Swifty's build of Howell V4

[Swifty]

Carrying on with the rocker arms, next step was to reduce the thickness on part of the arm. I used the jig that I had still set up on the mill, but drilled and tapped an M3 hole to clamp the parts, I still used a short dowel to locate and hold the other end. The picture isn't quite clear, but you will get the idea. After a quick modification to the jig, the second side was machined the same way.



After deburring, the next step was to machine the slot where the bearing will fit. The slot is .112"wide, but I used a slitting saw that was .060" thick, machining the slot in 2 cuts. Worked out very easy doing this part.



Now all I have to do is a bit of deburring and polishing to finish these parts.



Paul.

 

[gus]

48 pitch gear cutters.
Been buying from TracyTools.com. Just email for price and delivery.Will keep you posted.
Was flipping thru their 2012 Summer Catalogue.

 

[gus]

Hope you have better luck fishing than with the taps, I went flyfishing with a mate a couple of days ago, 1 small one each, but we always put them back.

Paul.

Was kind and thoughtful to release the fish from the wild. Hopefully this fish will get to spawn more to sustain fish population.


Fishing today not best but we did have hook-ups. The water was brackish and bites were not robust. Will try tomorrow. Tide prediction looks good. Hopefully with the very strong spring tide and the brackish water gets flushed out.

Planning to make my own electric fishing reel which will come with drag and line drop. Gear box will be DIY. In fast tidal current,we need to use heavy sinkers which hard to retrieve. A power reel helps.

 

[gus]

48 pitch gear cutters.
Been buying from TracyTools.com. Just email for price and delivery.Will keep you posted.
Was flipping thru their 2012 Summer Catalogue.

48 Pitch Gear Cutter,

I give up. TracyTools estimate is 80 B.Pounds per cutter. Need 4 cutters and thats 320 Pounds and about S$700. After the Howell Engines I have no projects that require 48 Pitch Gears. Its back to Module 0.8 or 0.5. Please advice which Module you are going for.

 

[Swifty]

Gus. I have to stick to 48DP as it just changes too much on the engine. The V4 has a compound gear train, 5 gears in total, the other alternative I have is to make a hob to cut the gears. Only one hob is required for all the different gears, but the only problem that I find with the hobs is that the teeth have no relief on the sides and end up rubbing a lot. I may make one and see how it turns out..

Not having seen the drawings for the V2, only some pictures, I assume that you only have the 2 gears, is it possible to buy some? I could always try to source some here for you if you like.

Paul.

 

[Cogsy]

Guys, I made a hob for my Upshur build and used the same one for my Rupnow Hit and Miss, from memory it was mod 0.8. I'm not exactly sure what you mean by 'side relief' of the teeth (I'm not 100% on gear terminology) but the straight toothed hob ends up cutting 5 flats on each side of each tooth and I'm told is quite a good approximation of the involute form, at least in the smaller sizes that we use. I suspect these flats blend together and round off with a little bit of running in.

What I do know is that my gears have held up well and seem to run relatively quietly (not like those noisy miter gears). The hobs are really simple to make and I recommend you make one up and test it out before you rule it out as an option.

Disclaimer : For my current V4 build I've purchased all the required gear blanks as I feel the gear-train in it is an extra level of complexity I'm not quite ready for. I do plan on making all the gears for my future V8 build though.

 

[Swifty]

Hi Cogsy, it's the teeth on the hob that end up with no side relief. I made a couple of Mod1 hobs in the past, and relieved the teeth as much as I could, but they still rubbed and threw up quite a burr. I ended up buying a full set of cutters and it was so much better.

Paul.

 

[Cogsy]

Ah, now I understand. I agree, the gears a hob produces do need a fair bit of deburring.

I haven't done it myself but supposedly it's not that difficult to make your own single tooth involute cutters, you just have to be able to accurately grind cutting tools into 'form' shapes. I have zero idea how you work out what shape each cutter needs to be without a template or something to compare it with though.

 

[Charles Lamont]

"Gears and Gear Cutting" by Ivan Law, ISBN 978-185242-911-2 explains how to get a close approximation to an involute using circular arcs, how to make a tool put the form on a fly-cutter using a pair of hardenend silver steel buttons, and for the really advanced, how to make a form relieving attachment for making multi-tooth cutters.

 

[Swifty]

Charles and Cogsy, thanks for the replies, I'm aware of Ivan Laws method, however the cutters will only cover a certain number of teeth each. Unless I build a form relieving attachment, I'm in the same position as I am with the hob, no side relief. There is a method of using the buttons to make a single point cutter and offsetting the centre to give some relief, but I have decided to make a hob again. I will back the teeth off as much as I can to prevent rubbing. When I last cut brass gears with a hob, there was a fair burr thrown up, however the brass was a fairly "sticky" type from the scrap yard, maybe I can seek some harder brass next time.

Paul.

 

[gus]

Hi Paul,

Here is contribution. Plan to go "Module'' on the gear train. Failure of which,will splash on Imperial Gear Cutters. The Howell Engine is a long term project. The carbs alone set me back three weeks.Working on the throttle barrels tomorrow. Just figured out the working procedure or routing list. The carbs looks good mounted on with fasteners to O/Heads.

There are 11 gears to cut. With this project, we can claim to have cut more than our fair share.

Still going snail pace and enjoying making this Howell V-2 Engine.

Take care.

 

[Swifty]

Gus, it's impossible to match up the centre distances for all those gears if you change to a Module form. I laid out the V4 gears on my CAD and gave up in the end, it is just too difficult to alter the centre distance dimensions. There are more gears on the V2 than the V4.

