### Help Support Homebuilt Aircraft & Kit Plane Forum:

#### lganderz

##### Member
Hello, Leo

I have a Geschwender PRSU and am wondering what the horsepower rating might be. This is one of the units for the Ford 400 motor. If you have any drawings or other detailed information I would be happy to pay you a consulting fee! Thanks.
The 2-inch wide Hy-Vo chain is rated at 20,000 lbs of tension load (torque plus centrifugal force). I've done the calculations for a 400 hp engine with 600 ftlbs of torque running at 5200 rpm and the actual tension is around 4,000 lbs. Derating the Hy-Vo chain by 80% (for engine torque pulses) increases the load to 7200 lbs of tension, which is only 36% of the capacity of the chain. The webpage: "HyVo Chain Drive Design Issues, by EPI Inc." describes this in more detail although the author does not back-up his conclusions with any real calculations. I'm working on a paper that will show that a Geschwender designed drive should handle 600 hp @ 5300 rpm with a considerable safety margin.

BTW: I've already placed an ad in Sport Aviation (October edition) requesting information on the durability of the Geschwender drives from anyone using them in their aircraft. If interested in participating, I can be reached at: [email protected]

Leo A.

#### lganderz

##### Member
Anyone have a link to a photo of this airplane?

BJC
Here is a photo of the P-38 plane built by Larry Buchanan. He said it has actually flown and was working towards building molds for kits when his backers ran out of money.

Leo a.

#### J Galt

##### Well-Known Member
Justin:

I recently bought the assets of the last company that built the Geschwender PSRUs (Alternate Airpower). I'm trying to assess if it is worth the effort to put this product back in production or just build one for my aircraft. Any thoughts on the market demand for this product?

Leo A.
Hello Leo,
I think the demand would be driven by cost. I personally know of 2 PSRU brands that are in the process of being brought back to market, with a third a possibility. That along with the others mentioned means there is certainly some competition. If you could sell them for $15k-18k or less then I think you could sell all you cared to make by yourself or maybe you and another. I have heard (first hand) of one specific V-8 conversion engine supplier who went kaput because of a lack of a full production PSRU in quantity, so maybe others out there are waiting in the wings for you to push it through. I hope that helps, it is just my opinion without real hard data to back it up. Justin #### rv6ejguy ##### Well-Known Member HBA Supporter I think the PSRU price needs to be less than the crate engine to be really viable. #### lganderz ##### Member Hello Leo, I think the demand would be driven by cost. I personally know of 2 PSRU brands that are in the process of being brought back to market, with a third a possibility. That along with the others mentioned means there is certainly some competition. If you could sell them for$15k-18k or less then I think you could sell all you cared to make by yourself or maybe you and another. I have heard (first hand) of one specific V-8 conversion engine supplier who went kaput because of a lack of a full production PSRU in quantity, so maybe others out there are waiting in the wings for you to push it through. I hope that helps, it is just my opinion without real hard data to back it up.
Justin
Justin:

The last price from John Worden's site (alternate-airpower.com) in 2007 was $9700. I'm guessing that price would be closer to$15,000 today. The biggest cost to restarting production is the cost of the molding technology (patterns). I've seen estimates between $20,000 and$40,000 depending on their expected lifetime. Currently I'm looking into 3-D printing the patterns and then calculating the costs for a run of a dozen or so units.

Leo A.

#### Aviacs

##### Well-Known Member
The biggest cost to restarting production is the cost of the molding technology (patterns). I've seen estimates between $20,000 and$40,000
Does that include the rigging, or just the patterns?
On a matchplate? Boxed?
Are there any loose cores? (Or can the entire mould be taken off simple cope and drag matchplate pattern? Perhaps with a little creativity?)
If loose cores, does it include shell core boxes?
What material?

No doubt you are familiar, but it is always good to have ID'd the foundry, be comfortable with their interest and input, and work with them on the design once past the simple form stage. They will advise matchplate size, e.g. Many will (prefer) to put the rigging on themselves. So they stand the cost of proving it. Although they keep it if you take your patterns elsewhere.

I can't find a current photo of the gershwender online. Any links?

smt

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
I can't find a current photo of the gershwender online. Any links?

#### lganderz

##### Member
Does that include the rigging, or just the patterns?
On a matchplate? Boxed?
Are there any loose cores? (Or can the entire mould be taken off simple cope and drag matchplate pattern? Perhaps with a little creativity?)
If loose cores, does it include shell core boxes?
What material?

No doubt you are familiar, but it is always good to have ID'd the foundry, be comfortable with their interest and input, and work with them on the design once past the simple form stage. They will advise matchplate size, e.g. Many will (prefer) to put the rigging on themselves. So they stand the cost of proving it. Although they keep it if you take your patterns elsewhere.

I can't find a current photo of the gershwender online. Any links?

smt
This part of the business is new to me. John Worden used a foundry in Indiana (now in Bankruptcy) and CNC machined the castings himself. I'm in the process of entering the 2-D drawings into SolidWorks (also new to me) with the intent to shop them around for pricing. I do have some templates for match-drilling holes for mounting the drive to a variety of engines, but nothing remains from his CNC artifacts.

Leo A.

#### lganderz

##### Member
I have heard (first hand) of one specific V-8 conversion engine supplier who went kaput because of a lack of a full production PSRU in quantity, so maybe others out there are waiting in the wings for you to push it through.
Justin:

Is it possible that your V-8 conversion engine supplier could be ressurrected?

Leo A.

