The G4 Bicycle , Potential MBB/Cruzbike Diversification Candidate?

[ak-tux]

I was watching the laidback bike report by Gary Solomon and they were discussing an interesting MBB style bicycle designed by Ron Thompson similar to the one formally built by the French, Kervelo, but this time using dual chain drive instead of a pinion drive.

It can make a good mid/low racer veriation of the MBB family, though a little bit more complicated.

Pros

• This potentially reduces the front flop problem typical of our cruzbikes.
• It is also seems easier to add fairing to.
• Works with a modified 1x12 drivetrain (possibly any 1x system).
• Low BB is potentially a better climber?

Cons

• Needs modified drive wheel hub
• Front wheel change not easy

Food for thought.

More details can be found at the site https://g4bikes.com/

 

[bladderhead]

Less angular momentum than a Cruzbike. If you are using a friction shifter it is easy to see the gear-change process and get the chain lined up with the cog. I wonder if it can accommodate mudguards? No, I am not obsessed.

 

[ak-tux]

Less angular momentum than a Cruzbike. If you are using a friction shifter it is easy to see the gear-change process and get the chain lined up with the cog. I wonder if it can accommodate mudguards? No, I am not obsessed.

Good points for discussion.

With a partial fairing over the cassette and derailuer it can be a pretty clean frontend without a flop.

 

[benphyr]

In the pictures above there seems to be a fair amount of "death-grip". I wonder if that is due to initial learning of MBB or if there is more that we don't know about the handling of this bike. Of course rake/trail, tiller, and MBB all are going to have significant impact on steering and handling.

 

[ak-tux]

In the pictures above there seems to be a fair amount of "death-grip". I wonder if that is due to initial learning of MBB or if there is more that we don't know about the handling of this bike. Of course rake/trail, tiller, and MBB all are going to have significant impact on steering and handling.

The grip may be just an instance of motion captured by the picture (I think he was accelerating) but looking at the brief videos it doesn't appear any different from the ordinary MBB though.

The engineering is pretty facinating though. It appears like the hands have a greater leverage than the legs against the pedal induced steer compared to the cruzbike design. Variety is the spice of life.

Esentially its a direct drive fwd recumbent . The basic direct drive is similar to what is found in unicycles, drift trikes and the penny farthing. Interestingly enough it looks like someone else had a similar idea in the past.

 

[Don1]

Doesn't look as sexy as a cruzbike. He talks like it's revolutional but really it's just another mmb.

 

[CoolBreeze]

“How do you build a Kervelo clone without the use of an internal gear hub?”
Congratulations to Ron Thompson, he has answered that question. Engineering a bicycle transmission that allows for the pedaling axis to coincide with the front wheel’s axis, using a fork mounted cassette on a hub and second chain to connect to the wheel hub. Ironically, in the interview on the video, he says “ a bike should be simple”
Mr. Thompson goes on for a great length of time in the interview talking about the upper body engagement this arrangement allows for, (a concept understood viscerally by members of the Cruzbike tribe). He also mentions Cruzbike with minimal admiration, and admitting that he could not get used to riding one.
In the case of the Kervelo arrangement, the amount of pedal steer is much less than that of Cruzbike, because it is limited by the length of the pedal arm, and for Cruzbike it’s the length of the chain stay that accounts for greater pedal steer. That requires upper body engagement, which we all agree is a good thing.
I can say from personal experience with a two chain transmission that it’s less efficient than the standard single chain setup we’re used to, or the longer chain, idlers, etc, on RWD recumbents that are familiar to many of us.
Especially miserable hauling a 35+ lb. bike uphill. Some may favor the lower pedals, but at the cost of greater complexity, weight, efficiency?
I think a greater feat of engineering is being able to build a MBB bike from spare parts and frames of other bikes, just from what’s available locally, as ak-tux has done in Kenya.
Thank you, ak-tux, for your videos, and your contributions to the forum. We are a collection of tinkerers, and you have provided inspiration.
However, I have to disagree, the G-4 bike can’t be considered a direct drive like a unicycle or penny farthing because of its complicated transmission. The exception would be if the Kervelo had a 1:1 gear ratio in its IGH.
An interesting design, but way too complex.

