Author Topic: Burrell Single Crank Compound Traction Engines - 4" Scale  (Read 40650 times)

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #105 on: August 17, 2017, 10:57:19 PM »
I think that is all the pictures in this thread updated. All I've got to do now is go through my other posts.  :???:

Andrew

Offline Kim

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #106 on: August 17, 2017, 11:59:46 PM »
Wonderful!  Thanks for taking the time and effort to update your pictures Andrew!  :ThumbsUp: :)

I was looking back through your build here and noticed one of the pictures still showed the PhotoBucket Ransom notification.  I was going to tell you that yo missed one, but then realized that it was actually Jo's picture that was missing!  Not yours!

I'll bet we end u with a bunch like that, where someone else has posted on a thread and doesn't remember exactly what or where so it doesn't get updated.   Ah well, such is life.

Your thread looks great!  Thanks for taking the time to update Andrew,
Kim

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #107 on: August 18, 2017, 10:51:16 AM »

I was looking back through your build here and noticed one of the pictures still showed the PhotoBucket Ransom notification.  I was going to tell you that yo missed one, but then realized that it was actually Jo's picture that was missing!  Not yours!


I noticed that too; don't suppose it'll get fixed, but there are worse things in life to worry about.

Andrew

Online Jo

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #108 on: August 18, 2017, 10:57:51 AM »
I am slowly going through and updating my own threads with Copper mine pics but it is difficult to know where I might have linked photos from Ransomsuckit  on others threads  :-\

Jo
Usus est optimum magister

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #109 on: August 18, 2017, 11:06:56 AM »
I recently fitted the drive to the water pump. I've been putting it off for months, as it would involve dismantling half the engine. And I knew I'd be disappointed if the tight clearance between the connecting rod and ram turned out to be wrong.

In the event just removing the flywheel side crankshaft bearing and housing, and loosening the other side, was enough to get the eccentric onto the crankshaft. There is a small U shaped bracket that sits into the ram and holds the gudgeon pin for the connecting rod. I made the pin and fitted the bracket. In passing I thought it was odd I couldn't find the bracket for the second engine; must have put it in a special place. Everything was fitted - and disaster. Something hard was stopping the ram being fully inserted into the pump as the crankshaft rotated.  :-[

After a sulk I fired up the 3D CAD model to track down the error. All seemed fine in the model. The first thing to check was the position of the ram when fully home. I took off the water pump and ram to investigate the internals. And out fell the second U shaped bracket, some special place!

With everything re-assembled I'm pleased to say that the water pump drive works fine. The eccentric drives the water pump quite happily when the flywheel is turned, despite there being no grub screws holding it to the crankshaft at the moment. So there can't be much friction in the system. Here's the complete assembly:



Andrew

Offline scc

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #110 on: August 18, 2017, 07:41:20 PM »
Glad to see you are back at it Andrew              Best Wishes    Terry

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #111 on: August 27, 2017, 09:25:10 PM »
That should be all my pictures updated across all my posts. Let me know if I've missed any. I can now give Photobucket a Harvey Smith.

After that back to governors. Like a lot of other things on my engines these have turned into a significant piece of theory and design. It's interesting to note that the governor can be described by a second order differential equation, the solution of which results in two complex conjugate poles on the s-plane, which determine the response of the governor. I'm familiar with the s-splane as it is fundamental to understanding filter design and characterisation. But it's going to take a bit of work to understand the application to mechanical governors. Of course that may be a load of old balls, but balls are important. Scaling works against one when it comes to the mass of the balls. So as well as increasing size a bit over scale I'm looking at high density materials. Gold, platinium and indium are out due to cost, and depleted uranium might bring a glow to the cheeks. Instead I am experimenting with tungsten and its alloys.

Andrew

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #112 on: October 09, 2017, 05:26:59 PM »
Machining tungsten has proved to be something of a saga.