#### piepermd

##### Well-Known Member
The 2-inch wide Hy-Vo chain is rated at 20,000 lbs of tension load (torque plus centrifugal force). I've done the calculations for a 400 hp engine with 600 ftlbs of torque running at 5200 rpm and the actual tension is around 4,000 lbs. Derating the Hy-Vo chain by 80% (for engine torque pulses) increases the load to 7200 lbs of tension, which is only 36% of the capacity of the chain. The webpage: "HyVo Chain Drive Design Issues, by EPI Inc." describes this in more detail although the author does not back-up his conclusions with any real calculations. I'm working on a paper that will show that a Geschwender designed drive should handle 600 hp @ 5300 rpm with a considerable safety margin.

BTW: I've already placed an ad in Sport Aviation (October edition) requesting information on the durability of the Geschwender drives from anyone using them in their aircraft. If interested in participating, I can be reached at: [email protected]

Leo A.
A few quick photos….

#### TFF

##### Well-Known Member
Mid 90s Sport Aviation had pictures of molds and such for an article.

It’s too bad that raw castings and mechanicals can’t be a kit. Yes the success is not the same, but there could be a fighting chance for the right person to either finish his own or have a symbiotic company doing some finish work. just having the big chunks available increase chances.

#### rv6ejguy

##### Well-Known Member
HBA Supporter
I'd be surprised if doing castings like this in small quantities (dozens at a time) is cheaper than machining these parts from billet, if you have to re-create the molds. In large quantities, castings would be certainly cheaper. I see maybe around \$1500 in material for the aluminum bits. Billet would reduce the initial outlay as well.

#### rv7charlie

##### Well-Known Member
I think the PSRU price needs to be less than the crate engine to be really viable.
This.
Any real market will need to see an installed price for the *entire engine system* at a lower price point than a *used* big LycCont. Otherwise, you'll never attract anyone who's 'sitting on the fence'. Here's what any comparison shopper will see:
Shop Stinger Drives
Yes, it turns the wrong way, but for the price difference, you could almost buy an electric prop.

Not wanting to be a DebbieDowner, but realistic market expectations are essential if you expect to do anything other than make a small fortune (out of a big one).

#### Aviacs

##### Well-Known Member
Thanks for the links and pics.

John Worden used a foundry in Indiana (now in Bankruptcy)
What happened to the original patterns?
If available or if you can recover them before the bankruptcy clear-out, they can be repaired for a fraction of the cost of making new ones. Even better, they are likely already be mounted on useable matchplates, perhaps with some of the basic rigging features still in place.

Ross made a good point about machining from the solid vs casting, for small batches.
It would be hard to predict at this point, really - it looks like there are 2 major castings, and a flat plate?
The back case/casting looks like it might be engine specific? Cutting from the solid does have some advantage for small batches there, if so.

You won't know without having a conversation with a foundry that is sort of interested in talking to you & willing to do some coaching with the cost projections, vs quoting with cnc shops. Some castable alloys aren't available in the solid, and vice versa. So some strength and heat treat comparisons with original material is a factor.

You can take an existing casting, sandblast, and build it up for shrink, distortion, and machining allowance with conventional pattern products. Make it all smooth and shiny. Take a mould in resin. Then cast your working pattern in resin, & work it up on a match plate. If working with an existing casting, be sure to verify that the allowances are all in the right directions. Castings do get distorted, and cores shift when molds are bumped on the conveyors.

If you decide you have to get familiar with patternmaking processes, there are worse places to start than Freeman Foundry Supply.
Loads of videos how to use their products even if you are more old-school. FreemanSupply.com - Mold Making, Casting Resin, & Foundry Materials

smt <-first hand experience with foundries (plural) going bankrupt and patterns "disappearing". ugh.

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#### lganderz

##### Member
Thanks for the pictures. I don't think I have any drawings for that model, but it has many similarities to Fred's other designs. It may also be bigger (to accommodate the 2.66:1 gear ratio). The adapter plate that attaches it to the engine is also more elaborate. Does it have a Geschwender Aeromotive data plate?

Leo A.

#### Wolfen1176

##### Active Member
Twin engine inboard boats always used a reverse turning engine. Those engines are under constant load at high power settings just like aircraft engines.

#### Lendo

##### Well-Known Member
Leo, I've done some sand casting but Die casting is better but also expensive. The suggestion to use Billet is the best for small quantities as RV6 suggested, it's not subject to any porosity like sand casting, it's denser and stronger than both. It does however have the added expense of machining, good design might minimize this.
George

#### Aviacs

##### Well-Known Member
Leo, I've done some sand casting but Die casting is better but also expensive. The suggestion to use Billet is the best for small quantities
Mostly it boils down to quantities and convenience.
As you mention, traditional green sand molds for aluminum castings can still be viable.

But other processes are available that IME are more convenient for intricate or more technically demanding shapes.
No-bake is very, very good and not much more expensive than green sand. I think it saves money overall due to better fidelity, surface finish, It's stronger, so less distortion, hence less "extra" metal needs incorporated in the design to cover distortion or core or pattern shifts, etc.

If you can make metal patterns, shell molds are are a good production standard.

The detail of no-bake and of shell molds is very good: I've seen light finger prints in castings out of no-bake molds made from my resin patterns; and inside the cavity from resin set cores taken from my shell core box, where the operator handled the mould or core in a way to imprint it, and it transferred into the casting.

These days lost foam casting is amazing for complex shapes, especially engine blocks and heads, but i have no familiarity with it. The cost there is making the tooling (dies) to make the foam models.

A problem with die-cast is the range of suitable alloys, and shrinkage-tear issues.
The dies are expensive due to erosion. Not ideal compared to shell moulds or lost foam if you are going to make metal tooling anyway.

Really, the only way to find out is to have a good understanding of the costs to work with a foundry vs the costs of producing the parts from solid blocks on cnc equipment.

smt

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#### Geraldc

##### Well-Known Member
3d printed lost wax casting is becoming more popular.