Back in July 2015, I resolved a problem with the engine installation by buying a set of Globe Drivesavers–prop shaft isolators that, in effect, add 1-1/8″ to the length of the shaft. The Drivesavers did resolve the immediate problem, which was a conflict between the transverse frames that support my engine stringers and the bolts that attach the vibration isolators to the stringers. Drivesavers also electrically isolate the running gear from the rest of the boat and reportedly lessen the transmission of running gear vibration to the boat. Sounds great, doesn’t it?
As I noted in the engine installation article, Drivesavers are expensive, but they look pretty good coming out of the packaging. I only did a quick test fit when confirming that it would resolve the big problem I was facing, but as I went through the actual installation I found problem after problem with Globe’s design and marketing of the Drivesaver.
According to Globe, there’s no difference between the variations on Model 5756. Globe’s ebay store sells the one I need–5756A– so I bought two. Note in the screen shot above that the Product Finder result indicates that a 5/8″ to 1/2″ Bushing Kit is required, but it’s unclear from the information provided exactly what that means. The red font doesn’t really convey much additional meaning, but more on that later.
Note that Drivesavers have a male and female end, just like gear and shaft couplers. Note also that the holes in the Drivesaver allow the socket head cap screws to be inset, while the hex bolts are not inset. When I started the installation, I discovered that neither the instructions that come with the Drivesavers nor the supplied hardware are appropriate for my ZF 280A gear. Globe’s online installation instructions demonstrate the basic problem.
The screen shot of Globe’s installation graphic above (locally saved for posterity’s sake) shows a female gear coupler. The Drivesaver’s male side attaches to it using socket head cap screws that are inset in the Drivesaver. Since the socket head cap screws are inset they don’t stick out, which permits the shaft coupler to mate up with the Drivesaver. The shaft coupler is male (by inference, since you can’t see it in the graphic), which goes into the female side of the Drivesaver. The shaft coupler and Drivesaver are held together with hex head bolts. The problem is, my ZF 280A gear doesn’t have a female gear coupler; it’s male.
From the looks of the instructions, you can’t just flip the Drivesaver since the hex bolts and socket cap screws are specific to the orientation of the Drivesaver. This induced a bit of panic since I was reading them at home, an hour from the boatyard where I’d left the new parts. Since I’d already epoxied and bolted the engine landing pads to the stringers and painted everything, if these Drivesavers didn’t work flipped in the other direction I’d be back at the drawing board.
But, as luck would have it, flipping the Drivesaver around so the female end meets up with my male gear couple works just fine. It’s disconcerting, though, to see instructions that are at odds with the actual parts. I mean, if these were Made in China I’d understand. But this is a proud American company selling an expensive, engineered component. The next time I was at the boatyard, I realized that flipping the Drivesaver around solved one problem, but the socket head cap screws provided with the kit don’t work.
The new Buck Algonquin shaft couplers I got when I decided to repower with Cummins 450 Diamonds have both 1/2″ and 5/8″ bolt holes, but the bolts they supply are the proper diameter for my ZF 280A gears: 5/8″. In other words, when Buck Algonquin tells you which coupling to use with the ZF 280A gear, they actually send you the right-sized hardware for the application in the box with the coupling.
By contrast, Globe tells you which of their Drivesavers fits the application, but the component itself and the hardware they send with it is too small in two dimensions. As shown in the picture above, the socket head cap screws are too short. By the time you install the washer and lock washer, there’s only 1~2 threads left for the bolt to attach to. The instructions that come with the Drivesaver indicate that the gear coupling has threaded bolt holes, but the holes in this ZF gear coupling are not threaded. The bolts Globe supplied would be long enough if my gear couplers were threaded…but they’re not. And the bolts are 1/2″, not the proper 5/8″ bolts used on this ZF gear.
This is when that note on Globe’s product finder web site finally made sense: “Requires 5/8″ to 1/2″ Bushing Kit” is Globe-speak for “Our Drivesaver kit isn’t engineered for your gear, and the hardware you will get with the Drivesaver will be wrong, too.” Given that these rubber donuts have a suggested retail price in 2015 of $454.59 each, you’d think the manufacturer would take care that the parts and supplied hardware actually fit the application, as promised.