First I tried pure tungsten. It turned ok with inserts, but didn't leave a particularly good finish. However, drilling and tapping proved to be very difficult. If the tool didn't break the material cracked, as it is brittle, just like the datasheets say! Here's what can happen when hand tapping:



Next I tried a tungsten alloy, 87% tungsten, plus nickel and a bit of iron and cobalt. This turned beautifully with insert tooling, leaving a nice finish on the order of 2m Ra. Drilling and tapping again proved difficult. The material is sintered rather than being truly homogenous and is quite abrasive. I found that HSS drills worked, but the tips were blunt after one hole. After some experimentation I tried slow helix carbide drills - they worked very well with the swarf coming out as fine particles, like brass. Tapping still proved difficult. The material suppliers advice is that since tungsten has a high Young's modulus it tends to grip the tap, so one should use spiral point, or spiral flute, taps intended for such materials. I bought some posh (and spendy) taps for same, and they didn't work. They'd do a turn or two and then the material gripped them so tight it would put a boa constrictor to shame. It's amazing how far a HSS tap will twist before it breaks.  :o  I dropped from a thread depth of 50% to 10% and still no success. I managed to make one trial ball, but it wasn't really satisfactory for production.

After a sulk, and to let the bank balance recover, just out of curiosity I tried a fairly worn set of M4 Dormer hand taps. To my surprise the taper and second tap cut a 50% depth thread very nicely. The bottom tap still had a tendency to get involved in a death grip if you turned it too far. Armed with this information I made a second test ball. Here are the parts before assembly:



The small holes are 1.2mm diameter and drilled 8mm deep before forming the hemisphere, which was done using a hydraulic copying unit. The small screw that holds the two hemispheres together is made from a tungsten/copper alloy. It machined well, and took a good thread with a die. I haven't tried threading it with a Coventry diehead yet. This is the complete assembled test ball:



All the tungsten and alloys were bought via Ebay. A local metal stockist wanted 689 for a 300mm length of 25mm diameter tungsten/nickel alloy. Told 'em that was more than the project could stand. Now that I've sorted machining the tungsten I can start designing the governor. This starts with the balanced valve, which will give me the movement needed for fully open to fully closed, from which simple geometry will give me the distance the balls need to move and hence the centrifugal forces involved. That will then allow me to calculate the controlling force needed from the leaf springs, and hence determine the size and material needed for the springs. Here is the basic balanced valve and body:



It'll need some fine tuning, and I also need to check the space available in the cylinder block.

Andrew

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #113 on: November 06, 2017, 11:07:24 PM »
The front wheels for my traction engines have been a bit of a saga. In order to roll the rims I designed and made a set of bending rolls, specifically to fit on the milling machine table:



Once rolled the rims were arc welded together. I had planned to cut a groove in the rolls to form the T-rings, but instead chose to get them laser cut. To save material I had them cut as quadrants which I then welded together. Care was taken with the measurements so that I ended up with rings rather than ovals. In retrospect it would have been quicker, and probably cheaper, to roll the T-rings. It was satisfying that the T-rings slipped into the rims with the aid of a few taps from a hammer. After fitting the T-rings were welded both sides. It may not look pretty but the wheels are not going to come apart.  :)

All the spokes were CNC milled from annealed cold drawn steel. I am building two engines, one of which will have steel tyres and strakes and the other will have rubber tyres fitted. The quadrants for the front wheel tyres were rolled as per the rims and riveted to the wheel rims with 3/16" steel rivets. Despite concerns that I had over done the countersinking on the tyres the rivets just filled said countersinks. Here are the spokes being fitted, using the same plate I use for welding the T-rings into the rims, so all the holes for clamps are already there:



The spokes are bent using a box 'n' pan folder, albeit some what over it's specified material thickness. :o  Here are two completely spoked wheels, one with steel tyres and one not:



Note that the three rivet holes on the spoke palms are on an arc not a straight line. That should keep the rivet counters quiet.  One last thing to try was checking the wheel runout. A crude check by spinning the wheel on its axle and watching a rule close to the rim suggests that maxiumum runout on the rim and side to side wobble on the side of the rim is about 1mm worst case:



Of course there's still a lot to do; all the spokes need riveting and then on to the rear wheels. Most of the parts for the rear wheels are done, but there is still some welding and machining on the hubs to do.

