HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Aug 18, 2011, 10:27 AM
Registered User
edi.winter's Avatar
Tirol
Joined Jul 2009
1,110 Posts
Quote:
You did mention that you did work on the bike set up (long wheel base, low CoG, etc) in order to avoid wheely ... but with 1kw power, and a top speed above 100km/h ... I think the set up is not enough for avoid the wheely even near full power ... probably not even at medium speed ... the 1920 has monster torque ... so ... do you have some ESC set up for avoid wheely ? Like limit the acceleration (the increase or RPM) ?
The Bike setup and the swingarm priciple with the motor mounted on the swingarm gives a huge advantage under acceleration. I think everyone there saw the superior acceleration the bike has.
Due to the rigid transmission system without the swingpivot inbetween every miliwatt goes directly to the rear wheel.
On conventional bikes when the power goes through the layshaft/pivot it pulls on the chain interacting with the rear suspension.
I call it "onpowerlockup" and "brake lockup". This on one side causes every bump that compresses the suspension directly "hit" into the transmisson and on the other side the transmission power causes the swingarm to be completly blocked out and the rear tire just bounces over the track.

One thing that really influences the bike tending not to wheely is the position of the CG.
If its up front then the horizontal lever is longer and its harder to lift up the front of the bike. If the CG is low down the vertical lever is quite short and the weight hardly can build up any momentum during accelleration.

On top of that the tendency to "snap wheely" is strongly reduced with the long swingarm. In my case I chose to put the pivot right below the CG. So this way the swingarm is always lifting the bike up in a balanced way without giving the CG any leverage to cause havoc under different load situations.
This als gives a very constant lifting movement under acceleration. The bike can easily recover out of near to vertical wheelies. Just imagine trying to balance a broom on its end with a wobbly sprung hinge in the middle....thats how a conventional design works in a way.

I got carried away somehow... sorry ... what was the question again???
ah yesssss.........
Of course the "big" secret to keep this motor under control is the ESC setup. It is really easy to drive if you do everything right....

Quote:
One more ... you mention you got a prototype motor from Lehner, but still they are not one of your sponsor ... how did you manage it ?
I just told him that I could not use it in my bikes with his conventional rear end. So he offered me to try it with the prototypes... thats all....and secondly money makes the world go round......
edi.winter is offline Find More Posts by edi.winter
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 18, 2011, 10:52 AM
Registered User
Austria
Joined Jan 2004
7,999 Posts
Thanks Edi ...

Very helpful as usual

I did check your ESC, actually is relative cheap too ... now it is sold for 159€ for the 120Amp version.
It is looking has nice power control features, and I guess these are a must for RC bike in the Mod class.

In the past I was reading that the 1920 Lehner was not suggested by Lehner theirs self for 1/10 RC cars ... I think the 1520 was the suggested one, since it can increase RPM much faster ...

It was your idea the 1920 ? How did you come to this motor ?

Anyhow, now that you won a world with it, Lehner should give you back some money , possibly with interests

Tchuss

e_lm_70

ps: BTW, when your Jabber will be available on rc-motorradshop.de ?
e_lm_70 is offline Find More Posts by e_lm_70
Reply With Quote
Old Aug 19, 2011, 04:13 AM
Registered User
edi.winter's Avatar
Tirol
Joined Jul 2009
1,110 Posts
Quote:
Originally Posted by e_lm_70 View Post

It was your idea the 1920 ? How did you come to this motor ?

ps: BTW, when your Jabber will be available on rc-motorradshop.de ?
I saw the Einibike drivers using that motor. So a gave it a try.

A Jabber will always be a exclusive handmade Bike.
But maybe sometime next year I can announce someone who will be making a kit bike.....
edi.winter is offline Find More Posts by edi.winter
Reply With Quote
Old Aug 20, 2011, 05:06 AM
Occasional useful idiot...
Joined Nov 2009
1,406 Posts
Did you ever get to the wind tunnel before Lostallo?

Did any aero tweaks make any difference?
Jonathan Bradbury is offline Find More Posts by Jonathan Bradbury
Reply With Quote
Old Aug 20, 2011, 06:10 AM
Registered User
edi.winter's Avatar
Tirol
Joined Jul 2009
1,110 Posts
no.

But the change I made made a difference.
106 down the straight in training and 99 in race...
edi.winter is offline Find More Posts by edi.winter
Reply With Quote
Old Aug 20, 2011, 06:24 AM
Occasional useful idiot...
Joined Nov 2009
1,406 Posts
The heavier back wheel making the difference maybe?

I assume that there was no wind to affect the top speed.
Jonathan Bradbury is offline Find More Posts by Jonathan Bradbury
Reply With Quote
Old Aug 20, 2011, 06:44 AM
Registered User
edi.winter's Avatar
Tirol
Joined Jul 2009
1,110 Posts
The back wheel isnt heavier at all, just a mere 10g.
THAT wasnt the difference.
And side wind effect is close to zero. The whole side of a bike
is huge anyway. If wind gets to the side it balaces itsself anyway.
We have so called "Föhn" Storms (hotwind storms). They always
are cross-straight. And I didnt feel the slightest difference with
or without the disc.
Under the line it uses approx. 200-400mAh less battery over a 10 minute run....
edi.winter is offline Find More Posts by edi.winter
Reply With Quote
Old Aug 20, 2011, 07:00 AM
Occasional useful idiot...
Joined Nov 2009
1,406 Posts
Sorry to ask, I'm just trying to qualify my thoughts on aero in post 489.

