Joined Aug 2008
756 Posts | 156+
England, Southampton
The technical adventures of Dr_C
- Thread starter Dr_C
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Joined Oct 2003
955 Posts | 1K+
Sweden
How about now?That steering angle looks a bit on the lazy side to me DrC!
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Joined Oct 2003
955 Posts | 1K+
Sweden
As the engine hopefully makes this build special, it would be a crime hiding it behind a trellis frame! So my current design proposal is with a more classic looking frame (3D CAD). This will allow a nicer front end of the tank and display the whole engine. The tank will be carbon fibre with some visual carbon fibre against the knee and some blue fields, matching the wheel hubs. The tank will be attached to the frame with a leather strap.
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Joined Oct 2003
955 Posts | 1K+
Sweden
Joined Oct 2003
955 Posts | 1K+
Sweden
Now the design has reached a level where it is good enough to send to the tooth gear machinist an to show the 5-axis CNC wizard. I will have to weld this extra casing onto the crank cases. Not ideal, but I will have to spread the extra load on the 5mm thin crank case walls. The front engine mount will be in rubber, taking up the last few tenths of mm of vertical movement.
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Joined Oct 2003
955 Posts | 1K+
Sweden
Wait until we see if this works! Otherwise this is all firecrackers and beer...
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Joined Jul 2015
141 Posts | 130+
Germany
Hi Dr_C,
it's always inspiring to see you working
How is the assembly procedure? Right crankcase half: drop the crank and the counter balancer in simultaneously? How to make sure the cb-bearing in the left crankcase half is in it's correct place? Or is it the other way around? You shim it from the right?
Does the welding weaken supporting areas for the crank bearings? Your's have to bear high loads I guess.
Like to see some more pictures/videos/posts from the engineering until the build. Great job!
Regards,
EDE
it's always inspiring to see you working
How is the assembly procedure? Right crankcase half: drop the crank and the counter balancer in simultaneously? How to make sure the cb-bearing in the left crankcase half is in it's correct place? Or is it the other way around? You shim it from the right?
Does the welding weaken supporting areas for the crank bearings? Your's have to bear high loads I guess.
Like to see some more pictures/videos/posts from the engineering until the build. Great job!
Regards,
EDE
Joined Oct 2003
955 Posts | 1K+
Sweden
Thanks for cheering, EDE!Hi Dr_C,
it's always inspiring to see you working
How is the assembly procedure? Right crankcase half: drop the crank and the counter balancer in simultaneously? How to make sure the cb-bearing in the left crankcase half is in it's correct place? Or is it the other way around? You shim it from the right?
Does the welding weaken supporting areas for the crank bearings? Your's have to bear high loads I guess.
Like to see some more pictures/videos/posts from the engineering until the build. Great job!
Regards,
EDE
The crank can be dropped into the left casing as usual and then the CB. I just simply turn the CB so the it´s weight is outside the crank.
As there is very little space between the crank halves, and I need a big "imbalance" from the CB, I have to use as wide CB as possible. The axial play at the crank, will have to be as low as possible, maybe 0,5mm. Then I hope to be able to shim the axial position, and play, at the CB, so there is enough room.
The crank case walls are only 5mm thick, so bolting the CB housing onto the crank case was not a realistic option. Welding will weaken the material, but ageing it after welding, at 150degC for a day will help. The fatigue stresses will be substantial, so that is a point of concern, for sure.
Joined Oct 2003
955 Posts | 1K+
Sweden
Kinda cool presentation features in Inventor! Had to try it out!
https://www.youtube.com/watch?v=ZIgpqx9zr_E
https://www.youtube.com/watch?v=ZIgpqx9zr_E
Joined Jul 2015
141 Posts | 130+
Germany
Nice video Dr_C,
maybe I'll test Inventor too some day. I'm sure you've already checked it - but still asking - is the bending, especially when accelerating, within tolerances? The bearings, of course, are mounted outside to the crank bell, but it looks like kind of long distance between bearings and counterweight on a thin shaft.
Counterweight and countershaft is one solid piece?
What about harmonics? All the engineering causes a lot of pain in the first place... you already know what I'm about to say. Anyway - I don't know your toolchain for engineering/design etc. but I just found an opensource tool that can manage Eigenoscillation/natural frequency analysis. I didn't use I myself yet - but I will try it out myself when I can find the time.
