So, as most of you know, RCTV’s Oli Meggitt is currently taking a bit of a break from racing. But HPI clearly decided they missed him, and so to try and lure him back, suggested he built the new HB Pro 5 Touring Car. So, over to Oli then as he walks us through the build of the latest competition chassis from the established manufacturer.
The electric touring car market now seems to feature more manufacturers than ever. With the rules behind the class having stayed fairly static for the past five years or so, the designs of the cars have converged around an ‘optimal’ platform. Just as in full-sized motorsport, this creates a very even playing field and thus the smallest differences or unique features define each manufacturer.
I first saw the HPI HB Pro 5 in the run-up to the 2014 IFMAR World Championships. I got to look at the car first hand at that event, and subsequently in the hands of Andy Moore at a couple of other events in the UK. It’s clear that the car follows the current philosophy of Touring Car design, but still manages to include a number of unique features – features I was very attracted to right form the initial pictures. And, with thanks to HPI Europe, I got my hands on one of the kits to build up.
The glossy manual features clear CAD drawings of each stage of the build, with to-size drawings of the fasteners required at each point. The kit comes bagged up by build stage – with all the parts needed for each part in a numbered bag (although the plastic trees and carbon parts are bagged separately).
I’m not going to try to compare the Pro 5 to the previous HPI/HB offering, the TCXX – the Pro 5 is a complete new platform, with practically every part re-designed. The most obvious difference, visually, is the departure of the purple aluminium, replaced by a stealth black look, off-set by HPI-corporate coloured orange shims – a look I personally really like.
The first stage of the build is to attach the bulkheads to the chassis plate. HPI recommend super glueing the edges of the carbon chassis, but this is a stage I’ve not done on my cars for a few years – if I’ve had an accident big enough to delaminate the chassis, it usually means it’s tweaked and due for a replacement anyway! The bulkheads are all identical – reducing the number of spares you need to carry and the number of parts shops need to hold. Checking all the parts out on my glass board, the chassis and bulkheads were perfectly flat – a great start (not that I would expect anything else!)
Next up is the drivetrain. A genuine Panaracer spur gear is included (I changed the kit one for a 48DP version to suit my range of pinions!) and the spool features steel outdrives. The spur gear mount is a wonderful piece of machining – deliberately kept as small as possible to minimise mass but with strength in the right areas to hold the pulleys on a hex-shaped fitting.
The rear gear differential is a key part of modern day touring cars, and I was very impressed with the way the Pro 5 one built up. I used the included HPI 7000 weight oil, although some advice I got from Andy Moore suggested I may wish to swap to a lighter weight for outdoor racing on the UK’s typically lower traction surfaces.
Before beginning any part of the diff assembly, the first thing I did was to tap the screw threads – allowing me to make sure I got the screws in perfectly straight without the worry of cutting the thread when the diff was assembled and filled with oil. The only downside to the gear diff was that the four small planetary gears have to be cut from a parts tree, and thus need a little work with sandpaper or a file to ensure all the flashing is properly removed. I was, however, pleasantly surprised that the front spool pulley didn’t require any side fences glueing on, as many other manufactures require.
So, that’s the basic drive train components assembled.
Last time, Oli got as far as building the basic drivetrain components. Now, it’s time to attach them to the chassis and get on with the next stage of the build!
The front spool and rear differential slot into the bulkheads on eccentric bearing holders. This is one area where HPI have chosen to take a slightly different approach to other manufacturers. Some have chosen to use a cam with notches to adjust the belt tension, whilst HPI include a number of different off-set oval shaped holders to move the spool or differential forward and back. This has the advantage that it doesn’t affect the height of each unit in adjusting the tension, and that you don’t have to try to ‘count’ the notches to ensure you get both sides the same!
