BenHawkins Posted July 24, 2015 Author Share Posted July 24, 2015 Thank you for your thoughts and the supplier suggestions. I had a good look on the shelf and found a similar looking gear from a newer Dennis gearbox: But unfortunately when I checked it is one tooth short and 5DP. I then tried the appropriate involute cutter against the existing gear. These cutters allow you to make gears with a good approximation to the correct tooth form; a set consists of 8 cutters. A number 1 cutter allows you to cut a 135 tooth gear to a rack and you select the other numbers for the number of teeth on the gear. This one is a number 3 (for 35 to 54 teeth) that I picked up at some point. But despite being the correct number for 37 teeth it does not fit well because it is for 14.5 degrees pressure angle and the gear appears to be 20 degree pressure angle. Early involute gears were usually 14.5 degree pressure angle but at around this time a 20 degree pressure angle found on modern gears was starting to be adopted. At 20 degrees the gear teeth are stronger. Quote Link to comment Share on other sites More sharing options...
nz2 Posted July 24, 2015 Share Posted July 24, 2015 I have counted 37 teeth and this ties in with the parts book that states it is part number 754/4 and a replacement costs £1.13s; perhaps I will call Dennis in the morning and see if they have one . . Like the idea. Was not sending a telegram the way to order parts in the day. Problem now is who would deliver the telegram if it could be sent. Boys on bicycles seem to have disappeared! (Telegrams are no longer available in NZ) Doug Quote Link to comment Share on other sites More sharing options...
Charawacky Posted July 24, 2015 Share Posted July 24, 2015 Hi Ben, I have had to replace gears in my 1913 Chalmers car, google these guys, Sovereign Gears Ltd, they looked after me and the gearbox is now like new. Andy I can also have had good service from these people with a number of sets of crown wheel and pinions, for the Crossleys. Tom Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted July 26, 2015 Author Share Posted July 26, 2015 I have sent off the drawing of second gear to get some quotes. I will then decide if both parts of third need replacing; these will be more expensive as there are splines etc. I ground a tool to 55 degrees and cut the threads in the 12 nut blanks I made last week. Then with a little bit of adjustment to the bolts (I damaged some of the threads getting them out) and drums (opening up the notch) the drums could be fitted to the wheels. I clamped up the brake linings and drilled through using a battery drill. Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted July 26, 2015 Author Share Posted July 26, 2015 Then came counter boring for the rivets. I found a Morse taper shank counterbore but as the two shoes are riveted together they are a bit of a pain to fit on my machines. I decided to machine the start of the taper to parallel so I could get it in the battery drill. It should still work in the machines if required. The shoes did not originally have linings and where they have been drilled they come through on the radius of the casting making the whole riveting process quite difficult and requiring extra long rivets (thankfully these were available from Bruce Pickles). Each rivet needed to be a different length. Luckily I had Sarah to help by holding the shoes whilst I hammered (but never once hit her fingers, so she will probably help again in future). Then came shaping some oak blocks that fit between the springs and the axle. Nothing too complicated just some sawing, drilling chiselling and sanding. They have now had a coat of varnish. Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted July 26, 2015 Author Share Posted July 26, 2015 The back axle and wheels are nearly ready for assembly. I need new felt seals and a day of good weather so I can get it all out in the yard to slide the wheels on. So I am back thinking about the engine and have been machining the tappet sleeves again this week. I started by roughing the one end. Then turned them around finishing the other end to final dimensions. Then finished the top end and transferred them to the milling machine to profile the flange. I set the zero on the x and z axis to suit the rotary table. For machining I would the x axis to the zero I had set then rotated 180 degrees before proceeding in the x axis. There is still quite a lot of work to do on these but at least I have made a good start and have the six replacements to this stage. I have been thinking about the broken rings that retain the gudgeon pin. From the top there are three conventional rings then a groove for oil control. The end of the gudgeon pin is slotted and is a floating fit in the piston. A ring then restrains the gudgeon pin; this ring if compressed into the piston groove does not close up so it plays no part in compression. As all these gudgeon pin retaining rings are broken it is difficult to know if they should be sprung out like a compression ring or sprung in (like an external circlip). The replacement rings should be fairly easy to make from cast iron as they do not need to end up circular when closed up after cutting the ring. But will they all break again? Presumably they are broken by the gudgeon pin binding up in the little end when there is poor lubrication. If the broken bits of ring could cause damage to the bores would it be better to leave them out and fit bronze buttons to the ends of the gudgeon pins? Quote Link to comment Share on other sites More sharing options...
Sean N Posted July 26, 2015 Share Posted July 26, 2015 ...The shoes did not originally have linings... What did the braking originally then, Ben? Was it just metal to metal contact? On the gears, I have to say with industrial machinery I've always ended up going to HPC and never had a problem; good prices as well. Quote Link to comment Share on other sites More sharing options...
