Rolling the shapes for a lockwood hiller pulsejet?

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pulsejetter
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Rolling the shapes for a lockwood hiller pulsejet?

Post by pulsejetter » Tue Jun 07, 2011 4:33 pm

Hi all, i'm building a 55LBS lockwood hiller as per bruce simpsons plans.

Can anyone tell me if the shapes can be rolled on normal horizontal slip rollers/ sheet metal rollers? The transition cones (3 off), do they need tapper rollers to roll them into shape?
How do people usually do this, because i've been to an engineering workshop and he says he cannot roll any of the metal, so i would like to know if for example the combustion chamber and inlet tube can be slip rolled on a normal sheet metal roller?

And is there a way to roll the cones up without tapper rollers?

Thanks a lot for your help.

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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by Mike Everman » Tue Jun 07, 2011 5:07 pm

Put a steel pipe horizontally in a bench vise, grab a hard rubber mallet and start pounding. You'll get good at it in no time.
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pulsejetter
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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by pulsejetter » Tue Jun 07, 2011 5:09 pm

Thanks for the reply.
Is that how most people form their pulsejets then?
This engineer place has a slip roller but says he cannot do the cones or the exhaust etc, is it possible to do cones on a normal slip roller?

Thanks.

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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by PyroJoe » Tue Jun 07, 2011 5:24 pm

It usually depends on the length of the cones and the minimum diameter of the cone. Sometimes its required that the cones be done in sections if the lengths are to long. Alot of variables.

Typically, If the cone is short, the rough shape can be slip rolled in one of these:
viewtopic.php?f=7&t=1776

and the fine imperfections worked out with a mandrel like this:

Larrys Rolling Mandrel
viewtopic.php?f=7&t=3971

Typically on the mandrel I lightly hammer the middle of the cone while turning it, making the strikes spiral out until reaching the ends.
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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by Mike Everman » Tue Jun 07, 2011 5:37 pm

http://www.youtube.com/watch?v=ekicY_oNE7I

Poke around some vids. Mine have all been hammered, and yep, sometimes you have to do sections.
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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by PyroJoe » Tue Jun 07, 2011 6:07 pm

Ha,
The ole bash it 'till it fits in the vise technique:

http://www.youtube.com/watch?v=f88__yAONNo

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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by pulsejetter » Tue Jun 07, 2011 7:11 pm

Thanks everyone for the links and videos etc.
But i did ask if you can roll cones in a normal slip roller as would be found in most engineering workshops?
Or is a taper roller needed?

Because i'd rather get them rolled on a slip roller than by hand tbh, i will be welding them though.

Thanks.

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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by Mike Everman » Tue Jun 07, 2011 7:46 pm

The answer is yes. The video link I posted shows exactly that, on a big one, but the method is the same. Just try, you'll see in short order what to do.
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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by pulsejetter » Tue Jun 07, 2011 8:48 pm

Mike Everman wrote:The answer is yes. The video link I posted shows exactly that, on a big one, but the method is the same. Just try, you'll see in short order what to do.
Great thanks for the answer and the link. I'll be going down to see if it can be done on saturday, so fingers crossed.

Thanks.

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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by Jack S » Mon Jun 13, 2011 6:02 am

Hi,
I am also trying to build Simpson's 55lb thrust Lockwood, and have a similar question so I thought I would post here instead of making a new thread.
I am using 16 gauge mild steel to construct it. I managed to make the smaller cones on either end of the combustion chamber, but I am finding it very difficult to form the cylinders of the combustion chamber and the intake tube and large exhaust cone. A slip roller that can handle 16g mild will cost at least $1000 and I don't want to spend that much. I called up a sheet metal workshop and they said it would cost about $800 if they formed all the parts for me, so I am definitely not going to pay that either.
I finally resorted to using a sandbag and an egg-shaped metal forming dolly and cutting the combustion chamber sheet in half. I can get a curve in the metal, but I am finding it impossible to get the curve consistent along the length of the cylinder. One end is always a bit skewed off to one side, and the two halves don't match up. I don't see how hammering around a thick steel pipe will be any different. Does anyone have any suggestions?
Is 16 gauge just too thick to form by hand? Do most of you guys use 18 or 20g instead of 16g? I was worried that if it was this thin the mild steel might melt. If not, is it worth buying some thinner sheet?

On an unrelated note, what happened to the Beck Technologies website? I found it very useful a few months ago but now it seems to be down.