Next up is the motor mount – again now in stealth black. HPI have taken the approach of a multi-piece mount – the largest piece being the motor mount and left-side layshaft mount, to which a centre post is then attached with two counter-sunk screws, and a separate right-side layshaft mount is attached to the chassis. Keeping the motor mount flat whilst attaching it is key to not tweaking the chassis – I carefully tightened the screws whilst holding the chassis flat on a glass board, which resulted in the carbon remaining flat. The motor mount also includes a battery stopper, made up of a countersunk screw, countersunk washer and additional spacer washers, giving a nice large surface area to keep your LiPo batteries away from the spur and pinion gear.
The bulkhead caps and shock towers are next on the menu, and includes one of the key features of the car. The camber link plates attach to the shock tower mounts with HPI-orange washers, allowing an infinite adjustment of camber link lengths, rather than the two or three fixed holes offered by other manufacturers. To me, when I first saw the car, this seemed like a very simple and neat solution, and I’m not sure why no other manufacturer has thought of anything similar before!
The carbon shock towers are then attached, using one countersunk screw and one button head – to hold the tower firmly in place but also minimise the risk of tweaking or not setting the tower on straight.
The only downside I felt to this stage of the build was the use of a combination of 5mm and 6mm button head screws. Being only 1mm difference in length, you really need to pay attention to not get these mixed up! Maybe it would have been more sensible to use just 6mm screws throughout?
The conclusion of Bag C attaches the steering rack and top deck. The top deck can be mounted to the motor mount either at the forward post, or on either side of the layshaft, or in all three points.
I built the car as per the manual (using all three), but will expect to use this tuning area when I run it as the flex of the chassis has a large impact on the traction generated.
We’ve now had the chance to see three of the unique features of the HPI HB Pro 5 which sets it apart from its competition. Next time, it’s the exciting installation of the suspension arms!
Part two saw Oli take a look at some of the parts that set the Pro 5 apart from the other offerings in the Touring Car market. The build now continues with the suspension components!
Bag D sees the suspension attached to the chassis. 3mm of wheelbase adjustment front and rear is possible with orange shims, whilst the roll centres can be changed with further shims placed under the suspension mounts.
As you’d expect, the toe angles can be adjusted – HPI choosing the route of different sized blocks, rather than an insert system. All the blocks are pinned to the chassis as well as screwed, to help keep them properly aligned. I was impressed that as I built it straight from the box, the wishbones had a very slight amount of play to keep them free, but didn’t require any additional shimming.
The front (double-joint) and rear (single-joint) driveshafts assemble easily and run smoothly – I used Tamiya anti-wear grease on the joints as I have done for many years.
The steering blocks feature another unique choice from HPI. A carbon plate attaches to the block to hold the steering link ball stud and set the maximum lock. This could mean that option parts are available soon with different ball stud positions or maximum lock angles.
Building up the steering hubs saw me also have the chance to test out a new tool, thanks to Chris Betts of OTM Racing. Chris realised that when screwing in the lower king pin and upper ball stud on typical touring cars, the screw needed to go in perfectly straight, otherwise camber and caster angles would change during steering movement. Therefore, he modified a hex driver tip by maching on a cutting thread half way down. You can slide the driver through the hub and then cut the thread – the other side of the hub making sure the thread is cut straight in the hub. Then just flip the hub over and repeat from the other side! So simple, no wonder he’s been rushing out batches of them to most of the top Touring Car drivers and teams over the last month or so!
When putting the front driveshafts into the hubs, I found the bearings to be a very tight fit into the hubs – be careful to make sure to press these in straight – using the driveshaft to help if necessary.
The front C-hubs and rear uprights are held into the wishbones through the usual outer hingepin – although, not so usual in this case! The hingepins taper to a point at one end. After discussing this with the HB team drivers, they said this was purposely done to allow them to accurately measure the droop to the centre of the hingepin (using a steel ruler).
Measuring to the bottom of the wishbone means the readings can be affected by wear on the plastics, but measuring to the pin centre always gives a consistent reading. Now, whilst this is a useful feature, it does create one of my personal ‘big’ dislikes on the car. The hingepins are held in place by a grub screw, inserted into the wishbone behind the hingepin (rather than through the hub like most other designs).
