More Bad News About Grubee G4 Gearbox

I

Irish John

Guest
After about a week of fairly low useage of the G4/HS kit described in another thread where I attempted to install it on a Grubee GT1 Cruiser bike I have to report that the freewheel drive sprocket has chewed itself to pieces. The pawls have ripped the ratchets to pieces carving through them like butter so in the end it freewheels in both directions and drives in neither.
The problem is that the power take-up from the new belt driven G4 (this is the model without the engager) is too strong or the metal forming the ratchets in the outer cluster is too soft and the attached pictures clearly show the result of a about 130 kms of useage.
This, added to all the other defects mentioned elsewhere, makes for a really disappointing experience of the total product.
I'm not sure how this can be fixed and even if there is a non-freewheel fixed sprocket that might work (which I think there is) it has only 10 teeth and the problem with the GB is that the 11tT isn't big enough anyway. With a 10T front drive sprocket youd need something like a 24T rear and that is impractical for obvious reasons. The sprocket needed to match the 11T is a lot (and I mean a lot) smaller than the kit comes with. What the correct size should have been is something Grubee should find out for themselves because I do not feel inclined to tell them without being rewarded in some way that fully compensates me for the many too large sprockets I've had to buy with numerous kits to date.
The G4 is really a back to the drawing board case.
 

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As the self-appointed master of the obvious, I will state: That ain't good.
 
G4 GruBee DEFECTIVE FREEWHEEL DESIGN

The question comes to mind if the material the freewheel is made from would take a heat treat and become serviceable?

Obviously something that would have to be done in the manufacturing process and not later in the field.

I am guessing there is someone here who has the knowledge of the factors involved for such a process?

I was also wondering if the freewheel from the older GruBee gear box is interchangeable with the one on the G4. Then is the material that same between them? I am not sure how you would test the strength of each part?

Jim
 
I'm betting that gear was either made from inferior metal, (probably a metal 'soup' of whatever they obtained the cheapest), or it was not hardened the way it should have been.
 
Must be a weakness in their design or construction(or both) & from what's been reported the old freewheels arn't much better.
Good idea by jim to see if there interchangeable,or get the vendor to replace it. :whistle:
Either way certanly let the vendor know. :mad:
 
Freewheel Problem With G4

If it is the same,(freewheel) then it must be the torque delivery to it? As John indicated the driven sprocket must be smaller, that to me is an indication the output of the belt drive is not a high enough speed?

Speed or torque, one goes down the other goes up every time. )

Jim
 
Must be a weakness in their design or construction(or both) & from what's been reported the old freewheels arn't much better.
Good idea by jim to see if there interchangeable,or get the vendor to replace it. :whistle:
Either way certanly let the vendor know. :mad:

George is replacing it but the problem remains - the 11T freewheel can't hack the increased torque that the belt drive delivers so it will chew through all 11T freewheel sprockets ad infinitum. The 11T is the same on all models as the pictures show.
What is needed is a new sprocket design and while they are at it they need to get the gear ratio right because the current 11T & 44T is slower than the horrid old HTs and that is not what a 4-stroke is known for. A 4-stroke is about high cruising speed albeit with less pulling power from bottom to top speed. The fact that they boasted that this G4 can pull away up hill from a standing start is indicative that it was delivering more torque to the chain and the old 11T can't handle it.
My most earnest advice to all the punters out there is to stick with the old Grubee gearbox because it works well and despite its noisiness it is infinitely better than the G4 will ever be in its current design.
Terrible news about the 2010 Schwinn cruiser models. I've been too depressed to go out today. Why would they axe the very frame that won the 2009 Bicycling Magazine Best Bike - Editor's Choice yet still show the model and its accolades on their 2010 website when they have ditched that very frame? It beggars belief. I'll take a large dollop of my MPG Lithium Grease in a cup of tea because I'm told lithium help with depression.
 
G4 Clutch Bell is Tack Welded

I was thinking that one way to reduce the torque on the 11T freewheel would be to try and get the three pole centrifugal clutch to grab at lower revs.
Something similar to what Cheetoh invented for the old centrifugal clutches (see pics) and which really made a marked improvement in how the clutch grabbed and released the clutch bell. From attached pics it's hard to see where the 3 pole centrif clutch could be lightened by drilling. I can't see a way but someone else might have a great idea to contribute as happens on MBc.
Why the clutch housing bell is only tack welded to the gearbox is beyond me but it looks very much like those JL Hoot engineers played a part in this.
The G4 is so unready for sale that it isn't funny. My heart goes out to the stockists because it's not as if the manufacturer will pay for the expense of recalling them and resupplying the old GB for the duration of the 'back to the drawing board' phase of the debacle. They look like they'll get badly burnt but anyone who stocks up too heavily with an unproven Chinese product in preference to a proven one is a fool. This GB is really seriously problematic so be very carefull you guys who think it might be the answer to your problems,
Incidentally in the Grubee picture the G4 has a fixed sprocket but it is the old 10T and that would exaccurbate the problem of the GB being already geared too low.
 

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I had that clutch drum "tack weld" idea on my Titan PTO & it failed after 1 week of gently run-in.I was assured that this was a fluke & i was only the second person ever that this had happened to....not very assuring when your on the opposite side of the world.
Tack weld is bad enough but chinese tack weld.......SHEESH. :rolleyes:
 
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