A recent bridge-building project has drawn a lot of favourable attention to Carlton Engineering. Forestry Journal spoke to owner John Carlton to get the long and short.

A properly located and constructed forest road is an essential first step in the preparation and management of a new forestry plantation. Where streams and rivers must be crossed, a bridge is naturally required, but one that must be up to enduring the heavy traffic of machinery and trucks across the working life of the woodland.

The challenge of building such a bridge was recently put to Carlton Engineering, becoming one of its most enjoyable projects and proudest achievements of 2021.

Based in Moffat, Dumfries and Galloway, Carlton Engineering offers fabrication, welding and general engineering services to the forestry sector – with a flair for bespoke projects.

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This one began, as so many of its more interesting jobs do, with a phone call from a client.

Contractor Simon Richardson asked owner John Carlton if he would be interested in building a bridge crossing a stream along a forest road. Specifications were that it had to be 16 m long and support 44 tonnes.

The road leads into a new plantation – essentially virgin ground, though it is close to existing forestry. A very small temporary bridge had been erected to provide access for road builders and forestry works for ploughing and mounding, allowing tree planters to make a start on the job.

Forestry Journal: Beams were welded and bolted into two pieces for construction on site.Beams were welded and bolted into two pieces for construction on site.

However, it was agreed something more permanent would be required to support management, harvesting and timber transport needs in the years ahead.

John spoke to a structural engineer who came up with a design, which was agreed with Simon and his client. He priced the job and several months passed before he received a call to say: “We need the bridge ASAP.”

John said: “We had to price the job again, because the cost of materials has been moving so fast. Once they agreed the new price, we immediately ordered the steel, which arrived a couple of weeks later, and began fabrication using the structural engineer’s drawings.”

The bridge was produced in the Carlton Engineering workshop in sections. Plate was cut for lugs and brackets on the CNC plasma cutter and the beams were welded and bolted together to form two separate pieces to be installed on site. Handrails, providing a bit of security to anyone crossing the bridge by foot, were also attached at the workshop.

Forestry Journal: Steel was purchased shot-blasted and painted for a higher finish, then given a top coat after welding.Steel was purchased shot-blasted and painted for a higher finish, then given a top coat after welding.

When the materials were ready, they were loaded up on a Monday morning and transported to the site, where civil engineering works to put in the concrete base had already been completed by the client. By Monday evening, all four beams were in position.

Forestry Journal: The bridge loaded up in sections for transport to site.The bridge loaded up in sections for transport to site.

John said: “The rest of the bracings went in the next day. It’s full of tubular bracing, which keeps the bridge square and rigid, but allows it to flex. Next it was a matter of putting the road plates on and making sure everything was nice and tight. Because we were unsure of a few factors, we drilled the floor plates on site, just so there were no issues with them not fitting properly. We then finished the handrails off, which had been made overlength. There was a debate over whether to make them longer and run fences to them, but it was decided to stop them at the end of the bridge.

“Once we were finished, the contractor came in and finished the road off either side of the bridge, putting the finished road base on it, and it was good to go.

Forestry Journal: Tubular bracing allows the bridge to flex under heavy loads.Tubular bracing allows the bridge to flex under heavy loads.

“We landed on site on the Monday and were finished on Thursday. I believe the road and the bridge was opened the following Wednesday.

“It was a very good job and we thoroughly enjoyed it. I’ve done a lot of structural steelwork in the past, so I know you can get the best drawings in the world, but there’s usually a hole out here or there.

Forestry Journal: Handrails were shortened and finished off on site.Handrails were shortened and finished off on site.

"However, this bridge all fitted together nicely and works well. It has already been noticed and given us the opportunity to work on three or four others, which are currently being looked at by structural engineers.”

Forestry Journal: The finished article The finished article

For updates on the latest projects from Carlton Engineering, look them up on Facebook or Instagram.

For enquiries, call John Carlton on 07754689257 or 01683 220582.