Member postings for brian jones 11

All my years in CAD and I never appreciated or noticed the difference between flipping and rotating 180

Gobsmacked - how many hidden errors did that create?

Still my by bridges are still standing but Hammersmith is in trouble but I have a cunning plan

OMG the Monsignor is RIGHT

10^3 apologies, I have flipped my gear blank wrongly????????. I will have to investigate

You do indeed have to angle the tap anti clockwise 11.4 deg for a 10 tpi (5.711deg ha)

GOT IT

My gear flipping created a mirror image which reverses LH to RH

Wow thats an easy mistake to make

Edited By brian jones 11 on 22/08/2021 13:45:03

Well this topic has certainly addled a few FES pates, like stirring up the suds sump

So to demystify the limits of plausible conjecture and give a platform to the deniably involved

What else on lockdown Sunday morning from the desk within my Anderson Shelter

I hope you can see the double helix (truncated Whitworth form BTW). I skewed 6 deg for fun and made from 2 identical blanks chived at the same time

For the follically scarified, note that the yellow gear has been flipped over 180 to make the red

also if you skew one gear wrt the other fractionally then you can mitigate backlash

Now with the appliance of science I shall endeavour to make an animated version showing meshing and also the reviled tap attacking gear blanks

My biggest challenge will be to post mpg or gif on this board, I havent seen any other Disneys on here

Anyone know how its done - maybe Dropbox?, Ive never done a Youtube upload yet (do you have to sell your soul?)

Sorry JP missed your eminent description above, most interesting

As you point out, this OP is not about using hobbing gear and all the expensive industrial attachments involved, way off topic

The point being that a hobbing method ties the spindle mechanically to the mandrel in much the same way as screw cutting on a lathe (excluding the tedious divider plate method)

This is examining whether FREE HOBBING has a place for the hobbyist NPI.  Its clearly demonstrated in making simple worm gears so this is just an extension of the topic. As seen above there are a lot of armchair misconceptions.

One point to note is that theoretical errors can creep in

eg

a) say you want to make a ruler with a 1" block.  Use it to scribe 12 marks then do you have 1ft - well clearly it depends on the accuracy of the block.  Hope you can see the implication of cumulative errors

b) Instead use the basic tech drawing trick use the block to make 12 ticks then project that onto a 1ft line and you have your accurate ruler with 12 inches

So the tap method is using method a)  and the dividing plate (or hob) is using method b)

Now thats the theory but what happens in practice

Edited By brian jones 11 on 22/08/2021 12:44:19

Edited By brian jones 11 on 22/08/2021 12:46:01

see what you can do with a big enough tap

https://www.youtube.com/watch?v=mtV8Zu5EtUE

Now I thought you could do something like that

The Anderton boat lift used 'herringbone' gears. Big ones. They were cast and then run in pairs in a sand bath to bed them in to my knowledge.

https://www.alamy.com/anderton-boat-lift-is-a-two-caisson-lift-lock-near-the-village-of-anderton-cheshire-in-north-west-england-image236836670.html

that should keep the back seat modellers quiet for a while

BTW have you all spotted the deliberate design error

Pay attention at the back

Or maybe you don't mean herringbone but just have two straight gears with some angular offset to take up the backlash.

I have a cunning plan

I am making up gear blanks using hard wax. I will set up a jig so i can rotate the tap by hand and closely observe what is happening

I will also look at some 3d dynamic modelling s/w i used many years ago (my brian hurts already)

Well it beats lock down dunnit

Sometimes I want to give up

https://en.wikipedia.org/wiki/Herringbone_gear

Well isnt the worm gear an endless rack?

Get creative, how about a spiral rack

Spur gear with round contour at edges, eg more tooth contact in the mesh

I am envisaging herringbone gear set , ie two spurs, one reversed against the other - no backlash

Waiting on mtl to start my modelling

After all who would ever dream up a pair of oval gears

https://www.radartutorial.eu/17.bauteile/bt08.en.html

Rack and pinion or worm gear, both have been shown to work to an extent.

so its not so far off the involute as expected then, hmm I must get on and make some

you see I have a large qty of plug taps 1" to 2"W and xl metric MS washers from M30 - M80 all 4mm thick

though I may have trouble with the steel used? Perhaps might need to anneal one, might be work hardened from being punched out of strip.

