KC's 4-stroke 3-speed on GT2A-S gas tank frame

Aug 6, 2013
11
0
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Las Vegas
OK girls and boys, the frame of reference here the Grubee GT2A which we know is made of aluminum. The picture below is a race bike built by someone who knows of what he speaks and I think his build on this frame speaks for itself......

Nashmoto is the guy who built this bike and he knows aluminum better than KC know's his wife......if Brian Nash tells me and also shows me how soft this aluminum frame is and is worried of it's strength, I just thought I'd pass on the info and fore warning of such.

If you don't get it, try riding it hard and do your double back flips and get back to us on how it's holding up......comprende?

I love aluminum frames most of all, but only if they are built right out of the strongest heat treated aluminum! 6061 T-10 is as strong as steel.....the frames that Grubee makes and sells are more comparable to soft thin walled lead......not heat treated aerospace quality aluminum.

Not capping on the bike or build here....it looks great!

brnot

Hey Scotto thanks for you concern.. But Your arrogant approach is what became note worthy.. comprende?

Misuse of any object will lead to undesirable results.. Pushing things ignorantly and extraordinarily will lead to malfunction.. One would even argue a motorized bicycle isn't a sufficient means of transportation within and on city roads..

Using the Grubee skyhawk aluminum bike frame improperly would result in damage.. For example, Using the Grubee skyhawk aluminum frame as a race bike would be negatively characterized by its appropriateness or suitability.. Also incorrect component usage for the given function would greatly compound damage to a bike frame..

Using the frame as a bicycle accompanied with use of a small motor is reliable for 30mph road travel.. The aluminum skyhawk frame does withstand casual riding for those looking to explore the city streets.. For example, I have rode my Grubee skyhawk frame mercilessly for a few years to contend I am unworried of it's strength..

In conclusion I will profess that given the options available for a motorized bike frame the Grubee skyhawk frame fits the bill functionally well.. The in frame gas tank conceals its motorized function.. The frame allows the option of utilizing better components for a custom build.. In addition, mounts correctly for the grubee motors which are a joy for commuting to the gas station for beer.. I have found that these cheap Chinese products do serve reliably if used properly for its intended function.. While racing, crashing, curb checking, smashing, over exerting, over motorizing, over arrogantly approaching things does cause damage..

I guess Scotto.. To say shortly ... I have rode my aluminum frame for sometime now and these things you speak of are not apparent in justification .. It makes me scratch my head in wonder what the heck are you doing and with what tools are you doing it..
dnut.wee.
 
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maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
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memphis Tn
While I have no dog in this race, I'm going to chime in with my two cents before this degenerates into more personal attacks.
It has been proven aluminum can withstand the harshest use in race bikes
WHEN THE MATERIALS ARE PROPERLY HEAT TREATED!
This is the single biggest difference between high-end aluminum frames and run of the mill walmart junk.
The name brand does not matter. The PRICE matters. There is a reason those $5k aluminum downhill frames cost that much. They are completely heat treated AFTER all welding and fab work is done which gives them the toughness and strength to withstand downhill racing. The average Schwinn or Mongoose aluminum frame is NOT heat treated to handle this kind of abuse and is nothing like as strong pound for pound.
The simple fact is the GT frames CANNOT be priced as they are without sacrificing materials or heat treating. Since there is very little room to remove material on a bike frame, lowering the cost of heat treating is the way the factory can sell them so cheap and still profit.
The GT frame is obviously strong enough to allow motorizing and normal use. Racing on a flat track with no jumps is still not out of the question since they do so all the time out west. The alloy chosen and the heat treating make ALL the difference in aluminum strength and toughness. The GT gas frames are clearly strong enough for some abuse from all available evidence.
Would I feel comfortable using one for freestyle jumping? **** no.
Would I build one for my personal daily ride? Absolutely.
I would even race one if no jumping is involved.
Both of you are right.
Shake hands and carry on.
 

silvaire

New Member
Jan 25, 2009
36
1
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North of the Golden Gate
There are two commonly used aluminum alloys for welded bicycle frames: 6061 and 7005.

For a bike frame 6061 absolutely requires heat treatment (almost always the T6 process) after welding. 7005 will naturally precipitation age harden after welding on its own, but it can also be heat treated to some benefit. Many 7005 frame manufacturers do not do post welding heat treatment, but there is not much strength difference between a frame made of heat treated 6061 or "as welded" 7005.

Aluminum vs. steel for a frame is about engineering, not the material itself. However, any steel used for a bike frame is much harder than any 6061 or 7005 aluminum, and steel can better handle the localized stresses (stress risers) induced by crudely made "U-bolt" type motor mounts and other similar fittings. As such, a steel frame is easier to work with and less prone to cracking than aluminum on an original motorized bicycle project.

If an aluminum frame is well designed to begin with, and any fittings bolted to it also properly designed to reduce localized stress issues, I see no reason an aluminum frame won't work as well as a steel frame.
 
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KCvale

Well-Known Member
Feb 28, 2010
3,967
51
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Phoenix,AZ
Final Assessment of 142F with 4G and SBP shift Kit​

This was a real pain in the butt to make work.

We ended up spending a week butchering the base mount to get the engine in and chains to work.

It CAN be done but there has to be a better way and as I alluded to in earlier posts it is in the mount.

I have started on a new base mount for the 142F/4G combo with much more flexibility than both the stock mount and SBP shift mount and for me anyway will replace both.

