Popular Post cute wee gem Posted November 10, 2020 Popular Post Share Posted November 10, 2020 Almost 2 years ago a chassis dyno popped up for sale on TradeMe with a starting price of 15k - I was immediately interested (after looking for quite some time) - so I called the owner to get some information on it. It turned out to be an old Vane 4000 bed with a Telma cc130 retarder, which had been upgraded to modern DTec data acquisition and brake control. Sweet! After talking to the seller for a while I got the impression it was rather traction limited with its smooth, small diameter rollers. It also sounded like the DTec wasn't that great at steady state retarder control. I threw in an autobid of 17k (my entire savings) and lost.. But over the couple of weeks that the auction was held, I got to thinking that maybe I could make a dyno for similar money? Google led me on a path to some pretty cool DIY dyno builds.. I thought, if they can do it, why can't I? - The only difference is that I'm not an engineer at all, bar 3 years of light fabrication work and the skills I'd acquired working on cars as a hobby. So after losing the auction I rang around truck and bus wreckers with no luck finding an eddy current retarder. Damn! - After a few weeks of hunting I found a Telma AC83-00 on Ebay in the UK which was a couple of decades old, but still new in the box. The quotes were quite horrendous at first to get it to NZ but with a very helpful seller who also sold the retarder to me for much cheaper than his listed price, the deal was done. I was pretty stressed for a few months as I had just sent a big chunk of money to a random bloke in the UK with no tracking and no contact with the shipping company - but 3 months later it finally arrived. You know that feeling you get when you buy a cool new car? This was almost better than that. 390kg potential paper weight... 42 1 Quote Link to comment Share on other sites More sharing options...
kpr Posted November 11, 2020 Share Posted November 11, 2020 Nice, what are you going to use for the rollers and controller? there is a diy dyno page on facebook, with a few dudes who seem to know what they are on about if you're not on there already Mines an old vane bed like the one your originally bid on. but a 6000, not sure if its a cc130 or cc160 retarder. previous owner had the rollers knurled seems to grip fine when car is tied down right. think the retarder is getting a little tired tho Quote Link to comment Share on other sites More sharing options...
cute wee gem Posted November 12, 2020 Author Share Posted November 12, 2020 I'm fabricating my own roller. I'm a bit further ahead than my first post so I will update in the coming weeks with more deets. I'm going to use the YourDyno controller and they have just bought out their own eddy power supply as well - it's constantly under development but appears to be quite decent. I would have gone with Sport Devices but they were way over my budget. PS I do watch your youtube stuff (love all the content btw!) - I assume your Vane is a modified one by torque performance? Knurled rollers do make a huge difference apparently. 2 Quote Link to comment Share on other sites More sharing options...
kpr Posted November 12, 2020 Share Posted November 12, 2020 sweet, keen to see how you get on. assume you are going to run a fairly large roller to keep the retarder speed down? yeh mine has torque performance (dyno torque) control setup. It must have been one of the last ones they done, before getting out of the game. Its no longer supported etc. so ive cloned the hard drives just in case one of the computers dies. does what it needs to do, so will keep it going as long as the controller board lasts. before looking into any other control setup for it. Quote Link to comment Share on other sites More sharing options...
cute wee gem Posted November 17, 2020 Author Share Posted November 17, 2020 Yep I'm going to use a 762mm roller as some of the bigger/older Telma's like mine are speed limited to 2100rpm (newer ones are 3000rpm for this frame size) - I have talked to Telma and they can do a new hub assembly which is capable of 5000rpm however, but are around $2700 before shipping and taxes. I had a look at the DIY dyno FB page today and there is some good reviews on the Yourdyno stuff, so that gives me some confidence. 1 Quote Link to comment Share on other sites More sharing options...
Popular Post cute wee gem Posted November 17, 2020 Author Popular Post Share Posted November 17, 2020 I talked to Egmont industrial supply who I had bought my lathe off previously, because I remembered they had stock of large diameter pipe in various sizes. After telling them I was making a roller, they said they could also supply end plates and shaft to suit. Mint! Fast forward a few weeks and this lot showed up. 2.1m of 762mm x 12.7mm culvert pipe, end caps, center plate and 70mm shaft. The reason for the large roller is due to the RPM limit of the retarder as explained in my previous post. One benefit to this though, is better traction than small rollers due to the increased contact patch, which also reduces stress on the tyre. It turns out that culvert pipe is hugely out of round. But that's nothing that a couple of dodgy 20t bottle jacks and some wood can't fix though! 20 Quote Link to comment Share on other sites More sharing options...
Popular Post cute wee gem Posted November 17, 2020 Author Popular Post Share Posted November 17, 2020 I then zapped the center cap in, followed by the end caps and shaft. - This took quite some fiddling to get it all as close to round as possible as well as getting the shaft as central as possible. With the roller sitting on it's bearings, I checked it all with a dial gauge near both ends and center, with the worst being almost 3mm out of round - which would give me 8.7mm or so minimum thickness after machining in a couple of small areas. Most of it was within 1.5mm, so I was happy enough with that. 15 1 Quote Link to comment Share on other sites More sharing options...