The program is called z88 (aurora-edition): https://z88.de/z88aurora/
Their statement about natural fequency analysis can be found here: https://en.z88.de/nat-freq-analysis/
The material thickness for the housing of the counterbalancer to me looks a little weak - especially when I think about a little stone gets thrown to the housing by the front tire. As well as the two screw holes to press both crankcase halfs together. Just a thought. I have to repeat it - great job - it's very rare to see something like this in a forum! Keep on going - we all are waiting for the pics from the build.
EDE
p.s.: Did Ben Ballard (former JBS-Racing) ever manage to sell his stiffer-crankcase castings?
maybe I'll test Inventor too some day. I'm sure you've already checked it - but still asking - is the bending, especially when accelerating, within tolerances? The bearings, of course, are mounted outside to the crank bell, but it looks like kind of long distance between bearings and counterweight on a thin shaft.
Counterweight and countershaft is one solid piece?
What about harmonics? All the engineering causes a lot of pain in the first place... you already know what I'm about to say. Anyway - I don't know your toolchain for engineering/design etc. but I just found an opensource tool that can manage Eigenoscillation/natural frequency analysis. I didn't use I myself yet - but I will try it out myself when I can find the time.
The program is called z88 (aurora-edition): https://z88.de/z88aurora/
Their statement about natural fequency analysis can be found here: https://en.z88.de/nat-freq-analysis/
The material thickness for the housing of the counterbalancer to me looks a little weak - especially when I think about a little stone gets thrown to the housing by the front tire. As well as the two screw holes to press both crankcase halfs together. Just a thought. I have to repeat it - great job - it's very rare to see something like this in a forum! Keep on going - we all are waiting for the pics from the build.
EDE
p.s.: Did Ben Ballard (former JBS-Racing) ever manage to sell his stiffer-crankcase castings?
Joined Jun 2007
4K Posts | 1K+
south east WA Australia
Joined Oct 2003
955 Posts | 1K+
Sweden
Thanks, EDE!
The counter weight looks large, but it is only 11mm thick, as not more is allowed between the crank cheeks. I'm planning to fabricate the whole thing out of a solid piece of SS2541, which is a tempered steel. the shaft is 20mm dia, which was about the same in my old TT600 engine. The counter balancer housing has the same wall thickness as the OEM crank cases, 5mm. If I get stones from the front Wheel, where I am using this bike, I'm on the wrong side of a crash...
Thanks for the resonance sw link! It is very difficult to predict how/where the vibrations will excite a resonance on the bike! it would have been better to place the counter balancer behind the cylinder, as it would be closer to the center of gravity of the engine (thus acting with a shorter lever).
There are three M6 bolts holding the cases together at the front. There is no space to put more bolts in, as they would possibly collide with the front wheel.
Thanks for the interest! I'm also waiting for pictures from the build!
Joined Oct 2003
955 Posts | 1K+
Sweden
It has crossed my mind, but I enjoy riding the thing more than fiddling around in the workshop! You might find that hard to believe...
I still come around here while not owning a berg any more mainly because of this thread...
Never stops to amaze me...
I wish for more photos, of actually anything related to your work around bikes...
And I dont believe you for a second about the riding/fiddling....
Btw...if I ever have a chance to come to Sweden you can count on having me sleep at your workshop. For a month.
Never stops to amaze me...
I wish for more photos, of actually anything related to your work around bikes...
And I dont believe you for a second about the riding/fiddling....
Btw...if I ever have a chance to come to Sweden you can count on having me sleep at your workshop. For a month.
Joined Oct 2003
955 Posts | 1K+
Sweden
Haha! Thank you very much for the appreciation! There is a locker room, shower, kitchen and an office in the workshop, so I think you'll get by! Oh, yes! A 1000Mbit/s internet connection too!I still come around here while not owning a berg any more mainly because of this thread...
Never stops to amaze me...
I wish for more photos, of actually anything related to your work around bikes...
And I dont believe you for a second about the riding/fiddling....
Btw...if I ever have a chance to come to Sweden you can count on having me sleep at your workshop. For a month.
All CAD models and drawings are now sent for manufacturing of toothed gears and complicated alu milling. Pictures will come eventually!
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