Western Construction had these Quad 9's pushing 631's building Hwy 80 in Wyoming in 1969. I was quite young and I went there with a friend who was looking for a job and I got on a DW-21 water pull. Later back home Peter Kiewit used a similar Quad 9 along with a single 9 to triple push 651's building the Dana Point Marina in 1970. An old black fellow named Riley Brown ran it, and I was on that job running a 651 Scraper. A good memory.....
I was working as part of the surveying crew on a stretch of I-15 between Idaho and Montana back in the summer of 1968 where they used a tandem D9 dozer set to push scrapers excavating the road base ar Spencer, ID just like this video shows. This really brings back memories!
great film! brings back memories of working on i-80 in iowa early 1960's running a d-9 pushcat , no air condition cabs in those days ! we were lucky to have an umbrella!
My Uncle Bud was in the SEABEES, He was an officer at The CB training base in Davisville R.I. I remember him taking me to watch the guys learning, on scrapers & dozers, clam shells. I use to love going to visit him in the summer... He retired after 32 yrs in The Navy as the last Commanding officer at Davisville, before they shut it down. He was active & deployed in WWII, KOREA< & V.N.
2009. Kentucky Speedway Parking Expansion. Sparta, KY. Due to maintenance issues and parts rarity, they were taken out of service a few years later. We bought them in the early 70’s so got many years out of them. I think they were the last set still out working. Thanks for all the comments
I saw the Quad 9's operating in the late 70's near Merced, CA. Front 2 had 9 foot riper shank. Back 2 were pushing. When turning 1 and 1/2 foot would not even come out of the ground. The ground rumbled like a constant earthquake from 1/4 mile away. It was awesome!
Awesome. This is how Beltsville dam was built in the 70's in eastern Pa. My dad was part of the many that helped. He would tell me about a "quad nine" set-up. Where 4 would be used in tandem. Very cool to see that since I was born in early 70's and couldn't see it.
Before I retired last, I hd a customer that i moved for maybe 25 years. Still uses Cat 21 scrapers with cable controls. He has a D9L and a D8H that has a pony motor to Start it. Everything is in tip top shape
Very cool! Caterpillar technician here and I have never seen or heard of a setup like this one! Without a doubt that those are D9's since they have the D342 engines. Only the 8's and 9's had the D342 Six cylinder engines, the 7's had a four cylinder engine. Seen pictures of D9's tied together side by side pushing one dozer blade, but not one set up for pusher duties. Thanks to whomever keeps these old iron beasts going!!
Hope there is some more video of these, real time warp but clearly can be seen doing an honest days work in what looks like sometime recently. That operator must surely be loving life! Great to hear the sound of real Caterpillar engines
I remember dad talking about working nights in page az. Running quad 9s he worked in most of the 50 states and canada from the fortys to the eighties RIP dad
Kiewit had some years ago. they insisted on using them. It was kind of a pig. It never could quite make the quota they wanted. It averaged about 50~60 loads an hour. Whenever it broke down, they'd put a couple of single cats double pushing and they could hadily beat the quad by 20 to 30 loads per hour. The best load counts I ever saw was three D-10s triple pushing. One daily average was 98 1/2 loads per hour. The cats would change order every push with the front cat giving the scraper a boost out of the cut and the back two returned back for the next push. The lead cat would then run back and pick up the back of the pack. It was quite busy. The cat skinners would wave off the scrapers when they had the right load. Once in a while the scraper wanted to keep stuffing the can until the material was pouring over the sides. They quickly learned to listen to the pushcat operator when they were left stuffed into the ground and stranded. One guy whined to the foreman about that and the foreman, who saw the whole thing, said "well, why the hell do you think they did that?" He knew exactly what was going on. Lol. Geeze, I feel like I must have pushed a million loads over the years.
I love seeing these old machines next to new ones. I worked on a job/for a company that ran 67-72 Clark 290m right next to the newest (2000) John Deere 8-wheelers with Miskin cans. Funny thing is the Clarks beat that setup in every way but air conditioning!
I've been a Heavy equipment mechanic welder for over 24 years on Cats and haven't seen 2 crawlers with one operator in action before , I've head about it but never seen it . Pretty cool I've seen plenty of single D-9s D- 7s and D- 8s do the same job sometimes two but only when its really muddy or supper rocky . Two Crawlers is twice the fuel and maintenance . BUT HELL ITS TWO CATERPILLARS and that's 2 COOL !!