I contacted Globe and described the problems. The initial response was “We are sorry that the installation has been problematic. We are unable to provide solutions based off the photos and you description.[sic] Our suggestions would be to work directly with a mechanic or return the purchases through eBay portal stating they did not fit properly.”
I wrote back and clarified that the instructions and supplied bolts are wrong, and that the installation is permanent–I set the engine where I did to match the Drivesaver thickness dimension. This is not something that can be easily changed. If somebody bought Drivesavers for an existing installation, the instructions indicate that you should pull the shaft and have it shortened if necessary to make space for the shaft isolator. Can you imagine having your shafts shortened for this upgrade only to discover the shortcomings and hear the manufacturer say, basically, “Meh…send it back if you don’t like it.” “Returning the purchase” would get me my money back (minus shipping) but it would also leave a 1-1/8″ gap between the shaft and gear coupler! Once you’re in this far, the only way forward is to make the Drivesavers work!
Globe’s response to my second message was “An image description of the drivesaver installation can be found at https://www.gcsmarine.com/content/drivesavers/dr_installation. I believe this information should be helpful.”
That image description is the graphic that shows the Drivesaver in the wrong orientation…I’d already seen it! I wanted to reach through the internet and wring that obtuse Globe representative’s neck! Instead, I wrote once more and reiterated that the problem is not with my execution, the problem was with their Drivesaver not actually fitting this application. I requested longer bolts that fit this application and also shared the results of an internet search; it turns out that other people have experienced these problems and taken the time to write about it.
A different Globe representative responded this time: “We are sorry to hear the bolts are a bit too short for your application. I think you bring up a good point regarding applications in general, they tend to all be a little different. I will pass on your comments regarding offering different bolt sizes with this Drivesaver model and we’ll take a look out on the web ourselves for their feedback. Unfortunately we do not currently have longer bolts available. One solution may be to source a set of longer bolts locally or you can always return the purchase through the eBay portal stating the item did not fit properly. Thank you for taking the time to provide such detailed information.”
This response was a bit better, but it highlighted yet another problem. The Globe Driversaver warranty says that it “shall be void with respect to, damages or defects arising out of any of the following:
- Installation or use of a Globe Marine product in a manner that is inconsistent with Globe Marine’s application information or specifications;…
- Defects in products or components not manufactured by Globe;”
In other words, if I install the Drivesaver backwards, which is the only way it fits my gear, my warranty is void. If there is a problem caused by the “set of longer bolts” I source locally, my warranty is void. This is especially sneaky, since the warranty elsewhere says “Globe Marine’s employees’ or representatives’ ORAL OR OTHER WRITTEN STATEMENTS DO NOT CONSTITUTE WARRANTIES, shall not be relied upon by the customer, and are not a part of the warranty stated herein.”
I wrote one last time to Globe’s ebay store rep and pointed out this warranty conflict problem. Globe’s final response was “We are sorry to hear that this has become a difficult project for you. Unfortunately we are not in a position to source longer hardware for your application. Our previous suggested solutions still stand.” So, basically, Globe’s first obtuse response is all you’re gonna get. Period.
I wrote to Globe’s chief engineer/VP to repeat the complaint and ask for specs on what kind of bolts I should “source locally” (Grade 5? Grade 8? Zinc-plated plain steel?) but never received a response.
While all of the emails were going back and forth, I kept the project moving forward by going back to Globe’s ebay store and ordering the “5/8″ to 1/2″ Bushing Kit” (Suggested Retail Price: $53.35). Imagine my surprise five days later when I got a bag of standard plated steel washers and a dozen short lengths of unremarkable plastic tube in exchange for my investment.
