The distance between “please quote” and a workable quote is almost entirely explained by what is in the first email. A custom cylinder enquiry with the right twelve items gets a price, a lead time and a drawing within days. The same enquiry without them gets a request for more information, and the round trip usually costs a week each time.
This is not a design process. It is the information set that makes a design unnecessary.
The twelve items
1. Bore and stroke, or the load and the space. Either pair works. Bore and stroke if you have a cylinder being replaced; load and available envelope if you are sizing from scratch. The second is safer, because a replacement order copies the old cylinder’s compromises along with its dimensions.
2. Working pressure and the pressure you actually run. These differ more often than expected. If the machine runs at 180 bar, quoting a 250 bar cylinder buys nothing. If it runs at 250 bar, a 180 bar cylinder is a failure waiting for the relief valve to be adjusted.
3. Mounting type at both ends, with a drawing. Clevis, flange, trunnion or lug at the base; eye, fork or spherical bearing at the rod. Specify by ISO 6020/2 code where possible, because a code is unambiguous and a photo is not.
4. The envelope: retracted length, and what it has to fit inside. Retracted length is the single most common cause of a quote that cannot be installed. Measure the actual space on the machine, not the old cylinder, and state whether 10 mm of extra length would be acceptable — that one concession often unlocks a stronger design.
5. Duty cycle: strokes per hour, per day, per year. This is the number that sets seal material, rod finish and rod diameter, and it is missing from most enquiries. “Continuous”, “intermittent” and “occasional” are not numbers.
6. Side load and misalignment. Does the load line stay on the cylinder axis, or does the geometry swing? Is the bracket machined or welded in the field? Both answers change the rod diameter and whether a spherical bearing is required.
7. Fluid type. Mineral oil, water-glycol (HFC), phosphate ester or biodegradable. This decides seal material and rod material, and it is not a detail — water-glycol and a chrome-plated carbon steel rod are a bad combination unless the plating is perfect.
8. Temperature range. Ambient and fluid, both ends. Cold start viscosity affects the first few seconds of operation; high ambient temperature halves oil life roughly every 10 °C above 60 °C.
9. Port size, thread standard and orientation. BSPP, NPT, SAE straight thread or metric, and where the ports sit relative to the mounting. Port orientation is a frequent rework cause: a cylinder that is otherwise identical will not fit if its ports point at the frame.
10. Rod end thread or pin dimensions. Thread size and pitch, or pin diameter and width. This is the interface to your machine and it is the item most often quoted wrong, because it is the item most often assumed.
11. Quantity: first order and annual repeat. Lead time and tooling decisions depend on it. A one-off and a 500-per-year program are different engineering problems, and quoting them the same way produces a bad price in one direction or the other.
12. What the cylinder is replacing, if anything. A photo and the old part number, or the machine make and model. Interchange work is far more reliable from a sample than from a description.
The six most commonly missing
In practice, four to six of the twelve are absent from the first email. Ranked by how much delay they cause:
| Missing item | What it causes |
|---|---|
| Retracted length with tolerance | A cylinder that cannot be installed |
| Duty cycle | Seal and rod specified for the wrong service |
| Port orientation | Rework or a hose that will not route |
| Mounting code | A quote that is technically right and mechanically wrong |
| Fluid type | Seal material that fails in months |
| Annual quantity | A price that does not reflect the real program |
The pattern is that the missing items are cheap to provide and expensive to guess. Ten minutes with a tape measure and a camera usually supplies six of them.
What a drawing should contain
If you are sending a drawing rather than a specification, six things make it quotable without a follow-up:
- Overall retracted and extended length, with tolerances.
- Mounting dimensions — pin centres, bolt hole pattern, flange thickness.
- Rod end geometry — thread, pin or eye dimensions.
- Port locations and thread specification.
- Stroke, and whether a stop tube or cushion is required at either end.
- Material and finish requirements where they matter — rod material, coating, paint specification.
Our own model tables use dimension letters for exactly this reason. The underbody telescopic table carries L, A, B, C, D and E alongside stroke and working volume, so an installer can check every interface against a drawing without asking which dimension meant what. If your drawing uses the same structure, the quote comes back faster.
Why the load case beats the part number
When an existing cylinder is being replaced, the instinct is to copy it. That is usually right and sometimes wrong, and the way to tell is whether the failure was a wear-out or a design issue.
If the old cylinder wore out after years of service, copy it. If it failed in months, copying it reproduces the failure. In the second case, send the load, the stroke, the cycle count and the failure mode, and let the replacement be sized from the load rather than from the old part.
A useful test: if the old cylinder’s rod is bent, the replacement needs a larger rod. If its barrel is cracked at the base weld, the replacement needs a different mount or a counterbalance valve. Neither is fixed by ordering the same part number.
What a good quote contains
You should expect, without asking:
- The model or the custom drawing reference, with bore, stroke and pressure rating.
- The mounting code and rod end type.
- The seal material and rod specification, stated rather than implied.
- The test pressure and whether a per-unit record is provided.
- A lead time range, and the quantity it applies to.
- What the quote excludes — hoses, mounts, valves, freight, and who owns dimensional responsibility for a drawing you supplied.
If a quote does not state the last two, ask. They are where disputes start.
When the drawing you send is the problem
A surprising share of custom orders go wrong because the drawing is internally inconsistent: the retracted length and the stroke do not reconcile, the port positions land inside the mounting bracket, or the rod end thread is a size that no standard rod end is made in. Those errors are not caught by quoting faster; they are caught by quoting from a drawing that has been checked against the machine.
Three reconciliation checks take two minutes and prevent most of it. Does retracted length plus stroke equal extended length, within the piston and gland thicknesses? Do the port positions conflict with the mount at either end of the stroke? Is the rod end thread a standard size for the rod diameter you have specified?
The one-page version
Send: bore or load, stroke, working pressure, mounting at both ends, retracted length and tolerance, cycles per hour, fluid, temperature range, port specification, rod end dimensions, quantity, and a photo of what it replaces.
Twelve lines. That is the difference between a week and a month.