I started out at Caterpillar in 1974 East Peoria plant building LL and worked briefly as a tractor shuttle driver, moving units from one area to another. The last of these sets we built were called D9 SXS ( side by side ) as they could be set either parallel or in tandem as seen here. The last ones were built I believe in the late 70's after Cat started pushing the original D10 high rise as the most powerful tractor on the market at that time.
the same job that we had the quads we got an x10 experimental for trials (Peter kewitt did that a lot for cat ).I heard they had to down size the d10 because the transmission wouldn't stand up to the power . the d11 is closer to the x10
the D10X originally used a stationary power plant V12 that had been adapted to use. This proved to be too much horsepower & torque and literally was tearing the tracks off the tractor at full power settings. Also the oiling system proved to be inadequate in the out of position running of a normally static engine.
i ran one of the early d-10 's with the single stack lot of problems with tracks hyd pumps leaking exhaust but after they went to different engine set up with dual stacks better hyds it was a very good dozer one of the best i ever run
Speaking of power, I was on a 657E for Independent, and the 651 spread was single and double pushing with D10T's. I'd cruise by and often they'd be sitting, so I'd drop in the 51 cut and get a quick pushed load. On more then one occasion I/we were loaded with a triple 10T push! With that much power, just hog, boil, and go. I took some pretty impressive photos too!.....
we had 2 on a I worked as an apprentice but we called them quad 9s . 1970 was the first time I saw alligator master link tracks and it sure made putting tracks on a quad easier .
Peter Kiewit had a pair of Quad 9's on their Dana Point, CA marina job around 1970 or so. It was operated by an old black guy named Riley Brown, and he had an umbrella just as pictured. I was a young scraper hand and the boss put me on the jump seat next to Riley to let me see how he ran it, but I never got the chance to do so. Bummer! They were triple pushing 651's and we had a flat out, bladed and bee gee'd haul road and we sure moved a lot of dirt!.....
Nothing like the Bark of those Old Cats, Still a few of those Great pushers around, Granite has 2 of them in Alaska, but they are getting pretty tired, put still Great Pushers
It's just the way the fuel systems in older diesel engines work. Old semi's used to have a mirror on the nose of the so the driver can see how much smoke is coming out of the stack. If too much black smoke is being emitted, the driver knows he has to give it less throttle or shift.
Fantastic. I have never seen anything like this. The closest is watching diesel locomotives working with synchronized controls from the main cab. Also, they must be from the 50's being that have no roll cages. I used to operate a D6 and a Case 560 Back-hoe,both without roll cages.
I run quad 9’s back in 1976 in Frt Mac Murray . Pushing Scrapers we had 23 scrapers in our Fleet. Loram International was the Contractor. Built the Worlds Largest Earth Dam 6miles wide. I am thinking these quad 9’s was Lorams. Tool box on back 9 is the same lol
saw these d-9's working a few years ago on a project in dry ridge ky for coppage construction who was based out of northern ky i think they are the same ones that may have pushed me back in the seventies when i was working for S J GROOVES on highway job near suttion west va i ran a 641 cat scrapper most of time but sometimes i ran a 666 cat scrapper really loved these big cat scrappers especially the 641 were the good old days for sure sure would like to go back to those west va days
Worked for Coppage 13 straight years, out of local 18c, Cinncinati. Retired in'06. Loaded in front of those very 99's, on many sites,.until they sold them. Coppage is based in Independence, Ky. Did you work for them, if so; who was the dirt boss? Sonny Belk, or Ron Colson or Danny Hardin?
Thats pretty cool. Most dont know how fast those scrapers can go also. Ive seen what looks to be 30mph or so when they gotta dump a long way from the excavation. They get sketchy.
To pittyokontora, I watched a few videos on the Mitsubishi BD2, and no doubt they are a good machine. In all the 50 years I watched bulldozers, big trucks, and farm tractors worked I never encountered anyone complaining about the appearance and smell of petroleum diesel smoke. It appeals to me just the same as it does for you. Luckily a lot of guys out there still work with the older machinery which is really the most fun to watch. I hope that my message to you can be translated properly in Japanese.
