Raychem Products for Motorsport Wiring, DR25, SCL and ATUM Explained
If you are building a motorsport wiring harness in Australia, Raychem products are the industry standard for protecting and finishing your work. Manufactured by TE Connectivity, the Raychem range is used in military, aerospace and professional motorsport harness builds worldwide. This guide explains the three main products you will encounter, what each one does and when to use each one.
What Is Raychem
Raychem is a brand of TE Connectivity, one of the world's largest manufacturers of electrical components. The Raychem range of heat shrinkable tubing and related products has been the go-to choice for professional motorsport harness builders for decades. When people talk about a proper motorsport harness build, Raychem products are almost always part of the conversation alongside Tefzel mil-spec wire and Deutsch connectors.
Raychem DR25
DR25 is the outer protective sleeving used to jacket and protect the wire bundle in a motorsport harness. It is a single wall, flexible heat shrinkable tubing made from a crosslinked elastomeric material. It has a 2:1 shrink ratio, meaning it shrinks to half its supplied diameter when heat is applied. The operating temperature range is -75 degrees Celsius to 150 degrees Celsius, with a minimum full recovery temperature of 175 degrees Celsius.
DR25 is specially formulated for optimum high temperature fluid resistance and long term heat resistance. It is resistant to aviation and diesel fuels, hydraulic fluids and lubricating oils, making it ideal for use in the engine bay environment. It is also flame retardant and compliant with MIL-DTL-23053/16 standards.
DR25 does not have any adhesive or glue inside. It is purely a protective outer jacket. It is available in a range of sizes to suit different bundle diameters and is sold per metre or per foot depending on the supplier. When choosing a size, select the smallest size that will comfortably slide over your wire bundle before recovery. DR25 will increase its wall thickness as it shrinks, providing increased protection at the recovered diameter.
Raychem SCL
SCL is a dual wall adhesive lined heat shrinkable tubing with a 3:1 shrink ratio. The outer wall is a semi-rigid crosslinked polyolefin and the inner wall is a meltable polyolefin that flows when heat is applied, sealing around the substrate. The operating temperature range is -55 degrees Celsius to 110 degrees Celsius with an installation temperature of 135 degrees Celsius.
SCL is used to terminate the ends of DR25 runs, to seal connector backshells, to provide strain relief at branch points and to cover splices. When heated, it can be pinched and shaped while still hot to form a clean wire breakout. SCL has a semi-gloss black finish and a stiffer construction than ATUM, which gives a very clean professional look on a finished harness.
SCL is the preferred choice when working with Tefzel mil-spec wire, as it requires a higher installation temperature that standard wire insulation can handle without being damaged by the heat needed to fully recover the SCL.
Raychem ATUM
ATUM is also a dual wall adhesive lined heat shrinkable tubing but with a higher 4:1 shrink ratio compared to SCL. The outer wall is a semi-rigid polyolefin and the inner wall is a meltable polyolefin adhesive. The operating temperature range is -55 degrees Celsius to 110 degrees Celsius with an installation temperature of 110 degrees Celsius.
The higher shrink ratio of ATUM means it can cover a wider range of substrate sizes with fewer different sizes in stock. It is more flexible than SCL and bonds to plastics, rubbers and metals. ATUM is typically the preferred choice when working with OEM style or TXL wire rather than Tefzel, as its lower installation temperature is safer for wire insulations that may be damaged by the higher heat needed to fully recover SCL. ATUM is excellent for connector backshell sealing, breakouts, splices and transitions.
SCL vs ATUM, Which Should You Use
Both SCL and ATUM serve similar purposes and the choice often comes down to the wire type and builder preference. If you are building with Tefzel mil-spec wire, SCL is generally the better choice. If you are working with OEM style wire or TXL wire, ATUM is the safer option due to its lower installation temperature. SCL has a slightly more rigid, polished finish while ATUM is more flexible and accommodates a wider size range due to its higher shrink ratio.
Buy Raychem Products in Australia
12Volt Motorsports stocks genuine Raychem DR25, SCL and ATUM in Australia. We are a Melbourne based motorsport wiring specialist and carry the full range of sizes needed for a professional harness build. We also stock Tefzel mil-spec wire, Deutsch connectors and milspec bulkhead connectors so you can source everything for your build in one place. Fast shipping Australia wide.