Paul.

 

[Swifty]

I had a go yesterday at making a hob for the gears, those teeth sure are small. I turned the tooth form in the blank first, that came out great. Next I milled the relief on the cutter, that was the downfall, the burrs thrown up by the cutter were just too hard to remove from the teeth, I tried putting the cutter back in the lathe and remachining the tooth form, but a slight mismatch ruined that.

Next move, I will mill the relief on the blank first, then turn the tooth form afterwards. Some pictures to follow later.

Paul.

 

[gus]

Charles and Cogsy, thanks for the replies, I'm aware of Ivan Laws method, however the cutters will only cover a certain number of teeth each. Unless I build a form relieving attachment, I'm in the same position as I am with the hob, no side relief. There is a method of using the buttons to make a single point cutter and offsetting the centre to give some relief, but I have decided to make a hob again. I will back the teeth off as much as I can to prevent rubbing. When I last cut brass gears with a hob, there was a fair burr thrown up, however the brass was a fairly "sticky" type from the scrap yard, maybe I can seek some harder brass next time.

Paul.

When hob is done ,please mail Gus drawing. I know nothing on making hobs.
48 Pitch with DIY Hob is a very wise choice. About to get off from PC Desk to work on throttle barrel. Enjoying every minute of throttle barrel making. Drilling the mini orifice is fun and challenging. Holding my breathe at every plunge.
Take Care and have a nice day.

 

[Swifty]

Here is the saga of making the hob, I'm lucky that I have a cutter grinder that I can put a 3/8" square tool bit in, this made it very easy to grind the required angle and relief on the toolbit. When I mounted the toolbit in the lathe, I clocked up the side of the toolbit to make sure that everything was nice and square.



I used 16mm dia silver steel for the blank hob, Machining the grooves in went extremely well, I measured the depth of the tooth using a 0.9mm drill bit shank, I had previously worked out the size required on the CAD.



I used a plunger dial indicator to get the correct spacing between the teeth.



Everything was going well until I machined the relief on the cutter, the burrs were just too hard to remove, I tried returning the form again, but there was a slight mismatch, so I scrapped that method.



Paul.

 

[Swifty]

The next thought was that I would machine the relief a bit deeper and then go back to the lathe and cut the grooves for the teeth. this gave a much better result. I hardened the cutter by heating with my Map torch and quenching in water, I didn't bother tempering as their is not a lot of work that the cutter has to do.



The cutter was set up in the mill along with the dividing head, I centered the tooth profile with the centre of the dividing head.



With everything set up, I cut the teeth to full depth in one go.



After going around once, I moved the cutter down by a tooth and ran the cutter through again, that's 78 indexes each time, By the time I was finished, my indexing hand was starting to cramp. The drawing calls up 12L14 free cutting for this gear, but not having any the required size, I used some brass instead. The rest of the gears will be 12L14 though. I'm not 100% happy with the finished gear, the tooth form looks slightly wide in the gap, maybe I'm being too critical. I will have to wait until I cut another gear to check the mesh.



Gus, if everything works out OK, and the hob is still good, I can send the hob over to you if you like. Will have to wait and see how it is by the time I finish all the gears.

Paul.

 

[gus]

Thank You .Uncle Paul. But Please let Gus make his own. Failure which,that is when I threw the towel,you throw me the hob. I am itching to make my very first hob.

Your very first gear looks great.

Following info required.

Hob Pitch.
Tool bit angle.
Depth.

Looks like in the future,Gus no longer buy Gear Cutters from ctctools,


Just cleaned up the two throttle barrels. Will make the Throttle Lever Hubs tomorrow.

 

[Swifty]

Hi Gus, the tool angle is 14 1/2 deg per side, pitch between teeth is 0.0655", now tool depth depends if you get your tool bit to a point or a slight flat. Going deeper with the tool bit isn't any problem, as only the top and sides of the hob need to cut. I made my tool bit smaller than theoretical size at the front and just went deeper. The hob gap width needs to be 0.0435", the size at the root is 0.019", the theoretical depth is 0.047". My toolbit was narrower at the front, so I had to go deeper, I used a 0.90mm drill shank and micrometer to check the depth required. Place the drill shank in the V and measure over the drill and the opposite side of the blank, just make sure that there are no burrs, you will be at correct depth when the size is .003" larger than the hob diameter. Of course you can use drill shanks in opposite sides, but the size will be .006" bigger over the 2 drills. I only used one, as it was too hard to balance everything, just remove those burrs.

Paul.

 

[ruzzie]

He are a couple of cutter I had made.
I used my Eureka form relief tool to make the 48DP cutters for my Howell.I have shown the finished gears along with my jig for checking the gear center distances
The hobb was for a gear used in a microscopes fine focus adjustment mechanism I think it was around 64dp. I was going to use the Eureka tool again but I found a site that showed you how to make a hobb and it look like a lot less work so I went with it.
http://www.helicron.net/workshop/gearcutting/involute-gears/

Paul R

 

[Swifty]

Hi Ruzzie, I like the fixture for checking the centres. I have now machined all the gear teeth, I need to just finish the bore on the 2 cam gears. I checked the centre distance of the crankshaft gear and the large gear in the milling machine, everything looks fine.

I was frustrated at one stage with machining the teeth, the teeth looked like they were being ripped off the blank, I couldn't understand it, I made another blank and the same problem, then I realised that I had not changed the quadrant arms on my dividing from the previous gear with a different tooth count.

Paul