I hauled a set like this many years ago but they had separated them I took one and the other driver took one we hauled them to a shop in Illinois they were going to be rebuilt and used on a job nearby
Been a pusher with D8 to Exclude 18 's & 24's on chalk in Kent waybackvwhen ,I have seen a tandem set up but pushing a E24 even with a then modern D8 took serious grunt and was very slow. This/these would have been the kit to have!
Is this a DD9G/Quad Track? built by Caterpillar and not just two D9's bolted together. The rear unit is controlled by air lines from the front so only one operator required.
Originally designed by Buster Peterson, and built at Peterson Cat ( look it up!) His original builds before CAT bought the rights to build, had steering clutch and brake oil from the front machine, running to control the rear machine.
Back in the days , their was a holland loader that was 2 D 9 s attached in a frame with a vertical dirt wall trimming blade for operating in circles with a conveyour belt and its own engine atop to run the belt , load out large belley dump trucks of 120 ton of dirt or other material , .
My apologies on video 1.You have a serious pushing animal there.We had one in Norman Wells that would rip and deliver 20 yards on a down hill push in oil shale.I believe it caried an 16 ft U blade so I know 1 but 2 ? wow,wow wow I love yer style folks.
See all those cables going to the rear D9, I assume those are throttle, gear and whatever else controls to sync the 2. Farmers used to do this in the old days, pair 2 tractors together for the horsepower.
Western Construction had these Quad 9's pushing 631's building Hwy 80 in Wyoming in 1969. I was quite young and I went there with a friend who was looking for a job and I got on a DW-21 water pull. Later back home Peter Kiewit used a similar Quad 9 along with a single 9 to triple push 651's building the Dana Point Marina in 1970. An old black fellow named Riley Brown ran it, and I was on that job running a 651 Scraper. A good memory.....
I was working as part of the surveying crew on a stretch of I-15 between Idaho and Montana back in the summer of 1968 where they used a tandem D9 dozer set to push scrapers excavating the road base ar Spencer, ID just like this video shows. This really brings back memories!
great film! brings back memories of working on i-80 in iowa early 1960's running a d-9 pushcat , no air condition cabs in those days ! we were lucky to have an umbrella!
My Uncle Bud was in the SEABEES, He was an officer at The CB training base in Davisville R.I. I remember him taking me to watch the guys learning, on scrapers & dozers, clam shells. I use to love going to visit him in the summer... He retired after 32 yrs in The Navy as the last Commanding officer at Davisville, before they shut it down. He was active & deployed in WWII, KOREA< & V.N.
My father was an eighteen year old Navy Seabee on Okinawa in WWII.
2009. Kentucky Speedway Parking Expansion. Sparta, KY. Due to maintenance issues and parts rarity, they were taken out of service a few years later. We bought them in the early 70’s so got many years out of them. I think they were the last set still out working. Thanks for all the comments
I saw the Quad 9's operating in the late 70's near Merced, CA. Front 2 had 9 foot riper shank. Back 2 were pushing. When turning 1 and 1/2 foot would not even come out of the ground. The ground rumbled like a constant earthquake from 1/4 mile away. It was awesome!
Awesome. This is how Beltsville dam was built in the 70's in eastern Pa. My dad was part of the many that helped. He would tell me about a "quad nine" set-up. Where 4 would be used in tandem. Very cool to see that since I was born in early 70's and couldn't see it.
Before I retired last, I hd a customer that i moved for maybe 25 years. Still uses Cat 21 scrapers with cable controls. He has a D9L and a D8H that has a pony motor to Start it. Everything is in tip top shape
Very cool! Caterpillar technician here and I have never seen or heard of a setup like this one! Without a doubt that those are D9's since they have the D342 engines. Only the 8's and 9's had the D342 Six cylinder engines, the 7's had a four cylinder engine. Seen pictures of D9's tied together side by side pushing one dozer blade, but not one set up for pusher duties. Thanks to whomever keeps these old iron beasts going!!
9s used D359 engines
D8 was a 342, D9 up to D9H was 353
. 😅mi88😮
Hope there is some more video of these, real time warp but clearly can be seen doing an honest days work in what looks like sometime recently. That operator must surely be loving life! Great to hear the sound of real Caterpillar engines
These double's are very amazing machines!!
Amazing hookup for cats. thanks for posting, Ive never seen cats with one operator before. Seems to work very well!!
I've never seen this before either. Imagine the power and traction!