Hhhmmmm. I need to knock up a homebrew wind tunnel and figure out how to measure drag using a strain gauge. The biggest problem of course is how to get the wheels rotating...(edit. Just thought of a rather easy way to do that. )
Jonathan Bradbury is offline Find More Posts by Jonathan Bradbury
Last edited by Jonathan Bradbury; Aug 20, 2011 at 07:14 AM.
Reply With Quote
Old Aug 21, 2011, 02:43 PM
Registered User
Tüsken's Avatar
Sverige, Västra Götalands Län, Lidköping
Joined Jan 2010
84 Posts
Quote:
Originally Posted by edi.winter View Post

Before anybody asks:
The motor is a Lehner 5T Prototype (1920/5 LK CAR) .

This should be the same motor execpt for the car end bell.
http://www.graupner.de/de/products/7...4/product.aspx
Tüsken is offline Find More Posts by Tüsken
Reply With Quote
Old Aug 21, 2011, 03:40 PM
Registered User
edi.winter's Avatar
Tirol
Joined Jul 2009
1,110 Posts
and the "LK" ... from /5 on he usually only sells with the "Fan" = "LK"
edi.winter is offline Find More Posts by edi.winter
Reply With Quote
Old Aug 21, 2011, 04:08 PM
Registered User
Whitham69's Avatar
Trowbridge UK
Joined Oct 2006
1,212 Posts
Quote:
Originally Posted by edi.winter View Post
Due to the rigid transmission system without the swingpivot inbetween every miliwatt goes directly to the rear wheel
Not so, you lose some though the chain or belt, it not 100% effent

Quote:
Originally Posted by edi.winter View Post
On conventional bikes when the power goes through the layshaft/pivot it pulls on the chain interacting with the rear suspension.
I call it "onpowerlockup" and "brake lockup". This on one side causes every bump that compresses the suspension directly "hit" into the transmisson and on the other side the transmission power causes the swingarm to be completly blocked out and the rear tire just bounces over the track.
your on about the bike jacking on and off power, seperate layshaft a better way to go as having the motor on the swing arm has lots of unsprung weight which is never good

Quote:
Originally Posted by edi.winter View Post
One thing that really influences the bike tending not to wheely is the position of the CG.
If its up front then the horizontal lever is longer and its harder to lift up the front of the bike. If the CG is low down the vertical lever is quite short and the weight hardly can build up any momentum during accelleration.

On top of that the tendency to "snap wheely" is strongly reduced with the long swingarm. In my case I chose to put the pivot right below the CG. So this way the swingarm is always lifting the bike up in a balanced way without giving the CG any leverage to cause havoc under different load situations.
This als gives a very constant lifting movement under acceleration. The bike can easily recover out of near to vertical wheelies.
.
I go with that, i used to build my bikes (Rear to front) with a 14cm swing arm, swingarm pivot, drive shaft, motor, saddle pack all as low as possable. I never got round the problem of spur gear hitting the floor as everything was to low but it never wheelyed and drove out corners harder.
Whitham69 is offline Find More Posts by Whitham69
Reply With Quote
Old Aug 22, 2011, 02:45 AM
Registered User
edi.winter's Avatar
Tirol
Joined Jul 2009
1,110 Posts
Quote:
Originally Posted by Whitham69 View Post
Not so, you lose some though the chain or belt, it not 100% effent
Well thats obvious and the same on any design

Quote:
Originally Posted by Whitham69 View Post
your on about the bike jacking on and off power, seperate layshaft a better way to go as having the motor on the swing arm has lots of unsprung weight which is never good
LOL I always have people picking on that point....
to be exact: the rear design is up to 30% "better" than the conventional design. Most talk about unsprung wheight but dont really understand that
thats not the whole story. You also have to take in account how far you
are moving this unsprung weight.... anyway.. it works.
edi.winter is offline Find More Posts by edi.winter
Reply With Quote
Old Aug 22, 2011, 03:15 AM
Registered User
Manuspain's Avatar
Joined Feb 2007
262 Posts
Eric Bezombes from France was using this system on his SB5 at Lostallo, separate shafts but in the same place.
He used a tube for rear arm pivot with a shaft inside for the transmission.
Manuspain is offline Find More Posts by Manuspain
Reply With Quote
Old Aug 22, 2011, 03:21 AM
Registered User
Whitham69's Avatar
Trowbridge UK
Joined Oct 2006
1,212 Posts
It works geat Edi with out a doubt, it a cleaver way around the problem. you have any problems with the swing arm twisting with the tourqe from the motor?


Eric bike was good, having both shaft in the same place would stop the chain becoming slack with the swing arm movment
Whitham69 is offline Find More Posts by Whitham69
Reply With Quote
Old Aug 22, 2011, 03:53 AM
Registered User
edi.winter's Avatar
Tirol
Joined Jul 2009
1,110 Posts
Quote:
Originally Posted by Whitham69 View Post
It works geat Edi with out a doubt, it a cleaver way around the problem. you have any problems with the swing arm twisting with the tourqe from the motor?
Not really. Even the earliest designs were okay with that.
I had problems to reduce torsional flex. The long swingarm
was too soft when you twisted it.
Here is a view on the swingarm of the 2011.
Alltogether the parts on the picture weigh 134g.
edi.winter is offline Find More Posts by edi.winter
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Oops, must stop showing off wildpalms Parkflyers 6 Aug 08, 2012 03:46 AM
OFF TOPIC: Pics From Air Show ProLeisure Slope 1 Aug 26, 2003 02:10 PM
Showing Off Corona at Flyin Breakfast AirVenture Electric Heli Talk 2 Jul 13, 2003 02:00 PM
New prototype from China microflyer77 Scale Kit/Scratch Built 8 Sep 10, 2002 05:55 PM
Showing off with the Mini Max Vonbaron Parkflyers 1 May 15, 2002 02:14 PM