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GrizzlyV6

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Jan 15, 2012
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135
Location
Lee's Summit, MO
Yup , and not
I need close to 2000RPM on prop (67") and i have max hp at ~8000rpm
Lots of info here:
Redrive-design : Redrive-design
register!
And you should check Dave Blanton's design it seems to be the most reliable (over 2000hs and working)

Dave Blanton passed away back in the 90's. No one picked up his redrive for continued production. Dave's 2.0:1 ratio gave way to the 1.6:1 because Dave said "HE WAS TRYING TO TURN THE ENGINE TOO FAST". You see, oddly enough, Dave Blanton and Jess Meyers were friends. One worked with the Ford, the other worked with the Chevy. It was merely a matter of preference.


Jim
 

Toobuilder

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Jan 19, 2010
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... It makes no sense to me to spend 35k on the low end to have a product "engineered" then not follow the engineering details....

...Happens all the time - particularily in aviation! We perform all kinds of engineering services that are never realized by our customer. We are paid to perform a service (invent stuff) and deliver the product (drawings). We don't follow up on whether our customers have turned the drawings into metal or not. We get paid to perform a service - what happens after that is none of our business.

Heck, I have $12k invested in drawings for a house that I never built - does that mean the architect didn't know what they were doing?
 
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orion

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Mar 2, 2003
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5,800
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Western Washington
Well, I did answer earlier today in somewhat more detail but unfortunately lost the post. I'm using one of the new mice from Apple but the touch top surface tends to be too sensitive so all it takes is an accidental brush to make things happen. This time it made a post disappear faster than I could blink.

Interesting story... Can you share more details on your designs ? The first one for the rotary apparently didn't get fully tested to prove its viability, strength, safety and durability as the company, according to you, ran its business improperly. The second one for the Subaru was put on the prototype only. Did it have any documented flight time ? how many hours ? Where is it now ?... Again, according to you it never got put into production so validating its potential is rather hard since it didn't get tested properly.
There were two drives developed for the rotary - the first one failed on the dyno due to a machine shop's failure to maintain tolerances on one of the planetary carriers. The drive used a common sun gear between to planetary clusters. The tolerance mismatch caused one set of gears to fight the other, which resulted in gobbs of friction that eventually simply cooked the bearings. The second drive was simplified a bit and ran fine. The drive had about twelve hours on the dyno before I left the program. But no, it did not fly.

The second drive was flown and last I heard (about ten years ago) it had about seventy or so hours on it operating in the Canadian bush.

But all this is not really the point - I do have the proper background for machinery design and I have worked in the capacity at a number of levels for quite some time but despite that, I wasn't so much interested in being in the redrive business. My responsibility is to my customers - when they ask me to evaluate a product for them I do so in the interest of their safety, not to come down on the industry. But I am critical of much of the industry simply because of the things I've seen and the attitudes i've come across, especially from redrive manufacturers who make very pretty products but have absolutely no engineering background that would allow them to fully stand behind the product.

Understanding the practical aspects of redrive design and fabrication, in addition to the engineering ones, is critical. I've often said, even in print, that I'd rather have a single really good machinist who understands the engineering process rather than a bunch of engineers who have never built anything. But in the same breath, I would never recommend to any of my customers to sit behind a product that has had no functional engineering behind it.

This ability to evaluate functionality and safety doesn't require that I have built a redrive, or anything else for that matter, as long as I understand the engineering issues at hand. It does not take a flight test program to have a person understand that if you make a shaft with a dramatic diameter change, with a sharp corner between them, that that shaft may be prone to failure due to the stress concentration at the juncture. Nor does it take a rocket scientist to understand that when you have a thousand foot-pound gyroscopic load on the prop and you support the output shaft with bearings only three inches apart, that you may be putting the bearings and the redrive case at risk. Or that if you have a set of high rpm gears and your only lubrication is a bath at the bottom of the small gear, that you may destroy the gears in short order due to lack of direct oiling. All these things, and many like them, are very basic yet I see similar examples over and over.

I guess my question is................ Do you actually have ANY redrives that have been properly tested, validated and analyzed by someone else to confirm your designs are legit ? Do you sell yourself to lawyers as a "expert witness" without any real world history of designing a operational redrive ? As you know it is very easy to draw something on a piece of paper, stamping it with a engineering stamp and claim it will work......People do stuff like that every minute......
I agree but quite frankly, I'd have more faith in a stamped design done by a qualified engineer to a much greater degree than something cranked out by a hobbyist who has no theoretical knowledge behind the product he's trying to sell me. Mind you that's not to insult the machinist, it's just a simple statement of fact simply because that machinist is asking me to put my life on the line with absolutely no proof claimed functionality. Any responsible drive manufacturer must be able to quantify the design - if they cant then they're no better than the old style snake oil salesmen, no matter how shiny it is or how "sturdy" it looks.