All of that extra traction makes loading a quick job
Хорошая техника, хорошая работа. Пока сущесвовал СССР работал на скреперах. Удовлетворение от проделаной работы. На работу ходил с радостью.👍👍👍✊🤚
I remember dad talking about working nights in page az. Running quad 9s he worked in most of the 50 states and canada from the fortys to the eighties RIP dad
Great video that brought back memories. Thanks, JB
Kiewit had some years ago. they insisted on using them. It was kind of a pig. It never could quite make the quota they wanted. It averaged about 50~60 loads an hour. Whenever it broke down, they'd put a couple of single cats double pushing and they could hadily beat the quad by 20 to 30 loads per hour.
The best load counts I ever saw was three D-10s triple pushing. One daily average was 98 1/2 loads per hour. The cats would change order every push with the front cat giving the scraper a boost out of the cut and the back two returned back for the next push. The lead cat would then run back and pick up the back of the pack. It was quite busy. The cat skinners would wave off the scrapers when they had the right load. Once in a while the scraper wanted to keep stuffing the can until the material was pouring over the sides. They quickly learned to listen to the pushcat operator when they were left stuffed into the ground and stranded.
One guy whined to the foreman about that and the foreman, who saw the whole thing, said "well, why the hell do you think they did that?" He knew exactly what was going on. Lol. Geeze, I feel like I must have pushed a million loads over the years.
I love seeing these old machines next to new ones. I worked on a job/for a company that ran 67-72 Clark 290m right next to the newest (2000) John Deere 8-wheelers with Miskin cans. Funny thing is the Clarks beat that setup in every way but air conditioning!
I've never even heard of one of these.. Holy crap!! That's awesome.
I've been a Heavy equipment mechanic welder for over 24 years on Cats and haven't seen 2 crawlers with one operator in action before , I've head about it but never seen it . Pretty cool I've seen plenty of single D-9s D- 7s and D- 8s do the same job sometimes two but only when its really muddy or supper rocky . Two Crawlers is twice the fuel and maintenance . BUT HELL ITS TWO CATERPILLARS and that's 2 COOL !!
I like heavy equipment. The operator is a very good skill. Very good engine sound. Thank you from Japan.
I started out at Caterpillar in 1974 East Peoria plant building LL and worked briefly as a tractor shuttle driver, moving units from one area to another. The last of these sets we built were called D9 SXS ( side by side ) as they could be set either parallel or in tandem as seen here. The last ones were built I believe in the late 70's after Cat started pushing the original D10 high rise as the most powerful tractor on the market at that time.
+Kevin Hippen I honestly just thought that was something some shop built no idea something like this was factory
the same job that we had the quads we got an x10 experimental for trials (Peter kewitt did that a lot for cat ).I heard they had to down size the d10 because the transmission wouldn't stand up to the power . the d11 is closer to the x10
the D10X originally used a stationary power plant V12 that had been adapted to use. This proved to be too much horsepower & torque and literally was tearing the tracks off the tractor at full power settings. Also the oiling system proved to be inadequate in the out of position running of a normally static engine.
thanks for the info , I always wondered
i ran one of the early d-10 's with the single stack lot of problems with tracks hyd pumps leaking exhaust but after they went to different engine set up with dual stacks better hyds it was a very good dozer one of the best i ever run
Spent many hours on the old D9er, probably why I can’t hear shit
WOW!,heard about the twin d9 pusher but never seen one working, brilliant video
Speaking of power, I was on a 657E for Independent, and the 651 spread was single and double pushing with D10T's. I'd cruise by and often they'd be sitting, so I'd drop in the 51 cut and get a quick pushed load. On more then one occasion I/we were loaded with a triple 10T push! With that much power, just hog, boil, and go. I took some pretty impressive photos too!.....
When I worked for Oman Construction Company we used them a lot
Didn't know those older cats could be doubled with just one operator, I can understand today but not then , good operator
Cat could do any thing
That is one interesting configuration. I bet it was a fun one learning how to steer it.
Frickin awesome! I missed the chance to get one of the Classic Construction Models DD9G sets. Pretty bummed about that. What year was this shot?
A very cool machine to operate, I saw this on the cut in the Hill project at the end of the 80's by Harper Constitution.
we had 2 on a I worked as an apprentice but we called them quad 9s . 1970 was the first time I saw alligator master link tracks and it sure made putting tracks on a quad easier .
