# Geshwender PSRU Business

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#### rv6ejguy

##### Well-Known Member
HBA Supporter
These are all simple parts here with no intricate passages. Easily machined on a CNC mill.

Additive manufacturing of these large parts would be prohibitively expensive.

We machine some lightweight Lycoming flywheels from billet and these are price competitive with the cast ones from Lycoming despite the fact that 82% of the original material is machined away. Ours are not PMA'd though. A big lathe or mill can whittle material away pretty fast.

#### Aviacs

##### Well-Known Member
Among airboat boxes, it is notable that some of the more interesting examples use cast cases.
(67 lbs)

Including the only geared, contra rotating prop offering (150 lbs!):

OTOH, Ballistic is among the more recent offerings and seems to have a really good rep for their gear sets.
They elected to cnc. There's certainly snazz appeal to a certain eye.

Torque gear drives are also cnc case:

Century offers belt or gear reduction units.
They seem to use a mix of cast and cnc parts in current offerings.
It's not always easy to tell without seeing the back sides, which are shown on their website for several different models:

There are several more manufacturers for airboats, some cast, some cnc.
Must not be a big difference.

FWIW - I realize that the specific airboat boxes may or may not have relevance to AC.
Stinger, e.g. (cast cases) has always marketed a box specifically designated for Experimentals with big V8's, but if it was good i imagine there would be more references to AC users on here. As noted, none accommodate constant speed props. However, all solve or attempt to solve, the same problems as AC PSRU's for high HP V8 engines. Most are advertised to accommodate 1000 or more HP. They tend to sell (except the contra rotator) for somewhere under $5,000 AFAICT. Listed boxes tend to be priced between$3200 & 4500. Which should be suggestive to anyone interested in entering the market.

smt

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#### Cardmarc

##### Well-Known Member
Is the Mistral redrive the only successful constant speed equipped planetary redrive that made it to production? I seek such a unit.

#### rv6ejguy

HBA Supporter
The airboat redrive market is much larger than that for aircraft so there is a big economy of scale there. Castings make sense when you're producing hundreds of units per year, probably not when producing dozens. The market for $15K+ drives is going to be even smaller. #### Aviacs ##### Well-Known Member You (at least suggest) that you are a machinist, too. So you must be willfully missing the point. The drive for an airboat or an airplane is the same thing, defined by the same parameters. Except possibly nth degree weight reduction, and plumbing for a constant speed prop. Since you state that you agree with the point i made in 2 previous posts that the airboat market is much larger, wouldn't it make sense for anyone who hopes to enter the industry, to target that market for prototypes, sell volume, and develop the aircraft version? Given the bling, gizmosity, and one-upmanship inherent in many popular passtimes, there's probably a market for a constant speed prop in airboat land, too even though there is no real need. Stinger, one of the earliest boxes, did that and the designer/developer's daughter still builds and sells product though it is apparently no longer a top-rated device & probably never was for airplanes. But they didn't go broke. #### rv6ejguy ##### Well-Known Member HBA Supporter You (at least suggest) that you are a machinist, too. So you must be willfully missing the point. The drive for an airboat or an airplane is the same thing, defined by the same parameters. Except possibly nth degree weight reduction, and plumbing for a constant speed prop. Since you state that you agree with the point i made in 2 previous posts that the airboat market is much larger, wouldn't it make sense for anyone who hopes to enter the industry, to target that market for prototypes, sell volume, and develop the aircraft version? Given the bling, gizmosity, and one-upmanship inherent in many popular passtimes, there's probably a market for a constant speed prop in airboat land, too even though there is no real need. Stinger, one of the earliest boxes, did that and the designer/developer's daughter still builds and sells product though it is apparently no longer a top-rated device & probably never was for airplanes. But they didn't go broke. I've been in the auto engine powered aircraft game for almost 25 years now with thousands of customers flying our EFI and custom machined parts so I think I have a bit of a handle on on PSRU costs, problems, production etc. in this market. I am familiar with almost all brands that have been offered over the last 20 years. I have customers who've used airboat drives with good success. Two with LS V8s balked at the prices being charged by EPI , CAM, Robinson and Geared (the$15K range ones) and didn't need a hydraulic C/S prop. They went with Ballistic instead. Few folks are going to drop more on the drive than the engine costs in my experience. Sure some with deep pockets will, maybe with a nice replica warbird like an S51 but those will be few and far between and you're talking dozens at best per year once your design is proven and you establish a good reputation for support. This all takes time and money and I've seen drives come in, fail and fade away. Lots of them priced way below this threshold where the market is much bigger. It's easy to lose your shirt if you are not careful on startup costs.

As has been discussed before, there is already competition in both these markets which give you an even smaller piece of the pie.

I laid out how I'd do it. CNC the prototype and get it running and tested. You won't sell anything without something tangible to show potential customers. If the deposits start flowing in in reasonable quantities, then look at doing castings. No way it makes sense financially to prototype this GB with castings with an unknown and likely small market size.

Looks like the drives in the airboat industry have a pretty good bling level already and some of those guys have deep pockets as I sell CNC'd stuff to them too but I don't see many sales there for a C/S capable redrive. The existing stuff is durable, simple and good looking at a 1/3rd of the cost. That's where most of your market lies.

Want to be successful in this sort of stuff? Offer a reliable, inexpensive, easy to work on, good looking drive with good customer support. Some of those goals may be hard to work in together.

The original Geshwender drives had a decent rep for reliability, the new owner can build on that but will have to re-launch production, follow it up with proper testing and grab users who haven't heard about this drive for 20 years. I believe you can sell some for sure. The question is will it be worth all the work to do so?

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