Gear question

[Gordon]

Has anyone tried cutting DP (inch) gears using Module (metric) cutters? I have been looking at the Howell V-2 engine which has 48 DP gears but I have metric cutters. .5 module cutters are close to the same size. It would would seem that as long as the gears were cut to the proper inch dimensions the slight profile difference should not be a big problem. I have tried making my own hob in the past with limited success and I would think that the metric cutters would be as close as my seat of the pants methods used to produce the hob.

For some reason the metric sets are relatively inexpensive and purchasing the proper inch sets gets extremely expensive.

Anyone tried it?

 

[Swifty]

Hi Gordon, I looked at using Module cutters instead of DP for the Howell V4 gear train, just doesn't work. I was trying to use full cut Module gears, I laid it all out using CAD, but I just couldn't get near enough. As far as using a Mod cutter and keeping the inch gear sizes, you will have trouble, it won't give you correct mesh as the gaps have to match the teeth. I had great success with using a Hob, and now another member plans to use it. I know that a 0.5mod cutter is close to 48DP, but it may as well be miles away as it makes a big difference.

Paul.

 

[MachineTom]

If I did not want to purchase 48 dp gears or cutters, Then just modify the position of the camshaft in the engine, so the mod cut gears work.

If given the choice between moving the camshaft position and buying a couple of little gears, to me its a no brainer, Just buy the gears.

I built a friction car for a client, I needed 16 gears in 6 different sizes. while I had the cutters for that pitch, the thought of cranking the dividing head many hundred times, made buying already made gears a easy decision. An issue I did not expect with the gears was that the mathematical C/C distance was a close but not good enough for the minimum friction I wanted.Just a thought is layout the C/C distance on scrap, and fit the gears, you may need to change the distance for smooth quiet running.

 

[Cogsy]

If given the choice between moving the camshaft position and buying a couple of little gears, to me its a no brainer, Just buy the gears.

This engine design makes the situation a little less straightforward. It has twin cams and a quite convoluted gear-train with something like 12 gears mating in various arrangements to drive them. Just shifting the cams wouldn't allow a change in DP and of course the cost of 12 gears would be a bit pricier than more traditional designs.

Personally I'd be looking towards having another go at making a hob. It can be made out of scrap so your only real cost is time. I've sucessfully made a MOD 0.8 one but I appreciate making a 48 D.P version may be more difficult.

 

[Swifty]

Hi Gordon, you can see here how I made my 48DP hob.
http://www.homemodelenginemachinist.com/showthread.php?t=24215&page=10

Paul.

 

[Gordon]

Thanks. I tried to make gears with a hob when I made the Rudy Kouhoupt steam traction engine and was not too satisfied with the results. I did not spend a lot of time then because I found the module cutters were quite inexpensive so I just calculated new centers with CAD and went with the module cutters. I still have the hob which I made at that time so I may just spend a little time trying it again. On the Howell laying out new center distances is not really practical.

Good thing I do not have to make a living doing this.

 

[gus]

Hi Gordon,
Are you doing the V-2 or V-4 ?
I am in the same dilemma. Paul Swift gave me a DP 48 hob and I will hobbing timing gears oil pump gears etc. Going metric will be scary. I have Module 0.8 and 1.0 Cutters. The V-2 has many mini parts and the list seems unending.I am still at the top end-------the outerheads. Meanwhile I am taking a break as I am near to burnt-out. Much as I want to go faster but working with mini lathe and mill is just not possible. WeekEnd fishing helps.

 

[Gordon]

Gus:
I am working on the V-2. Just got started. Presently squaring up the crankcase. I have been watching your build log. I hope to learn from your errors. I can make my own mistakes so I am hoping to learn from others. I have a hob that I built for the Rudy K steam engine. They were also 48DP so I will give it a try when I get to that point. That is still a long ways down the road.

Gordon

 

[bazmak]

Nice engine Gus for a fisherman.Dont burn out.Do you eat the fish?
My ideas,being the same age and with the same limited space and money in the bank,was get the the biggest and best lathe and mill that suit.Dont struggle
and make an enjoyable hobby hard work.You cant take the money with you

 

[gus]

Hi Bazmak,
I was running a machineshop with a good compliment of machine tools and no time to really get hands on .
Being couped up in a balcony size machineshop with mini lathe,mill,bench drill and a good size grinder can be quite frustrating when handling bigger jobs. But on the other, its working smarter and getting a job piece done well. Cash wise, I am surviving on dividends paid out twice a year. Agree. Best watch the spending and buy ''needs'' not ''wants''. RTs are so expensive landed in Singapore. China RTs are cheap and nasty. Taiwanese RTs no cheap too.
Next week taking darling boss for a 4 day eating holiday in Penang which known for unique hawker food. Its a three week break from V-2. Those small parts are so challenging and so easy to mess up. Meanwhile I am doing something more relaxing--------------carpentry making instrument cases. Getting to be pretty good with corner joints. Using tooth picks as dowels. Is this normal practice with small boxes??

Eating your own catches is so enjoyable. Its fishy dinner 2----3 times a week.Freshly caught fish is good eating. Fish is kept alive in the live tank with continuous supply of sea water. These fish tend to belly up and best to deflate their float bladder by pricking at the swim fin body portion to let air out . Properly done and they back to normal and stay alive.Fast swimming fish have no float bladders and will die fast.

Take care of health and wealth.

 

[kvom]

The design of a gear train starts with desired ratio(s), then maximum space available, then DP/module. The center spacing and gear diameters is the output of the design process; trying to change the DP and module while retaining center spacing is almost impossible.

 

[FCJimmy]

I just noticed your thread and thought maybe one of you guys could tell me how you cut two gears of differing diameters on the same blank with very little space between them. It would be impossible with a gear hob, and I can't find any end mill type cutters anywhere which will cut gear teeth close to another disk. Does someone make gear-cutting endmills, or is that something out of my imagination ?

 

[Swifty]

I believe that they cut the smaller gear with a gear broach, it's a short up and down movement where they can stop in the gap between the 2 gears. I think that they do similar for internal gears.

In your case, depending on the size required, you could make the smaller gear with a shoulder and shrink the larger gear onto the shoulder, they could even be pinned to make sure they stay aligned.

Paul.

 

[Swifty]

Here's a large gear loctited on to a small gear, the pressure on these gears is not great, if it was, they could have been shrunk on for a tighter fit. This is the largest gear on my Howell V4 build. The gears are 48DP, cut with a home made hob.



Paul.

 

[Gordon]

In doing some quick searching on Amazon it looks like it is possible to purchase the gears needed for the V2. They would require some machining for bore and hub etc but that is much easier than making the whole gear. The gears are about $7 each so that is certainly reasonable. I would still have to make the spline gear but I do have a hob for the 48DP so that should be fairly easy to make. Heading out of town for the next few days so I will pursue it next week.

 

[Cogsy]

If you have the hob anyway, and you are forced to hob at least one gear, then you might as well hob them all. The math can be a bit tricky, but once you have all the figures the blanks are simple to make and the hobbing itself is straighforward. The sense of satisafaction will also be much more than if you buy them. I'm starting to regret buying the gears for my current build now...