Heavy Hobby
M18 3D Printed Running Gear
Heavy Hobby 1:35 HH-35050
Review by Terry Ashley


The Set:
The number of update sets for the new Tamiya M18 Hellcat keeps growing with this one from Heavy Hobby offering the full running gear, Drive Sprockets (Late), Road Wheels and rear Idlers in 3D printed resin. Heavy Hobby also do a set of 3D printed track (PT-35081) to supplement this set but we'll just look at the running gear set HH-35050 here.

First off, don't be confused by the printing on the box "Wheels Under Research Wheels A for WWII US Army M10 Tank", there is definitely M18 running gear parts in the box, nothing to do with an M10, so I've no idea what the box label is all about or why it's not been corrected? But there we have it.

The quality of the printing is good with clean details on the outer surfaces and all the print channels on the inner faces of the respective sprocket/wheel halves. You will need to clean the remnants and file the surfaces flat as the insides can be seen on the assembled road wheels and Idlers in particular after assembly. Also the mating surfaces on the hubs have to be perfectly smooth to get a good fit with the right spacing between the inner and outer sprocket/wheel halves. This is especially important on the Drive Sprockets because if the halves are not seated snugly the outer teeth discs can be slightly too wide apart to fit the tracks correctly. So dry test fitting of the sprockets to ensure the correct spacing for the best track fit before gluing would be the way to go.

Unfortunately there are a number of detail issues with these 3D parts if the modeller prefers more accuracy with their builds. The numbers on the corresponding images equate to the issues mentioned below for the respective sprocket/wheel parts.

Box and contents as they come
Heavy Hobby
Drive Sprocket, Idler and Road Wheel parts
Heavy Hobby
Heavy Hobby
The parts showing the inner faces needing to be filed smooth, the resin material allows for fine filing without any problems.
Heavy HobbyHeavy Hobby
Heavy Hobby

Drive Sprockets:
These are designed to enable the Tamiya kit 'poly-caps' to be fitted between the inner and outer drive sprockets halves so they attach in the same manner as the kit sprockets. The two sprocket halves are printed as one unit each with the holes cleanly rendered and have no central join seam to deal with. They also have the correct 31 teeth included on each sprocket disc.

There are some areas of concern with the details on these drive sprockets;
1. The drive teeth have a uniform shape with rounded ends while the actual drive teeth have more tapered pointed teeth (see image).

2. The extended rim lip should have a large circular weld around the sprocket face but this is not included with the HH sprockets. (see image)

3. The twelve main rim bolts aren't evenly spaced around the actual M18 rim as with most contemporary sprockets but has a cluster of two bolts fitted closer together than the rest, which also means the space between these two and the adjacent bolts is wider than between the evenly spaced bolts (see image).
Both the Tamiya and the Fat Frog 3D late sprockets have this feature correctly depicted but unfortunately the Heavy Hobby sprockets don't with all bolts spaced evenly around the rim. (Note; both early and late type sprockets had the two bolt cluster feature)

4. The inner join of the hub disc and outer rim has a large indent on the but should have a smoother, shallower join, again better depicted on both the Tamiya and the Fat Frog 3D late sprockets. (see images)

Heavy Hobby Drive Sprockets with the Tamiya kit Sprockets, the Fat Frog Late Sprockets
and actual M18 Drive Sprockets for comparison The numbers correspond to points lists above.
Note: The outer weld is present on the Fat Frog sprockets but understated and slightly too far towards the center.

Heavy Hobby
Heavy Hobby

Road Wheels:
WWII M18 road wheels were fitted with sheet metal guards around the outer rim faces as depicted correctly on the Tamiya kit wheel rims but unfortunately not included on the Heavy Hobby wheels. These wheels can be used on the M39 Armored Utility Vehicle serving in the Korean War. Many museum M18's are fitted with the post war wheels or a combination of both depending on availability, this can lead to miss-interpretation when just taking what you see at the museum on face value, not just with these but with many details as we've seen with different kits/update sets over the years.

The main detail issues are:
1. The wheels in this set are post war wheels without the sheet metal guards and as such aren't accurate for WWII period M18's. (see image)

2. The Central hub is too tapered resulting in the end cap being undersized. (see image)

Heavy Hobby Road Wheels with the Tamiya kit wheels
and actual WWII M18 Drive Road Wheels for comparison The numbers correspond to points lists above.
Heavy Hobby
A reference image of the actual road wheels (source unknown)
Heavy Hobby

Idler Wheels:
The Idlers, like the drive sprockets have the halves printed as one unit each with the holes cleanly rendered and have no central join seam like the kit Idlers but have some detail issues similar to the others.
The main detail issues are:
1. The outer rim lip is too tapered on the inside and should have a squarer lip junction as per images.

2. The outer elongated rim holes are too long resulting in the space between the holes being too short.

3. The Central hub is again too tapered resulting in the end cap being undersized. (see images)

Heavy Hobby Idler Wheels with the Tamiya kit Idlers
and actual WWII M18 Idler Wheels for comparison The numbers correspond to points lists above.

Heavy Hobby

Additional images showing the Fat Frog Sprockets and tracks compared to the Heavy Hobby Sprockets and tracks.
Heavy Hobby

When you think of 3D created update sets or any AM update set for that matter you'd normally assume the sets are accurate, additionally with the 3D ones being computer generated CADs from which a print is made, but there is an old saying, "you only get out what you put in". Sadly not a lot of research has gone into this set and as a result the Tamiya kit parts actually have many of the details more accurately rendered but with the join seam to be eliminated on the Drive Sprocket and Idler rims being the main assembly issue.

With all the detail issues this set really has nothing to offer by way of improvements over the kit parts especially for those desiring accuracy with their models.
If you want 3D printed Drive Sprockets to eliminate the joins of the kit rims then at this time the sets offered by Fat Frog (Early, set DE35003 and Late, set DE35004) are the way to go.

Rating 2.5/10

Thanks to my CC and Hobbyeasy for the Review sets.
to help the reviews continue, thank you

Page created October 14, 2022

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