CUL8R Posted November 17, 2020 Share Posted November 17, 2020 Will you have to weld a mesh of sorts for "grip" or make a knurling of some type? Pretty cool project Tom Quote Link to comment Share on other sites More sharing options...
cute wee gem Posted November 17, 2020 Author Share Posted November 17, 2020 Yep there are a few different options. Knurling being the most popular on rolling roads, machined traction grooves aren't as common but is meant to be better than diamond knurling, and I have also seen a spray welded texture finish on brake testing machine rollers at the local truck COF station 1 Quote Link to comment Share on other sites More sharing options...
gibbon Posted November 17, 2020 Share Posted November 17, 2020 Just a question for fun, has anyone tried using a stack of wheels with tyres as a roller? Quote Link to comment Share on other sites More sharing options...
kpr Posted November 17, 2020 Share Posted November 17, 2020 Should be good for a stack of power with that roller, the inertia will take a lot of load off the retarder 1 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted November 17, 2020 Share Posted November 17, 2020 1 hour ago, gibbon said: Just a question for fun, has anyone tried using a stack of wheels with tyres as a roller? The more I think about logistics, the worse this idea seems. Quote Link to comment Share on other sites More sharing options...
cute wee gem Posted November 23, 2020 Author Share Posted November 23, 2020 On 17/11/2020 at 20:39, kpr said: Should be good for a stack of power with that roller, the inertia will take a lot of load off the retarder According to my rough math it should suck about 80-100kw + another 5kw (for the retarder rotors) to accelerate the roller over a 6 second ramp run. But not only am I not an engineer, I'm also not a mathematician lol Retarder when cold can fully brake about 150kw at 500 rpm (roller speed) and about 470kw at 1500 rpm and about 620kw at full song (2000rpm) To put it into real terms, using my Gemini for example - makes roughly 40kw at 2500rpm (500rpm roller speed) and 180kw at 7700 (1500rpm roller speed) So the retarder should be able to steady state a car with 2.5 - 3.5 times the power and who knows how much more with ramp runs? Surely 700-800kw? Time will tell. 3 Quote Link to comment Share on other sites More sharing options...
rusty360 Posted November 23, 2020 Share Posted November 23, 2020 That would have taken some machining! Good size lathe. Cool project. Quote Link to comment Share on other sites More sharing options...
h4nd Posted November 23, 2020 Share Posted November 23, 2020 On 17/11/2020 at 20:06, cute wee gem said: Yep there are a few different options. Knurling being the most popular on rolling roads, machined traction grooves aren't as common but is meant to be better than diamond knurling, and I have also seen a spray welded texture finish on brake testing machine rollers at the local truck COF station Paint with sand in it? Quote Link to comment Share on other sites More sharing options...
kyteler Posted November 24, 2020 Share Posted November 24, 2020 1 hour ago, h4nd said: Paint with sand in it? It would have to be pretty amazingly durable sand and paint or you'd be reapplying it constantly. Quote Link to comment Share on other sites More sharing options...
tortron Posted November 24, 2020 Share Posted November 24, 2020 I had some real good stuff, but it was end of line and had about 20 warning labels on it. So chances are anything modern wont hold up lol Quote Link to comment Share on other sites More sharing options...
Popular Post cute wee gem Posted November 28, 2020 Author Popular Post Share Posted November 28, 2020 While I was fabricating the roller, I visited a bunch of engineers in the region and found that no one had a lathe big enough to machine it. Bugger. After getting some quotes from further abroad that would have blown my entire budget by themselves (15-20k). I decided that I'd just build my own lathe.. I jumped onto Ebay and ordered the cheapest set of linear rails I could find, including the ball screw and bearing blocks. 3-4 weeks later I got set to mocking up the "lathe" using the compound slide from my Stanko mounted to some adapters. Spinning the roll by hand with the compound slide clamped to the linear rail, I took the first test cut. "Fuuck yeah, this'll work" I said.. It would have taken forever to machine the 3mm x 25mm weld bead off, but I remember once when @kpr mounted his angle grinder in the lathe to cut through some hardening on a set of axles from memory? (that image is burnt into my mind, probably thinking it might be a useful trick one day. cheers dude!) The grinder worked really well and made short work of it. Spinning the ball screw with a battery drill. 43 2 Quote Link to comment Share on other sites More sharing options...
Stu Posted November 29, 2020 Share Posted November 29, 2020 ^ Thats awesome! 2 Quote Link to comment Share on other sites More sharing options...
Popular Post cute wee gem Posted December 7, 2020 Author Popular Post Share Posted December 7, 2020 On 29/11/2020 at 08:46, cute wee gem said: "Fuuck yeah, this'll work" I said.. The ideal speed for machining something so large would probably be 50rpm or less. So I bought an old concrete mixer pulley off trademe (around 560mm) and a 50mm pulley for the 3/4hp electric motor I scored from work. This gave me about 130rpm. This worked pretty well at first as I machined off the high spots, but as time went on and the cuts became longer things got complicated. The carbide inserts were over heating and wearing out well before half a pass. I found a home built saw bench on facebook marketplace for cheap, which had some different size pulleys and a stand alone shaft with bearings, so I snapped it up. I then modified my original setup and managed to gear it down using the shaft from the saw bench with an isuzu crank pulley on the other end, to around 62rpm. The lower surface speed was much better but the tips were still wearing out before a full pass, and I was starting to fight some serious chatter. It became apparent that the linear rail support had some flex, causing the compound slide to tilt forward and spring back causing the chatter. I braced it up with some random offcuts which made a big difference. (The linear rails should have ideally been much further apart and properly supported) Still getting chatter, I added 30+ kg to the back of the compound slide. This was enough band-aiding to get me through to the end, without changing the whole thing completely. I also upgraded from a battery drill with a cable tied trigger to a Nema 34 stepper as I needed a much slower feed rate. 37 2 Quote Link to comment Share on other sites More sharing options...
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