And just to give you a condensed version of my background - I started out working as a mechanic, eventually working my way into a shop that specialized in exotics and racing products. At the time I also had a bit of involvement with racing (amateur level) and restoration. Following that I worked as a machinist and sheet metal fabricator (Boeing), before going to the university to get my degrees (Mechanical Engineering with a minor in Aeronautical Engineering).

Although I made my career in aerospace, I kept my connection to my earlier work by maintaining an involvement in the Society of Automotive Engineers for about fifteen years after. This allowed my to stay current with the technological changes in metallurgy, drive train component design, lubrication, etc. I've consulted and provided engineering assistance on a number of drivetrain programs, the largest being the power system (water and air) on the Westfoil hydrofoil, which was wholly my work.

So to answer your implied criticism, I do have a fairly good background in mechanical design and manufacturing, although I choose not to make it my career. And as such, I do offer my services to other companies, as well as to customers who may have interest in following some form of legal action against suppliers of poorly developed products. I really don't like to do the latter as I do try to support our industry, but unfortunately there are some out there who really shouldn't be in business.

My suggestion is to market your designs to people like the OP here so they can build their own redrive.
I've thought about it but really, given the amount of time investment to do this right, I really don't have the time and realistically, it's not a business to hang one's hat on. The volume of sales, even assuming a perfect product, just isn't there to make a living off of. But one of these days i'd still like to do a boosted inverted V-8, direct drive. But business comes first, oh well.
 

Toobuilder

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I think this thread is a good example of why people line up to by something like a FWF package based only on the fact that it has flown once or looks pretty. Engineering expertise is so often trumped by "Well, it works on Jimbob's, cousins airboat, so it MUST be OK on my Lancair IV".

I'm glad our customers don't hold us to the unrealistic standard of producing several thousand units of an item before they are willing to shell out their money. We get contracts for millions of dollars to design and fabricate things that heve never been built before... Because that's what engineers do.
 

bmcj

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Apr 10, 2007
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Fresno, California
A few thoughts here....

FIRST, engineering is not an end-all to the process of designing and building a successful project; neither is fabrication an end-all to the process. Each has its place in the development cycle. engineering can help develop a direction and rule out unworkable ideas before moving on to the costly fabrication phase. Conversely, fabrication and testing proves out the engineering and shows what works and what needs improvement or redesign. Going straight from concept to fabrication and testing might work because successful fabricators develop a little "natural sense" of engineering, but by no means the ability to fully engineer a product. Going straight from concept to fabrication stands the costly risk of failure for something that a qualified engineer may have been able to identify in advance.

Beyond design and fabrication, there are other processes (financing, marketing, etc) which have nothing to do with engineering or fabrication, but still play an equal role in the success or failure of the design. Failure of the financing or marketing does not equate to failure of design or fabrication.

SECOND, this conversation has taken a strange turn that I do not understand, and it is (in my opinion) not healthy for this forum. It seems that it has gone from a redrive engineering discussion to more of a witch hunt for certain people or skills. Oddly enough, all of the players involved in this are normally reasonable, level-headed members. I find myself thinking that this part of the thread be broken out into a separate thread, but I also wonder if it should also be squelched or locked.



Come on guys, let's keep this civil and friendly. No reason to call someone's skills or trade into question... I see no one making any false claims here.
 

Topaz

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Orange County, California
...SECOND, this conversation has taken a strange turn that I do not understand, and it is (in my opinion) not healthy for this forum. It seems that it has gone from a redrive engineering discussion to more of a witch hunt for certain people or skills. Oddly enough, all of the players involved in this are normally reasonable, level-headed members. I find myself thinking that this part of the thread be broken out into a separate thread, but I also wonder if it should also be squelched or locked.
Thanks Bruce. You're right. This thread has gone far off-topic, and into a really strange place. As the moderators were just talking about this sort of thing the other day, I think this is a good place to begin. I've deleted most of the off-topic stuff (including my own), keeping what I thought was even remotely relevant to the OP's question.

Please note: Some of you had posts that weren't argumentative, but were part of the off-topic stream. No offense intended with the deletion - I just want to get this thread back on the rails. If it doesn't, or if this conversation about the original topic is over, I'll lock it down.
 

hogheadv2

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Feb 7, 2010
Messages
127
Location
Booger finger of Michigan
SuperChargers and Open belt Drag bikes have used them forever, [Belt primary harley type]
I have seen hundereds go 50 to 80k miles running next to the dirty road, shocked every shift, rain, trash, and some bootlaces fed though them. All fine.
Bearing load is what your design will need to be most concerned with.

**** I have often wondered why a homebuilder has not used Quick change gears for a PSRU? Easily take 600-800 lb-ft TQ. [Winters / Franklin ] [Tiger quick change]
May be worth building to fine tune engine RPM.
 

clanon

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Jun 6, 2007
Messages
1,101
Yup! it seems like the transmission of choice , will be Cogged Belts replacing even chains on some applications...
Time will say.
 

