theTRUTH

See cars and bikes being built for the salt

Moderator: DLRA

russelllowe
Posts: 96
Joined: Mon Jan 06, 2014 2:21 pm

Re: theTRUTH

Post by russelllowe » Sat Nov 18, 2017 2:41 pm

Thanks Graham, up front enclosed by the GSF650 frame tubes it is then.

Cheers

Stayt`ie
Posts: 910
Joined: Fri May 13, 2005 11:47 pm
Location: Mackay

Re: theTRUTH

Post by Stayt`ie » Sat Nov 18, 2017 9:55 pm

Russell, would it not be better to have the water up front with the fuel midships or there abouts ??, reason being that during a run the depleating fuel load (weight) wont have as much effect on wheel bias ??,,
First Australian to ride a motorcycle over 200mph at Bonneville,,,

User avatar
Greg Watters
Posts: 759
Joined: Mon Sep 27, 2004 8:57 pm

Re: theTRUTH

Post by Greg Watters » Sun Nov 19, 2017 8:03 am

russelllowe wrote:
Sat Nov 18, 2017 7:58 am
Hi Greg, thanks, it might look a little exaggerated in the pic ... it's 45 degrees; main reason was to get the steering head tube down as low as possible. Hoofhearted used 45 degrees on his bike and by all accounts that was very stable, so I went with that. It'll have quite a bit of trail ... which I could adjust by shifting the position of the axle relative to the fork tubes (which I'm making). I think the main issue with so much rake and trail is low speed flop. I'm happy to sacrifice that for high speed stability. One of the reasons why I changed my design to go head forward, rather than feet forward, was because I felt I could be more in control at low speed that way around. What will you be running in your streamliner?
Cheers!
I think there is a lot of misinformation out there about rake , when did you ever see anything except custom build bikes or show Harleys with rake like that ,
factory fast bikes dont have it, factory dirt bikes dont have it , I believe our salt bikes are somewhere in between
On 2 wheels stability comes from good wheel alignment , good COG/COP in all planes not just front to rear , but top to bottom and left to right , and the centrifugal force of the wheels
Fast salt cars in the US are going closer to 0 caster to reduce corner jacking when you need to control a problem

I am planning 23-24 deg

russelllowe
Posts: 96
Joined: Mon Jan 06, 2014 2:21 pm

Re: theTRUTH

Post by russelllowe » Sun Nov 19, 2017 9:28 am

Hey Greg,

Yes, true, mainly Harleys. Can't really compare a rear engined land speed bike with either a sports bike or dirt bike though. Well, you can, but theres such a massive gap in so many parameters its hard to argue that first principles would hold. Agree that there is a lot of opinion on it.

Top fuel drag bikes are doing the same kinds of top speed (and would face a lot of instability off the line) so rake/castor on them would be interesting to know.

I tried finding the rake and castor on Sam Wheelers bike ... which I think is the only fast/big streamliner that uses a conventional telescopic fork. It looks really laid down (the head tube seems below the tire height). It also has a very short head tube so that might let it be steeper than 45.

I'm pretty sure my bike is wider than his (I guess/hope mine is shorter to compensate), so that also probably makes comparisons a little dodgy.

Totally agree re wheel alignment ... my 2017 bike was fine to 140 and would only turn left at 185. A quick "tent string and socket" wheel alignment transformed it. Wheels where probably 10mm out of plane but at least they pointed in the same direction! Being really careful about getting the 2018 bike aligned properly.

I like the idea that getting the aerodynamic centre behind the center of mass will pull the bike back in line if it gets out of shape. Here's an opinion ... I recon the guys who think they can react fast enough to counter a large and unexpected deviation from straight ahead (with quick steering) are pretty hopeful. My guess is that they are more likely to make it worse. My goal is to build a bike that's better off without my input if there is a big dynamic change (hit some slippery salt for example). Could be totally wrong, but thats why we build these things aye ... only one way to find out.

When will yours be ready?

Cheers!

User avatar
gennyshovel
Posts: 823
Joined: Tue Mar 29, 2005 10:10 am
Location: Broken Hill

Re: theTRUTH

Post by gennyshovel » Sun Nov 19, 2017 12:06 pm

[/quote]
, when did you ever see anything except custom build bikes or show Harleys with rake like that ,
factory fast bikes dont have it, factory dirt bikes dont have it , I believe our salt bikes are somewhere in between
On 2 wheels stability comes from good wheel alignment , good COG/COP in all planes not just front to rear , but top to bottom and left to right , and the centrifugal force of the wheels
Fast salt cars in the US are going closer to 0 caster to reduce corner jacking when you need to control a problem

I am planning 23-24 deg
[/quote]

Factory bikes need to be able to change direction rapidly, this is achieved by compromise.

I have ridden bikes with 40+ degree rake (yeah Greg, Harleys) & the straight line stability is incredible, the agility, not so much eg. rolling down the road @ 140 & wondered how quickly I could change lanes, a casual heave ho of the bars and hips resulted in a lane change that took maybe 5-8 seconds, so I put more effort into it, gradually increasing to a all balls heave ho & body throw, the lane change time was the same.
Riding with heaps of rake (providing trail is kept moderate) is like riding on rails.
It seemed to work for Willie Buchta (Rip)
http://www.landracing.com/forum/index.p ... 771.0.html
Tiny DLRA# 484
Postiebike Racing , created & funded by TwoBob Engineering

