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Lahr Carbon Gear Box bike

no skid marks

Monkey
Jan 15, 2006
2,513
27
ACT Australia
It looks like Derek got the Carbon Gear box bike all built up. It is just a single speed right now because the transmission needs some more fine tuning before it goes into the bike. I think that if he can produce them unlike the frame builder with a very similar last name "Lahar" people will buy them. Check out his web site at http://lahrcycles.com/
Unfortunatly he will suffer all the same issues that Lahar has. People have difficulty in thinking for themselves and are scarred to be different.
Both the Lahr and Lahar are brilliant logical designs,non supported by marketing and mass sales.
Look forward to seeing it running with the gearbox.
 

ire

Turbo Monkey
Aug 6, 2007
6,199
4
his paper about the CVT is interesting, way over my head, but interesting nonetheless. I think he has a chance of succeeding becuase he has a truly innovative gearbox, instead of a Rohlof hub
 

rollertoaster

Monkey
Aug 7, 2007
730
177
Douglassville , PA
A CVT transmission is in my opinion the best idea I've seen in a long time. You can set it up to be at your ideal cadence and just pedal. No worrying about being in the right gear, that's my biggest problem on the bike.

I think it's an awsome idea, and I hope they have great success with it.
 

wannabeabonedoc

Turbo Monkey
Apr 19, 2004
1,035
1
Wytheville Virginia
I'm sure he'll get right on changing his last name... Word on the street says that there may be an aluminum version coming out sooner than a carbon version... but that's especulation.... I will say he has quite the testing grounds right out his back door at the VT freeride farm...
 

p-spec

Turbo Monkey
May 2, 2004
1,283
1
quebec
you think a nother cyclist compagny baught his idea and thats why hes out?!?!?!?

Spread the hype.
 

MinorThreat

Turbo Monkey
Nov 15, 2005
1,632
41
Nine Mile Falls, WA
He's probably busy pursuing his doctorate now and no time. Wasn't that his Masters thesis project an VT? Last I looked, I think he's on the university's roster of doctoral candidates.
 
May 12, 2005
977
0
roanoke va
crazy...
derek is my house mate, that frame is sitting in the basement right now, the carbon chainstay seperated from the alu pivot bit at diablo(?) last year. MinorThreat is right and he is busy, or that's been his excuse for not working on it. hasn't sold out yet to the best of my knowledge.
rode it when it was single speed, it was a shreader not to mention a beautiful frame. lowish bb, shortish CS, slack HA and the carbon rear end had such a small moment it tracked like no other.
I've been bugging him about it, but it's way cool to see all this intrest about it(Sandwitch). I'l show him the tread in hopes it gets him stoked again. love to see that rolling again.

btw, the interbike best of show thing is bonk. they don't have prizes, it was a trophy his dad gave him. i totally fell for the MBAction caption way back when.
 
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Sandwich

Pig my fish!
Staff member
May 23, 2002
16,676
1,401
01776
I've been bugging him about it, but it's way cool to see all this intrest about it(Sandwitch).
yeah dude, let him know he was on to something. It was a great looking frame and the CVT is a neat concept even if it's wrangled as a set of clicks vs. infinite adjustment. I was just thinking about how it worked the other day and wanted to see what happened to it/him.
 

Inclag

Turbo Monkey
Sep 9, 2001
2,376
98
MA
Carbon is known for not wanting to be stuck to Alu.
Would be gret to see it's return, or the MkII.
Actually there are plenty of great adhesives that would do the job for those two substrates. It's not like we're talking about any low surface energy plastics...
 

MrPlow

Monkey
Sep 9, 2004
630
0
Toowoomba Queensland
Carbon is known for not wanting to be stuck to Alu.
Would be gret to see it's return, or the MkII.
Nah, they bond great together provided you don't have an anodised surface.
I tested some bonding and I delaminated the carbon before it broke the bond.
Anodised surface I could pull off with my fingers though.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
16,676
1,401
01776
Nah, they bond great together provided you don't have an anodised surface.
I tested some bonding and I delaminated the carbon before it broke the bond.
Anodised surface I could pull off with my fingers though.
big surprise, it's an early prototype. At least he wasn't selling it even though the headtube was too short and there were too many torx.
 