Jay Kempf

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Warren, VT USA
SuperChargers and Open belt Drag bikes have used them forever, [Belt primary harley type]
I have seen hundereds go 50 to 80k miles running next to the dirty road, shocked every shift, rain, trash, and some bootlaces fed though them. All fine.
Bearing load is what your design will need to be most concerned with.

**** I have often wondered why a homebuilder has not used Quick change gears for a PSRU? Easily take 600-800 lb-ft TQ. [Winters / Franklin ] [Tiger quick change]
May be worth building to fine tune engine RPM.
You are right, but it isn't just bearing loads (meaning loads and reactions), it can be dynamics. Bearing loads have several categories and then there are the rest of the assembly parts to deal with. Stiffness when dealing with belts is a big deal mainly because most people do not hold the cogs from both sides. They are normally cantilevered slightly. Bearing loads have to also be reconciled over the entire RPM range as well because the largest vibration peak may not (read normally isn't) at the peak RPM or the largest prop force that the entire assembly will see. The good news is that the boat people deal with for the most part the same thing as long as you aren't talking about comparing a boat to a competition aerobatic aircraft it is probably a good comparison. Every time I run through the numbers it isn't the trust load. The RPM of the bearing at the nose of the crank is problem one for RPM and axial load is the first problem and then the next order of magnitude is the radial forces and stiffness of whatever holds onto the prop next. Then after that you have to look at the largest vibration peaks and make sure that the first two design choices will cover that last one. Few times I have looked at a belt drive did I find that covering the first two didn't give me an adequate bearing selection for the third and in the case of the not having adequate bearing selection for the third looking at a damper was a better solution than upping the specs on the weak bearing choice. The reason being if you are leaving those peaks and haven't isolates say your automotive crank from it then you have other issues to reconcile. Once working with a customer on a non aviation design we were limited to designing around a single Timken bearing part number because Dn got in a corner where there are almost no off the shelf solutions. With belts stiffness of the housing that the whole thing is mounted in is a huge factor.

As far as quick change gears like the Porsche G50 for instance, that is a great off the shelf parts library to pull a matched ratio set from. But like everyone has already stated it is the vibration peak that is the killer. I believe as well that there are existing tranny gears that are adequate to the task if the design is handled correctly. One way to do that is imagine building a reduction gear output bolted to the front of the motor. Then build an entire prop adapter isolated from that. Use a one to one belt with a damper on it. Then the reduction drive is isolated from the prop forces and the prop forces and stiffness are not part of the reduction drive. Complex and probably too heavy but is separates the failure modes and puts the prop bearings in the RPM range of the prop and the motor bearings in the RPM range of the motor without seeing the prop peaks so protecting the weaker automotive crank.
 

clanon

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Jun 6, 2007
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What about viscous dampers ?
And yes the PTO of the crankshaft should have a massive external bearing on a real rigid support...
And what yoy mean by:
" because the largest vibration peak may not (read normally isn't) at the peak RPM or the largest prop force that the entire assembly will see"
could it be that vibration shift my maximum RPM up ?
and if so , how much could it be ?
 

whiteknight

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Jan 19, 2011
Messages
36
Location
Medford, Oregon/USA
Yup , and not
I need close to 2000RPM on prop (67") and i have max hp at ~8000rpm
Lots of info here:
Redrive-design : Redrive-design
register!
And you should check Dave Blanton's design it seems to be the most reliable (over 2000hs and working)
How can I open that file? What format is that? I want to have an open minded look at as much information as possible. Thank you.

Jason
 

clanon

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Joined
Jun 6, 2007
Messages
1,101
Any CAD applicationWhat are you engine specs and propeller you want to use ?PS: that will be max HP (continuous) @RPMYou should start with an adjustable prop (land) to get close to engine specs.and see what your goal is ; thrust or speed (for the prop i mean)And this is how i choose my bearings:SKF - Design / performance search6061 is the most used supporting metal4140 and 4340 steel are the most used on the shaftsMine is a modest project ~ 50 hp
and this group :
AirSoob : AirSoob
 

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TXFlyGuy

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Apr 25, 2012
Messages
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Republic of Texas
You would have to give Jess a call for current pricing on the redrive. You can get long block engines delivered to your door for less than 2500 bucks. A good source for those are S&S engine rebuilders in Washington state. PRE COUNTERBALANCE SHAFT ENGINES. Do the neat little mod of vortec heads on the pre-vortec block and now your over 200hp out of the little v6 at the 4000 rpmpeak. I know you can get the geared airboat redrive rated for 1000 hp for 2100 bucks.

Your Bearhawk and my Bushmaster aren't far apart as far as type. I got with Craig Catto about the prop. Craig designed a prop for me that is slightly bigger than what took first place in Valdez last year. It was an 80x37 I believe. Mine is 80x54 but has a cord of 7 1/4 inches.


Jim
You can get an "aluminum" long block for this price? I would be interested if you can!
 
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