I’m struggling with attaching a nylon gear to the end of a steel shaft. It’s part of the drive for a small cart that is hand pushed with a 5.5kg flywheel inside but it’s geared up to x9 by the time it hits this nylon gear so I want it to be a solid connection. It’s a 65mm diameter by 15mm wide helical gear, the shaft is 12mm diameter but could be increased to 15mm if that was needed. So far I’ve these three ideas:
A.Drill and tap a M4 or M5 hole through the shaft then drill right through the gear one side to the other and have a threaded bar the width of the gear run through it.
B.The same but instead of drilling through the gear and damaging the teeth I could cut a slot into the face of the gear and slide it into place.
C.I could machine a 3mm counter bore on the side of the gear. Weld a little metal disk to the end of the shaft then sink bolts through the disk into the gear.
I’m new to all this kind of stuff so I thought I’d come here and ask if anyone knows of any better ways to go about this?
It seems that a 5.5 kg (12#) weight that is spinning on a shaft (60 - 100 rpm maybe more) is going to be way too much torque for a nylon gear. I am guessing, but that seems like a lot of potential torque and a potential weakspot in your design.
You could also look at drive trains on lawnmowers, snow blowers or other go carts. They have solved these problems already so no reason to reengineer it. Maybe some sort of clutch, centrifugal clutch (ala a snow mobile) might be a better solution. Since there might be a sudden stopage (likely will be at some point running into something, etc.) I would lean towards a metal solution drilling holes through the shaft and gear assembly and use a shear pin to protect the joint.
I am not clear if your situation needs a right-angle conection or not, but I recently designed a project, where I used a V-belt as a gear. I included an adjustable tensioner, so that I could deliberately keep the belt only as tight as necessary for the typical load. This way, it functions as a type of clutch when it is over stressed.
Note that V-belts are designed for a good grip, and a flat belt is actually better for clutching. But, it can be difficult to find flat pulley’s and belts.
Thanks for the replies guys. It’s a small rail based dolly/slider for a camera and its metal and nylon alternating helical gears so that it makes no noise.
It shall not be going fast and wound not be running into anything I hope. The reason for the fly wheel is to have very controllable acceleration and deceleration at very slow speeds. The centrifugal clutch would defeat the purpose I think. It would be nice to have some safety in there though.
A belt might work on the last stage, be quiet too. I’m not sure I understand how you can use the v belt as an actual gear. I’ll have a look at some belts but I don’t think they will be appropriate for this situation. I do have a clutch mechanism of sorts as it has 2 gears and I could maybe build some release mechanism in there incase of an accident.
It would only be being push gently along while operating the camera and only at a crawl on the highest gear but I guess you never know what will happen, it’s a valid point and I’ll have a think about it. The cart though would be the last thing on your mind if you crashed the whole camera rig into something for some reason.
I will try to use as much metal to hold it there as I can, I’m leaning towards the third idea of the disc spot welded to the ends of the shaft with bolts through it.
Thanks for the replies guys. It’s a small rail based dolly/slider for a camera and its metal and nylon alternating helical gears so that it makes no noise.
It shall not be going fast and wound not be running into anything I hope. The reason for the fly wheel is to have very controllable acceleration and deceleration at very slow speeds. The centrifugal clutch would defeat the purpose I think. It would be nice to have some safety in there though.
A belt might work on the last stage, be quiet too. I’m not sure I understand how you can use the v belt as an actual gear. I’ll have a look at some belts but I don’t think they will be appropriate for this situation. I do have a clutch mechanism of sorts as it has 2 gears and I could maybe build some release mechanism in there incase of an accident.
It would only be being push gently along while operating the camera and only at a crawl on the highest gear but I guess you never know what will happen, it’s a valid point and I’ll have a think about it. The cart though would be the last thing on your mind if you crashed the whole camera rig into something for some reason.
I will try to use as much metal to hold it there as I can, I’m leaning towards the third idea of the disc spot welded to the ends of the shaft with bolts through it.
There may be off-the-shelf gearmotors with motors attached that you can use. It doesn’t even need to be weight bearing, and you can reduce your gearing needs just using a fairly small wheel pair that squeezes the rail that your trolly sits upon. In other words, the smaller your wheels, the slower the speed, and the greater the force it can apply. Since you are not driving over rough terrain, you can use a fairly small wheel
If you search on www.mcmaster.com for “Drive wheels” you will see many selections. Many have set-screws or keyways, and in a great variety of hole sizes. Note that on the left side, once you choose a wheel style, you can select multiple criteria, and multiples of each category after you choose one side, the “show” text next to it will re-open the other size choices.
