View Full Version : Over center manual cone clutch

brian Rupnow
10-18-2018, 12:48 PM
I seem to have clutches on the brain this last couple of months. This design incorporates a cone seating into a cone shaped recess to transmit torque from the left hand shaft to the right hand shaft. There is a very powerful coil spring that holds the clutch in the engaged position. When the handle is swung to the left it allows the powerful spring to seat the cone firmly into the cup and transmit torque. When the handle is swung to the right it separates the cone and cup and compresses the spring. The fact that the spring will be compressed by this action will make the linkage lock into an "over center" condition and stay there until it is changed by someone manually swinging the red handle.

10-18-2018, 12:54 PM
That looks like a compact, robust design with positive engagement and disengagement. Is it your creation? I don't recall seeing a similar one.

10-18-2018, 01:26 PM
A beautifully compact inline design. And I see you've arranged the parts to ensure no possible creeping.

Have you picked out a couple of suitable metals or steel alloys for the cup and cone yet? Any thoughts doing a quick stationary mockup to check for torque transfer rating of the materials, angle, spring pressure and diameter before committing to the full build?

10-18-2018, 01:44 PM
My tapping heads with a cone clutch work fine with steel on one side and cork on the other. Steel and sheet rubber might work too.

10-18-2018, 01:46 PM
That looks like a compact, robust design with positive engagement and disengagement. Is it your creation? I don't recall seeing a similar one.

The clutches on the apron of my Pacemaker are cone clutches with a cam lever instead of the dual link mechanism that Brian shows. Basically, that linear motion that moves the cone and the over-center feature is provided by a cam instead.

brian Rupnow
10-18-2018, 01:46 PM
The shafts and cup will be steel. The cone will be oak and the cone holder will be aluminum. The two main housings will be aluminum. The bearings are sealed ball bearings, 3/8" diameter. I have a similar clutch I built a few years ago and it transfers all the power my small engines are capable of producing. The design is my own. --And yes, no possible creeping.

10-18-2018, 01:49 PM
A beautifully compact inline design. And I see you've arranged the parts to ensure no possible creeping.

Have you picked out a couple of suitable metals or steel alloys for the cup and cone yet? Any thoughts doing a quick stationary mockup to check for torque transfer rating of the materials, angle, spring pressure and diameter before committing to the full build?

Machinery's handbook has a chapter on designing cone clutches and gives tables for coefficients of friction for various materials, including steel on steel, steel on wood, etc. It also gives equations for how much force is required to transmit a given torque, how to calculate an appropriate angle for the cones (too "flat" and you need lots of force, too "steep" and it won't release).

Cone clutches are great because you can transmit a lot of torque without any special friction material. They do tend to be "all or nothing", though. I used them on my home-made shifter-karts but it was always a bit jerky compared to a disc clutch.

brian Rupnow
10-18-2018, 02:23 PM

old mart
10-18-2018, 02:25 PM
A good design, as the retraction mechanism is not subject to wear when the clutch is locked. And when the clutch is disengaged, the output shaft stops and doesn't wear the retraction mechanism.
Will the output shaft be splined to the inner cone?

10-18-2018, 03:00 PM
Using wood for the cone wasn't even on my radar... :) Should be a nice option for providing the required friction though.

What about the grip of the wood cone in the cone side holding cup? Glue or some sort of internal toothing to provide a good solid grip? And what about the shaft coming through the wood cone? With the wood at such sizes being prone to splitting I'm thinking that simply compressing it into the holding cup without a center hole for the shaft might be a better option. And certainly simpler to make.

10-18-2018, 04:25 PM
The old Gravely lawn tractors used cone clutches to instantly reverse direction. My dad brought home the drive mechanism from a tractor used for loading rail cars with a cone drive mechanism too.

brian Rupnow
10-18-2018, 06:02 PM
OldMart--No, not a spline, but a slot in the shaft center and a 1/16" diameter hardened steel pin thru the aluminum cone holder. Does the same thing as a spline and is much simpler when dealing with only fractional horsepower engines like mine. BCRider--I have built other cone clutches using oak epoxied into aluminum holders, and the center hole doesn't seem to weaken them.---Brian

brian Rupnow
10-18-2018, 06:42 PM

brian Rupnow
10-19-2018, 10:17 AM
The design is easy.--The finessing not quite so much. I lay in bed last night thinking of how these parts would fit together, and realized that if that center hoop was built as a single part I would never be able to fit it into place around the carrier that holds the oak friction disc.--So--we make the carrier a two piece so it can be assembled.

old mart
10-19-2018, 02:39 PM
I see that the key/slot allows the inner cone movement relative to the output shaft, but in #8 drawing, there is no apparent axial location of that shaft, unless the red spacer between the bearings was either made integral or fixed to the shaft.

