Making venturi's?

[Phil Hawkins]

If a guy was looking to make custom venturi's out of delrin and/or aluminum rods, what would be the minimum lathe required? I found some very rudimentary lathes on ebay for as little as $35-$45 with drill press type chucks, but I am obviously not looking at making high end pieces, just converting non traditional engines over to stunt.

Another question is can a 3D printer make venturi's that can endure the heat, vibration and fuel we use?

Thanks for any experience and insights!

[James Lee]

Phjl
I started with a Taig lathe.   Very smooth and accurate.   Delrin is a good choice for material.
Thanks
Jim

[Steve Berry]

Another question is can a 3D printer make venturi's that can endure the heat, vibration and fuel we use?

Fuel & vibration, yes, no problem.

Heat is another issue. There are some materials out there that can take it, to a point. The nice thing about a venturi is that it doesn't always see a lot of heat, but there is creep from the crankcase itself. It might be worth it to print a few different versions, try them, and which ever works best, turn on a small lathe out of aluminum or delrin for a finished product.

Or....contact James Lee at Lee's Machine Shop (see vendor corner) and have him do it. He's already got the setup and probably already has something "in stock" that can be used.

Steve

[Mark Schluter]

I was facing a similar situation several years ago and after looking all over I ended up with the mini lathe from Harbor Freight. I know its far more pricey and cant be justified on venturis alone, but the learning experience and other things you can do helps mitigate that. IMO you will need a "real" lathe-type chuck, a drill press type chuck for the tail and very good stability + precise control of everything. Littlemachineshop.com was a wealth of information getting me started, and venturis pose some interesting challenges in terms of the inside configuration and dimensions that you may be shooting for.

[944_Jim]

Mr. Hawkins,

I can't answer regarding a lathe. However, regarding 3d printing, I can say it is doable. I have a few custom printed horseshoe back plates for Cox reedies. The "engineer" took liberty to measure and scale down the typical Cox .049 backplate to the Pee Wee .020 engine. There is a thread on CoxEngineForum related to the construction and plastic used. So I'll take that to mean the same material can be used for a venturi.
https://www.coxengineforum.com/t13389-3d-printed-peewee-020-tank-backplate

[GallopingGhostler]

I was facing a similar situation several years ago and after looking all over I ended up with the mini lathe from Harbor Freight. I know its far more pricey and cant be justified on venturis alone, but the learning experience and other things you can do helps mitigate that.

I don't mean to derail this thread, Mark. But I am reminded of a humorous situation when 25 years ago, I purchased a Sears Craftsman (Devilbliss) air compression with 25 gallon air tank. My wife kept asking me why I needed such a piece of seemingly useless equipment. After, I'd occasionally air up tires, paint a couple items, etc.

I've had my share of time in the doghouse over things I've bought. 

[Chuck Matheny]

 The first venturis I ever made were from 1/2" alum round stock chucked up on a drill motor that was strapped to a table.
The cutting tool was a sharp screwdriver that was ground to  a "half round" contour.
The tool rest was a block of wood.
I used a  wood dowel, with a lengthwise slit cut into one end so that a scrap of sandpaper could be inserted into the slit and this was turned by the drill motor to "fine tune" the rough edges that the screwdriver laft behind.
At some later date I "moved up" to using [and abusing]a drill press....and then even later an honest to goodness $1000 lathe.....so that I can make these $10 parts whenever the mood strikes.
 "If there is a will...there is a way"....
Delrin works OK but it leaves a fuzzy surface that I found to be a pain to clean up. I'm sure there is a trick to working this material that I am not privy to.

[Chuck Matheny]

25 years ago, I purchased a Sears Craftsman (Devilbliss) air compression with 25 gallon air tank

Howdy GG....wanna impress the wife...?
She might have some  intricate nick nacks and doo dads that have all sorts of nooks and crannies that collect dust.
Harbor Freight sells a super dooper "dust gun" that some how SUPER CHARGES whatever air your compressor can deliver and it will make short work of the most tedious dusting jobs...

[Mark Schluter]

The first venturis I ever made were from 1/2" alum round stock chucked up on a drill motor that was strapped to a table.
The cutting tool was a sharp screwdriver that was ground to  a "half round" contour.
The tool rest was a block of wood.

