cute wee gem

Summer 20/21 - We didn't do a lot bar finishing body work and getting it all back in primer and painting the engine bay. We also put the motor in temporarily and painted all the front crossmember and suspension parts.

Also started a new ITB manifold for it.

Summer 21/22 - We did a final guide coat and block sand, then got it painted. Pretty happy considering we painted it all outside, over 3 days. It was probably too hot and too breezy making it a little orange peeley.

Feels good to finally have it painted.

Bought a couple 10.5kw, 30" fans 2nd hand, which should be enough to suck the nasties out. These are 3 phase so I really need Mr sparky to come and wire them in.

On 30/12/2020 at 08:41, tortron said:

gona insulate the shed for late night pulls?

You read my mind. Except more just to keep noise down a little for the neighbors in general and get rid of the tin can feeling inside.

I had some left over noise batts at home and some normal batts I scored from work for a box of beers, so I banged them in the walls and threw up some noiseline gib for now.

Built a false wall to enclose the fans as well.

I bought some sheets of 60mm polystyrene for the ceiling too, but will wait for mr sparky to do his bit first.

Also finishing off 2020 with a quick hit in the gem.

Did some dodgy sparky work and got the retarder working, as well as doing a 4th gear pull to see how everything is looking. So far so good.

A few months back I bought the 4 items in this link to make it all work https://yourdyno.com/shop/ - I had to wait a couple of weeks for it but it was perfect timing as they had just released their own eddy current power supply. After checking out his youtube and forums it seemed like a good option for a reasonable price.

I then bolted some tie down points to the concrete, hooked the speed sensor up to the YourDyno controller and connected it to the laptop. I set it up for inertia mode with a moment of inertia number based on some weight calculations of the roller (educated guess for now). Strapped the trusty old NS250R to the roller and just eased into to things to get an idea of how it was all going.

I popped it in 3rd and did a run right out to 10,000 rpm or so. This was a pretty epic moment for me honestly.

Everything felt smooth and nothing looked out of place, so the next day I mucked about shimming bearings and coupling the retarder to the roller. Still in inertia mode, I strapped the paddock basher MX5 to the roller and did a test run in 3rd. Once again everything looked pretty good at this stage so I am very happy.

Here's a video.

Shed up 

Stripped the boxing and bucketed all of the water out of the pit. My parents then popped around with their tractor and we managed to get all the heavy bits in the hole.

I then mounted a 2jz cam gear to the end of the roller, this will be used as a trigger wheel for the speed sensor.

I then set to rewiring the Telma retarder. These have 16 coils wired in parallel for a 24v system on a truck - this is no good for a dyno.

I wired the coils into series so it now runs on 192v, which can be wired to mains power through a power supply.

With the retarder wired to a 12v car battery, the coils can be checked with a compass to make sure the wiring is correct. They should read north - south - north - south around the circle to form the eddy currents, which are transferred into the rotors to apply braking.

While I waited a few weeks for the concrete, I built a frame for the dyno.

Speed sensor bracket

Load cell bracket. This is what measures the torque.

Electric drum brake to lock the roller when mounting a car.

Frame painted. The part sitting next to it bolts into the top to support the floor coverings (steel checker plate)

Other concrete truck companies were booked out until 2021 so I couldn't even get the concrete to attempt it myself.

Early December I started begging the concrete company boss. I told him all I needed was the concrete truck, a man with a screed and a bull float and I'll finish it myself by hand. Hoping this would persuade him as I'd only need an hour of his placer's time.

December 14th. I rang him to ask if we were still on for that day. "Yeah but it'll be late in the day" - My hopes were low by this point as other jobs could have dragged on and it be too late in the day to do mine.

But finally they came, and were gone in less than an hour.

I spent the rest of the evening doing the door rebate, steel floating the slab by hand and drinking beer. I'm no concreter but it came out alright.

Dyno pad poured

Pit walls boxed and poured. They bowed a bit more than expected on the outside, but a little bit of extra concrete never hurt.. Except for my back due to doing it all by hand with a mixer.

Molesealed the outside and used 3 layers of polythene underneath and up the walls to stop water getting in (water table gets quite high here)

Finished the prep ready for concrete.

The last photo was on November 26th. I let the concrete company know 6 weeks prior that it would be ready at the end of November as I know they are extremely busy, and kept mentioning it to them so they knew where I was at.

Getting stressed about it not happening as December was rolling on and the Christmas rush was in full effect for the building trade. Not only that, it kept raining when we planned to pour! 

Catching up on progress now, this update is from 3 months ago.

With the chain coupling finished, I could finally mate the roller to the retarder and get an idea of the frame dimensions. Which I needed to know so I could build a pit for it to sit in.

I have no room in the current workshop/house, so I'd have to build another shed, as a dedicated dyno cell.

I decided to drop a day from work each week to try and get something built before the Christmas holidays. So I borrowed the digger from work and got to it.

I went to a local engineer who let me borrow his mill to cut the keyway into the hub, GC! - I then had to wait another 6 weeks to get him to cut the key into the 8018 chain coupling

Another issue was the keyway in the shaft for the roller. Being to large to mill, I had to spend an entire day cutting it by hand. Angle grinder, die grinder then hand file finished, being careful to get it as close to perfect as I could and not over cut it.

PS the sleeve was welded using a series of hot tacks to keep it from moving hence the ugly welds 

Sent the roll to Qualtex in Hamilton to have it properly balanced. It turns out my balance weights were actually in the correct location, just not heavy enough! Well worth the money considering the fine tolerance they balanced it to.

It was about this point I had a bit of a problem on my hands. For some reason one end of the shaft had almost 0.5mm run out (warpage from welding?) which I never really noticed during machining

I ended up sleeving the shaft either end to 90mm until I had the whole lot within 0.1mm - which was a bit of drama in itself.

I also attempted to balance it myself at home using a chinese vibration meter, a bit of trial and error and plotting the data as a spread sheet I managed to significantly improve the balance - however getting it up over 400rpm was a little scary when it wanted to take off across the workshop - so I gave up.

Photo of the sleeved shaft, new 90mm bearing and balance weight.

I then machined some hubs for the Telma retarder out of 200mm 1045.

50kg down to 9kg

The next step was to machine in some traction grooves.

I came up with a few ideas in my head along the lines of using a small router with a carbide end mill mounted to the linear rail. But after realizing that could be quite expensive if I kept burning out end mills, I came up with a rather crude yet effective method, albeit extremely slow.

I mounted a chamfer tool 90 degrees on the compound slide and ran it along the face almost like a shaper would, but slower. This seemed to work pretty well on the first test cut, so I carried on with this method, and used the same carbide tip for all 475 grooves (much cheaper than carbide end mills)

When I say slow... Each groove took 7 passes to get a decent depth and a decent looking cut. One pass taking around 4 minutes, times 7 for every groove, times 475 grooves = 13,300 minutes or 220 hours. I had done well over half before the lock down in April/March - I then spent 10-11 hours a day for the first 7 days of lock down finishing it off. I tried several times to speed the process up, but that was the sweet spot with this method unfortunately. It also took some time to figure out the best quality cut. (blunt tip worked best in the end)

There are a few cuts with tearing along the edges, but over all I'm happy with the outcome - it should do the job at least.

I uploaded a video of my cat who loves to hang out with me in the shed, even when I'm making loads of noise. The video also shows my redneck contraption in action

Tortron, I think about 100kg of steel wool was made lol

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.

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.