Andrew

Offline Kim

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #114 on: November 07, 2017, 01:45:24 AM »
Nice to see more progress on your traction engines.  The wheels look great!  And, of course, I can't go too long with out mentioning how HUGE they are!

Nice set of rollers you made there too.  The seemed to do the trick.
Kim

Offline Jasonb

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #115 on: November 07, 2017, 07:19:01 AM »
Andrew, will you rivit the ones to be vulcanized before having that done? I have seen some sent with just bolts in the holes so that the wheel can be taken apart and cleaned up afterwards then rivited with the rubber on.

Looking good, you will soon be pushing them around the house making chuff, chuff noises!

Offline kvom

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #116 on: November 07, 2017, 10:55:38 AM »
Just caught up with this thread.  Superb work.

WRT to tapping tungsten, I suspect thread milling would have worked well.

Offline jadge

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #117 on: November 07, 2017, 12:01:04 PM »
And, of course, I can't go too long with out mentioning how HUGE they are!

Yep, the OD of the front wheels is 15", the rears will be 24". The bending rolls are initial pinch, so if you swap the work end for end at each pass you don't get flats on the ends. The process can be modelled as simple beam bending, fixed at one end and a point load at the other end. The stresses need to be high enough to exceed the yield point of the material. If I recall it was something 1000lbs force?

The company I spoke to regarding the rubbering (Reliant Rubber in Batley) wanted the wheels assembled beforehand. At least I think that's what they said; I had some difficulty with the accent.  :embarassed: They also shot blast and prime after vulcanisation. So I think I will rivet the wheels aforehand, but leave the hub covers off. Ideally I would collect the wheels without priming so I can add neat fillets to the wheels. I will be consulting a mate who has already used the company.

Thread milling was suggested on another forum for the tungsten alloys. I'd like to try thread milling, but I could see me breaking a lot of expensive cutters learning about thread milling with M4 in tungsten. That would have deeply upset my wallet.  :'(

Here are the front spokes:



And the rear spokes, which need a bit of a clean up:



All the spokes were cut with a 6mm cutter, three roughing passes full width and 2.2mm deep, and a finish pass at full depth, taking off about 0.4mm. The rear spoke design has been changed to incorporate four rivet holes as per full size. The palms are slightly narrower than originally drawn. The specified width is 2-5/8" which is not a standard size. Buying 3" wide stock would have been a lot more expensive than 2-1/2", so I went with the latter. The rear hubs are ovoid, so the rear spokes are of different lengths. However, having drawn everything in 3D CAD it was clear that I could get away with only two lengths, trimming on assembly, which I will be doing anyway. I also had some machining problems. After an initial issue with over-ambitious feedrates all was going well until I heard a 'orrid noise coming from the workshop.  :o The milling cutter had lost it's teeth and to give the Tormach mill it's due it was still pushing a by now rather crude ballnose mill through the work. I changed the cutter, and the blank and continued without a problem. At the end I tried the blank which had broken the cutter previously. The cutter went a bit further, but then broke in the same way. All I can think of is that something was wrong with the material, possibly something in the mix that shouldn't have been there.

Andrew

Offline Jasonb

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #118 on: November 07, 2017, 01:13:06 PM »
I had similar with a bit of 2"x1" black bar recently, found a hard spot in it that killed 3 carbide cutters not to mention the HSS ones that found the hard spot first. It wa smentioned that the very end of a bar from the mill can have hard spots, I assume when being rolled the end cools quickest or gets chilled

Offline scc

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Re: Burrell Single Crank Compound Traction Engines - 4" Scale
« Reply #119 on: November 18, 2017, 08:19:53 PM »
Andrew,       Reliant did my tyres. I chose them on a balance of price and reccomendation . Their service and their product is excellent.
                    I would only have your wheels left unpainted if you intend to collect them as soon as they are ready. They will be blasted and start to oxidise immediately. Reliant's primer on my wheels was a fine, even coating that needed minimum flatting.

Best Wishes          Terry