible that the front suspension is compressed as a reaction to the bike driving the dyno drum around.

my rs would rise up as the back wheel moved closer to the frount wheel pushing the seat and tank up

[casal-fan]

Sorry, I hadn't realy thought about it and should have explained that the squating compresses both the front and back suspension. I think the bike basically hinges in the middle at the swing arm pivot and the whole bike squats down. I will try and get a video clip of it next time its on the dyno and then we can see for sure whats happining.

Its possible that the front suspension is compressed as a reaction to the bike driving the dyno drum around.

Maybe the piece that is missing is simple.
Squat alone, will unload the front wheel. But there are countermesures in the chassi design to control squat, and reestablish chassi geometri.
Simplyfied, these countermesures would be swingarm angle, lenght, and chain sprockets position in relation to each other.

Saying that squat alone will not unload the front wheel, might cause misunderstandings.

http://www.youtube.com/watch?v=XflVAlCbIKI
In this video, the machine is fastened very close to the swingarm pivot point.
Watch how the front compresses when wheel is under acceleration. In a normal dinamic situation, rear squat would occour.
Rear squat, combined with chassi contermesures, and chassi tune would have something to say in a out of corner acceleration f.exe.

[TZ350]

http://www.youtube.com/watch?v=XflVAlCbIKI
In this video, the machine is fastened very close to the swingarm pivot point.
Watch how the front compresses when wheel is under acceleration. In a normal dinamic situation, rear squat would occour.

Good video, yes my bike compresses the forks like that, will try and get a video next time.

[wobbly]

The back squating under power is a function of the top chain pull force vector pulling the rear wheel upwards, not a C of G shift issue..
But get the front sprocket position in relation to the wingarm pivot correct,and you can reverse this force and produce anti squat.
This is why many production type class racers convert to way smaller front and rear sprockets, it lowers the top chain pull.
Look up the many references to anti squat geometry, its easy to understand when you see the forces at work.
I first saw this at Fast By Ferrachi in USA where he had a 916 on the Dynojet.
By simply moving the swingarm pivot up or down, they could make the rear drop, or rise under full throttle power runs - the bike effectively didnt move at all to change the C of G - it simply raised or dropped
the rear due to chain pull.
Rear squat that cant be dialled out by geometry change, can be ameliorated by adding some rear preload and some more compression damping.
We did this on Discombes TZ350 , then he went from not just winning Junior Pre 82 , and breaking lap records,to getting to the front of Senior as well.
An extra 3 turns of rear spring preload and 2 com clicks stopped the rear squat from unloading the front, that even with emulators would go mad as he came off trailing throttle into the power on sweepers.
With the new setting he can power drift both ends, mid turn, with the throttle pinned.

[husaberg]

The back squating under power is a function of the top chain pull force vector pulling the rear wheel upwards, not a C of G shift issue..
But get the front sprocket position in relation to the wingarm pivot correct,and you can reverse this force and produce anti squat.
This is why many production type class racers convert to way smaller front and rear sprockets, it lowers the top chain pull.
Look up the many references to anti squat geometry, its easy to understand when you see the forces at work.
I first saw this at Fast By Ferrachi in USA where he had a 916 on the Dynojet.
By simply moving the swingarm pivot up or down, they could make the rear drop, or rise under full throttle power runs - the bike effectively didnt move at all to change the C of G - it simply raised or dropped
the rear due to chain pull.

Performance bikes (I think)did a write up on dialing out squat in relation to the Kawa ZX900R.
The initial 900 suffered a lot from squat it unlike the ZXR750 was not equipped with an adjustable swing arm pivot.
If we were to take a look at pretty much all the Gp500's and most all the superbikes from the 90's on, the GP500's also had movable engine mounts for the most part had this feature.(they incidentally alleviated the situation with a new shock with more comp damping and and link plus a different counter-shaft sprocket)

A notable exception was the Honda RC45 and look how long this took to get right and in the end it needed a 5 foot psycho.
I am not say the bucket needs it as moving the engine is a much better idea.

[SwePatrick]

This is cool..

It confirmes my theories about how 'wheeliehappy' different chassies are.
I have on my MB5 raceproject made adjustable brackets för swingarm.
Very very simple and only three different holes to choose from.
It´s a test this summer.. i´m hoping i´ll manage without wheeliebars just to get the look of the bike correct

Rgds.

[F5 Dave]

2nd bump. I don't want to run thrust washers if I can avoid it.

ok, a question for the panel;
. . .
So I'm left with the suitability question over 17mm wide MB SE bearing in a Yam piston with 19.2mm between the bosses, so 2.2mm clearance. With a wider rod it should not make it out of the small end.

I'm not overly happy with the 2.5mm rollers (making for a 14x19 bearing) that only has 11 rollers, but they seem to go ok in std bikes. Most of the 18x14 brgs seem to run 12 rollers.