Thanks

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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by PyroJoe » Mon Jun 13, 2011 1:20 pm

Hi Jack,
I use 16 gauge mild in some of my larger chambers. When going very large in diameter I use a wooden post mandrel that is slightly smaller in diameter than the chamber. It must be relatively round on the portion you will be hammering against, and able to withstand repeated striking. The process may be lengthy and exhausting to achieve good results, plan to take several hours with many 15 min. rests. Apply cold beverages as needed.

18 is about as thin as I like to go for the bigger stuff. Stainless will tolerate thinner thickness to a point.

There is a relatively simple technique to correct the skew (if its the type i'm thinking of), I'll post the method in a illustration. It may require repeated correction during the process. If it is close, I usually will apply a weld tack to the top corners as they come together. After the a tack is applied to each end of the seam, and one in the middle, I usually continue the above spiral hammer pattern. Flipping ends occasionally. Use big hammers striking softly to form, try to avoid significant dents, after it is near done, use smaller hammers to smooth out any dents from the large hammer.

Not sure what is up with Eric.
Welcome to the forum :D
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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by Mike Everman » Mon Jun 13, 2011 4:28 pm

Eric is out of the business as far as I know. its never been easy to reach him in the best of times.

Best to just start hammering. It's very satisfying work, and you'll get the hang of it in short order.
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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by Jack S » Tue Jun 14, 2011 10:26 pm

Thanks for the replies.

PyroJoe wrote:I use 16 gauge mild in some of my larger chambers. When going very large in diameter I use a wooden post mandrel that is slightly smaller in diameter than the chamber. It must be relatively round on the portion you will be hammering against, and able to withstand repeated striking.


The problem is I don't really have anything that is as thick as 7 inches around. I tried placing a thick PVC pipe in a vise, but it kept slipping out when I hammered around it.
I guess I will keep trying with the metal shaping dolly until it very slowly gets into shape.
PyroJoe wrote:The process may be lengthy and exhausting to achieve good results, plan to take several hours with many 15 min. rests. Apply cold beverages as needed.
Yeah, this Texas heat is killer.
PyroJoe wrote:18 is about as thin as I like to go for the bigger stuff. Stainless will tolerate thinner thickness to a point.
If I decide to build another pulsejet, I will definitely use a thinner gauge. Is 18g significantly easier to work with, or is the difference only slight?
PyroJoe wrote:There is a relatively simple technique to correct the skew (if its the type i'm thinking of), I'll post the method in a illustration. It may require repeated correction during the process. If it is close, I usually will apply a weld tack to the top corners as they come together. After the a tack is applied to each end of the seam, and one in the middle, I usually continue the above spiral hammer pattern. Flipping ends occasionally. Use big hammers striking softly to form, try to avoid significant dents, after it is near done, use smaller hammers to smooth out any dents from the large hammer.
Yes, that is the skew I meant. When I tried your method of hammering on the top, the metal kept bending bending around instead of shifting that side downwards, if you understand what I mean. I think it might have helped fix the skewness a little bit, but I am not really sure. Maybe it has to do with the fact I am using half circle pieces instead of a full circle. I might just try flattening that piece and starting again.

Thanks

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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by PyroJoe » Wed Jun 15, 2011 4:31 pm

Pretty much anything at 18 or thinner in mild steel is a cakewalk (unless it has been unusually tempered).
Sometimes you have to open up the wide end of the cone and hit with the narrow end on the wooden block before it bends correctly.

Look at it closely before opening the wide end, it will almost be intuitive after you see which side needs to be opened.

Typically the narrow end requires the most attention. The spiral hit pattern can be reversed going from the narrow end to the middle to help work the skew back into the cone. A repeated process of end hits on the wooden block, and sprial hits working from the narrow end back into the cone typically will correct it. Apply the most attention to the narrow end until you can apply stitch weld or two.

Alot of sweat equity in 16 gauge.

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Re: Rolling the shapes for a lockwood hiller pulsejet?

Post by rob1 » Thu Jun 16, 2011 12:44 am

I use just 2- 2inch pipes on threaded rods mounted on a stand to beat the cones and pieces into shape, larger pieces hand bent using 16G mild steel while placed between the 2 pipes total cost of the contraption was around 30$ , it was made from a picture metiz showed me.. works charms
Built the AFW and the M40 using it. PS the wooden block is most of the time a must.

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