This isn't a product review..... honest!
Building a Caterham 7 requires a reasonable level of skill, and also quite a few tools, but none which you'd consider too specialized, although I suspect certain models with their inherent challenges might require a few additional tools. During my build, I didn't need to purchase that many tools as I already had a reasonable set, however, I've since purchased an interesting tool which is the topic of this blog post. I'm not aiming to write a review here, but if like me you don't have a 3/4" torque wrench then please read on!
Before I get into the core of the topic, if you want to review typical tools needed can I suggest reading PurpleMeanie's post on the topic as it provides excellent detail on the typical tools needed.
Let's discuss a little of the background of how the aforementioned purchase came about. For that we need to look at the assembly guide, I'm going to refer to the 2015 publication, page 144, Table 22 Torque figures for rear suspension. The torque setting for the Hub Nuts is 270Nm, it's also a pretty large nut, requiring a 34mm socket, which is typically 3/4".
In my toolset all the torque wrenches I had applied a maximum torque of 220Nm, and those capable of such a specification were 1/2" inch wrenches. This seemed to be a pretty common situation for any I found on the market. To apply a torque of 270Nm you need a 3/4" torque wrench.
For example a 3/4" torque wrench from Teng supporting, 90Nm to 450Nm, competitively priced by Screwfix, £148.99. https://www.screwfix.com/p/teng-tools-drive-torque-wrench/58074#product_additional_details_container
I am not averse to purchasing tools and quality ones at that if I can justify the need. In this case however, the Hub Nut on the 7 is the only time I've needed such a relatively high specification and so purchasing such a costly tool seemed expensive and rather wasteful. I needed to find a more wallet-friendly and well, useful solution.
During the original build I used my 220Nm max Teng 1/2" torque wrench and a 1/2" to 3/4" adapter both of which I already had to torque the nut to 220Nm and then intentionally went further, over tightening the nut to the approximately 270Nm. I also marked the nut and hub assembly with a paint marker to ensure any reduction in the torque was visible. While I am confident the nut wasn't over tight, and it certainly wasn't going to come loose it did bother me it wasn't built with the appropriate precision I desired. It's for this reason I looked for a solution.
Step in the Clarke Pro Digital Torque Adapter PRO 238, with its incredibly flexible range of 30Nm - 360Nm, supplied by Amazon at the amazing price of £53.99, it's 1/2" too!
A quick breakdown of the product specs courtesy of Amazon is as follows;
Torque range 30 - 360Nm, 265 -3186 lb-in, 22.12 - 265.5 lb-ft or 3.05 - 36.7 kg-m
Large LCD digital display shows selectable units Nm, lb-in, lb-ft or kg-m
Target torque value preset & audible alarm
Low battery indicator
Calibrated to BS EN ISO6789, Weight 0.3kg
Clarke tools aren't usually my first, second or even third choice of brand, but this tool seemed to be a perfect fit and there were few others matching the specification, so I cautiously placed an order.
I appreciate the Clarke tool is not sophisticated, and doesn't for example cease applying torque once the desired torque is reached, but given it's limited use I didn't see this as an issue. Also its massive range would be ideal for applications where precision wasn't that important.
Wow, this is a little wordy, time for a picture, so here it is, the Clarke Pro Digital Torque Adapter PRO 238.
A quick video too.
The product is supplied in a simple but effective hard case, it is a little large for the purpose, so I suspect the case is a general mass produced case Clarke uses on a variety of similarly sized products. The tool is supplied with two large watch batteries required to operate the device, they are installed by removing the battery cover on the side. The tool is also supplied with documentation supporting calibration and testing, certifying the accuracy of the device and based on those results its certainly more than appropriate for the use I've planned.
I've since used the tool to apply 270Nm to the Hub nuts and thus resolve any concerns I had about the precision in this area.
What I thought might be interesting is to compare the application of torque with the two torque wrenches I commonly use when working on the 7 and other cars I own. The idea being to secure the Clarke Torque adapter within a bench vice and then apply torque using the other wrenches to a set level, reviewing the results on both the Clarke adapter against the wrenches.
The two torque wrenches to be compared are as follows;
My trusty Snap-on digital 3/8" drive wrench which was used for much of the build.
Followed by the larger traditional manual twist Teng 1/2" drive wrench typically used for larger jobs as it's capable of 220Nm.
Given I'm comparing with the Snap-on which is 3/8" drive and capable of a lower maximum torque specification, I'll limit the test to 40Nm. This test is more for simple curiosity than some harden scientific calibration test.
With the Snap-on wrench set to 40Nm, the Clarke Pro 238 recorded;
38.5Nm for 40.8Nm on the Snap-on,
38.4Nm for 40.3Nm on the Snap-on,
38.6Nm for 40.6Nm on the Snap-on.
The Teng was also set to 40Nm, although it was not possible to confirm exactly what was applied due to the nature of the tool. The Teng did show higher results on the Clarke gauge for the Teng, at 43.4Nm, 42.7Nm, 43.5Nm. I'm not sure if this was due to 40Nm being the lowest possible value on the Teng tool. It's interesting the Clarke split the Snap-on and Teng wrenches mind!
I suspect there was some inaccuracy introduced during the test as the Clarke Pro238 was permitted to twist slightly in the vice, even though I'd protected it with a microfibre cloth I didn't want to clamp it too tight and risk damage.
In case you've just read through this blog and thought, why isn't he out driving the 7 instead of writing such a blog, well it's 50 mph winds and driving rain, the ferry is cancelled, the dog (Riley) doesn't want to go for a walk. I think you get the idea, that amazing April seems to have disappeared. Tomorrow looks a better day mind!