Cel Posted July 26, 2015 Share Posted July 26, 2015 I would guess brake linings as we know them did not exist back then. Our Peugeot had cast iron linings rivetted to the shoes. If the retaining rings were too tight in the gudgeon pin slots they would be under a constant oscillating pressure because the pin is floating axially and thus will move as well in a radial direction. I think they should sprung in so that more oil can pass through the holes and give a bit of extra lubrication to the little end? You can make the circular if you split them with a sharp chisel and file the ends in order to give room for expansion. Then heat them to dull red and they will keep the shape. I have made piston rings for a stationary engine and they seem to work well. Good work you are doing there! Marcel Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted July 27, 2015 Author Share Posted July 27, 2015 What did the braking originally then, Ben? Was it just metal to metal contact? Yes, originally it was just the cast iron shoes pressing on the cast iron drums. I have driven a few vehicles without linings and they work reasonably well. Although I like to keep things to the original specification I am happy to improve the brakes a little given I had a set of shoes modified to take linings already. Ben Quote Link to comment Share on other sites More sharing options...
Old Bill Posted July 27, 2015 Share Posted July 27, 2015 As all these gudgeon pin retaining rings are broken it is difficult to know if they should be sprung out like a compression ring or sprung in (like an external circlip). Hi Ben The gudgeons on the Thorny are secured the same way. The rings are actually spring steel and squeeze into the bottom of the groove leaving 1/16" clearance between them and the bore. I don't think you want the rings to try to do two jobs as you may get into trouble. Steve Quote Link to comment Share on other sites More sharing options...
andypugh Posted July 27, 2015 Share Posted July 27, 2015 If the broken bits of ring could cause damage to the bores would it be better to leave them out and fit bronze buttons to the ends of the gudgeon pins? "Better" is such a subjective word. Do you mean "better" as in "not a totally crazy way to retain a gudgeon pin"? If so, then it is better. But then the whole point of these old vehicles is that they are old and different. It is interesting to ponder if the 60hp should have floating pins and spring clips, interference-pins and compression rings or floating pins with compression rings. It now has floating + buttons, but used to be interference + compression. Maybe there was a misunderstanding at some historical point that led to the (horrible) interference + compression ring arrangement. Quote Link to comment Share on other sites More sharing options...
andypugh Posted July 27, 2015 Share Posted July 27, 2015 But despite being the correct number for 37 teeth it does not fit well because it is for 14.5 degrees pressure angle and the gear appears to be 20 degree pressure angle. If you are making both halves of the pair you could make both at 14.5PA. Is http://www.ebay.co.uk/itm/DP6-PA20-Gear-Hob-Cutter-/271648140579 Cheaper than having gears made? Quote Link to comment Share on other sites More sharing options...
ruxy Posted July 27, 2015 Share Posted July 27, 2015 A hob is only any use if you have a suitable hobbing machine where the work rotates (indexing) + feeding along with the cutter , hobbing is production . It is not like jobbing (low quantity) a gear using a dividing head on a milling machine where you index each tooth for a pass of the cutter. Quote Link to comment Share on other sites More sharing options...
andypugh Posted July 27, 2015 Share Posted July 27, 2015 A hob is only any use if you have a suitable hobbing machine where the work rotates (indexing) + feeding along with the cutter Indeed. And I have such a machine: Quote Link to comment Share on other sites More sharing options...
Sean N Posted July 27, 2015 Share Posted July 27, 2015 Hi Ben The gudgeons on the Thorny are secured the same way. The rings are actually spring steel and squeeze into the bottom of the groove leaving 1/16" clearance between them and the bore. I don't think you want the rings to try to do two jobs as you may get into trouble. Steve Steve, I should be more confident of my knowledge. I nearly suggested that might be the way to do them this morning, but wimped out! That would keep them away from the bores (unless they work hardened and broke up) and would give them some resistance to the pin rotating. Quote Link to comment Share on other sites More sharing options...
ruxy Posted July 27, 2015 Share Posted July 27, 2015 Indeed. And I have such a machine: That is a bit like re-inventing the wheel for Mr Koepfer , bit more developement work if you go off spur ! His machines I worked on that were built late 1960's / early '70's were quite something until the gearbox oil knocked a quick reverse or feed height clutch wire off. In comparison the present Koepfer machines are out of this world, but I suppose the basics are unchanged. I think I would rather gash out the conventional way for low volume , conventional tool-room practice I prefer , even using a shaper LoL I spent little time on Fellows gear shapers because they were so reliable , spent a fair bit of time at W.E. Sykes factory at Staines , machines and tooling - brilliant stuff their shapers & shavers were . New jobs - I tried to keep the production engineers on the right track ! Quote Link to comment Share on other sites More sharing options...
