Juice

Hello everyone,

The first three pictures are of the Solo prop and hub I got for Christmas. Those are 16" blades. The Corsair is the .60-size H9 Corsair (1/8 scale). The Solo prop and hub looks really cool and changing the pitch is a quick and easy task. How does it look?

The next three pictures are of some full size Corsairs. I tried to choose pictures of approximately the same angles for comparison.

As good as the Solo prop and hub looks, I personally think it is too big for a 1/8 scale Corsair, such as this H9. It is more suitable for 1/6 scale and up. Dismayed that I can't use such a good looking functional prop, I started thinking how I can make it work.

I ended up reverse engineering the original Solo Hub (using AutoCAD). Then I shrunk the design as close as possible to 1/8 scale. I made sure to keep the important dimensions in areas of high stress, such as the blade saddles. The result is in last picture. On the right is the larger original Solo Hub. On the left is the smaller 1/8 scale clone. What do you think?

The 1/8 clone will still use stock, unmodified Solo props (not drawn). Also required from Solo will be their extension nut (not shown). The spinner will be a 1-1/4" Tru-Turn hub. With the smaller package, there was not enough space for the pitch adjustment dial used in the original Solo design. It will be a little more work (not a lot more work) to change the pitch, but like the Solo design, the pitch of all three blades are automatically synchronized. I thought that this feature is an important one to keep.

Here's one catch: It is designed specifically for the RCV SP type engines. The 60SP may be too small, but for sure the 90SP and the 120SP. The reason for this is because Solo doesn't offer prop blades less then 16" diameter. That and the fact that I am only going to clone the 3-blade hub, the only two engines I know of that can turn a 16" 3-blade prop for a 1/8 scale airplane are the RCV 90SP and 120 SP. If you can prove otherwise, I'll make the necessary design changes.

Here's another catch: The CNC costs. I simply cannot justify the cost of a one-off hub for myself. If there is enough interest, we can all split the CNC costs. I'm not asking for money now. I'm asking for replies showing STRONG interest. From the response, I'll propose a $/hub figure that we can all vote on. Then I'll order the appropriate number for a production run, paying out of my own wallet. Then I'll sell them, and ask for money individually when I'm ready to ship each individual hub.

Last catch: This is one-time offer. I talked to Carl of Solo Props about the legal and ethical issues. There are actually no legal issues (as of this moment, I think). There is the ethical issue of me copying Solo Prop's design. Carl says he's okay with me doing this as long as it's a one-time, not-for-profit, not-for-business production run. Having said that, we need to have Carl on board with the project because we still need to buy his propellor blades and extension nut.

I'm sure there is a lot more that still needs to be said, but this post is long enough. If you have any questions, just post a reply.

So... Anyone interested?

Josh

Juice

I'm saving this post for future edits as the project matures. I'll eventually put important information here that should be easily findable.

Josh

Juice

One last thing...

I am in no way affiliated with Solo Props. I started this project as a challenge to myself for my personal love of the RC airplane hobby and scale warbirds. I am not a business man and I do not intent start a business out of this. I am putting in valuable time and risking my own money. I'll try to do my best, but I can't really promise or guarantee anything.

I do not intend on stealing business away from Solo Props. A 1/8 scale hub for RCV SP engines is a very small market that they are currently not supplying. I think this project will actually give them a short term boost in prop sales. I also think this project will give Solo Props valuable market research if they ever decide to make smaller scale stuff.

All that being said, if what I'm doing is illegal or infringes patents or copyright laws, even if it alienates Solo Prop in any way... I'll stop the project.

Anyways... Enough of the boring disclaimers!

Josh

saramos

Since Carl at Soloprops seems to have the equipment necessary for his hubs, do you think he might be interested in producing your reduced version? This would eliminate any ethical questions and I would guess the product would be priced at about what he charges for his hub.

Either way, I do have a 60 size Royal corsair kit, and it would go well with the 120SP. I would be interested in a 1/8 version of the hub.

The only other possible alternative to the RCV SPs would be electric. I'll be exploring this with my current Top Flite P-51B build.


Scott

Juice

Scott... That possibility came up when I talked to Carl. He basically said that he doesn't have enough time to get into something new, and that it would require too much setup time. I'm sure he's watching very closely how this project goes. I'm currently waiting for a quote from one CNC house. They said they'll have numbers for me next week. I'm also looking for other CNC companies for additional quotes.