Hichamalwani
Hicham Alwani yes
@@maximumhardcore4362 mi gli
@@marinomorandin7018 most likely
Peter Kiewit had a pair of Quad 9's on their Dana Point, CA marina job around 1970 or so. It was operated by an old black guy named Riley Brown, and he had an umbrella just as pictured. I was a young scraper hand and the boss put me on the jump seat next to Riley to let me see how he ran it, but I never got the chance to do so. Bummer! They were triple pushing 651's and we had a flat out, bladed and bee gee'd haul road and we sure moved a lot of dirt!.....
Nothing like the Bark of those Old Cats, Still a few of those Great pushers around, Granite has 2 of them in Alaska, but they are getting pretty tired, put still Great Pushers
It's just the way the fuel systems in older diesel engines work. Old semi's used to have a mirror on the nose of the so the driver can see how much smoke is coming out of the stack. If too much black smoke is being emitted, the driver knows he has to give it less throttle or shift.
Fantastic. I have never seen anything like this. The closest is watching diesel locomotives working with synchronized controls from the main cab. Also, they must be from the 50's being that have no roll cages. I used to operate a D6 and a Case 560 Back-hoe,both without roll cages.
I run quad 9’s back in 1976 in Frt Mac Murray . Pushing Scrapers we had 23 scrapers in our Fleet. Loram International was the Contractor. Built the Worlds Largest Earth Dam 6miles wide. I am thinking these quad 9’s was Lorams. Tool box on back 9 is the same lol
They used quads on Oroville dam in the sixties
This is awesome u can level land in no time
saw these d-9's working a few years ago on a project in dry ridge ky for coppage construction who was based out of northern ky i think they are the same ones that may have pushed me back in the seventies when i was working for S J GROOVES on highway job near suttion west va i ran a 641 cat scrapper most of time but sometimes i ran a 666 cat scrapper really loved these big cat scrappers especially the 641 were the good old days for sure sure would like to go back to those west va days
that's my Dad Greg running the D-9s at the Kentucky Speedway in Sparta Ky around 9 or 10 years ago.
Worked for Coppage 13 straight years, out of local 18c, Cinncinati. Retired in'06. Loaded in front of those very 99's, on many sites,.until they sold them. Coppage is based in Independence, Ky. Did you work for them, if so; who was the dirt boss? Sonny Belk, or Ron Colson or Danny Hardin?
@@tallen4520 Coppage never sold them they still have them , broke down which they were most of time as I could remember
@@noway769 Just what I heard ; but they were used for several years with no breakdowns.
@@tallen4520 I am don coppage’s grandson Eric they are out of commission, these were always neat to operate
Loram International had this quad D9Gs in Fort Mac Murray in 1976. They build the worlds biggest earth dam. Syncrude Canada.
Thats pretty cool. Most dont know how fast those scrapers can go also. Ive seen what looks to be 30mph or so when they gotta dump a long way from the excavation. They get sketchy.
I live in Stockton, California. Where the Caterpillar was invented by Benjamin Holt.
I like ur canopy.😁👍👍
To pittyokontora, I watched a few videos on the Mitsubishi BD2, and no doubt they are a good machine. In all the 50 years I watched bulldozers, big trucks, and farm tractors worked I never encountered anyone complaining about the appearance and smell of petroleum diesel smoke. It appeals to me just the same as it does for you. Luckily a lot of guys out there still work with the older machinery which is really the most fun to watch. I hope that my message to you can be translated properly in Japanese.
Sir。あなたからのメッセージは理解できている。最新機種と比べ思うことで、当時の古いBD２を物理法則、力学が理解できていない男が使用した場合はよく履帯を外し、困難な状況に陥ってしまうことがたびたびある。また、精密な敷均しでは非常に繊細な操作を必要とし、ブレードが派手に上下して暴れ踊り、敷均し施工面が乱雑となり多くの経営陣を悩ませているのが現状のようだ。このような古い機種を使いこなし、過激な作業をものともしない熟練者が減少している事が残念だ。この損失は計り知れないと私は思う。
Now that cool never seen that type of set up on heavy crawlers be for !
thanks for posting
Very cool stuff. Good show.
Damn those scrapers are huge, even if i see the cab it doesnt look too large until i see the driver
Articulated D9's? Never did see that setup. What power!
