Online Community of Zenith Builders and Flyers
I believe that they make it themselves at Zenair. Just by the price I can tell that it's not Grove.
Nothing against the Zenith part, but if they make one buy the Grove gear.
I originally had the Zenith piece for my 701, but did a bad job drilling the bolt holes. It was replaced with the Grove gear for two reasons:
1) It comes pre-drilled for you.
2) Gun drilled brake lines.
Having flown a 701 with the stock and my Grove, I certainly prefer the Grove.
Checked the Grove website, they list the 701 gear as rated to be 1,060lbs. Maybe a typo? I would like to think they rated their gear conservatively. Anyone know??..DonB
John , could you please elaborate on your choice of the Grove gear ?
I need to make a gear choice decision for a 701 soon .
750 gear may be plans built, or purchased from Zenith (about $500), or purchased from Grove (about $2000 for the pre-drilled version, that therefore hides the brake lines).
The plans specify material, bends, and bending jigs. A hydraulic press is required, along with several steel bending jigs and some wood pieces as well. Makes the $500 look pretty good, actually.
Grove gear costs more for a reason. The Zenith gear does the job, can be made by the builder to plans (a major project, that's pretty thick metal to be cold bending) or bought at a very fair price from Zenith. The Grove gear is an upgrade of sorts - it is made of a stronger alloy (and, I believe, is heat treated after it has been bent to shape to add strength), comes pre-drilled if you want that option, comes with "gun drilled" brake lines if you want that option. (Gun drilled is a long drilled passage similar to the bore of a rifle - it takes special equipment to drill holes that long accurately. They drill the brake passage into the metal bar before the gear leg is bent to shape and a threaded connection is added at both ends to hook brake plumbing to. It makes for a very tidy gear leg and a simple effective way of getting brake fluid under pressure down to the brake caliper.) The final virtue of the Grove gear is it weighs about half as much as the Zenith gear - it is made of a stronger alloy so it can be made of less metal and still be just as strong.
Like so many things in aviation this is a trade off decision. Is the extra convenience of pre-drilled axle mount holes and a tidy brake line installation and a huge weight savings worth the extra cost? Each builder has to make his or her own decision on that one. There is no one right decision, we each have to make our own. I plan to use a Grove gear for my build, that huge weight savings is too good to pass up.
One word of caution - the Grove gear is heat treated so one must be careful about applying heat to it. Put enough heat onto it in the wrong way and the strength imparted by the heat treatment goes away and your gear legs are much weaker. Check with Grove before taking a torch to it or even having it powder coated - powder coating melts the pigmented powder onto the piece with 400 or more degrees of heat and that might mess with the heat treatment. I have heard some folks say you should NEVER powder coat Grove's heat treated gear and others say one can do it if very careful. I plan to either leave it bare aluminum or paint it rather than take a chance.
Wow, I had no idea about "half the weight". Worth every penny, IMHO. I'm ordering one ASAP.
as to the weight savings mentioned below I would like to see the actual numbers comparing both. When I look at the grove site they show the 701 weight to be 21 pounds, when I look at the online metals site and use their weight calculator for the raw aluminum stock the weights are virtually identical. Zenith uses 6061 stock while the grove uses 7075 which is heat treated and stronger. For the gear to be half the weight the 701 gear would only be 1 5/8 inches wide by 3/4 inches thick. I realize that this is for the 701 and the 750 uses a larger gear but the baseline comparisond for weight should be the same.
I just weighed a 750 gear, factory from Zenith. Just the alu, no axles or other parts.
When I was looking at the grove site they didn't show the 750, but they show the 801 gear as weighing 40.3 pounds. I think the weights for all the Zenith planes will be nearly the same between the zenith and grove gear
Yeah, I think you are correct.
I've sent a question to grove, to see if they make CH750 gear. I'm sure it will be Monday at earliest before hearing back.
The claim that Grove gear weighs half of what Zenith gear weighs is not even close to accurate.
I talked with Robbie Grove years ago and he told me that while there was a weight savings to be had on the 701 main gear spring, Zenith got smarter on designing the 750 gear and there was very little weight savings to be had on that spring. Additionally, a member of this forum (Elmer Webster) long ago replaced his stock 701 gear with Grove gear and I believe he reported that Grove gear weighed one pound MORE than stock 701 gear.