 

[jond]

“How do you build a Kervelo clone without the use of an internal gear hub?”
Congratulations to Ron Thompson, he has answered that question. Engineering a bicycle transmission that allows for the pedaling axis to coincide with the front wheel’s axis, using a fork mounted cassette on a hub and second chain to connect to the wheel hub. Ironically, in the interview on the video, he says “ a bike should be simple”
Mr. Thompson goes on for a great length of time in the interview talking about the upper body engagement this arrangement allows for, (a concept understood viscerally by members of the Cruzbike tribe). He also mentions Cruzbike with minimal admiration, and admitting that he could not get used to riding one.
In the case of the Kervelo arrangement, the amount of pedal steer is much less than that of Cruzbike, because it is limited by the length of the pedal arm, and for Cruzbike it’s the length of the chain stay that accounts for greater pedal steer. That requires upper body engagement, which we all agree is a good thing.
I can say from personal experience with a two chain transmission that it’s less efficient than the standard single chain setup we’re used to, or the longer chain, idlers, etc, on RWD recumbents that are familiar to many of us.
Especially miserable hauling a 35+ lb. bike uphill. Some may favor the lower pedals, but at the cost of greater complexity, weight, efficiency?
I think a greater feat of engineering is being able to build a MBB bike from spare parts and frames of other bikes, just from what’s available locally, as ak-tux has done in Kenya.
Thank you, ak-tux, for your videos, and your contributions to the forum. We are a collection of tinkerers, and you have provided inspiration.
However, I have to disagree, the G-4 bike can’t be considered a direct drive like a unicycle or penny farthing because of its complicated transmission. The exception would be if the Kervelo had a 1:1 gear ratio in its IGH.
An interesting design, but way too complex.

Well said. very good. My mate was going to ride the kervelo in the last Paris Brest Paris audax but with one month to go they pulled out citing trust issues with the igh. He rode his ice b1. He was pretty disappointed. The kervelo looked good last time I looked at that low racer. Well done on this mr Thompson but I can’t think why I would be tempted by the drive train complexity.

 

[ak-tux]

..
Thank you, ak-tux, for your videos, and your contributions to the forum. We are a collection of tinkerers, and you have provided inspiration.
However, I have to disagree, the G-4 bike can’t be considered a direct drive like a unicycle or penny farthing because of its complicated transmission. The exception would be if the Kervelo had a 1:1 gear ratio in its IGH.
An interesting design, but way too complex.

Thank you very much @CoolBreeze . Much appreciated.

I always try to keep an open mind to any good ideas, becuase somewhere in the multitude and diversity of ideas there is wisdom. This is how improvements come, by thinking out of the box.

Every bike design has pros and cons, but the recumbent world is blessed with many great thinkers, tinkerers and innovators.

The most studies on the geometry of this type of bicycle have been done by the Canadian Jeremy M. Garnet , M.A.Sc.

More technical Reference information on direct drive below:
https://www.hupi.org/HPeJ/0017/0017.html
https://www.velotegra.com/directdrive

 

[jond]

Thank you much @CoolBreeze . Much appreciated.

I always try to keep an open mind to any good ideas, becuase somewhere in the multitude and diversity of ideas there is wisdom. This is how improvements come, by thinking out of the box.

Every bike design has pros and cons, but the recumbent world is blessed with many great thinkers, tinkeres and innovators.

The most studies on the geometry of this type of bicyle have been done by the Canadian Jeremy M. Garnet , M.A.Sc.

More technical Reference information on direct drive below:
https://www.hupi.org/HPeJ/0017/0017.html
https://www.velotegra.com/directdrive

still waiting on strava follow approval. Tsk.

 

[ak-tux]

still waiting on strava follow approval. Tsk.

Oh, I must have missed the notification...I will check that.

 

[Don1]

To change tyres, that would be interesting exercise......

 

[bladderhead]

Not as interesting as the one that I am in the middle of. I prefer tyres that are boring.

 

[ak-tux]

To change tyres, that would be interesting exercise......

Yeah, one will need to undo four clamp bolts. How does that compare to through axles though? QR skewers were always the least difficult I guess.

Probably unknown to Ron Thompson, that frontend design is very similar to what was already in existence built by Trivek. Or Trivek was unaware that Ron was working on a similar frontend. A true convergence of ideas.