I have ordered som mtl to make a simple mandrel jig to be held in my lathe QCTP. In theory I can raised the tooll holder so as to get a straight cut across the witdth

I think I can see one reason why it will fail and that is that when starting the cut your tap tpi will spread across the OD of the blank but as you go deeper the tpi have to spread over the inner ID of the thread so less space for the original cut? which is why teeth numbers turn out less than expected?

Edited By brian jones 11 on 20/08/2021 17:18:34

Yes indeed I fully recognise its a crude method hence "rogue method" but there maybe some mileage for simple apps

After all there is a whole science you could spend years on perfecting the perfect tooth cos users wanted efficiency and also quiet operation and long life

none of the above would be satisfied by my dirty method

As you can imagine it would vibrate under load

Something tells me this isnt the thread form I am going to get, it doesnt feel right, I am assuming a tpi tap of 16

Perhaps its why members have reported that they didnt get the number of teeth they expected? Hmmmm

Edited By brian jones 11 on 20/08/2021 15:52:22

Edited By brian jones 11 on 20/08/2021 16:56:55

Remember the original proposition

" Primitive but very quick and only suitable for light load low speed apps and probably noisy "

Some mentioned mechano gears - well Im not pompous - it worked for a million kids

I asked if anyone else had actually tried this method rather than generate a whole sheaf of plausible conjecture

Its not helpful to throw a hissy fit, I did this already

this is the link from the pic above

http://www.maedler.co.uk/

try it yourself, for me it just leads to a dead end back to germany

being given a dead link is very frustrating and wastes a lot of time

you found your link by doing a separate search for Huco

Well I shall try out this free hobbing method

I agree the gears will only mesh with others produced by the same tap

but it will be interesting to see how two such gears perform together and if they would suffice for light duty

dont you think

and BTW I belong to the school of thinking first and asking around before making chips, unlike the suck it and see brigade.

quote

It doesn't take that long to cut spur gears by conventional methods, provide one gets on with it rather than pontificating on forums

as per AJ with his superior minded 4 axis CNC machine

Obviously forgotten how long it does take to cut spur gear - the point of my original post = as they used to say "read the question carefully first, dont give an answer you would like to be asked."

I was just thinking out of the box

followed up on Madler website, very comprehensive, BUT I cannot see how to buy anything, no on line shopping cart or any hint of a sales facility

I am lost here pls advise

I have seen vids of using diving head for use with a milling form tool for cutting a spur gear say 3" dia, 1/4" thick with say 80 teeth

OMG what a painfully slow process as you mill each one

Yes there are powered head linked to spindle to cut these also - v expensive attachment

Now I was looking at some large bsw plugs taps i have and wondered if these might work

Then I saw a vid on making worm gears using this method, where the blank is mounted freely rotating on a mandrel. The rotating tap held in a lathe chuck and the blank is brought crossways to meet the tap. The action of the tap screws the blank around as it cuts and you end up with a worm gear which can be operated by a bolt

https://www.youtube.com/watch?v=XIzlg_uObwQ

Now I can see the FES going nuclear on this

Yet I have not found a vid on using this technique for a spur gear

Consider a 3/4" bsw x 10 tap on a 3" x 1/4" thick blank gives ca 100 teeth

So the tap is mounted in the spindle and the blank on a horizontal mandrel

First pass will get the thread depth, then the bed will be slid across on the x axis to get a flat bottom for the tooth form (I think)

Primitive but very quick and only suitable for light load low speed apps and probably noisy

put them in a gearbox with heavy oil and used nylons or sawdust

Anyone ever tried this

Seems too good to be true

Thnx JB as you can see I was looking in the wrong place with the wrong keywords - its in the aesthetic world of CNC and timing belts etc. but prices I saw for large driven cogs were silly money for a hobbyist £50

Industrial suppliers will also have unaffordable prices.

so a new door has opened for me and I have acquired an electric window assy for a tenner - well its a start and I agree that going to stepper motors really is overkill for this duty.

thats more like it, they sell the SS belt and the sprocket (small 1" dia)

presumably one would need to make a larger driven wheel say 75mm dia oneself

hmm another chalenge

would one calculate the pcd and drill a set of teeth with a 5mm drill (or less probably) in an ally blank

probably be noisy

I will have to check torque requirements

Bed speed I think a max of 3" per min down to say 0.3/min (must recheck) so 10 tpi gives 30 rpm max on the lead screw.