Stayt`ie
Posts: 910
Joined: Fri May 13, 2005 11:47 pm
Location: Mackay

Re: theTRUTH

Post by Stayt`ie » Sun Nov 19, 2017 9:42 pm

My thoughts are that if you are using conventuial telescopic forks, rake is your friend, due to the instability (non stiffness) these forks bring,, there was no way with tele forks you could go over 80mph without experiencing the heebeegeebeese, a fork brace (stiffness) soon made things more comfortable :D ,,, today, with upsidedown forks, rigidity is there, mitigating the necessity for excessive rake angles 8)

In 2008 at BUB's, I crawled all over Sams Liner, your comment sparked my memory, as I recall thinking that the rake looked interesting, in that it appeared not center hub, and not telescopic, it was different :?
First Australian to ride a motorcycle over 200mph at Bonneville,,,

User avatar
BONES
Posts: 354
Joined: Wed Mar 15, 2006 4:28 pm
Location: Killara Sydney

Re: theTRUTH

Post by BONES » Mon Nov 20, 2017 4:18 am

Hi Russell
Here is my 2c worth
Greg is correct about the steering head angle. Not sure about 24deg though.
30deg is plenty and about 120mm trail
I use 30deg on my bikes and have had no problems. The bike is very stable ( ask Greg) and will change direction at speed.

Moto GP bikes will go 200mph and stop and turn--
Top Fuel bikes have a rule about minimum wheel base which would have the rider sitting on the engine if it wasn't for the rake.
Top Fuel bikes DON'T turn Don't stop and only SOMETIMES go where they are pointed.
I think rake with dragbikes is a left over from the old days
.
Sam Wheeler's liner used front suspension similar to the front on an modern road race sidecar. Two forward facing control arms and
a vertical upright for the wheel to attach,
Don't use hub center or front ends similar for comparison to conventional forks. Modern sidecars use less than 10deg on the upright.

Russell--- I haven't said recently--- use the BUSA :D :lol:

cheers Bones

russelllowe
Posts: 96
Joined: Mon Jan 06, 2014 2:21 pm

Re: theTRUTH

Post by russelllowe » Mon Nov 20, 2017 9:18 am

Hi Guys,

Sorry, it wasn't Sam's bike ... it was Bub 7:

Image

Doesn't look like 45 degrees, but looks like more than 30.

Bones ... thanks, I could probably fit 4 of them in the engine cradle, have any spares?

As I kind of alluded to in my last post my feeling on the rake and trail debate is that there really is only one way to find out if the rake and trail numbers on a specific bike will work or not ... which is to try it and see. The two negatives to a 45 degree angle seem to be resistance to turning and flopping at low speed. I don't plan on doing a lot of either so I'll give 45 a go and see what happens (which was actually a decision I made in the design stage a couple of months ago). I have weight distribution and center of aerodynamic drag to go yet ... and as Greg says, both might have an effect that is potentially bigger than the rake/trail contribution.

Cheers

harky
Posts: 164
Joined: Fri Feb 09, 2007 9:03 am
Location: Adelaide

Re: theTRUTH

Post by harky » Mon Nov 20, 2017 9:08 pm

ok while we are on this topic
the FF thing i have started ( built diary to follow - one day soon ) will have Centre hub steering ( being made as we speak)
bones , greg —-what “ caster “ would you set the “ king pin” ?
i am along way off doing that adjustment, but we are discussing this stuff @ the minute
oh yeh forgot to add
may the busa force be with you —— sorry the devil made me say it
ps nice pipe work and lots of notching
harky
harky
DLRA #643
so far 120mph for$2000---imagine how fast I can go for $20,000

russelllowe
Posts: 96
Joined: Mon Jan 06, 2014 2:21 pm

Re: theTRUTH

Post by russelllowe » Tue Nov 21, 2017 7:54 am

Hi Stayt'ie, missed your question earlier ... yes, that was how I originally designed it. I ended up using more of the GSF650 head stem section than I first planned and made the spine a simple box shape; where before it was going to be a bit tapered in at the top. I used more of the frame because the tubes just lined up better and went for a simple box shape in the spine because ... it was simple ... and I could simply drop the water tank in from above. An added advantage is that it can be much bigger (I'm going for a 50 litre tank minimum). The GSF650 frame leaves a nice hole, but it's no where near 50 litres and can only be accessed from the side ... in other words there is a max size and that's it (unlike the spine area which is open at the top so can expand outwards without any frame getting in the way). I'm actually going to use the top of the water tank as my seat and the rear end of that to guide air over the motor.

I'll post a pic next to show what I mean.

I'm using 4mpg as a basis to calculate how much gas I'll need. 5 gallons will give me a range of 20 miles ... enough ride down from the pits to the start, do the run and get back to the pits with some left in the tank. I think that's conservative ... maybe not for the run itself, but I should definitely do better than that on the cruise down and back. Anyone know how much fuel a LS3 uses at max rpm?

Cheers

russelllowe
Posts: 96
Joined: Mon Jan 06, 2014 2:21 pm

Re: theTRUTH

Post by russelllowe » Tue Nov 21, 2017 7:59 am

Hey Harky, very keen to see your progress. I've been thinking about getting a Hayabusa as a nice little around town bike ... would also be good for cruising the pits ... I'll keep you and Bones ("the Devil") posted.

Cheers!

russelllowe
Posts: 96
Joined: Mon Jan 06, 2014 2:21 pm

Re: theTRUTH

Post by russelllowe » Tue Nov 21, 2017 1:34 pm

Hi Guys, some more progress shots:

Rider fitting...

Image

with locations for fuel (in red) and water (in blue) ...

Image

and showing how the GSF650 frame section attaches to the main spine ...

Image

Cheers

Post Reply