10-19-2018, 05:39 PM
Was gonna say, the pre-1930's farm tractors often had cone clutches down to a fine art, particularly the big old steel-wheeled steam tractors. Maybe worth while to study some existing examples on smokstak.com ?? https://www.smokstak.com/forum/forumdisplay.php?f=22

brian Rupnow
10-19-2018, 08:53 PM
OldMart--It took me a while to figure out what you were asking, but you were right. Both shafts are now "located".---Brian

10-19-2018, 10:27 PM
I had a Volvo marine diesel engine that used a double cone clutch running in oil in the transmission. The cones had a spiral machines into the face which made the clutch self energizing. It had a small eccentric mechanism that moved the cone and the rotation applied the clutch pressure. The engine had to be brought back to an idle before disengaging the clutch or going to the other direction. I had the boat for 30 years and put thousands of miles on it with absolutely no problems with the clutch.

brian Rupnow
10-20-2018, 01:19 PM
I managed a little shop time this morning. Machined the steel carrier for the oak cone and the shaft it rides on.

10-20-2018, 02:11 PM
The cone clutches on my old Hendey shaper were whit cast iron and ran dry. The cone clutches on an old Buda drilling rig used an iron female cone and what looked like conventional brake lining riveted to the male cone. The Hendey cones were about 8" dia. and the Buda cones closer to 12" dia.

brian Rupnow
10-20-2018, 04:22 PM
I made the shaft and cup that the cone fits into. To save myself a ton of machining I made it from two pieces, then Loctited and pressed the two pieces together. Tomorrow when the Loctite is well set up I will drill a 1/16" hole thru both and Loctite in a piece of 1/16" drill rod. I will machine the cone into the face of that solid piece tomorrow.

brian Rupnow
10-21-2018, 06:10 PM
Not a real lot done today. The two external shaft collars and the two bearing spacers. The two bearing spacers got a lot fatter, because if I left them as thin wall, sooner or later I would want to pull a shaft out of the assembly, and when you do that the spacer falls down between the two bearings and it's a devil of a job getting them lined up again to get the shaft back in. The tunnel they fit into is 0.906" diameter, the outside diameter of the spacer is 0.875" diameter. I spent this morning going with youngest grandson Jake (3 year old) and his mom and goodwife out to a local farm that sells pumpkins. Of course you have to pay the $12 per person to get in, which entitles you to a wagon ride out to the pumpkin patch and one pumpkin. Lots of plastic ghosts and skeletons and scary witches along the trail the wagon takes to get out to the patch. Jake was very pleased with the entire event but wife and I damned near froze to death!!! I had to come home and have a snooze to recover, then headed down to the shop to make at least a couple of parts.

brian Rupnow
10-24-2018, 04:44 PM
No great strides made on this project today, but my bearings came in from Canadian Bearings. I have spent the entire day running around like a chicken with no head, trying to source replacement gears for my three ball governor. Someone purchased the plans but the gears I have in the plans call for an 8 tooth pinion, and nobody makes a bevel gear in that size anymore.

brian Rupnow
10-26-2018, 11:52 AM
Things have been a little crazy around here for a few days, however progress is being made. The center bearing carrier is made and the two small bearings have been Loctited onto the stub shafts, which are silver soldered to the outer frame. The outer frame is two piece, and the tapped holes for the bolts which hold the two pieces together are tapped thru the stub shafts after brazing.

brian Rupnow
10-27-2018, 01:02 PM
All of the inner workings of the clutch are finished. The next step will be to make the outer housing of the clutch. I do have a spring, but it has to be shortened a bit.

brian Rupnow
10-28-2018, 12:50 PM
Its been a very boring morning (cough-gag--bad pun). The boring went fine in the four jaw chuck of the lathe. I really don't like working inside something like that where I can't see whats happening. It just requires a lot of faith in the dials and digital read-outs. I have to buy a piece of aluminum big enough to make the other housing from.