andypugh Posted July 28, 2015 Share Posted July 28, 2015 That is a bit like re-inventing the wheel for Mr Koepfer It is a CNC universal mill. It takes very little to convert it into a hobbing machine. (and back) Helical gears should be easy enough, but I can't do bevels. Quote Link to comment Share on other sites More sharing options...
ruxy Posted July 28, 2015 Share Posted July 28, 2015 It is a CNC universal mill. It takes very little to convert it into a hobbing machine. (and back)Helical gears should be easy enough, but I can't do bevels. What make is it ? ---- I have a Centec for vertical & horizontal - mint for a Centec , PRC Vertical thing , Original Emco - mint and , a BCA Jig borer that is Ex-University and hardly used. + two Boxford Shapers . I may go bigger , should have taken a absolute mint Bridgeport with a floor strewn with extras & tooling all for £1000 cash - just no storage at the time. Quote Link to comment Share on other sites More sharing options...
andypugh Posted July 28, 2015 Share Posted July 28, 2015 What make is it ? Harrison. It wasn't CNC when it left the factory some time in the 70s. http://www.cnczone.com/forums/vertical-mill-lathe-project-log/109301-cnc.html I might put it into a blog at some point. Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted July 31, 2015 Author Share Posted July 31, 2015 A selection of felt seals have arrived from Hardy and Hanson. I filed notches in the bulkhead mounting holes. Dennis fitted a lot of metalwork this way, using coach bolts with three of the corners filed off the square. So I did the same using a Grover spring washer under the square nut. I have very limited stocks of Grover washers so will have to be quite selective about where I fit them (unless anyone knows of spare stocks). I then trimmed the side plates to fit around the dash irons and drilled them to fit the holes in the chassis. So I am now able to measure for the bonnet. Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted July 31, 2015 Author Share Posted July 31, 2015 I then bored out all the tappet plungers to size. Followed by cutting a circumferential oil control groove on the inside with a different boring bar. Turning the High Speed Steel tool through 90 degrees and winding it through by hand allowed me to cut the grooves that return the oil back to the crankcase. The tool was just aligned by eye as the exact position is not critical. A milling machine was used to cut the slot for the roller. There is still a bit of work to finish shaping the flange and then repeat these operations five times for the other broken tappets! Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted August 9, 2015 Author Share Posted August 9, 2015 We have been away on holiday so no progress for a whole week! But with the good weather forecast we decided to bring all the back axle bits out into the yard where there is a bit more space. We started by cleaning up all the surfaces and then fitted the new felt seals to the back wheels. The axle was jacked up to approximately the right height then the axle tubes were smeared with oil. The steel thrust washer could then be lubricated prior to fitting. Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted August 9, 2015 Author Share Posted August 9, 2015 The bronze bearing was then slid over the axle tube and more oil applied. The pallet truck was then used to slide the wheel on. Then the driving star was fitted. This has a square hole in the middle that fits over a square milled on the end of the half shaft. The eight protrusions then mesh with the slots machined in the wheel. So the driving star/half shaft hold the wheel on as well as transmitting torque. Quote Link to comment Share on other sites More sharing options...
BenHawkins Posted August 9, 2015 Author Share Posted August 9, 2015 We repeated the process for the other wheel and removed the blocks from under the axle so it could rest on the wheels. The first torque arm required some fettling to get the holes to line up (this is a mix of parts from different axles). Sarah could then use the torque arm to stabilise the axle whilst I pushed the axle into position under the rear springs. There is still quite a lot to do before the axle is actually fitted but it does seem like a big step forward. If nothing else there is a bit of room to move in the garage again! I need to order some more steel including the 5/8 EN8 for the spring bolts. I have come across an anomaly with the Dennis gear drawing. The one I have shows 37 Reinecker teeth, 6Pitch; however it also states an OD of 6.4284". Obviously we would expect it to be 6.5" ((37+2)/6). The pitch diameter is stated at 6.166 as would be normal (37/6). Obviously I now need to get the gear pair out to measure but does anyone know why this smaller OD would be used? Quote Link to comment Share on other sites More sharing options...
andypugh Posted August 9, 2015 Share Posted August 9, 2015 I have come across an anomaly with the Dennis gear drawing. The one I have shows 37 Reinecker teeth, 6Pitch; however it also states an OD of 6.4284". Obviously we would expect it to be 6.5" ((37+2)/6). The pitch diameter is stated at 6.166 as would be normal (37/6). Obviously I now need to get the gear pair out to measure but does anyone know why this smaller OD would be used? What is the tooth count of the mating gear? It is quite common to shift the profile of gear teeth pairs with low tooth-count pinions to avoid undercutting the smaller gear. This is an offset of the pitch circles of the two gears by equal and opposite amounts. Alternatively they might be using nominal pitch-curdles but unconventional addendum and dedendum proportions. Quote Link to comment Share on other sites More sharing options...
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