Elbows are the most labour-intensive fitting on a round duct line, and for most shops they're also the most subcontracted. The machine that changes this — the gorelocker — forms the locks on curved elbow segments directly, so you stop cutting, rolling and hand-locking each gore. The real question isn't "hydraulic or electric," it's which one your diameter mix and material force you into.
This page gives you the geometry first (because that decides machine choice), then the hydraulic-versus-electric decision, then the springback numbers we use on the shop floor.
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What Actually Decides Hydraulic vs Electric
Forget the brochures. Four answers on your side of the table settle the choice, and they're all about your work, not the machine's spec:
- Largest diameter you form. Above roughly 630 mm, an electric frame won't hold the short-radius segments without springback — hydraulic is the only practical answer.
- Material. Stainless or anything over 1.2 mm needs hydraulic force. Galvanized up to 1.0 mm is electric territory.
- Power available. Hydraulic units want three-phase and a fixed station. Single-phase or a machine that has to move around site points to electric.
- Volume. Under 30 elbows a shift, electric keeps up. At 60+, the hydraulic machine's speed and repeatability earn their premium.
Mixed answers are normal — the common configuration is one hydraulic unit for 450 mm and up plus an electric machine on a mobile stand for site and small-diameter work.
Elbow Geometry: Segments, Radius and What SMACNA Allows
An elbow is defined by three numbers: diameter, centre-line radius and the number of segments. Get these wrong and the fitting will not match the straight duct, or it will whistle at high velocity.
| Diameter | Min segments (90°) | Standard centre-line radius | Recommended gore pattern |
|---|---|---|---|
| 100 – 200 mm | 5 | 1.0 × D | 5-gore |
| 250 – 400 mm | 5 – 7 | 1.0 – 1.5 × D | 5-gore |
| 450 – 630 mm | 7 – 9 | 1.5 × D | 7-gore |
| 710 – 1000 mm | 9 – 11 | 1.5 × D | 9-gore |
| 1100 – 1600 mm | 11 – 15 | 1.5 – 2.0 × D | 11-gore |
Why Segment Count Drives Machine Choice
A 5-gore elbow needs one gore profile and four identical intermediates. An 11-gore elbow needs far more individual pieces, each cut and locked. Hydraulic gorelockers hold the short-radius segments that a light electric frame cannot form without springback, which is exactly where the two machine types diverge. If your work is mostly 100–400 mm, an electric unit is sufficient. Above 630 mm, or on stainless, the hydraulic machine is the only practical answer.
Calculating Gore Blank Dimensions
Each gore in a segmented elbow is a portion of a truncated cone. The standard layout uses the neutral line of the bend.
- Angle per gore = total elbow angle ÷ number of gores. For a 90° 7-gore elbow using two half end-gores and five full intermediates: end gore = 90/(2×6) ≈ 7.5°, intermediate = 15°.
- Developed gore length = π × centre-line radius × gore angle ÷ 180.
- Blank width = developed length + two lock allowances (typically 2 × 12 mm for a Pittsburgh lock on spiral tube).
- Blank height = π × diameter ÷ number of segments around the circumference, plus seam allowance.
Shortcut for Spiral Tube Elbows
Because the gorelocker forms the lock directly on the cut blank, you do not need a separate lockformer for the curved seam. Cut the blanks on the plasma or shear, then form. Shops that switch from "cut, roll, hand-lock" to a gorelocker typically cut elbow labour from 25 minutes to 6 minutes per fitting.
Hydraulic vs Electric: The Decision in Four Questions
| Question | Answer points to hydraulic | Answer points to electric |
|---|---|---|
| What is your largest diameter? | Above 630 mm | Below 400 mm |
| What material do you run? | Stainless, or 1.2 mm and up | Galvanized up to 1.0 mm |
| Do you have 3-phase power? | Yes, and a fixed station | Single phase, or machine must move |
| How many elbows per shift? | 60 or more | Under 30 |
Mixed answers are normal. A common configuration is one hydraulic gorelocker for 450 mm and up, plus an electric unit on a mobile stand for site work and small-diameter jobs. The two together cost less than one large hydraulic machine with full tooling.
Springback Compensation by Material
Springback is what separates a good elbow from a fitting that needs persuasion on site. Compensate by over-bending, and by understanding that stainless springs back roughly twice as much as galvanized.
| Material | Springback, 90° bend | Over-bend required | Notes |
|---|---|---|---|
| Galvanized 0.7 mm | 2 – 4° | 3° | Predictable |
| Galvanized 1.0 mm | 2 – 3° | 2.5° | Predictable |
| Aluminium 1.0 mm | 4 – 7° | 5° | Softer, more variation |
| Stainless 304, 0.8 mm | 6 – 10° | 8° | Requires hydraulic machine |
| Stainless 304, 1.2 mm | 8 – 12° | 10° | class="best">Check machine rating first |
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View Product Details →Frequently Asked Questions
How long does delivery take?
Standard machines ship within 15-30 days of order confirmation. Custom configurations may take 30-45 days. We provide production progress videos throughout the manufacturing process.
Do you provide installation and training?
Yes. We offer detailed installation manuals, video guides, and optional on-site installation by our engineers. Most customers are fully operational within 3-5 days of receiving the machine.
What about spare parts?
We keep common spare parts in stock and ship them free of charge worldwide. Critical components like PLCs and motors are industry-standard and available locally through our agent network.
Can I see the machine before buying?
Absolutely. We encourage factory visits and can arrange live video inspections. You can also review our 159+ product demonstration videos on our video page.