 

[Robert Holler]

Looks like a more complicated Kervelo. Nope.

 

[Opik]

http://www.bentrideronline.com/messageboard/showpost.php?p=1705564&postcount=43

and there has been someone with similar ideas.

Still I think it is worth pursuing. Compared to a cruzbike
1. it has lower BB, and lower seat height, potentially more aerodynamic.
2. Central of mass is lower, more control
3. ground to pedal distance shorter, easier to put foot down to ground and up to pedal (very huge thing for many people)
4. This reminds of childhood trikes (probably it will be more populat if they made a trike version)
5, By playing the seat height to BB relationship, I think people can have more power and a shorter bike. Didnt Jonathan Garcia said his Rans Phoenix has similar Height-BB to Tour Easy for more power?

Also about the fork, I wonder why He put the connection of the gear Cassette to the forks below, not like a cruzbike which puts it at the headset, I just think That Cruzbike decision to put the boom on the headset rather than the bottom forks is a huge factor in the strength and stability.

and the comparion with Kervelo, I think this is better as it allows use of cassettes and deraileurs which are more common

 

[Opik]

TBH, I think Cruzbike and G4 should really try each others bike and compare. We shouldnt be shunning something new just because its different or is threatening . If something is better at least in some aspects, I think Cruzbike should evolve and adapt it.

http://www.bentrideronline.com/messageboard/showpost.php?p=1705337&postcount=21
The three guys I beat to win the WUCA 12 hour time trial last month at Mount Saint Mary's University in Emmitsburg were all on CB V20's.
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It s clear that G4 type can be made more aero and lower to the ground, so it has potential to be more aero and have more leg power because the rider is more upright

 

[bladderhead]

What is the silver thing sticking out at the back of the frame?

 

[jond]

What is the silver thing sticking out at the back of the frame?

seat exhaust

probably something to do with tilt. To the google mobile

actually from Perth Western Australia. Leantrike is the company. Don’t know if it actually came to market.

@Opik if you want a lower bb get a shorter chainstay. Beating three guys on v20 hey. I reckon I could beat my mum riding a v20 on my sofrider pulling a trailer. Please.

it’s great to think outside the box with groundbreaking ideas but some things are better to stay in it or just be the incredible loved oddities that they remain. I’m talking about the design two chains etc. Casual observance tells me the more reclined v20 is faster given same wattages. Vendetta is far less complicated . It’s light weight , easily serviceable , uses standard road bike grouppo available anywhere . Factory supported niche professional evolving quality product and a successful commercial reality.

Yay that’s a bigger win to the “ Cruz “. There were three of them apparently at that 12 hour ridden by my mum’s boyfriends father and uncles.

I certainly hope new bents come to market but it’s few who succeed or stay around unfortunately. Long live difference.

 

[Opik]

seat exhaust

probably something to do with tilt. To the google mobile

actually from Perth Western Australia. Leantrike is the company. Don’t know if it actually came to market.

@Opik if you want a lower bb get a shorter chainstay. Beating three guys on v20 hey. I reckon I could beat my mum riding a v20 on my sofrider pulling a trailer. Please.

it’s great to think outside the box with groundbreaking ideas but some things are better to stay in it or just be the incredible loved oddities that they remain. I’m talking about the design two chains etc. Casual observance tells me the more reclined v20 is faster given same wattages. Vendetta is far less complicated . It’s light weight , easily serviceable , uses standard road bike grouppo available anywhere . Factory supported niche professional evolving quality product and a successful commercial reality.

Yay that’s a bigger win to the “ Cruz “. There were three of them apparently at that 12 hour ridden by my mum’s boyfriends father and uncles.

I certainly hope new bents come to market but it’s few who succeed or stay around unfortunately. Long live difference.

I was just thinking how similar G4 and Cruzbike are if we change the pedals and Cassette position.
Pedals on the wheel, cassette at the BB.

ofc things will change too
1. The bike will get longer
2. Change to fitting the bike now should be my moving the seat, so need to change the fixed seat position we have now,
3. Seat height should be lower
4. The Boom could be short and fixed as it doesnt need to change length
5. others?