Gridds

Monkey
Dec 18, 2008
266
0
Great Britain
Nah, they bond great together provided you don't have an anodised surface.
I tested some bonding and I delaminated the carbon before it broke the bond.
Anodised surface I could pull off with my fingers though.
Yeah you can bond carbon to alu and get a good bond - initially.

In the long run however it's a different story. There are various factors that affect the bond integrity including: galvanic corrosion, stiffness mismatch and differential in CTE. All of which lead to bond failures between the carbon and alloy after not such long periods of time. There are various things like oxide treatments you can give the alloy to prevent corrosion but you can't get away from the CTE and stiffness differentials which over time will break down the bond. So many people/manufacturers overlook this simple science.

I've been studying it and testing ths kind of thing professionally for about 7 years.

You're best off bonding carbon to titanium if you need metal parts coupling with carbon. There is no corrosion (Ti is inert) and the stiffnesses and CTEs are very similar. But again correct surface treatment is paramount.
 

fluider

Monkey
Jun 25, 2008
440
9
Bratislava, Slovakia
What do you mean by bonding Alu with Ti? What about bonding complicated surfaces like joint of 3 tubes or larger pivots of a suspension arm ? I've heard only about using glass fiber to isolate carbon fiber from Alu material.
 

Gridds

Monkey
Dec 18, 2008
266
0
Great Britain
What do you mean by bonding Alu with Ti? What about bonding complicated surfaces like joint of 3 tubes or larger pivots of a suspension arm ? I've heard only about using glass fiber to isolate carbon fiber from Alu material.
I didn't say anything about bonding Alu with Ti. I was talking about bonding carbon to Alu or carbon to Ti.

Yes a layer of glass fibre will isolate and prevent galvanic corrosion but you still have the stiffness and CTE differentials with aluminium.
 

Gridds

Monkey
Dec 18, 2008
266
0
Great Britain
Coefficient of Themal Expansion.

Basically a carbon to Alu joint over it's working life, while being stressed, will see the carbon and alu straining at different (due to the different stiffneses) rates leading to bond breakdown. This also happens due to the differential in CTE over any kind of thermal cycle, no matter how small, but even a bike can see temperature ranges from sub zero in winter to mabye 50C+ if say it was left in the boot (trunk) of a car on a hot summers day. If taken in the hold of an aeroplane (airplane) the temperature ranges can be even more extreme.
 
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Inclag

Turbo Monkey
Sep 9, 2001
2,376
98
MA
Coefficient of Themal Expansion.

Basically a carbon to Alu joint over it's working life, while being stressed, will see the carbon and alu straining at different (due to the different stiffneses) rates leading to bond breakdown. This also happens due to the differential in CTE over any kind of thermal cycle, no matter how small, but even a bike can see temperature ranges from sub zero in winter to mabye 50C+ if say it was left in the boot (trunk) of a car on a hot summers day. If taken in the hold of an aeroplane (airplane) the temperature ranges can be even more extreme.
Interesting.

Neat to know this is your area of expertise. I've unfortunately had to deal with a couple adhesive challenges recently bonding low surface energy substrates which led to switching from HDPE to a PPS.

Do you work in the aviation industry? I'm aware that aluminum would ideally need to have a surface treatment, but I'm surprised that the bond is so poor over such small areas. I could envision variations in CTE affecting large bonds with significantly fluctuating delta T's like on an airplane, but have a harder time seeing it with a bike, especially as there are plenty of cycling parts out there with structural alu/carbon bonds such as frames and forks. Anyway, I find this quite interesting. You know of any good resources worth reading?
 

fluider

Monkey
Jun 25, 2008
440
9
Bratislava, Slovakia
Do I understand it right when I think the different strain rates of carbon and Alu (caused either by mechanical stress and/or change in temperature) lead to disjoining those 2 materials on their interface? Like the epoxy between Alu and 1st laminate layer starts to disjoin from Alu? If I'm at least a little bit right, is there any possibility to use some additive into epoxy in order to slow down the disjoing or to compensate it?
 