The itself is a great feature, however it means the grub screws are inserted from inside the chassis (rather than from the outside – if that makes sense!). I found it really annoying to get these in place! But, if that’s one of my big moans, it’s not really too bad, just me trying to find something I didn’t like!
That’s the majority of the build done then. The final part will see Oli finish everything off and get the car ready for some track testing!
Last time, Oli just about finished the build of HPI’s new HB Pro 5 competition touring car. To finish off the build, it’s now time for the finishing touches on the car!
The car is pretty much complete, just finished off by the installation of the turnbuckles – a job no one likes, so I’ll quickly move past this bit! The roll bars are then fitted, and it was great to see HPI including a full set of 3 front and 3 rear roll bars, to offer useful tuning options right in the box.
The shocks absorbers make up Bag G, and fall together nice and smoothly. In short, follow the instructions and you can’t go wrong! Full alloy parts all the way through the shock make things nice and highlight this as a top end kit. Some advice I got from Andy Moore was to polish the shock shafts with some metal polish prior to assembly – I did this and the shocks were super smooth! The kit includes a new HPI Green spring, which feels very similar to the standard ‘go-to’ spring, the classic HPI Silver – I’ll compare the two back to back on the track! The kit includes HPI 500 weight oil, but I chose to use MR33 450 weight when building them. There’s nothing wrong with the HPI oil at all, but I have a full set of MR33 oil, making it easier to make adjustments and changes.
The final stages are attaching the bodyposts – which feature much closer-together holes than any other I’ve seen, allowing for fine bodyshell height adjustment – and then the steering servo mounting. As is pretty much standard now, a ‘floating’ mount is included. The carbon top plate fits very tightly to the inner mount to minimise movement. I fitted a Sanwa BLS Version 2 servo to my car, which fitted neatly into the mount. The only other change I chose to make was the use of an MR33 alloy servo horn from Tonisport, rather than the standard plastic part. That’s only to give a little bit more of a ‘direct’ feel to the steering – but is not necessary by any means.
I then just had to fit the electronics to the Pro 5. A Sanwa 471 receiver matches the servo, and with thanks to David Spashett at Zen Racing, I used the G Force TS160 ESC and G Force Super Sonic motor range – 13.5 turn for my initial outing! I also pressed into use my trusty Moorespeed LiPos, thanks again to Andy Moore.
To top it off, a Protoform bodyshell is the only choice, and Rob Sawell was kind enough to paint up a lightweight Mazda Speed 6 in my usual colours for the review, to which I fitted an MR33 high-downforce heavyweight wing. I’ll also make sure I go to the track armed with an LTC-R as well.
Overall, I was really impressed with the build of the Pro 5. The parts all fitted very well with no shimming or filing required, and the quality throughout feels great. It does follow the ‘standard’ Touring Car ethos and layout, but adding in a few nice unique features to really set it apart.
The first track test for the car will be a shakedown run at a UK club, before I head to the ETS in Luxembourg – I may as well test it at the highest possible level! Stay tuned for some track test reports and further updates!
Optional / Additional Parts Used
General:
• Panaracer 48DP Spur Gear
• Tamiya Anti-Weat Grease
• Metal Polish
OTM Racing:
• 2mm / Steering Hub Thread Cutting driver bit
Tonisport:
• MR33 Shock Oil
• MR33 Alloy Servo Horn (Sanwa)
• MR33 High Downforce Wing
Zen Racing:
• G Force TS160 Speed Controller
• G Force Super Sonic motor range
Moorespeed RC:
• Moorespeed 7.4v 80C LiPo batteries
Sanwa:
• BLS V2 Servo
• 471 Receiver
Protoform:
• Lightweight Mazda Speed 6 bodyshell (paint by Rob Sawell Design)