In short it is a base mount that will move the engine as far forward as possible and work just dandy as a direct drive, but it will accept an add-on for the right side to extend the 4G shaft to the right side for a shifter with no left side chain, gear, or anything behind the seat.

I have this mocked up on the gasbike stock kit base using an old shaft but you get the idea.





I'll make a new topic for that project as I progress this week but for building on this frame with that drive it is something to consider building yourself if you want to drop that in this frame as it is TIGHT.
 

MotoMagz

Well-Known Member
Aug 2, 2010
1,683
740
113
Michigan
Looks good...If you take another cam from a 4G and use that in place of just the bearing then you will also be able to contol the tension on belt and output sprocket.I had that set up and it worked out good.
 

KCvale

Well-Known Member
Feb 28, 2010
3,967
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Phoenix,AZ
On this off topic of a different base mount it all comes down where the pedals have to go to clear the whole engine and 4G, which is 11" wide 4G cover to pull start cover.

With the SBP cartridge BB with long shaft and keyway for the Freewheel and gasbike DD kits funky crank arms I got 11.25".



My base mount will drop the compete mount with JS right in there, at least so far it is coming along but again for another topic later.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
16
0
memphis Tn
The funky crank setups are one reason I have not done a four stroke build yet...
but stuff like yours makes me want to.
 

KCvale

Well-Known Member
Feb 28, 2010
3,967
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Phoenix,AZ
FINAL COMPLETED PICS





She does 0-20 in ~4 seconds and tops out at 38 MPH (61 KPH) on flat ground by the speedo.

An absolute pain the butt to build with existing base mounts but an absolute dream to ride ;-}
 

LR Jerry

Well-Known Member
Dec 19, 2011
1,153
76
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58
Rockwood, TN
Now just hook it up with one of Paul's saddle bag trunks and it'll be ready for a long road trip. Great looking bike.
 

GearNut

Active Member
Aug 19, 2009
5,104
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San Diego, Kaliforgnia
That came out looking awesome! Your perseverance with the mount plate really paid off well.
It does not look like you ended up using the bent crank arms from gasbike. Which ones did you use?
 

KCvale

Well-Known Member
Feb 28, 2010
3,967
51
48
Phoenix,AZ
That came out looking awesome! Your perseverance with the mount plate really paid off well.
It does not look like you ended up using the bent crank arms from gasbike. Which ones did you use?
Thanks guys, I'm proud of it ;-}

The cranks are the SBP kit crank arms, the engine was high enough to clear the crank tops.

Depending on where the engine winds up most any 3-spiece crank arms may work but not likely.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
16
0
memphis Tn
Send it on over KC...I'll test ride the $Hizznit out of it and save you all that effort.
I'll treat it like a rented mule!
If I can't kill it....
 

massdrive

New Member
Oct 3, 2013
454
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Las Vegas

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,508
6
38
Ridin' inSane Diego, CA.
I've built two GT2 frames, an "A" and an "S". I used china 2 strokes in both.

The Rattletrap:
http://motorbicycling.com/showthread.php?t=51707

Lil' Blue:
http://motorbicycling.com/showthread.php?t=51339

I have to agree that the aluminum is soft and the frames are not that strong. I also agree that I made countless trips to hardware stores and bike shops. I also went way over budget on both builds. I'm about to enlarge the fuel tank on the rattletrap to 1 full US gallon.
I believe massdrive knows of what he speaks here KC.........as I was saying. And don't think one is stronger than the other.....just sayin'.......again.
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,508
6
38
Ridin' inSane Diego, CA.
brnot

Hey Scotto thanks for you concern.. But Your arrogant approach is what became note worthy.. comprende?

Misuse of any object will lead to undesirable results.. Pushing things ignorantly and extraordinarily will lead to malfunction.. One would even argue a motorized bicycle isn't a sufficient means of transportation within and on city roads..

Using the Grubee skyhawk aluminum bike frame improperly would result in damage.. For example, Using the Grubee skyhawk aluminum frame as a race bike would be negatively characterized by its appropriateness or suitability.. Also incorrect component usage for the given function would greatly compound damage to a bike frame..

Using the frame as a bicycle accompanied with use of a small motor is reliable for 30mph road travel.. The aluminum skyhawk frame does withstand casual riding for those looking to explore the city streets.. For example, I have rode my Grubee skyhawk frame mercilessly for a few years to contend I am unworried of it's strength..

In conclusion I will profess that given the options available for a motorized bike frame the Grubee skyhawk frame fits the bill functionally well.. The in frame gas tank conceals its motorized function.. The frame allows the option of utilizing better components for a custom build.. In addition, mounts correctly for the grubee motors which are a joy for commuting to the gas station for beer.. I have found that these cheap Chinese products do serve reliably if used properly for its intended function.. While racing, crashing, curb checking, smashing, over exerting, over motorizing, over arrogantly approaching things does cause damage..

I guess Scotto.. To say shortly ... I have rode my aluminum frame for sometime now and these things you speak of are not apparent in justification .. It makes me scratch my head in wonder what the heck are you doing and with what tools are you doing it..
dnut.wee.
I usually just throw my tools in frustration cuz they are cheapies from harbor freight laff

I was just relaying a bit of realtime concerns of these particular frames.....nothing more. I love aluminum frames. Anyone that actually knows me would know this and I have no reservation about putting engines on them, including the ones of subject here.

And I'm sure you know I could care less what you think of me or what I have too say.....don't you?

Oh....I never throw my real tools.....ever!

laff