Thats a lathe!  Historically lathes are pretty interesting; as the first true machine tool (powered manually by a string-and-bow apparatus) it opened up so many possibilities in production plus allowed for creation of more "advanced" tools.

I'll bet your first venturis worked great.  I love how human ingenuity and skills combine with artistic expression in CL stunt!

[Phil Hawkins]

I have been thinking that I would be making more than a few Venturi's every now and then, but then again, dealing with a shot of reality, probably not so much. My old faithful Craftsman benchtop drill press would suffice to get me started. If I make a couple "prototype" pieces, I can get them to a friend who is running an ebay business selling 3D printed stuff.
Thanks for the input! I will be ordering some delrin soon and will post when I have something.

[Dave Hull]

In a pinch, I've cobbled several using the drill press and a tapered reamer. Not pretty, but made more difficult by starting with the gummy nylon spacers you can buy at the big box hardware.

Much nicer was using a borrowed Unimat. Not enough stiffness to do more than Delrin, aluminum or brass--but that covers two of your likely candidates. I found the precision was definitely there after a bit of a machine tuneup. You can achieve excellent results when making venturis as long as you not in a hurry. (No big cuts. Not so much an issue of power, but of lack of stiffness in the ways, thereby resulting in chatter.) And, there are still plenty of Unimats out there having gone thru who knows how many owners.

It's nice to be able to make or modify your own. The next best thing is to have a knowledgeable modeler making them for sale to your specs. We're lucky to have Lee Machine available.

Dave

[Steve Glass]

Check out my no-lathe venturi thread on the Barton forum.  I've made a set of venturis for OS engines with 0.1mm steps. 

http://controlline.org.uk/phpBB2/viewtopic.php?t=16596&highlight=lathe+venturi

Steve

[Dan McEntee]

Check out my no-lathe venturi thread on the Barton forum.  I've made a set of venturis for OS engines with 0.1mm steps. 

http://controlline.org.uk/phpBB2/viewtopic.php?t=16596&highlight=lathe+venturi

Steve

    I would like to see more details on this method, and more information about the air filter you use. A step by step description in the engine forum would be appreciated by many, I would bet.
   Type at you later,
   Dan McEntee

[Gerald Arana]

    I would like to see more details on this method, and more information about the air filter you use. A step by step description in the engine forum would be appreciated by many, I would bet.
   Type at you later,
   Dan McEntee

Times two Dan.

Jerry

[Gary Dowler]

For $500-700 you can get an old Unimat DB200 lathe that will do a very respectable job of making venturis for you.  Check Ebay, they re on there frequently.  They can also make things like prop extensions, etc.

Gary

[Steve Glass]

Times two Dan.

Jerry

I'll start a new thread in the engine section this evening.

Steve

[Dan McEntee]

For $500-700 you can get an old Unimat DB200 lathe that will do a very respectable job of making venturis for you.  Check Ebay, they re on there frequently.  They can also make things like prop extensions, etc.

Gary

   Using any kind of lathe takes research and practice. Lots of ways that you can get hurt even using a small Unimat type machine. A lathe is very useful, and exactly what for is one of the things that you will need to learn! The lathe is the only machine tool that can be used to replicate itself! At least that is what they teach in some trade schools. It's like I say about any tool, (even hammers !!) it's only as good as the nut on the handle!! I learned on the job out of necessity how to use lathes, mills, surface grinders and such and always had access to them where I was working at. In job interviews I just called my self  "a meatball machinist", familiar with hand operation of most basic machine shop machinery. Now that I have retired, I miss that access A LOT!! I have an Atlas 10" lathe that I need to get operable. It came out of a notable race car fabricator's shop in Indianapolis by way of my late younger brother who had his own machine shop business. I also got a smaller 6" Sears bench top lathe that needs to come out off the shelf to get running for small stuff. I just need a major clean out and rearrangement of my garage to achieve both!! The biggest one I ever saw was at the machine shop that I first went to work for 40 years ago or so. It came out of ship yard on the east coast some where. You had to climb a ladder to get up to the operators station!! I think it could handle up to 10 feet swinging over the bed and was at least 50 feet long  !! I think it was made for working on turbine and main drive shafts for ships and submarines and the like.
   Type at you later,
   Dan McEntee

[Dan McEntee]

I'll start a new thread in the engine section this evening.

