Any mechanical engineers?

[Escapee]

I wonder if anyone can help with a little project?

I am looking for an identical pair of worm and wheels, something like a 60 tooth wheel. They must be fairly hefty as they will be involved in moving about 250Kg each.

I thought about car steering boxes, and have stripped down one from a Reliant Robin. (had a few hanging about like one does) I am now wondering of there are any worm drive winches available, I have a nice big old worm drive winch but no use cannbalising because I need a matching pair.
I have a milling machine and lathe but didn't want to go to the effort of machining a pair myself, as that will take a serious amount of hours to set-up and I'm OK with the Gear wheel but not sure how good the worm would turn out.

I have done all the usual searches and only found one single worm/wheel pair on ebay. I was hoping that someone here might be in the engineering business and possibly know of something used somewhere that would suit my purpouse.

I know it's a long shot! Any help would be appreciated though.

[altis]

You could try these:

http://www.rarodriguez.co.uk/

[Escapee]

Originally Posted by altis

You could try these:

http://www.rarodriguez.co.uk/

Thanks for that, didn't find that company in my search.

I just have the feeling this project is going to be expensive

[paulyoung666]

wait till i go to work tomorrow and have a look , i know we used to have a load of gears that were redundant , now if they are still there i might just be able to spirit some out for you , just to make sure , is it 2 pair you want ?????????

[Escapee]

Originally Posted by paulyoung666

wait till i go to work tomorrow and have a look , i know we used to have a load of gears that were redundant , now if they are still there i might just be able to spirit some out for you , just to make sure , is it 2 pair you want ?????????

Hi Paul, I am preferably after a pair of matching worms and wheels. I am making an electric gate opener, and it needs one worm and one gear wheel per side. I have a sloping drive and theres nothing available ready made, so I have to have a clever arrangement that lifts the centre of the gate before it opens.

I even considered some large threaded studding inch diameter and making some nuts so it acted like a satellite actuator, but I will still need a reduction gearbox. If I only had one gate to open it would be easy, but whatever I find in the scrap box it needs to be doubled

I am planning to use the worm drive as a reduction gearbox to drive an arm to open/close the gate. They will probably drive Reliant Robin steering boxes to give circular to linear conversion and about 3:1 reduction as a bonus.
The worm/wheel will also drive a winch that has wire rope to lift the bottom 18 inches of the gate hinged at the end nearest the gate post, so it will clear the sloping driveway as it opens, The romote control will be easy as I can just buy a module from RF Solutions/maplins.

I have been to look at something similar made by someone locally using a garage door opener and a very large reduction gearbox, he has the one motor opening both gates with the arms under the conctrete. Unfortunately thats not easy for me because of the water and gas pipes.

I even considered a pair of electric hoists to lift the gates ie: the gate has a short pipe welded top and bottom, fitted over a pipe fixed to my gatepost. This arrangement would lift the gates out of the ground fixing and the pipe would have a scroll to twist the gate open when it was high enough to clear the ground. I also thought one gate could open a few seconds after the other to allow a piece of channel fixed to the first opening gate to cover the second for a secure fixing. The only thins thats put me off that idea is it is almost impossible to have a backup plan in case of a power failure.

This is another one of my hairbrain ideas, I have ordered the material for the gates and the posts are already concreted in place. I will be making a start on the gates shortly, I have had and dismissed lots of ideas including hydraulics and think the worm/wheel arrangement will be the easiest.

So what I am really after is 2 off 60 ish tooth gear wheels and 2 off worm wheels to suit.

very tall order I know!

[paulyoung666]

sorry mate , nowt doing at work , they got rid of the redundant stuff a while ago , the only place that i can think of that might be able to help you is a company in sheffield called TDR , they do out g'box repairs for us , you could try calling them

[Scrubbs]

the only suggestion I can make is the local scrappy, He might not have what you're looking for but may know someone or somewhere that does industrial scrap?

[keithwalton]

If the reliant steering column isnt upto scratch then perhaps a set out of a bigger / heavier car that has rack and pinion steering as they would be deisgned to turn heavier loads. Thinking about it a car that has power assisted steering would be geared to be more aggresive than a normal rack and have the power steering lighten up the feel. So somthing from a big bmw or merc might do it. Failing that a truck might have what your after.
Worm gears are incredibly inefficent, but that wont really factor into your work as your not carrying around any weight, just bare that in mind when doing any motor calculations that a worm gear arrangment has a power / torque transfer of approximatly 40%

You'd be best off borg'ing the stuff out of somthing second hand as new gears are muchos expensive.

If i get your idea right you want the gears to lift up the gates from the outside edge (axis of pivot), if your going to do that you'll have a quite a large moment from the gates themselves (depending on how wide they are) you would mostly likely want to stifen the base if they are anything but metal allready, even then you might find it sloping down.