I haven't even thought of electrics! More to research and think about...

Josh

Juice

I'm still waiting for some quotes to come in from a couple CNC shops. In the mean time I played around with the CAD drawings. For thoroughness, in the original sized Soloprop hub, I added the bolt holes (previously missing). Also in the original sized Soloprop hub, I added the required space between the back half an the front half (previously drawn together).

In each picture the middle hub has 4 bolts per side. It'll be more scale with 4 bolts, but it may look a little too crowded in the 1/8th version. Which do you prefer?

In the last picture, I put the hubs in front of 1/8 scale Corsair shaped cowls. In the 1/8 hubs, the prop root saddles are a little wider and protrude a little further than scale, but otherwise it looks just the right size.

Josh

saramos

I guess the big question is, are 2 bolts enough to secure the props, or will 4 bolts add enough extra insurance against failure to justify the cost. Based on looks, I like the 4 bolt. I may like it for peace of mind too.

Scott

77chickenhawk

Hello Juice !!..

What a great idea you have there, and I to would be interested in getting your hub. My first Warbird was a Hanger-9 Corrsair. started bashing it rite off the bat. I also got the Solo prop thinking it would be perfect for it. But after getting it, I knew rite away the hub was out of scale. I'm putting the OS-FT-160 flat twin in it, and am going to fly it with a 18in. diameter prop. Also being so big for the Carrsair it was a little to much rotating mass. So I put the solo on the shelf for a while. Waiting for something else to come up, (Like Now !!! )Sweet....
Anyways I found a metter match for the Solo. My !/5th scale P-40

I want to see someone remake some blades for the VarioPROP design. Seen here

http://www.ramoser.de/home_e/variopr...rioprop_e.html

I own one, and the hub is the rite scale and the prop blade base isnt so thick either. They make hubs for gas and glow 2,3,4,5 blade assy's But the downfall is there biggesr diameter is a 14, and the profile is more like a Spitfire and not a Corrsair. But you could CNC some different molds with the correct profile (shape) and legnth.. would be sweet..

77chickenhawk

4 bolts on each side

Juice

It's unanimous then... we'll go with 4 bolts.

I had a look at the VarioPROP design. It is much better suited for smaller glow and electric engines. The Soloprop design is more suited for gas and larger glow engines. Because I'm targetting a mid-size glow engine, the Soloprop design would be a better start. I think it would be more risky to start with the smaller VarioPROP hub and use a larger prop than it was originally designed for. It's less risky to start with the larger Soloprop design and shrink it (keeping important structural dimensions).

It's interesting that both designs are VERY similar. It looks like they both use the same technique to synchronize the pitch of each hub. The larger Soloprop design uses a dial to set the pitch (a really slick feature). The small VarioPROP design uses some kind of screw to set the pitch. Small difference, but essentially the same.

Josh

tony-howard

My Feedback: (224)

Josh

I'm interested in this project for a Brian Taylor glass Hellcat that I have stored away. It would be a perfect fit. My current thinking is electric power. I have other applications that it would fit as well.

Whistling Death

I can tell you that a machine shop is going to want an arm and a leg to do a small number of hubs unless it is a small shop. I might be interested in it if the price is right. I am putting my H9 Corsair together now with a RCV 90SP.

Juice

The machine shop whose quote I'm waiting for gave me a ballpark figure of "3 digits". Divide that by the number of people who want one. Maybe the price will go down to an arm or a leg.

Josh

Juice

I got the first quote via e-mail...

CNC Shop A:
1 unit for $825.
10 units for $600 each.
50 units for $475 each.

The cost for 1 unit is near what I expected. The cost for 10 and 50 units is much higher than what I expected. I'm going to talk to him about possible design changes that will lead to the greatest cost reduction.

I'm already talking to another shop for a second quote. There are also a few leads from members of my club that I have to follow up on.

Josh

saramos

Wow, that's higher than I would have thought. On the other hand, I've never priced a custom CNC job before. But in general, even at the $475, that's a bit more than I could justify for a hub on a 1/8 scale model.