Steve

  Thanks Steve!! This may really come in handy.
  Type at you later,
  Dan McEntee

[Gary Dowler]

   Using any kind of lathe takes research and practice. Lots of ways that you can get hurt even using a small Unimat type machine. A lathe is very useful, and exactly what for is one of the things that you will need to learn! The lathe is the only machine tool that can be used to replicate itself! At least that is what they teach in some trade schools. It's like I say about any tool, (even hammers !!) it's only as good as the nut on the handle!! I learned on the job out of necessity how to use lathes, mills, surface grinders and such and always had access to them where I was working at. In job interviews I just called my self  "a meatball machinist", familiar with hand operation of most basic machine shop machinery. Now that I have retired, I miss that access A LOT!! I have an Atlas 10" lathe that I need to get operable. It came out of a notable race car fabricator's shop in Indianapolis by way of my late younger brother who had his own machine shop business. I also got a smaller 6" Sears bench top lathe that needs to come out off the shelf to get running for small stuff. I just need a major clean out and rearrangement of my garage to achieve both!! The biggest one I ever saw was at the machine shop that I first went to work for 40 years ago or so. It came out of ship yard on the east coast some where. You had to climb a ladder to get up to the operators station!! I think it could handle up to 10 feet swinging over the bed and was at least 50 feet long  !! I think it was made for working on turbine and main drive shafts for ships and submarines and the like.
   Type at you later,
   Dan McEntee

Meatball Machinist....I like it.  Thats sort of my title as well.  everything I know about the machining, I have learned on this job.  We dont do anything with metal, its all machining carbon brake disks for aircraft (last night was C-130's, tonight its 737-9's).  Attached is a pic (web image) of what Im running as I type this.  Two chucks, one at each end, pivoting spindle can work either direction (plus vertical), automatically transfers the part from one chuck to the other (OD clamp on one end, ID clamp on the other), etc.  Does all lathe and mill work in one operation. Load a part on one chuck, take it off the other chuck at the end.

Edit:  cant upload the web image   Look up Mazak E-420H-S

[Steve Helmick]

Quote from Chuck Matheny..."Delrin works OK but it leaves a fuzzy surface that I found to be a pain to clean up. I'm sure there is a trick to working this material that I am not privy to."

Sharp cutters are the deal with any sort of plastic, fairly low rpm and fairly high feed rate. REAL Delrin is very nice stuff, but I'm not a fan of the generic version, which is called "acetyl". A length of 5/8" Delrin rod is 10' and probably under $20...though I haven't bought any in years. They'll probably cut it in half for you for free, if it won't fit safely in your vehicle. Nylon and UHMW are MUCH WORSE!

If I turn the end of a Delrin rod just a gnat's butt too large to fit into the crankcase, I've found that it sands pretty nicely with 400 > 600 grit. My procedure is to face the end, center drill, double drill to finish size, turn the spud that goes into the crankcase/throttle boss, then do the other end. There, I start by bandsawing off with excess, face it off to a length I like, and use a single flute countersink to rough in the bellmouth. A little scraping with a #11 Xacto finishes it off. That part needs some experimenting with rpm, angle you hold the Xacto knife, pressure, and how sharp it is. Too much rpm is no bueno. 

My lathe is a Grizzly 4" that they don't sell anymore. It's the same as a Hobo Freight 4" lathe, except cost more, it's green and has a longer bed. The length was why I got Grizzly. Micro Mark sells an even longer version, for even more money. From what I've read, they all come out of the same factory in PRC, and the factory has a basic menu of options for the importers. Length, brand name, color, and even tolerances are on the menu. Not a bad little unit for intake restrictors, plus spinner and head mods. The thing I don't like is that the dial on the cross feed is metric...about .040" per hashmark, ...that's one mm per side of your part. Big lathes sometimes were per side, and some refer to the diameter...which I prefer. But never fear, there aren't any manual lathes made in America anymore, so you just gotta deal with it.

I've reworked spinner backplates, counterbored spinner cones, modified spinner adapters, and cleaned up cylinder heads that had ugly 'scuff marks' on the top of the fins. Also have used it to modify a pendant  lamp for the bathroom remodel, and make a new pivot pin for the neighbor widow's yardwaste bin lid...among the more spouse pleasing projects. I'm a retired machinist, from 1974 until 2010.

Planning your sequence of operations is KEY. Otherwise, you might find yourself with no good way to hold onto the part. 
    Steve