Ever seen the side-by-side? About a 30' wide blade!
My god theres a long day. Good thing the dirt is wet and no wind blowing.
Pretty high tech even by today's standards
Pre-treehugger machines..........awesome!!!!!
I am from India ...we are serving cat from our four father's ...I love machines
I ran d9 like this for year best days of my life
Very interesting to see such engineering skills of people in the old days
Few still exits. They were real difficult to service and very expensive.
I have been pushed with a quad 9 push cat , I was operating a cat 657B scraper..
Интересный паровозик получился.
Nice to see a classic pair of Cats doing what they do best, and still running good after all these years.
I hauled a set like this many years ago but they had separated them I took one and the other driver took one we hauled them to a shop in Illinois they were going to be rebuilt and used on a job nearby
When they are placed side by side for a supper wide blade they are called a sxsd9
the pure YELLOW CAT POWER the best ever
excellent video buddy. v guy operating these babys is nearly as big as v tractors.
Great video. Thanks
Been a pusher with D8 to Exclude 18 's & 24's on chalk in Kent waybackvwhen ,I have seen a tandem set up but pushing a E24 even with a then modern D8 took serious grunt and was very slow. This/these would have been the kit to have!
That was cool stuff man
Last time saw those two old girls was when your company was moving the dirt at Bridgewater Falls.
Nobody’s ever seen the old tandem tractors ? IH had the 2+2 that was similar to the tandems.
Only 1 motor though.
that was hardcore man...
a million dollars of D 9s at that time and the guy has a make shift sun umbrella...this company really takes care of their operators...
i wonder how steering works when they're connected like this
Это две D 6, но как он в них спарил переключения?
Is this a DD9G/Quad Track? built by Caterpillar and not just two D9's bolted together. The rear unit is controlled by air lines from the front so only one operator required.
Originally designed by Buster Peterson, and built at Peterson Cat ( look it up!) His original builds before CAT bought the rights to build, had steering clutch and brake oil from the front machine, running to control the rear machine.
www.equipmentworld.com/video-vintage-cat-dd9g-gave-single-operator-power-of-2-dozers-in-tandem/
man that is awesome. I wonder how the rear 9 is controlled
they used air and they were always broke down
Where's the other 46 minutes of the video ??
Really!!! I could watch another 46 minutes easily.
bellissimo video
the golden age of hp
Just an observation, Are these units straight pipe exhaust ?? I remember the muffler assembly above the engine hood back in the day
, nice work, greetings one Chanel from Indonesia 👍
yes never saw a two dozer push from one operator,a lot of power in those Dozers and the earthmover ,would not want to pay the fuel bills.
How did that happened when there is only 1 driver on D9?
Safety umbrella? 🤔
Back in the days , their was a holland loader that was 2 D 9 s attached in a frame with a vertical dirt wall trimming blade for operating in circles with a conveyour belt and its own engine atop to run the belt , load out large belley dump trucks of 120 ton of dirt or other material , .
I have been pushed by a quad-D9, I was operating a 631C scraper in rock, you have plenty of loading power..
Where is this? What project is this and what is being built?
The true quadtrack
Pros tag on the fly , a little riskier in rocky material , but it can be done , saves fuel and cycle time
Just awsome 👍👍👍🇬🇧
I just want to know what they're building And airport Or what ..
Any videos of two side by side?
who needs a roof anyway, or a roll cage nice umbrella mate hahahaha
I like it so awesome
My apologies on video 1.You have a serious pushing animal there.We had one in Norman Wells that would rip and deliver 20 yards on a down hill push in oil shale.I believe it caried an 16 ft U blade so I know 1 but 2 ? wow,wow wow I love yer style folks.
v
Northern Kentucky in 1993?
Talk about a quick fill up.
Nice pair...
Wow Multiple-unit buldozer.
An amazing piece of engineering but I can't help wonder if there's an unemployed "cat skinner" standing way off to the side cursing under his breath.
My question is why are they using the quad 9 to shove load a set of push pull scrapers?
Saveing tires. Rock
'
wow first time to see this video about one driver can driving twin bulldozers same time...
how how
See all those cables going to the rear D9, I assume those are throttle, gear and whatever else controls to sync the 2. Farmers used to do this in the old days, pair 2 tractors together for the horsepower.
Are these still working?