[TZ350]

Year: 1991 HONDA RS125R
Item Specification
Wheelbase 1,260 mm
Dry Weight 68 kg
Half dry weight 71 kg (156 lbs)
Frame Caster angle 25 °
Trail length 95 mm
Suspension-Front Telescopic 90 mm
Suspension-Rear Swingarm 110 mm
Fork oil capacity 210 cc
Fuel system Fuel capacity 12 liter

1997 Honda RS125 Specifications
Item Specification
Wheelbase 1,215 mm (47.8 in)
Half dry weight 71 kg (156 lbs)
Front suspension Telescopic, inverted type
Rear suspension Swingarm, Pro-link
Fuel capacity 13.0 liter (3.4 US gal)
Caster angle 23 ° 30'
Trail length 84mm (3.3 in)

NSR MC16

Wheelbase 1360mm
Seat Height: 750mm
Weight: 125Kg
Castor: 26° chopper like
Trail: 103mm as above

My NSR MC21 Frame

Castor 23° 15'
Trail: 87mm
Wheelbase 1340mm
Seat Height: 770mm

Some basic data on my FZR250 3LN Frame:
Caster Angle 24.5 deg which is 0.5* less than a 91 RS125 @25*
Trail 87mm which is 8mm less than a 91 RS125 @ 95mm
Wheelbase 1,375mm which is 115mm longer than a 91 RS125 @ 1,260 mm
Front fork travel 130mm which is 40mm longer than a 91 RS125 @ 90 mm
Fork Oil 10w
Front Spring Rate 7.8N/mm
Rear wheel travel 117mm which is 7mm longer than a 91 RS125 @ 110 mm
Shock absorber travel 50mm
Spring free length 173mm
Fuel Tank capacity, 14Ltrs
Original dry weight 146kg, oil and full tank 166kg



Some other quickly measured comparisons.

Rear axle to swing arm, 3LN 510mm 91 RS125 455mm
Front axle to swing arm, 3LN 860mm 91 RS125 815mm
Seat Height, 3LN 730mm 91 RS125 675mm
Foot Peg to Seat 3LN 415mm 91 RS125 340mm
Front Axle to crank 3LN 630mm 91 RS125 480mm

And Stearing Head to the front of the Seat, 3LN 630mm 91 RS125 630mm

So I wont be shortening the chassis rails to bring the front wheel back but I might shorten the forks to lower the front end and steepen the caster angle. Also reducing the height of the tank and implementing some of Yow Lings weight forward suggestions and Richbans rear end lightening ideas could be the go.

[husaberg]

Some basic data on my FZR250 3LN Frame:
Caster Angle 24.5 deg 22 deg
Trail 87mm
Wheelbase 1375mm 1275
Front fork travel 130mm
Fork Oil 10w
Front Spring Rate 7.8N/mm
Rear 117mm
Shock absorber travel 50mm
Spring free length 173mm
Fuel Tank capacity, 14Ltrs
Original dry weight 146kg, oil and full tank 166kgn 75kg

A bit easier to do with the computer than for real

NSR MC16
Length: 2035mm
Width: 705mm
Height: 1105mm
Wheelbase 1360mm
Seat Height: 750mm
Ground Clearance: 135mm
Weight: 125Kg
Fuel Tank: 16 litre (primary)1.2 litre (reserve)
Castor: 26° chopper like
Trail: 103mm as above

[richban]

My NSR MC21 Frame

Castor 23° 15'
Trail: 87mm
Length: 1975mm
Width: 655mm
Height: 1060mm
Wheelbase 1340mm
Ground Clearance: 135mm
Seat Height: 770mm

[husaberg]

Some basic data on my FZR250 3LN Frame:
Caster Angle 24.5 deg which is 0.5* less than a 91 RS125 @25*
Trail 87mm which is 8mm less than a 91 RS125 @ 95mm
Wheelbase 1,375mm which is 115mm longer than a 91 RS125 @ 1,260 mm
Front fork travel 130mm which is 40mm longer than a 91 RS125 @ 90 mm
Fork Oil 10w
Front Spring Rate 7.8N/mm
Rear wheel travel 117mm which is 7mm longer than a 91 RS125 @ 110 mm
Shock absorber travel 50mm
Spring free length 173mm
Fuel Tank capacity, 14Ltrs
Original dry weight 146kg, oil and full tank 166kg



Some other quickly measured comparisons.

Rear axle to swing arm, 3LN 510mm 91 RS125 455mm
Front axle to swing arm, 3LN 860mm 91 RS125 815mm
Seat Height, 3LN 730mm 91 RS125 675mm
Foot Peg to Seat 3LN 415mm 91 RS125 340mm
Front Axle to crank 3LN 630mm 91 RS125 480mm

And Stearing Head to the front of the Seat, 3LN 630mm 91 RS125 630mm

So I wont be shortening the chassis rails to bring the front wheel back but I might shorten the forks to lower the front end and steepen the caster angle. Also reducing the height of the tank and implementing some of Yow Lings weight forward suggestions and Richbans rear end lightening ideas could be the go.

I would be interested to see the measurements against the NX4 in the ESE stable.
I found this on the Speedpro's thread (i hope he doesn't mind) i also seen this Lovely RS50 framed H100
2001 2003 RS50 Aprilia
24 rake
Trail 102mm
Wheelbase 1280mm
120mm front suspension travel
110mm Rear suspension travel



Coments re Speedpro FZR framed Bucket.

I've made changes to the riding position. Avalon commented it was like riding a couch with the seat and handlebar positioning. Because of that I've put the original FZR seat back on the bike rather than just sitting on the fibreglass tailpiece and placed the handlebars under the top triple clamp in the original position. Basically it's back to a stock FZR250 riding position. After riding the scooter all week it has a definite head down arse up feel to it. It was OK at the track today and I'm gonna give it a go tomorrow but my thoughts are that the handlebars are going back on top of the triple clamp. For some strange reason I was uncomfortable in the right onto the back straight, running clockwise, and tended to run wide. It also feels like I'd have less chance of saving it if something happened. My right wrist was letting me know about it as well as it's still unhappy after a big crash 30 odd years ago. It "looks" right so I'm thinking it's just me. My son has also commented that I sit upright more than others. could be that I know something others haven't figured out yet though that'd be a first.