McMaster has always had a web catalog that is by-far the best in the industry. If there are technical details missing on an item, just contact them and they can often supply you with whatever their manufacturer makes available to them. Many of their items also have CAD models available. I often go there just to get a dimensioned drawing of a fastener. But,be aware that many models and fasteners especially are WAY too detailed and will bog down a CAD system very quickly.
Many of the categories have a general information page, that can often help guide you. For example on the Drive Wheel result, you will see a yellow area towards the top of the display, that gives you a link with info about durometer ratings. Air cylinders will have an area that describes the types of air cylinders. The fasteners page will give you charts with dimensions of the fasteners. If you click on “Catalog Pages” on the right side of that yellow area, it is often easier to browse that way.
Speaking of browsing, I don’t know if McMaster still make their print catalog available. It is the type of thing that equipment designers just like to browse through, as though it were a coffee-table book.
Thanks for the wheel advice; I’m using little inline skate polyurethane wheels sandwiched together with a 10mm spacer. I’m at about 60mm diameter given the contact point and don’t feel comfortable going smaller, I did look at the off the shelf gear boxes and it would of been a real pleasure to have avoided designing the one I have but they don’t take any consideration for sound and are very expensive. MCmaster certainly looks like an amazing place but I’m in the UK so no joy there. When it comes to shopping for industrial components you have a much better time in the US than here in the UK
Take a look at some of the photo and vidoe related designs that they have on the projects page. That might give you some ideas and the stuff they sell is excellent. There are several examples of people doing exactly what you are trying to do.
Yeah I should have been a bit clearer Bill. I’ll have a look through but most of the projects I find deal with smaller gears under less torque so set screws or even interference fits are used
I doubt you need your flywheel, if you are using a typical motor controller. Many, like my Sabertooth 2x32, have a changable accel/deaccelerate ramp. Also, the mass of your cameraman and gear is a type of flywheel itself, and I imagine it would work fairly smoothly. But, I am not speaking out of any real experience.
Of course, there is the idea of a guy pushing/pulling on a rod attached to the trolly.
It’s a camera dolly not a ride on dolly. About 30cm by 30cm and rolls down parallel scaffolding poles suspended at either end. Even the best camera dollies struggle with a few different problems at slower speeds and this flywheel solves them. I’m not having much luck; maybe the gear is a bit bigger than is normally used in projects on this forum. I might try one of those engine building forums instead.
I have re-read your post and converted to English units, so that they will be more familiar to me, and I can get a better feel for it.I had formed an image of gears/shaft a bit smaller in my mind before. How about simply machining a keyway? Your gearbox output shaft may already have that as an option from the manufacturer. There is often a set-screw on the gear just to hold the keyway in place. But, you might simply use a dab of hot-melt glue instead.
Another approach is to purchase, or machine, a metal hub, that gets screwed to the gear. I just checked Robot Shop and they have many hubs for attaching wheels to shafts. Their 12mm hub sells for under $10 USD. I suspec this is you best option. https://www.robotshop.com/en/set-screw-hub-12mm.html
As an aside, in the U.S., all the companies I have worked for, over my 30 year career, have used English units, unless it was foreign owned. This even included a medical device firm. The only time we use metric is if we can’t find what we want in English units. Of course, the transfer of U.S. manufacturing is strongly encouraging the changeover to Metric, but it is perhaps also simultaneously reducing the number of people needing to do it in the U.S. The engineers now are educated in Metric units almost exclusively. I also suspect the robotics industry is more metric, since they are very much the world of the university research lab. But, the years since 1976, when we “officially” converted, the educational push has not worked with the general public. Rather, their inexperience with English units can make them look inexperienced when they start work at a firm that uses English units. I even did a survey of some US students, and they really didn’t know how to picture metric units. They were just random numbers to them.
I wanted it silent so I wanted to use helical and alternating metal and nylon gears. This means I could not find a gear box of the shelf. This gear I’m asking about is part of the gearing I’ve put together. The problem with this nylon gear is that there is very little clearance on both sides, about 4mm with no boss, so no room for the hub you linked, this is why I was talking about the little plate welded to the end of the shaft, I’m thinking now that it might be better to weld something like the hub and then cut it down, maybe that’ll keep it true on the shaft.
I’m in the UK so we’ve been metric for some time in most stuff, but not all. Gears go both ways. The decimal system is just a lot simpler to work in.
I just happened upon a blog entry by Allied Motion about direct-drive motors. These are very high torque motors that are actually integrated into the wheel with no gearing. http://www.alliedmotion.com/torquemotor/
They tout that, "Where low audible noise is an issue, no other solution beats the direct-drive design."
Of course, it is an advertisement, so I don’t put 100% confidence in that statement, but I though I should pass it on to you.