brian Rupnow
10-29-2018, 05:34 PM
As I work my way into this clutch business, I have to keep updating the solid models to reflect what I am actually building. This involves adding shoulder bolts at the pivots, and socket head capscrews and flatwashers, and a mechanism to dial in just how far "over center" I want the handle to move before locking up. I had to go to Toronto on business today, and then had a bit of real work, so nothing actually happened except updating the solid model.---Brian

brian Rupnow
11-01-2018, 03:47 PM
Things are not happening at a blazing pace, but they are happening. The second half of the main body is completed, and all of the bearings and spacers are loctited into place with a solid alignment rod thru everything until the Loctite sets up. Two of the external links are made and shown in place. All of the inside components are finished and waiting to be assembled. I have been sick with the sore throat from Hell, but will probably live thru it.---Brian

11-01-2018, 07:31 PM
Brian, I think you got oil or grime on your lens, it's softening the pictures you take, needs a good cleaning.

brian Rupnow
11-01-2018, 09:00 PM
I think you are right. Will do that right now.--Brian

brian Rupnow
11-02-2018, 05:06 PM
First results are in, and they are very positive. When the clutch is disengaged, there is absolutely no connection between the cone and the cup, and no drag at all. When the clutch is engaged, it locks up the cup and cone shafts. The pressure required to get the handle to "cam over" is quite small. I may rethink the adjustment I had modelled, because it looks like I can add one adjusting screw to the bar under the handle to limit how far it goes before it locks.

brian Rupnow
11-03-2018, 11:25 AM
I have changed the adjusting mechanism for the "over center" condition to something a lot simpler and less work. Sometimes when I am designing and building things, I will reach a point part way thru the assembly where I can see a better solution to a problem than I designed in the first place. This is not unusual, and as everything I design is a "prototype" it doesn't bother me. (as long as I haven't already made the part). The last thing I need to build is a baseplate which will allow me to bolt this clutch down to my worktable.

brian Rupnow
11-03-2018, 01:46 PM
So in the end----The baseplate becomes a "Use what you have". I wasn't going to run downtown to buy a piece of 3/8" plate. The clutch is finished now, and I have to figure out a good way to set up a YouTube video. I wanted to use my driveshaft with universal joints between whatever engine I used and the clutch.--Problem with that is that of all my engines, only one or two have a crankshaft extension out the side opposite of my starter set up. I will figure something out, and make a demonstration video.--And before you ask---That backdrop is not for sale. I have already been offered two million by the Canadian art institute, but I'm holding out and negotiating for three.

brian Rupnow
11-03-2018, 04:10 PM
All I needed was a little nap. Woke up knowing how I was going to make the video.--Tomorrow---

brian Rupnow
11-04-2018, 02:15 PM
Right on the cusp of an exciting new video---and one of my universal joints flew apart. Video will be delayed until Loctite holding one of the universal joint pins in place sets up. It's colder than a witches tit out in my main garage, and I've been sick for a week. Will put a heat lamp on the offending parts and maybe a video later today--maybe tomorrow. I do know this much---The flathead engine has enough beans to run the clutch mechanism in it's disengaged mode. I was just reaching to engage the clutch when the universal joint flew apart.

brian Rupnow
11-05-2018, 03:59 PM
So, today we have the video I intended to make yesterday. The clutch operates just as I had hoped, and the video gives a good overview of the clutch in operation. I have a set of 21 engineering drawings of this clutch, which can be built using a small manual mill and manual lathe. I sell the plans for $25 Canadian funds, contact me at brupnow@rogers.com The input and output shafts are 3/8" diameter, and both shafts ride on double sealed ball bearings. hope you enjoy the video.---Brian Rupnow

11-05-2018, 04:42 PM
Nicely done, Brian. I like the engineering of that one a lot. It seems like a very good design.

brian Rupnow
11-05-2018, 08:12 PM
Thanks Toolguy. I knew the concept of the cone clutch would work, because I built one a few years ago which worked very well, except that it has a "dead" central shaft. I wanted to recreate it, only this time with a "live" central shaft, which offers more versatility. The big issue with any of these smaller "home brewed" clutches is how to keep them engaged or disengaged. If you don't have a lever with a shift gate which the lever snaps into, they have a propensity for jumping into or out of engagement, which can be quite alarming. The "over center" mechanism works very well to solve that problem. It is the same mechanical locking principal as is used on Destaco clamps. This will be my last clutch build for the foreseeable future.---Brian Rupnow