As a lot of you know I am back driving for Schumacher UK again after just over two years awayÖ and my timing could not have been more perfect with the new incarnation of the Mi4 just arriving… the Mi4CX.
A bit of historyÖ back in November 2008 I did a review of the Schumacher Mi3.5 (you can see it here; http://rcracingni.co.uk/?p=600) and at the time Schumacher was starting to introduce some innovative ideas. But there was more to come when Chris Grainger joined the UK based company to start designing the Mi4 from the ground up. The Mi4 was a great success and introduced a lot of great ideas including the new clamp motor mount to adjust the motor position both back to front and side to side for great balance, split rear transmission housing to adjust chassis stiffness, quick release layshaft etc. etc. the list goes on. Schumacher did not rest with the Mi4 and with the UK fully embracing Lipo, brushless motors and also a new weight limit they brought out the Mi4LP which added a proper lipo designed chassis.
The next incarnation, the Mi4CX is the next evolution, and some have said it aims to address some issues that people have had with the driveshafts, spools etc. Personally I have not had any problems with these parts and my Mi4LP stood up to some good testing (high speed crashes!) with no issues. But hey strengthening parts and losing weight is always a good thing.
And on with the review…
When you open the box you are presented with a manual, chassis and neatly bagged parts;
Something that Schumacher do very well is mark each bag for each step in the instruction manual. So, in the manual step 1 is screwing the rear bulkheads onto the chassis so in bag 1 you will find the bulkheads and required screws, no more, no less. When you are finished a step you do not have left over parts that are for another step.
The first stage for me on any build is to sand the edges of the chassis and glue it – for me it is less about the chassis delaminating as I think modern carbon fibre is pretty good and more about the look. In saying that I like the idea that, for carpet racing in particular, if your suspension is too soft then the car will not catch on the carpet. My nicely edged chassis;
Next up is adding the new black bulkheads to the chassis, again all nicely bagged;
And these simply screw onto the chassis;
They say they are stronger but looking at the picture above I just think the black bulkheads look so well on the chassis (and I also like the Mi4cx logo routed into the chassis – probably saves some weight as well!).
Next up comes the rear diff and the front spool – these are the other big changes to the car from the LP. As I said before some people have had issues with the previous spool and the outdrives in particular. I never had any issues but the new diff is built up as per the previous one (if you have not got a pair of circlip pliers I would recommend you get a set – Schumacher do a pair, part no. HW010 I believe, and it just makes life so much easier). Once the diff is built you then add plastic sleeve and then over that a 7075-T6 metal sleeve. Quick tip here is that there is a rubber O-ring that goes on before the sleeves – just wet it ever so slightly and gently push the sleeve over it – once in place the sleeve will not simply fall off. The diff really is a thing of beauty;
And another thing that I like is that the diff holder for adjusting the diff height and the belt tension have high and low written on them to make it easy for people like me to ensure that the diff is definitely at the desired height on both sides.
And the rear diff in place;
When building the car you have a choice of flipping the belts left to right (and the diffs along with it) to allow the chassis to be balanced – shown above is option 2 but in the end I went with option 1 to get my electrics in as I use a Sanwa receiver with my M11x that is quite big. Also note in the picture above that the front spool has not been installed so the front belt looks like it is not on right!
As I said the spool is also new and is a work of art made from one piece of 7075-T6 alloy;
This is made up in a similar way to the rear diff with the plastic and alloy sleeves and here it is fitted;
And below you can see the top deck fitted with the car still sporting the option 2 belt configuration;
The steering in the car is built up from a nice piece of purple alloy with washers fitted to give different ackerman (simple and it works!). This all rotates on two bearings on a metal post and finally attached to this is a piece of carbon fibre to allow you to attach the steering to your servo horn and servo of choice. I forgot to take a picture before it was all fitted to the car…
In the picture above you can see 4mm of washers for the ackerman – Chris Graingers Ardent setup which was the initial setup that I put on the car. I have since moved back to 3mm of washers and I know that Chris Ashton has run with 2mm so something that is worth playing with to tailor your steering to your own tastes.
Moving swiftly on to the arms etc. they are so easy to build up and I did not have to ream out any of the arms etc. to get them to rotate on the hinge pins. It was all so easy I put them together in a very short period of time and only then remembered to take a photograph;
You can see in the photo above the new driveshafts which are very stong and are 45.7mm in the front and 44mm on the rear. You may also notice that I use alloy washers to space the arms on the hinge pins – the car comes with plastic clips but the washers are just a personal preference (if you are going to do it you need washers with a 1/8th inch hole).
And here they are fitted;
On to the rear and its pretty much the same;
And all fitted… getting close;
The shock build was very good and for those of you that have built shocks from different cars I would say that the Schumacher ones are up there with the best. Some people swear by Tamiya shocks and I think that Schumacher’s are easily as good. Schumacher even go as far as providing a bottle of 35wt shock oil;
As per Chris Graingers setup I went with 50wt oil and this has worked well for me so far in my trials with the CX.
I also have a set of the Schumacher Big Bore shocks which I really liked on my LP and will be giving them a go on my CX at some point;
And for comparison;
All shocks built and ready to go on;
And next up is one of the features that I think is the most innovative on the Mi4 family of cars and makes the car really easy to spot in the pits; the motor mount. Schumacher made a great clamping system that allows the motor to move in and out of the car (remember the two belt options I described earlier) and it also allows you to move the motor forward and back on the car. This is great during a race day when you want to take the motor out without changing the pinion and gear mesh – you simple unscrew a screw at the bottom of the motor clamp and the motor, with pinion attached, can be taken out of the car. Bearings etc. in the motor checked you simply slide the motor back in and the mesh is the same and you just tighten up the screw again.
Because I run my car with the spur gear to the far side of the car (away from the motor if you know what I mean – not shown in the picture above) I can push the motor in that bit further and this can be used to tune the balance of the car.
All that really remains of the build is the bumper and roll bars and that sadly is the build complete.
The bumper in place – you can raise and lower the body posts by loosening off a grub screw, moving the posts up or down and retighten. Great for a quick bodyshell change;
And the view form the rear;
Lots of nice purple and the black T6 alloy bulkheads.
Front steering again;
And the motor mount from a different angle;
And finally the finished car
Overall the build of the CX is very impressive – I did not have to ream out arms to get them to fall freely on the hinge pins. I really like the way all the parts for each step is in an individual bag. And the support from Chris Ashton, Chris Grainger and the rest of the Schumacher team is great – they have been going well at Ardent and sharing their setup sheets with the world and Schumacher now have Chris Grainger doing some videos on YouTube that give some professional tips on building the car (the diff and shock videos are well worth watching).
My thoughts on my initial run with the CX was that it felt a lot different to the LP. It was strange – I put on my LP setup expecting it to be the same car just with lighter parts and new diffs. And I was wrong! The car seemed to have more steering and to me felt a but nervous (I like a safe car that I can push). I did a few simple changes to the car and I now have a car that is very easy to drive and is definitely faster than my old LP. Basically I played around with the shock tower positions and I changed the hub carriers to medium instead of the flex that came with the car – personal preference but something to play with.
I would definitely recommend the Mi4CX and with the support from a UK manufacturer it is a worthy contender against the other top manufacturers out there.
Article by Stephen Coyle at RC Racing NI