Called 'The Collision King', the machine has already been grasped by Martin Johnson, the England manager, the Welsh and Irish managements and Scotland's Andy Robinson, who began working with it at the start of this summer's pre-World Cup training camp.
After four years of secret planning and legal and patenting challenges, Gray has now signed a ten-year licence deal with Rhino, a leading global manufacturer of rugby equipment, and orders for the 2,000 machine are rolling in.
"It is quite phenomenal," he said yesterday. "I knew I was on to something just watching the game develop the way I thought it would over the last few years, and to see the reaction of Martin Johnson, Andy Robinson, Warren Gatland and Declan Kidney reassured me that it had the potential to make a difference to rugby.
"But it's when the orders come in and international coaches start using it that you really see your idea come to fruition. Over 35 have gone out in the past two weeks across the UK and Europe and we've got an order in from Mark Hammett at Wellington Hurricanes, Sale bought four last week and even Harrow School bought two."
Explaining the theory behind the 'Collision King', Gray said: "I watched the last World Cup and tried to work out where the game was going. It was very defence-orientated and so with defences getting better and players becoming stronger, faster and fitter, I felt the collision in the game was going to become crucial to teams' ability to play it.
"And that's what has happened. The number of collisions in the game has doubled to around 160 per game - 180 on average in last year's Tri Nations. There is a lot of talk about law changes and this and that, but the only way players and coaches will make the game better is to make those stoppages more dynamic, to keep it going.
"I have analysed the game to death for the past four years and while the collisions and rucks are becoming more important they are still not very dynamic. On the whole players' body heights are poor, they're slow to get off the ground, slow to get into the collision and don't work hard when they're in there. So to get to the bottom of it I studied three things - force, angles and patterns - and came up with the 'Collision King' concept, a machine that can bring outstanding dynamic body height time and time again, with every angle and centimetre on the machine is relevant to create the perfect hit."
Reg Clark, CEO of Rhino Rugby, said: "The key to the development of this training aid is that it has been invented by a rugby skills coach with an outstanding knowledge of skill acquisition. The brilliance of The Collision King is in its simplicity - it is a machine that every player, back, forwards and sevens alike, will benefit from using. In my opinion there has never been a rugby training aid like it."Perhaps the machine's key strength is its ability to allow players to improve their technique in an area that they cannot usually practise against each other, without the fear of injury. In fact, a significant number of injuries have been suffered by players during contact sessions where they are striving to improve their ability to contest the breakdown/collision.
Gray, a former league and cup-winning Gala captain, SRU development officer and now college lecturer, has always been a creative character, so does he see a new career as an inventor?
"Who knows? Scots have a reputation as inventors and I've always liked a challenge. I've had a great team of people around me, from Scottish Enterprise, patent lawyers, intellectual property consultants and my own lawyers, and it's a minefield, but now that we've got the registration mark, the logos registered, the patent ongoing, domain names and all the European design rights, and it's selling I can say it's worth it.
"It's been a great journey, from making the first one with DCB Welding of Walkerburn last summer, where we all got into the garage,, built it at night and everyone signed non-disclosure agreements, to inviting coaches like Jim Telfer and Andy Robinson and Reg Clark to Galashiels, and getting them to sign the agreements before seeing it, and now putting it out there in the market-place. I've got more ideas that I'd like to pursue, so it's maybe just the start."