Bush65 Posted January 9, 2011 Share Posted January 9, 2011 ... Gears that have run together for several thousand miles will have bedded nicely so using recycled gears would be best for noise Unfortunately far from real. The surface pressure (and resultant hertzian stress) between mating gear teeth changes greatly at the contact area on the tooth flanks as teeth move in and out of mesh. Also rolling contact occurs only at the pitch line and sliding contact velocity increases as contact moves away from the pitch - so wear changes the profile and increases the profile error resulting in loss of conjugate action and noise. I can't put my hand on tables of tolerances for various gear quality numbers, but I can say that the change between allowable tolerance for profile and pitch errors that affect quality number are very, very small. Most commercial helical gearboxes made by the well known manufactures employ hardened and ground teeth for a very good commercial reason often to do with reducing the size of the unit. About the only alternative to gear grinding that I recall for achieve a high'ish gear quality number is lapping with a master gear - this was a method used many years ago but largely replaced by gear grinding. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted January 9, 2011 Share Posted January 9, 2011 Sorry if that sounds skeptical or cynical for that matter. We will get there - and I hope it's them that do it - but I'm yet to be convinced! No, all your points are very valid, and especially the venture capital ones are applicable in this circumstance. However, I know that the motors exist and perform, in the real world, as we've sold them the kit for a test rig. What motor have you got? Has it a Siemens part number? If it's an Asynchronous 3AC motor it might be a 1PH7? Quote Link to comment Share on other sites More sharing options...
simonr Posted January 9, 2011 Author Share Posted January 9, 2011 What motor have you got? Has it a Siemens part number? If it's an Asynchronous 3AC motor it might be a 1PH7? One of these: There is some more info on my entire build here: http://www.diyelectriccar.com/ although you may need to register to see the photos. There is also some info on this forum here John & Zoltan - thanks for the info. I've left my Machinarys handbook at work so cannot consult it at the moment. I found this document on line which gives reasonably useful info. The thing that you tend to notice however is that in real world applications, the tooth sizes are much smaller than this type of document suggests. For my app, it thinks that I would need somewhere between MOD 16 and 25 gears, about 100mm wide to cope with the power, torque and speed. However, in the BMW box, the biggest gears were about MOD 6 and 20mm wide. Is it just that the tables in papers like this are very conservative or that it's based on making the gears out of Chocolate and once you make them out of EN36 they can be slimmed down a bit? Gears are a bit of a hole in my knowledge! I must have been asleep / drunk for that bit at University! Si Quote Link to comment Share on other sites More sharing options...
landroversforever Posted January 9, 2011 Share Posted January 9, 2011 Is it worth trying someone like Parvalux for a gear box? Ihey should cope with that sort of RPM, but not sure about the torque Quote Link to comment Share on other sites More sharing options...
simonr Posted January 9, 2011 Author Share Posted January 9, 2011 Just thought I'd post this picture from the EV forum. This is part of a chain gearbox with 13k miles of use being driven by an 8Hp motor. I think it shows that regular chain / sprockets are not an ideal solution. Do any of you know about the type of chain used in Borg Warner transfer boxes? Can you buy the chain and sprockets off the shelf? That clearly copes with the torque OK - and might cope with the speed? Si Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted January 9, 2011 Share Posted January 9, 2011 This one is about 2.3:1, and will handle the torque. Might be a bit big though, and won't appreciate much over 1000 rpm either.... Quote Link to comment Share on other sites More sharing options...
