Thread: put a hard point on a small bolt ?

Originally Posted by nearnexus

I agree on the OP question bit - and that a pointed bolt is not the way to go.

But I have to disagree on the more surface area, the greater the friction - not so for a given force. Stays the same.

This is probably the only experiment I remember from skool days Oh, and burning out the see through OHM meters we had.

Look it up and you will see what I mean.

Rob

Hi Rob, You are correct of course, I remember a high school physics experiment doing something similar.... the thing that jumped into mind, as soon as you mentioned it, was "what's the point of wide tyres on cars?" I still can't answer that question with any degree of satisfaction.... I google it, and not sure I agree with some of the answers... we need Stuart for a tricky one like this...

Regards
Ray

Originally Posted by RayG

Hi Rob, You are correct of course, I remember a high school physics experiment doing something similar.... the thing that jumped into mind, as soon as you mentioned it, was "what's the point of wide tyres on cars?" I still can't answer that question with any degree of satisfaction.... I google it, and not sure I agree with some of the answers... we need Stuart for a tricky one like this...

Regards
Ray

Well walking on a wet piece of mild steel sheet can be quite slipery but checkerplate or diamonmd plate mech , or even 2" arc mesh mesh or even flat sheet with blobs of weld stuck all over it all are a lot less slippery even though the "same material "[mild steel]

Thats why the pointy bolts work on the mill , untill they get blunt then they slip . Same with tyres - the same with tyres , the same rubber but those with sharpish lumps or ridges get more traction than bald smooth ones . A lot of the "science " I leared at school has now been replaced with new "theories '

Originally Posted by RayG

we need Stuart for a tricky one like this...

Good luck posting a picture of that.

Originally Posted by Machtool

Good luck posting a picture of that.

I'll pass....

Originally Posted by RayG

"what's the point of wide tyres on cars?"

Arent you assuming that the wide tyres are made from the same stuff as the narrow ones?

Originally Posted by Stustoys

Arent you assuming that the wide tyres are made from the same stuff as the narrow ones?

Yes, both made of rubber...

Googling has lead me to a number of different answers and complications, but the bottom line is that friction is independant of area, however in the case of car tyres there are a lot of other factors involved, and race car tyres are run hot and sticky, so the tyres stick to the road, and it's more about adhesion than friction... also, Wider tyres give greater roll stability in cornering..

Back to the original question, the friction caused by the locking bolt, isn't just the area involved, the sharp point digs in and it's not about friction anymore beyond that point.. Either way it need to be re-designed with a better clamping system.

Regards
Ray

If the tubes are a reasonably close fit you could split the sleeve, weld on a couple of lugs for a bolt and you'd have a simple split clamp that should not damage the upright. I think 25 & 30mm square tubes can fit nicely if you choose a suitable wall thickness and grind a relief for the seam. You could make the sleeve longer and add more bolts till it gripped enough. OTOH a close fit may cause jamming issues. I'm not familiar with the application.

Originally Posted by RayG

Yes, both made of rubber...

If by that you mean "they are both round and black" then yes
If you mean "rubber is rubber" then not so much. Just like oils

Ok I'll leave now.

Stuart

This type of clamping system works quite well on round or square tube.

Not a very good pic but I think it should give you an idea how to go about it

One of the most intriguing locking systems I've seen (and owned) was the double knuckle system that old air cooled VW's used on their car jack.

How that system locked onto a round piece of smooth steel pipe and held the weight of the car was quite amazing.

Anyone that's ever had a vee dub beetle and seen the jack will know exactly what I mean.

Rob

Originally Posted by Mathuranatha

G,day fellers , I need to put a hard point on a small bolt . Thought of hard facing the end and grinding it to a point but cant seem to find any hard facing rods smaller than 3.2 which is a bit big . Anyone got any ideas --- thanks ---Mat--

have used the hard facing rods with oxy acet before to build up valves on old cars ex valves where you cant find replacements as the stem length is the problem. just break off the flux and weld with neutral flame better control and you can see where to place the filler rod material.0.02cents worth John.then grind to suitable angles.

Originally Posted by nearnexus

One of the most intriguing locking systems I've seen (and owned) was the double knuckle system that old air cooled VW's used on their car jack.

How that system locked onto a round piece of smooth steel pipe and held the weight of the car was quite amazing.

Anyone that's ever had a vee dub beetle and seen the jack will know exactly what I mean.

Rob

You can even used them as a mechanical ''porta power'' with a suitable piece of pipe slipped over the top,used then before boy they will push too ''amazing'' and no oil no mess and no bulky bits in tight places ie pump hoses. john.

Originally Posted by nearnexus

One of the most intriguing locking systems I've seen (and owned) was the double knuckle system that old air cooled VW's used on their car jack.

How that system locked onto a round piece of smooth steel pipe and held the weight of the car was quite amazing.

Anyone that's ever had a vee dub beetle and seen the jack will know exactly what I mean.

Rob

I have never owned a vee dub but I have helped a mate and recall jacking his up. The jack mounted into tubes under the running boards and when the pressure was applied you could not open the door. Don't remember anything about the jack mechanism tho and I am intrigued.

Dean

Edit I just googled them. I think I need one of these re j.ashburn's suggestion.

Originally Posted by Oldneweng

I

when the pressure was applied you could not open the door..

Yes, the shaft got in the way.

Using one as a porta power would be interesting.

Getting back to the pointy tip question, if you want to go this way maybe you would be better off putting a hard bronze tip (brazing rod) on the bolt end.

This would not gouge the metal it's screwing against, yet is very hard and durable.

Rob

Originally Posted by Oldneweng

I have never owned a vee dub but I have helped a mate and recall jacking his up. The jack mounted into tubes under the running boards and when the pressure was applied you could not open the door. Don't remember anything about the jack mechanism tho and I am intrigued.

Dean

Edit I just googled them. I think I need one of these re j.ashburn's suggestion.

Will see if I can dig 1 up for you here some extras around here in the mass of junk. they work well and should be in everyone's tool kit. i will be up your way next week and if you want 1 p/m me John. think is 3/4 pipe that slips over we pushed out the pillars of a side swiped datsun 1600 many yrs ago it came out perfect. Was poor and still am but do have hydraulic friends now.Porta power not the other ''hydraulic friends'' those who will lift any thing Lol. John.