What a rip off! If the plastic parts were some super-engineered, proprietary product I wouldn’t complain. But this is garden variety acrylic or polycarbonate that sells online for $1~$2/ft. Also, the paper instructions that came with the bushing kit are identical to the instructions for the Drivesavers. The only difference is that there’s a sticker at the top that says “1/2″x 5/8″x 5/8″ BUSHING KIT.” Oddly, there is absolutely no mention in those instructions about what you’re supposed to do with the bushing kit. They might as well send instructions for baking a cake! Though, in retrospect, cake instructions might actually be useful…
I mean, it’s obvious how Globe intends for these parts to be used, but I couldn’t help wondering if these cheesy plastic bushings are really going to hold up to a Cummins-powered 1,029 lbs-ft beating? It might be nice if the accompanying literature explained how it all works out. At this point it was just really irritating to see the uncaring incompetence continue nonstop.
$50 and ten days later, I had hardware that would work. I still had to go with 1/2″ bolts instead of the 5/8″ ones that ZF and Buck Algonquin spec’ed, but 5/8″ bolts simply won’t fit in the Drivesaver. After discussing the size difference with some resident engineers, I’m reasonably sure that these bolts will hold up just fine; 5/8″ would just give a larger safety factor. As always, I’m using Tef-Gel on all threaded parts.
But when I tried to tighten the bolts, they bottomed out before the Drivesaver seated on the gear coupler. What the …???
I once again wrote to Globe and asked about the bushings. Globe’s helpful response was to tell me to cut or sand them down to size. So I used my ShopSmith 12″ disk sander to knock 1/8″ off the length of the bushings.
Aircraft mechanics will freak out about the non-spec safety wire twist, I’m sure, but I think it will be fine. 😉
Also, I used Loctite on the hex head bolt threads that went into the Drivesaver, and Tef-Gel on the part that goes through the coupling.
I feel oddly compelled to note that the T-bolt clamps that came with the Buck Algonquin packing box fit the application. I didn’t have to order any overpriced bushings to make them work or even machine the parts…they just fit out of the box. How refreshing!
Given my experience, I couldn’t in good conscience recommend Globe Drivesavers. I understand the desire to maximize the utility of expensive tooling. But when a gear manufacturer and a shaft coupling manufacturer both spec out 5/8″ bolts, a shaft isolator manufacturer should match the spec if its going to claim compatibility. It’s my opinion that Globe engages in false advertizing. They’re cheap bastards when it comes to product support. It’s especially dishonest for Globe to basically shrug and suggest local bolt sourcing since doing so voids the warranty. My advice: Do not buy Globe Drivesavers.
Other options, if I had to do it all over again:
The R & D Marine coupling works about the same way as Globe drivesavers, but it’s got a get-home feature that reportedly keeps the gear connected to the shaft via metal straps in the event that the plastic part fails. It’s also a machined part rather than cast, like the Drivesaver, so the tolerances are reportedly tighter. The cost is comparable to Globe Drivesavers.
An even neater approach is the Evolution Company’s Evolution Marine Shaft System. This is a super slick concept that, if I understand it correctly, completely eliminates the need for stuffing boxes, shaft zincs, and cutlass bearings. Instead the EMSS completely encloses the prop shaft in an oil-filled shaft log from the engine room bulkhead to the propeller. It’s got roller bearings that waste far less power than conventional cutlass bearings, and double seals to keep the water out and the oil in with less energy wasted than conventional packing boxes. Dripping stuffing boxes are a thing of the past. Since the prop shaft spins in a fixed, full-length shaft log, the energy lost to normal shafts spinning through the water goes to the prop instead. I’ve heard from reliable sources not affiliated with Evolution that this shaft-within-a-shaft approach can add 5kts to a pleasure yacht hull with no other factors changed. The downside is cost: $51,000 for twin EMSS systems for my boat ($2,700 in tax, presumably because without the government none of this could happen), which is ~10x what the conventional shafting, bearings, etc cost brand new. Since I’m already this far along it’s not something I’m going to do now. But if I had to do it all over again and money was no concern…
Next up on our 1969 Chris Craft Roamer 46 Refit: Sanding the Salon