Gridds

Monkey
Dec 18, 2008
266
0
Great Britain
Do I understand it right when I think the different strain rates of carbon and Alu (caused either by mechanical stress and/or change in temperature) lead to disjoining those 2 materials on their interface? Like the epoxy between Alu and 1st laminate layer starts to disjoin from Alu? If I'm at least a little bit right, is there any possibility to use some additive into epoxy in order to slow down the disjoing or to compensate it?
You are right in the first part. However it's not really the epoxy that causes the problem, so any additive to that would not really see any benefit for those problems. The problem lies with the alloy itself and the carbon fibre reinforcement. You can treat the alloy with oxide conversion layers but that only part solves the problem - you can't change the bulk properties of the alloy material. The carbon fibre fabric governs the composites property of stiffness. You could design a laminate so that the stiffness gradient through it lends itself to a more matched performance of the alloy at the bond surface but then carbon composites are highly anisotropic so the properties are different in different directions, so you'd still have a problem.
You can by all means make a good bond between Al and carbon but generally they don't tend to last very long.

Many historical failures of carbon bike frames have been at the junctions between the alloy inserts. This is most likely due to galvanic corrosion though, which is greatly accelerated in the presence of moisture (epoxy absorbs moisture as well), and the stiffness differentials rather than the CTE differential but it still has an influence.

Inclag - I work in Formula 1. There are probably many sources of literature out there but we tend to do all our own research as many of the fields of enquiry we have are not commonly covered to my knowledge. I guess you could consider us being at the 'cutting edge' and when we need to know something we need to know it now, so we do our own tests as and when they're needed. Also in F1 intellectual property is generally highly secretive so no one really shares their knowledge within the industry.
 

Inclag

Turbo Monkey
Sep 9, 2001
2,376
98
MA
Inclag - I work in Formula 1. There are probably many sources of literature out there but we tend to do all our own research as many of the fields of enquiry we have are not commonly covered to my knowledge. I guess you could consider us being at the 'cutting edge' and when we need to know something we need to know it now, so we do our own tests as and when they're needed. Also in F1 intellectual property is generally highly secretive so no one really shares their knowledge within the industry.
Cool, I figured your work was in an industry where the application of bonding agents between those two substrates was a bit more atypical and where performance specifications were at the higher end of the spectrum only because you made it sound as if bonding aluminum and CF was a not ideal.

I think there's been enough benchmarking at least in cycling applications to prove out that with adequate design consideration it's acceptable to bond the two materials.

If you don't mind, what team/manufacturer do you work? Sounds like you have a pretty cool job :thumb:
 

Gridds

Monkey
Dec 18, 2008
266
0
Great Britain
Of course you can bond them, with adequate design considerations, even we do it but then we don't need our parts to last very long. In our experience fatigue failures are much much more common in carbon/Al than carbon/Ti, especially at elevated temperatures.

Personally, if I were to design and build a bike frame from carbon I wouldn't bond any Al to it at all. Ti all the way. I think a bike frame should last a lifetime.

I work for Williams by the way :thumb:
 

xy9ine

Turbo Monkey
Mar 22, 2004
2,869
267
vancouver eastside
I think a bike frame should last a lifetime.
i like this philosophy. i'm pretty sure it's achievable using composites. affordability is another matter altogether. though people seem ok w/ spending upwards of $3k on aluminum frames w/ acknowledged limited lifespans, so paying a premium for longevity doesn't seem much of a stretch.

would love to see what a shop of your expertise would develop if given the program to build a dh frame - clean slate approach, no bike industry biases.
 

LMC

Monkey
Dec 10, 2006
683
0
Yep. Trust me, I've thought about it....... A lot!
Go for it! you have everything you need under one roof, providing your bosses don't mind of course.

Would you F1 guys normally build female molds for the body panels from a male clay/foam model?