Rock solid Hobie drive arm upgrade group buy ... UPDATED WITH ORDER INFO!!

I'll be interested as well if the price is right
Thanks
John

I think I would like to have a set to carry on the water when a failure happens. I have read of many, but to do a change on the water extra pedals should already be attached. I have the newest drive been on the water three times so far. 

I think I would like to have a set to carry on the water when a failure happens. I have read of many, but to do a change on the water extra pedals should already be attached. I have the newest drive been on the water three times so far.

I have an older V1 drive but I think the arm attachment is the same with V1 and V2 drives. If that is the case the arm swap requires at least three tools and the removal of a small allen screw and a spring loaded part. This is not a change I would like to attempt on the water. These arms are designed to be a permanent solution to arm failure.

I have a pair of T7075 solid aluminum bars cut to the correct size. What would be the charge to fabricate and anodize them?

I have a pair of T7075 solid aluminum bars cut to the correct size. What would be the charge to fabricate and anodize them?

Sorry .... It wouldn't be feasible to have people send me raw material.
The only discount will be from getting in on the first round group buy.

In.

   Even at twice the price of Hobie's,   it's a great deal.         Think of it as insurance.

The only discount will be from getting in on the first round group buy.

Is it too late for this?  If not, I'll take 2.

The only discount will be from getting in on the first round group buy.

Is it too late for this?  If not, I'll take 2.

Not at all ... You're on the list.

I am very interested.  One for sure, maybe 2.

Please add me to the list.  One pair for me.

Rey

It would seem that the cart has been put before the horse. An assumption has been made that the material used is the problem and that someone can make a solid aluminum arm that is stronger than the Hobie solid aluminum V1 arm.

That a single set has been in use and not broken proves absolutely nothing. I have been involved in the manufacture of products using ANSI 5083-H32 aluminum and understand the overall process and potential design pitfalls. The material used is important but more important is the design itself. I do destructive testing with every prototype to determine with what load and where the item is weakest.

Have you gotten samples of broken arms to know where the V2 ones are failing? According to the Hobie product engineer for the Mirage drive the V2 are stronger than the V1 shafts. I would want to look at where the V1 arms have failed and where the V2 arms have failed and compare the two. Without knowing the point of failure it is not likely that the engineered fix will work in the real world with thousands of users.

Going to longer arms as was suggested is only going to put more stress on not just the arms but the entire mechanism. It makes for more leverage for the user with weak legs but it will reduce the durability of the Mirage drive as a whole.

Anodizing is also no panacea as it is microns deep and easily scratched off the surface. It is more cosmetic than anything else. For greater strength and durability the better material to use is 304 stainless steel.

304 SS can be cast and machined at costs on par with CNC machining aluminum and yet the steel arm will be much stronger and resist fatigue much better than an aluminum arm. 
The weight of the 304 SS arm would be roughly double that of an aluminum one the actual weight difference would have a negligible impact on the effort required from the user.

The nature of the drive and the adjustment mechanism restrict the size of the arm and the easiest and best way around this is to use a stronger material. It costs more to produce a part out of 304 SS but there are ways to minimize the increase and to do so with a limited production run in the hundreds of units.

I don't have all the answers for you, but here is what I know and have seen first hand.
I have personally seen three sets of hollow V2 arms break at the adjustment hole. After seeing the first failure I removed and inspected my hollow V1 arms. I found a nearly complete crack at the bottom mounting hole. I have never heard of the solid V1 arms failing.
I made three sets of prototypes. Tested by three different guys who have all had arms fail on them in the past. So far no issues.
The ano is thin but fairly robust. This part has no moving surfaces and I will be using the same metal and ano that our troops M16s are made out of and those weapons take a beating.
If you would be willing to failure test a pair for me and report back I would be more than happy to send you a set to try and break. Let me know if you are interested.
~Bill

It would seem that the cart has been put before the horse. An assumption has been made that the material used is the problem and that someone can make a solid aluminum arm that is stronger than the Hobie solid aluminum V1 arm.

That a single set has been in use and not broken proves absolutely nothing. I have been involved in the manufacture of products using ANSI 5083-H32 aluminum and understand the overall process and potential design pitfalls. The material used is important but more important is the design itself. I do destructive testing with every prototype to determine with what load and where the item is weakest.

Have you gotten samples of broken arms to know where the V2 ones are failing? According to the Hobie product engineer for the Mirage drive the V2 are stronger than the V1 shafts. I would want to look at where the V1 arms have failed and where the V2 arms have failed and compare the two. Without knowing the point of failure it is not likely that the engineered fix will work in the real world with thousands of users.

Going to longer arms as was suggested is only going to put more stress on not just the arms but the entire mechanism. It makes for more leverage for the user with weak legs but it will reduce the durability of the Mirage drive as a whole.

Anodizing is also no panacea as it is microns deep and easily scratched off the surface. It is more cosmetic than anything else. For greater strength and durability the better material to use is 304 stainless steel.

304 SS can be cast and machined at costs on par with CNC machining aluminum and yet the steel arm will be much stronger and resist fatigue much better than an aluminum arm. 
The weight of the 304 SS arm would be roughly double that of an aluminum one the actual weight difference would have a negligible impact on the effort required from the user.

The nature of the drive and the adjustment mechanism restrict the size of the arm and the easiest and best way around this is to use a stronger material. It costs more to produce a part out of 304 SS but there are ways to minimize the increase and to do so with a limited production run in the hundreds of units.

I have seen that statement from Matt Miller who works for Hobie about the tubed aluminum arms being as strong as the solid arms. That may be true on a stress test with new arms but the SS adjustment pin can "erode" and over time weaken that spot faster in tubed than solid aluminum. It isn't just this forum that reports breakage. The North West yak anglers and the Australians also complain about broken arms. I don't think that engineering tests, despite sophisticated testing devices and stress measurements, are as accurate as sustained use in the real world.

Please add me also to this group buy!!

Don't know how I didn't see this early....