As for the mountings you'll want the worm gear to do the lifting only, you'd want a set of roller bearings to take the load of the gate pulling down on it. and possibly some form of choking system that came in and stopped the gate from slipping down and to take the idle load off the gearing system

[Escapee]

Originally Posted by keithwalton

If the reliant steering column isnt upto scratch then perhaps a set out of a bigger / heavier car that has rack and pinion steering as they would be deisgned to turn heavier loads. Thinking about it a car that has power assisted steering would be geared to be more aggresive than a normal rack and have the power steering lighten up the feel. So somthing from a big bmw or merc might do it. Failing that a truck might have what your after.
Worm gears are incredibly inefficent, but that wont really factor into your work as your not carrying around any weight, just bare that in mind when doing any motor calculations that a worm gear arrangment has a power / torque transfer of approximatly 40%

You'd be best off borg'ing the stuff out of somthing second hand as new gears are muchos expensive.

If i get your idea right you want the gears to lift up the gates from the outside edge (axis of pivot), if your going to do that you'll have a quite a large moment from the gates themselves (depending on how wide they are) you would mostly likely want to stifen the base if they are anything but metal allready, even then you might find it sloping down.

As for the mountings you'll want the worm gear to do the lifting only, you'd want a set of roller bearings to take the load of the gate pulling down on it. and possibly some form of choking system that came in and stopped the gate from slipping down and to take the idle load off the gearing system

Thanks to all of you.

Paul thanks for having a look for the gears for me.

keithwalton thanks for advice, I had also been thinking about a couple of landrover steering boxes, I did also think about the rack idea, as I have a couple of old MK2 Escort ones in the shed. My local scrapyard is good for industrial scrap, but the requirement for a matching pair of gearboxes is a bit much to hope for.

I phoned a number of companies that sold/installed automated gates yesterday asking if they had come across any similar problems. Most of the companies were just salesmen, but a company in the midlands that "easygates" recommended were very helpfull. He listened whilst I bored him with all my ideas and said my suggestion of the off-set hinges would probably be the best solution.

Each gate will be 81 inches and I will need to allow 16 inches of lift at that distance up the drive. It works out at around 11 degrees, so if the bottom hinge is set back around 12 inches the gate will open at a 11 degree angle.
This is quite manageable as it would just require a triangular piece welded from some angle to mount the bottom hinge on. The gate will still be vertical but the hinges will be at 11 degrees, I will just have to be sure they are perfectly in line with each other. The guy then suggested I use a strain gauge to see if the required effort is within the spec of the worm and wheel gate autmation kits they have, He suggested to use the arm type as they have a greater starting torque than the satellite actuator type, these are more effective as the gate opens and gets closer to 90 degrees.

He said he sold a system to a guy a while ago who wanted a 6 inch lift with some very heavy gates, and the guy was happy with them. He said he would not recommend the solution in case it doesn't work, but he cant see why not as the devices are designed to open gates weighing 300Kg each at 2.5M per leaf. The opening arm mechanisms will then have to be mounted at 11 degrees off line to match the hinges.

This system including 2 arm actuators, 2 remote controls and PIR is about 600 notes including vat, so with the material I have bought for fabrication the gates its well in budget compared to some companies offerings. I have the first week off in September and hope to have the gates fabricated and hung (And my central heating installed!!) I will then be able to tell if the suggested system is upto opening/closing the gates.

If not, landrover steering boxes and a few scrapyard visits.

Thanks all.

[Nikko]

Have you considered rising butt hinges? I have no idea if these are available for the size/load of the application, but domestic ones do a good job of allowing clearance over a carpeted room.....

You could then use proprietary openers allowing for some form of free rise to the actuators.

[Escapee]

Originally Posted by Nikko

Have you considered rising butt hinges? I have no idea if these are available for the size/load of the application, but domestic ones do a good job of allowing clearance over a carpeted room.....

You could then use proprietary openers allowing for some form of free rise to the actuators.

16 inch rise though! thats an awful lot to lift in a 90deg turn.

My idea with the winch and scroll was fairly close to that, I think it would have to lift instead of pull or push for that to work.

I wish I had a level drive

[Nikko]

Originally Posted by Escapee

16 inch rise though! thats an awful lot to lift in a 90deg turn.

My idea with the winch and scroll was fairly close to that, I think it would have to lift instead of pull or push for that to work.

I wish I had a level drive

Assuming there is no way of reversing the swing - ie to open over the slope, how about horizontally hinging the lower 16" as a 'flap' with a jockey wheel arrangement so the flap folds up?

[Scrubbs]

Can't you leave a 16" gap at the bottom of the gates?

[paulyoung666]

Originally Posted by Scrubbs

Can't you leave a 16" gap at the bottom of the gates?

and let the chavs in

[Escapee]

Originally Posted by Nikko

Assuming there is no way of reversing the swing - ie to open over the slope, how about horizontally hinging the lower 16" as a 'flap' with a jockey wheel arrangement so the flap folds up?

Thought of that as well, I have an hours drive to work each day to think about it

I even considered using 2 garage door openers to open the gates and a pulley with a wire to lift the bottom 16 inch section. I even ordered a pair of nice rubber tyred jockey wheels from RS in case I chose that option.

I made up a model of the sloping gate/hinge with some pcb board to check the maesurements and scale up, one of the guys in work even bent one up out of some wire and poked it through the side of a cardboard box so it could operate, and we could check out dimensions.

This sloping drive is such a damn nuisance!