Night Train Posted January 9, 2011 Share Posted January 9, 2011 I think it shows that regular chain / sprockets are not an ideal solution. Do any of you know about the type of chain used in Borg Warner transfer boxes? Can you buy the chain and sprockets off the shelf? That clearly copes with the torque OK - and might cope with the speed? Si Look up 'Silent Chains' Again Ashcrofts should be able to help on that one too. I remember speaking with him on it 20 years ago when I was designing my Tbox. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 9, 2011 Share Posted January 9, 2011 Simon, Here's a pic of the internals of a BW box, they look pretty sturdy, it's a Morse chain http://rangerovers.net/forum/viewtopic.php?f=4&t=39971 1.201:1 ratio however... Low range is 3.244:1. Quote Link to comment Share on other sites More sharing options...
elbekko Posted January 9, 2011 Share Posted January 9, 2011 You could always fit some portals Quote Link to comment Share on other sites More sharing options...
simonr Posted January 9, 2011 Author Share Posted January 9, 2011 You could always fit some portals I did wonder about using reduction hubs as fitted to tractors & plant - but then looked up the cost of even small ones! Used they go for over a grand! Tomorrow, I'm going to ring these people http://www.industrial-gearbox.com/ramsey_silent_chain.php who sell silent / morse chain and sprockets. Never know, they may not be too expensive! Si Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted January 14, 2011 Share Posted January 14, 2011 What about some sort of variable speed gearbox? Obviously your motor has variable speed but it might help keep the motor operating at an efficient rpm at high road speeds? Quote Link to comment Share on other sites More sharing options...
pugwash Posted January 14, 2011 Share Posted January 14, 2011 404 Axles can be picked up pretty cheap- last set (admittedly a few yeras ago) cost £250- that would give you 4 portal boxes to play with. NO idea if they would take the speed though- perhaps getting something cheap, then cryo-treated and REM finished. Quote Link to comment Share on other sites More sharing options...
Superpants Posted January 14, 2011 Share Posted January 14, 2011 Going back a few posts- Protean have come out of PML Flightlink. I have heard various rumours of how/ why, but not really to be repeated on a public forum. I had a conversation with them at a trade show a few years back, and have kept my eyes on what they are doing, and whilst I believe fundamentally their technology, and the idea in general of in-wheel motors is sound, we are some years off seeing a practical solution available. The biggest hurdles seems to me around braking. The motors really do fill the wheels and have no space for any braking components. Whilst regenerative braking is possible, it is still some-way off being practical in a usable car. Firstly mechanical brakes are required by legislation- so for the time being these need to be fitted somewhere- putting them inboard is possible, but you still end up with prop shafts which starts negating some of the benefits of the in wheel motor. Current commercially available battery technologies are not up to handling the full braking currents generated (although there are lab scale demonstrations of chemistries that can around), so super-capacitors would be needed to store the braking current, adding significantly to weight, cost and complexity (and what happens in a long downhill when the energy re-generated is greater than the capacity of the caps? It will come in time, but these are all quite difficult challenges to overcome in a way suitable for a production car. There does appear to be quite a lot of ‘Greenwash’ round this area. Quote Link to comment Share on other sites More sharing options...
Daan Posted January 14, 2011 Share Posted January 14, 2011 To be honest, I dont think the suzuki transfer box should have any problem coping with the torque, it seem to live behind some pretty potent engines with a gearbox gearing it down as well. Is it not simply a case of rebuilding what you have got? Daan Quote Link to comment Share on other sites More sharing options...
simonr Posted January 15, 2011 Author Share Posted January 15, 2011 You're right - it's plenty up to the torque. It's the RPM that caused a problem. That and the fact that it was a 25 year old box that was knackered before I bought it - well, actually it was free. What's I've decided to try is a Jimny transfer box. Unlike an SJ box, it uses a chain drive and a planetary reduction. Being 20 years newer than the SJ transfer box, I hope it might last a bit longer. The tolerance is significantly better and there is virtually no backlash in high or low. I have a much better feeling about this one. I'll let you know how it goes! Si Quote Link to comment Share on other sites More sharing options...
