I've recently started the whittle v8 and am doubling the size. I saw one poster on here that started doing the same, but he hasn't posted in his build thread since late last year. Has anyone else attempted this project? If so, where did you obtain the bearings and gears, and what size should they be for the double size? Would you just double the size from the original plans, i.e. the pg48-18 gear becomes pg48-36 and the pg48-36 gear becomes pg48-72?
doubling the whittle v8?
- Thread starter mfarris
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There was a good series on a doubled up one in Model Engineer Mag a while back, worth reading.
Usual method is to half the DP when you double the scale which keeps the same number of teeth
Usual method is to half the DP when you double the scale which keeps the same number of teeth
Thanks Jason. The original plans call for 48dp gears, so I guess the double would require 24dp? I know absolutely nothing about gears. I do have the ME editions where Mick Knight builds the double size whittle, but I haven't seen anywhere where he mentions where he gets them or what sized gears he used. The bore in the rear bearing housing would obviously be determined by what sized gears are used, so that might actually be one dimension that is not necessarily doubled. do you have a good online source for these types of gears you would recommend?
What part of the world are you in?
Yes 24DP, you should be able to double the housing size as 24DPx18T has dia of 0.833 while 48DPx18T is 0.417"
J
Yes 24DP, you should be able to double the housing size as 24DPx18T has dia of 0.833 while 48DPx18T is 0.417"
J
I'm in the US.
Yeah, looking at HPC gears, the OD of the 24dp-18t and the 24dp-36t are double what the 48dp-18t and 48dp-36t are, but the bore dia is not. The bore diameters on the 24's are .3125. The doubled up plans calls for the cam and crank shaft to be .375 (I've already made the crank). I guess I could either bore the gears to .375 if they are machinable, or either turn down the shafts on the crank and cam to .3125. I was hoping I could get some advice on what others have done that have tried to double up the Whittle.
Yeah, looking at HPC gears, the OD of the 24dp-18t and the 24dp-36t are double what the 48dp-18t and 48dp-36t are, but the bore dia is not. The bore diameters on the 24's are .3125. The doubled up plans calls for the cam and crank shaft to be .375 (I've already made the crank). I guess I could either bore the gears to .375 if they are machinable, or either turn down the shafts on the crank and cam to .3125. I was hoping I could get some advice on what others have done that have tried to double up the Whittle.
I would have thought Boiston Gear is you best bet in the US. The HPC ones are easy enough to bore out, I've done it with theirs several times.
J
J
I've done some searching, and have yet to find a pair of gears that would fit perfectly with no mods to either the gears or the shafts. How important are the pitch and the number of teeth? As long as the number of teeth on the large gear are twice the number on the small gear, it would work wouldn't it? I guess pitch and number of teeth determine the gears strength and durability? In other words, if I could find a set of gears that are 20pitch instead of 24, and had 28 and 14 teeth instead of 36 and 18, but had the correct OD and bore I needed, would those work?
Provided the centre distance of teh two gears is the same as the centre distance between crank and cam shafts and the number of teeth are 2:1 you can use whatever combination you like.
You can work out teh ctr distance by adding PCD of gear a to PCD of gear B and dividing the result by 2
http://www.hpcgears.com/pdf_c33/27.48-27.60.pdf
If you can't buy what you want off the shelf then why not cut your own, compared with some of the other machining required to make the engine gear cutting will be a walk in the park.
J
You can work out teh ctr distance by adding PCD of gear a to PCD of gear B and dividing the result by 2
http://www.hpcgears.com/pdf_c33/27.48-27.60.pdf
If you can't buy what you want off the shelf then why not cut your own, compared with some of the other machining required to make the engine gear cutting will be a walk in the park.
J
Yes, I have thought about cutting my on. I've never cut any before as I'm new to the hobby of machining, but I have a rotary table and should be able to do it. But the info you have given me is very, very helpful. I think now I should be able to find a set of gears that will work. Thanks so much for your very helpful info.
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