Klaatu

My Feedback: (4)

I am truly intrigued by RCV SP engines but their price per power seems extravagant. Add a $500+ hub and all the other necessary bits and you are nearing turbine land money for fairly low powered system that only displays its real coolness when parked in the grass.

The coolness factor is high, for sure. It is just way too expensive for me. Even using Solo's off the shelf parts, it seems easy to have more money in the prop than the engine. Very cool, but beyond my reality check. I wish you luck. I will chime back in with a potential order if the price gets under $200 (way under). :-)

- Jan

Juice

$200 is my absolute maximum also.

$475 was just the first quote. I'm going to get a few more quotes before I give up.

Does anyone here know a CNC operator who is friendly to hobbyists?

Josh

Whistling Death

Just as I expected. The company I work for has a sister company that is a medium sized machine shop. Anything like the solo prop hub with such tight tolerances and multiple compound machined angles just blows the price way up there. It is a shame that we can't get something like this a little cheaper. These props are exactlly what RCV engines need because of the high pitch requirements.
If we had access to a Chinese machine shop then you would get the price i a decent range. Keep it up Juice, you might get lucky.

kahloq

77chickenhawk.....
The largest diameter is not 14, but 15.2"
The varioprop is available in the states directly from here:
http://www.e-flightline.com/varioprop.htm

A 15" diameter prop would basically be the right size for any 1/7 -1/8 scale warbird. The H9 Corsair is 1/7.5 Mine was using a Saito 100 with a 14x7 3 blade MAS prop at 8800 rpm's. I have the H9 hellcat Im using a saito 125 in, so either Juice's hub or the varioprop hub would probably work. The varioprop hub goes up to 8mm shaft diameter and that would allow the use of them on any saito from a 100 up to 180(although the very back part of the motor shaft on the 180 goes from 8mm to 10mm)....so realistically, the varioprop hub could be used up to a saito 150.
A saito 100 will not turn a 15" diameter prop well at all, but a saito 125 and a 150 will definitely(after break-in). So, if using a 3 or 4 blade hub, the varioprop would be a choice for NON RCVSP motors....and definitely those that are a 125 class or smaller since you can choose what blade diameter you want(from 13 to 15.2 on an 8mm shaft). A Saito 150 can turn a 16" 3 blade prop, so Juice's hub, if it were 8mm shaft diameter, would work for that.

Juice, I like the idea of what your doing, especially since even a rcv60-sp can turn a 16x10 3 blade(I know as I have one) and could be used for other medium size glow motors(1.20 to 1.50) since the blade diameter is minimum of 16 as you stated.

timothy thompson

My Feedback: (1)

i cant see why you and solo couldnt collaborate, they may offer you the job!

Juice

Maybe I should approach Soloprops again. When I talked to him the first time (a couple weeks ago), he said he didn't have the time for something new. If I don't get lucky in the next couple quotes, I'll talk to them again.

I'm glad this thread has caught the interest of a few more people. It makes me feel a little less crazy for trying to do this.

Josh

saramos

Keep at it Josh!

The Royal is a great scale kit and it would be wonderful to have a more scale prop/hub on the front of it and to take advantage of the RCV SP. The kit I have was inherited from my father, so it has a lot of sentimental value and I want to do it up right.

Scott

77chickenhawk

remember scale for a 60 size F4-U is 19" prop and 1/7 scale would be a 18 3/4

correction on that quote..lol oops. I typoed i meaning to say the biggest downfall of the VarioProp was that its (only) 15" and not bigger. What would the cost be to make a mold for bigger blades and better scale like profile for the varioprop? thats what would be cool. or even bwetter, the design of the V/P hub is way simpler. so whats the cost to machine 10mm hub design and say ahhh maybe a 19 inch diameter prop. im pretty sure its something that could maybe be done my a machinist and not a cnc.? any thoughts?


i have a H-9 F4-U with a os ft160 twin and that baby will turn a 18 inch 3 blade but V/P dont make any bigger than 15

Klaatu

My Feedback: (4)

I wonder what the MTBF of these hubs and props are. I especially wonder how they will hold up on a RCV SP engine which has vibrational modes entirely different than other engines.

- Jan

Kmot

My Feedback: (24)

They didn't have CNC back in the 40's. The hubs were cast, and then machined with manual machines operated by machinists. Perhaps you could look around at some 'old fashioned' machine shops and foundries?