landmannnn Posted January 15, 2011 Share Posted January 15, 2011 You're right - it's plenty up to the torque. It's the RPM that caused a problem. That and the fact that it was a 25 year old box that was knackered before I bought it - well, actually it was free. What's I've decided to try is a Jimny transfer box. Unlike an SJ box, it uses a chain drive and a planetary reduction. Being 20 years newer than the SJ transfer box, I hope it might last a bit longer. The tolerance is significantly better and there is virtually no backlash in high or low. I have a much better feeling about this one. I'll let you know how it goes! Si It might be worth looking at the bearings though. There are several calculators on the internet showing the max rpm of each bearing type. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted January 15, 2011 Share Posted January 15, 2011 If its doing much higher RPM's than the box is designed for, then you might need to look at lubrication. Oil may just be flung off shafts rather than getting into the bearings? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 15, 2011 Share Posted January 15, 2011 Can you not just swap out the lower speed bearings for ones with a higher rating? As far as lubrication, just topping it up a bit higher would probably help.... Quote Link to comment Share on other sites More sharing options...
Bush65 Posted January 15, 2011 Share Posted January 15, 2011 There are a number of issues with bearings for such speeds; the rated speed of the bearings, lubrication and a big one is cooling of the bearings - note also that after the input shaft the reduction gearing results in lower rpm at the other shafts. Quote Link to comment Share on other sites More sharing options...
simonr Posted January 15, 2011 Author Share Posted January 15, 2011 Not sure about the bearings - but the main bearings have fairly big balls compared to the diameter - presumably to minimise the speed the balls are rolling. The planetary reduction is at the bottom, half submerged in oil. The top of the box just contains the input from the motor with a chain drive from one to the other. I suspect the chain will carry a fair bit of oil to the top of the box. Whether at that speed it will make it to the bearings is another matter. The Jimny's 1.3 engine probably revs to 5000 rpm? So I guess in 5th gear, the transfer will be running at up to 5500 so it will likely have been designed to cope with that.. Since I will have the facility to change gear - I'm hoping that it won't have to run above 5000 rpm very often. In high range, 5000 rpm will give 75mph. In low range, 5000 rpm will give about 35mph. Although I will be able to get to 70 in low at 10,000rpm, it's probably not necessary. Not sure how it will change on the move as it has no synchros. The electric motor has almost no rotational mass so I hope that if I switch it off then change gear gently, even though it is still spinning, it should engage. There is only one place on my journey where I need low - turning right across a busy road going up hill and turning up another hill. Trying this from stationary and trying to nip between traffic is taxing. If it isn't happy changing on the move, I can change at the next junction while stationary. Si Quote Link to comment Share on other sites More sharing options...
landroversforever Posted January 15, 2011 Share Posted January 15, 2011 So when you have this sorted... is XEng releasing a bolt in kit? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 16, 2011 Share Posted January 16, 2011 Red line in a Jemima is 6k, if not 6.5k.... Quote Link to comment Share on other sites More sharing options...
simonr Posted January 16, 2011 Author Share Posted January 16, 2011 Jemima? Si Quote Link to comment Share on other sites More sharing options...
Night Train Posted January 16, 2011 Share Posted January 16, 2011 The planetary reduction is at the bottom, half submerged in oil. The top of the box just contains the input from the motor with a chain drive from one to the other. I suspect the chain will carry a fair bit of oil to the top of the box. Whether at that speed it will make it to the bearings is another matter. You could add a splash catcher to catch the oil that is flung from the chain to the top of the casing and then drain it into the bearings. that will keep the oil in the right place. A carefully placed (and fixed) bit of tin can would do it. The gear change will depend on how the gears are selected. If it is dog clutch then you may stand a chance. If it is sliding gears then less easy. I used to double declutch high to low and back with a S3 transfer box when I had used the yellow knob while moving. Then I resolved the red knob yellow knob problem and happily did high low changes on the move. It was just a slow change with lots of rattling. Quote Link to comment Share on other sites More sharing options...
simonr Posted January 16, 2011 Author Share Posted January 16, 2011 Looking at the inside of the casing - I think it's been designed such that oil centrifuged off the chain at the top is carried into the bearings. It's just a case of quantity. If the red line is 6500 rpm then thats 41mph in low and 90 in High - so even if I were to drive it in low all the way to work, it would only exceed 6500 rpm for about 10 sec each way per day. Si Quote Link to comment Share on other sites More sharing options...
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